mission to europa - northwestern universitylunar.earth.northwestern.edu/courses/351/europa.pdf ·...

Mission to Europa

Brian Kristall, Matthew Strumpf, Josh Townsend, Oliver Williams

The Family Portrait: Galilean Satellites

Io Europa Ganymede Callisto MoonRadius (km) 1822 1561 2631 2410 1738

Mass (1021 kg) 89.3 48.0 148.2 107.6 73.5Mean density (g cm-3) 3.53 3.01 1.94 1.83 3.34

Surface Temperature (K) 118 103 113 118 253Period (days) 1.769 3.551 7.155 16.689 27.322Eccentricity 0.004 0.0101 0.0015 0.007 0.055

Semimajor axis (RJ) 5.91 9.40 15.0 26.4 5.38

NASA/JPL

Chyba & Phillips, 2007

Interior Models of Europa: Gravity Field Indicates Complete Differentiation

NASA/JPLAnderson et. al., 1998Kivelson et. al., 2000Zimmer et. al., 2000


NASA/JPL

•Central Core Fe/Fe-S

Anderson et. al., 1998Kivelson et. al., 2000Zimmer et. al., 2000


NASA/JPL

•Central Core Fe/Fe-S•Anhydrous Rocky Mantle



NASA/JPL

•Central Core Fe/Fe-S•Anhydrous Rocky Mantle•Surface Layer ρ ≈ 1 g cm-3

~100 km thick



NASA/JPL


~100 km thick

Ocean vs. Ice - Magnetometer



NASA/JPL


~100 km thick

Ocean vs. Ice - Magnetometer•Europan induced magnetic field



NASA/JