A Milillo and K C Hsieh

(and the SHEA fans)

2nd SERENA-HEWG meeting - Mykonos June 2009

Why energetic neutral atoms are a useful tool for planetary investigationsThe neutral atoms do not interact with electromagnetic fields Hence if their energies are high enough to consider the gravitational effects negligible they have the property to maintain their characteristics (energy distribution and direction) unchanged since the generation time In this way the information about the (remote) generation process can be obtained through energetic neutral atom detectionWe know two main generation mechanisms of atoms at energies well above the gravitational effects Charge-exchange and ion sputtering processes

Plasma

ionsions

keV ENA

ENA features in the solar system

Charge-ExchangeCharge-Exchange

SurfaceSurfaceIon-SputteringIon-Sputtering

10s eV ENA

ionsions

AtomosphericAtomosphericIon-SputteringIon-Sputtering

10s eV ENAionsions

(fm Orsini et al SERENA-HEWG meeting Santa Fe NM USA)2nd SERENA-HEWG meeting - Mykonos June 2009

OutlineSurface ion sputtering process Other surface release processes

(example of Mercury)Expected outcomes from Sputtered

High-Energy Atoms (SHEA) observations in the Hermean environmentin the solar wind - asteroid

interactionin the Jupiterrsquos system

Conclusions 2nd SERENA-HEWG meeting - Mykonos June 2009

Surface Ion Sputtering process

Ion sputtering products depend onbull the composition and the chemical structure of the surface bull the impinging plasma flux

Release of neutrals due to bombardment of a surface by energetic ions

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion-sputtering processThe emitted neutral flux n is proportional to the yield Y (the number of sputtered atoms produced by one single impinging ion) much higher for higher energies and for heavier ions (Baragiola et al 2003)

max

min

E

E

iieSi

I

e

n dEEEfdE

dcY

dE

d

c is the surface relative abundance of the atomic species considered I is the ion flux and fs is the energy distribution function

2nd SERENA-HEWG meeting - Mykonos June 2009

Note that the yields obtained by laboratory simulations could be different (lower or higher) in the planetary environments since the aggregation status of the surface material could be different from the sampleNew observations are really

important in this frame

Energy distribution function

Directional neutrals

Ei incident particle energyEb binding energy 1 eVEe Energy of the released particle

2

1

221

213 4

1

mm

mmE

EE

EE

EcEEf

i

be

be

enieS

0

1ees dEEf

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Why energetic neutral atoms are a useful tool for planetary investigationsThe neutral atoms do not interact with electromagnetic fields Hence if their energies are high enough to consider the gravitational effects negligible they have the property to maintain their characteristics (energy distribution and direction) unchanged since the generation time In this way the information about the (remote) generation process can be obtained through energetic neutral atom detectionWe know two main generation mechanisms of atoms at energies well above the gravitational effects Charge-exchange and ion sputtering processes

Plasma

ionsions

keV ENA

ENA features in the solar system

Charge-ExchangeCharge-Exchange

SurfaceSurfaceIon-SputteringIon-Sputtering

10s eV ENA

ionsions

AtomosphericAtomosphericIon-SputteringIon-Sputtering

10s eV ENAionsions

(fm Orsini et al SERENA-HEWG meeting Santa Fe NM USA)2nd SERENA-HEWG meeting - Mykonos June 2009

OutlineSurface ion sputtering process Other surface release processes

(example of Mercury)Expected outcomes from Sputtered

High-Energy Atoms (SHEA) observations in the Hermean environmentin the solar wind - asteroid

interactionin the Jupiterrsquos system

Conclusions 2nd SERENA-HEWG meeting - Mykonos June 2009

Surface Ion Sputtering process

Ion sputtering products depend onbull the composition and the chemical structure of the surface bull the impinging plasma flux

Release of neutrals due to bombardment of a surface by energetic ions

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion-sputtering processThe emitted neutral flux n is proportional to the yield Y (the number of sputtered atoms produced by one single impinging ion) much higher for higher energies and for heavier ions (Baragiola et al 2003)

max

min

E

E

iieSi

I

e

n dEEEfdE

dcY

dE

d

c is the surface relative abundance of the atomic species considered I is the ion flux and fs is the energy distribution function

2nd SERENA-HEWG meeting - Mykonos June 2009

Note that the yields obtained by laboratory simulations could be different (lower or higher) in the planetary environments since the aggregation status of the surface material could be different from the sampleNew observations are really

important in this frame

Energy distribution function

Directional neutrals

Ei incident particle energyEb binding energy 1 eVEe Energy of the released particle

2

1

221

213 4

1

mm

mmE

EE

EE

EcEEf

i

be

be

enieS

0

1ees dEEf

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Plasma

ionsions

keV ENA

ENA features in the solar system

Charge-ExchangeCharge-Exchange

SurfaceSurfaceIon-SputteringIon-Sputtering

10s eV ENA

ionsions

AtomosphericAtomosphericIon-SputteringIon-Sputtering

10s eV ENAionsions

(fm Orsini et al SERENA-HEWG meeting Santa Fe NM USA)2nd SERENA-HEWG meeting - Mykonos June 2009

OutlineSurface ion sputtering process Other surface release processes

(example of Mercury)Expected outcomes from Sputtered

High-Energy Atoms (SHEA) observations in the Hermean environmentin the solar wind - asteroid

interactionin the Jupiterrsquos system

Conclusions 2nd SERENA-HEWG meeting - Mykonos June 2009

Surface Ion Sputtering process

Ion sputtering products depend onbull the composition and the chemical structure of the surface bull the impinging plasma flux

Release of neutrals due to bombardment of a surface by energetic ions

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion-sputtering processThe emitted neutral flux n is proportional to the yield Y (the number of sputtered atoms produced by one single impinging ion) much higher for higher energies and for heavier ions (Baragiola et al 2003)

max

min

E

E

iieSi

I

e

n dEEEfdE

dcY

dE

d

c is the surface relative abundance of the atomic species considered I is the ion flux and fs is the energy distribution function

2nd SERENA-HEWG meeting - Mykonos June 2009

Note that the yields obtained by laboratory simulations could be different (lower or higher) in the planetary environments since the aggregation status of the surface material could be different from the sampleNew observations are really

important in this frame

Energy distribution function

Directional neutrals

Ei incident particle energyEb binding energy 1 eVEe Energy of the released particle

2

1

221

213 4

1

mm

mmE

EE

EE

EcEEf

i

be

be

enieS

0

1ees dEEf

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

OutlineSurface ion sputtering process Other surface release processes

(example of Mercury)Expected outcomes from Sputtered

High-Energy Atoms (SHEA) observations in the Hermean environmentin the solar wind - asteroid

interactionin the Jupiterrsquos system

Conclusions 2nd SERENA-HEWG meeting - Mykonos June 2009

Surface Ion Sputtering process

Ion sputtering products depend onbull the composition and the chemical structure of the surface bull the impinging plasma flux

Release of neutrals due to bombardment of a surface by energetic ions

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion-sputtering processThe emitted neutral flux n is proportional to the yield Y (the number of sputtered atoms produced by one single impinging ion) much higher for higher energies and for heavier ions (Baragiola et al 2003)

max

min

E

E

iieSi

I

e

n dEEEfdE

dcY

dE

d

c is the surface relative abundance of the atomic species considered I is the ion flux and fs is the energy distribution function

2nd SERENA-HEWG meeting - Mykonos June 2009

Note that the yields obtained by laboratory simulations could be different (lower or higher) in the planetary environments since the aggregation status of the surface material could be different from the sampleNew observations are really

important in this frame

Energy distribution function

Directional neutrals

Ei incident particle energyEb binding energy 1 eVEe Energy of the released particle

2

1

221

213 4

1

mm

mmE

EE

EE

EcEEf

i

be

be

enieS

0

1ees dEEf

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Surface Ion Sputtering process

Ion sputtering products depend onbull the composition and the chemical structure of the surface bull the impinging plasma flux

Release of neutrals due to bombardment of a surface by energetic ions

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion-sputtering processThe emitted neutral flux n is proportional to the yield Y (the number of sputtered atoms produced by one single impinging ion) much higher for higher energies and for heavier ions (Baragiola et al 2003)

max

min

E

E

iieSi

I

e

n dEEEfdE

dcY

dE

d

c is the surface relative abundance of the atomic species considered I is the ion flux and fs is the energy distribution function

2nd SERENA-HEWG meeting - Mykonos June 2009

Note that the yields obtained by laboratory simulations could be different (lower or higher) in the planetary environments since the aggregation status of the surface material could be different from the sampleNew observations are really

important in this frame

Energy distribution function

Directional neutrals

Ei incident particle energyEb binding energy 1 eVEe Energy of the released particle

2

1

221

213 4

1

mm

mmE

EE

EE

EcEEf

i

be

be

enieS

0

1ees dEEf

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion-sputtering processThe emitted neutral flux n is proportional to the yield Y (the number of sputtered atoms produced by one single impinging ion) much higher for higher energies and for heavier ions (Baragiola et al 2003)

max

min

E

E

iieSi

I

e

n dEEEfdE

dcY

dE

d

c is the surface relative abundance of the atomic species considered I is the ion flux and fs is the energy distribution function

2nd SERENA-HEWG meeting - Mykonos June 2009

Note that the yields obtained by laboratory simulations could be different (lower or higher) in the planetary environments since the aggregation status of the surface material could be different from the sampleNew observations are really

important in this frame

Energy distribution function

Directional neutrals

Ei incident particle energyEb binding energy 1 eVEe Energy of the released particle

2

1

221

213 4

1

mm

mmE

EE

EE

EcEEf

i

be

be

enieS

0

1ees dEEf

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Energy distribution function

Directional neutrals

Ei incident particle energyEb binding energy 1 eVEe Energy of the released particle

2

1

221

213 4

1

mm

mmE

EE

EE

EcEEf

i

be

be

enieS

0

1ees dEEf

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes

(Killen et al SSR2008)

Thermal Desorption (TD) mainly volatiles at very low energies (lt5 eV)

Photon Stimulated Desorption (PSD) mainly volatiles at low energy (~ 1 eV)

Micrometeoroid Impact Vaporization (MIV) all the surface components at high energy but anyway below few eVs

Ion Sputtering (IS) all the surface components at higher energy up to 100s eV

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Particle release processes at Mercury Na case TD PSD

IS MIV

(Milillo et al PSS in press2008)2nd SERENA-HEWG meeting - Mykonos June

2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Detection of exospheric gas Observation of the global exospheric distribution (released particles) with characterization of composition can be obtained by mass spectrometers as well as UV spectrometersNa K and Ca densities of the Hermean exosphere can be obtained by ground-based observationsThese exospheric observations cannot provide univoche information about the parent surface release process neither about the location of the releaseOnly speculations about asymmetries induced by solar wind-planetary magnetosphere interaction or preferential released species can be done to discriminate the ion sputtering process

Why is it important to discriminate the action of the ion sputteringThe ion-sputtering process is one of

the main processes responsible for refractories release and escape Its action could be much more important in the last phases of the Solar System formations (about 45 Gy ago) when the early Sun was emitting a 100-times more intense slar wind (Lammer et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEAThe Sputtered High Energy Atoms (SHEA) that is the

high energy tail of the sputtered distribution (letrsquos say at energy Eegt10 eV) are between few and tens of the total release depending mainly on the ion impacting energy

2nd SERENA-HEWG meeting - Mykonos June 2009

Directional neutrals

Why do we wish to detect SHEA (neutrals at energies gt10 eV) to investigate the ion sputtering processBecause below 10 eV the ion-sputtering

product is negligible compared to other release process and the particles do not maintain the initial direction since the gravitational effects are not negligible

Energy distribution of the sputtered H2O particles emerging from the surface of Europa in case of S+ at 10 keV and 100 keV Binding energy is assumed 045 eV

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

(Environment Simulation ToolIFSI)

Particles released at different energy rangesEnergy range lt006 eVEnergy range 006-03 eVEnergy range 03-15 eVEnergy range 15-10 eVEnergy range 10-40 eVEnergy range 40-200 eV

2nd SERENA-HEWG meeting - Mykonos June 2009

SHEA detection provides a map of plasma precipitation regions and an imaging of particle emission from surfaceWe do not need to perform line-of-

sight integration hence the geometry of deconvolution is easier The problem here is the number of

unknown parameters Y (surface mineralogy Eb ) c Fion (species energy impact angle)

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Expected outcomes of SHEA observations Mercury case

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

The Solar wind and IMF at MercuryThe Parker spiral forms an angle of

about 20deg with the solar wind radial direction less than half of the value at the Earthrsquos orbit (~45deg) this implies a change of the relative ratio of the Interplanetary Magnetic Field (IMF) components with respect to the near-Earth conditions and an increase of the weight of the IMF Bx component

The average solar wind density is about ten times higher than that at the Earth but this value varies considerably due to the high eccentricity of the orbit of the planet (from 32 cm-3 to 73 cm-3)

B

The IMF intensity changes by a similar factor

B v

v

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Mercury has an internal magnetic fieldThe Mariner 10

observations confirmed by the first MESSENGER flyby reveal the existence of an internal dipolar-like magnetic field (Ness et al 1975)

(Milillo et al 2005)

The estimated dipole moment ranges between 284 and 358 nT RM

3 nothward oriented

Hermean magnetosphere is only 5 of that of the Earth In a zero order analysis the spatial dimensions must be scaled by a factor of ~7 or 8

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Solar wind entry in the Hermean magnetosphere

Density of the solar wind protons in from 105 to 1085 m-

3 The yellow lines represent the magnetic field (Kallio et al 2008)

The IMF orientation and intensity and the weak internal magnetic field of Mercury likely produce a direct entry through the cusps inside the Hermean dayside magnetosphere

Solar wind plasma circulates inside the magnetosphere and eventually may hit the surface

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

SW precipitation

(Massetti et al 2003)

BIMF =(00-10) nT

BIMF =(05-10) nTPdyn=16 nPa

BIMF =(05-10) nTPdyn=60 nPa

Flux(cm

-2 s sr keV)

-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Color and albedo controlled by maturity and composition

PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

MNF (minimum noise fractionsimilar to PC) 2-1-3 as R-G-B

Lowalbedomaterialldquostreakrdquo

From Robinson et al LPSC 2008

2nd SERENA-HEWG meeting - Mykonos June 2009

Fm Sprague et al SERENA-HEWG meeting Santa Fe NM May 2008

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

As well as for the cameras a FOV perpendicular to the sc motion is the most suitable for this kind of surface imaging

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Simulation of SHEA detection at Mercury by

BepiColomboMPOSERENA-ELENA

(Orsini et al 2008)

2nd SERENA-HEWG meeting - Mykonos June 2009

Thanks to the BepiColombo mission we will have simultaneous measurements of precipitating plasma (MIPA) surface composition (MIXS) and mineralogy (MERTIS) and neutral composition (STROFIO and PHEBUS) and SHEA observation (ELENA) for a complete investigation of the IS process

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Near Earth Object (NEO)bull have orbits with perihelion distances q lt13bull appear heterogeneous in shapes sizes spin rates and compositionsbull are subjected to continuous interaction with the interplanetary medium

bull solar wind interaction with surface (ion sputtering)

bull solar and cosmic ray bombardment

bull micrometeoroids gardening

NEO (433) Eros (John Hopkins

University)

The NEO superficial composition is modified by this space weathering

2nd SERENA-HEWG meeting - Mykonos 8-11 June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering NEObullIon fluxes Solar wind at 1 AU 1-keV H+ flux 108 (cm-2 s-1 sr keV)

bullThe binding energy Eb holding the regolith (strongly dependent from NEO type) ranges between 05 and 3-4 eV (Lammer et al 2003) We consider 2 eV

bullThe average yield Y in this case is about 005 (Lammer et al 2003)

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

100100100Total

111Ni28

151713 Fe26

111 Ca20

536 S16

161914 Si14

221 Al13

182015 Mg12

12811 C6

302938H1

Tagish Lake(atoms)

CM(atoms)

CI (atoms)

ElementZ

Bulk element abundances for CI type chondrites

(Plainaki et al 2008 adapted from Brown et al 2000)

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtered fluxes of individual species

bull The most important contribution to the total sputtered particle flux comes from sputtered H bullMg is also significantly lost for ion-sputtering action (Plainaki et al 2008)

m-2 s

-1m

-2 s-1

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Total sputtered flux from a CI type NEOm

-2 s-1

Particles fluxes (up to 1011 particles m-2 s-1) appear in a region up to 1 km above the NEO surface (in the solar wind direction) The erosion rate fω

is 03 Aringyear where ω=10-29 m3 is the atomic volume in a solid substance (Plainaki et al 2008) This result is similar to

the estimation performed for the lunar surface 02 Aringyear in case of solar wind sputtering (Starukhina 2003)

2nd SERENA-HEWG meeting - Mykonos June 2009

The SHEA (gt10 eV) flux results in about 109 particles m-2 s-1

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

ENA in the Jupiter environment

SHEAfrom Europa

and GanymedeC-E ENA

from plasma ndash tori interaction

C-E ENA from auroral regions

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

2nd SERENA-HEWG meeting - Mykonos June 2009

(Paranicas et al GRL 2002)

Krupp et al 2001 showed that the radiation belts extends inside the Callistorsquos while the energetic particle fluxes decrease abruptly out of these distances Plasma precipitation on the inner moonsrsquo surfaces produces SHEA

Giovian radiation belt

Ganymedersquosorbit

Callistorsquosorbit

Europarsquosorbit

H+ O+ S+

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Europa

Surface composed mainly by water ice and other components as Na K etc In fact Na and K atmosphere has been observed (Brown and Hill 1996 Brown 2001)Traces of non-icy material (a hydrate compound of H2O2 (013) SO2 and CO2) (Tiscareno and Geissler 2003 Johnson et al 1983)

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

The surface composition of Europa

Highest albedo among all the Galilean satellites (Kuskov and Kronrod 2005)

Probably geologically young surface (crater preservation yields an age estimate of ~10ndash100 Ma) (Moore et al 1998)

Possible existence of liquid water beneath the outer icy crust that ranges from a few kilometers to at least a few tens of kilometers (McKinnon 1999 Ruiz and Tejero 2003)

Disrupted ice crust in the Conamara region of Jupiters moon Europa (NASA courtesy)

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Ion sputtering EuropabullIon fluxes based on values given by Cooper et al (2001) and Strazzulla et al (2003) at energy about 10-100 keV

Particle Flux (ions cm-2 s-1)

H+ 15 ∙107

C+ 18 ∙106

O+ 15 ∙106

S+ 9∙106

bullThe binding energy Eb holding the ice molecules on the surface of Europa is characterized by the sublimation energy of water 045 eV per molecule (Johnson 1998) Particle Sputtering Yield

(moleculesion)

H+ 5

C+ 10

O+ 50

S+ 30

bullThe yield Y are based on the results by Shi et al (1995) Johnson (1990) and Ip et al (1997) as well as on the Galileo observations

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Sputtering Europa

SHEA flux produced by S+ impinging particles

(Plainaki et al Cospar meeting 2008)

particlessm2

The estimated SHEA (gt10 eV) signal at 200 km over Europarsquos surface is f=107 (cm2 s)-1

Flux (particles m

-2 s-1)

H+ O+C+ S+

(Plainaki et al EGU 2009)

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Similar energetic ion fluxes observed by Galileo spacecraft at Europa (Paranicas et al GRL 2002) are expected at Ganymede that is composed by a similar iced surface but it has the peculiarity of an internal magnetic field that could shield the plasma or define preferential entries and plasma precipitation regions

Comparative observations

2nd SERENA-HEWG meeting - Mykonos June 2009

From the NASAESA JOINT SUMMARY REPORT EUROPA JUPITER SYSTEM MISSION

On the contrary the ion fluxes at Callisto are two order of magnitude lower

Similar observations in different environment like the two moons Europa and Ganymede would offer the chance to investigate the different satellites evolution in the Jupiter system

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Conclusions Why is ion-sputtering investigation important

Interaction plasma-surface or plasma-atmosphere

Characterization of the surface propertiesInvestigation of the particles escape mechanismsPlasma entry and circulation in planetary

environmentsCharacterization of the effect of space

weathering on the surfacesEventually investigation of the evolution of Solar

system2nd SERENA-HEWG meeting - Mykonos June

2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Conclusions Why is SHEA imaging important as well as of surrounding gas analysis The detection of particles above 10 eVs is a method to identify that the ion-sputtering is active and to define the region of its action A joint observation of surronding gas and SHEA will permit to know where when and how the ion sputtering release takes place and will permit a clearer estimation of the escaping material

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

ENVIRONMENTS I

NVESTIGATED V

IA S

HEA

2nd SERENA-HEWG meeting - Mykonos June 2009

ENCELADUS

NEO

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009

Thank you for your

attention

2nd SERENA-HEWG meeting - Mykonos June 2009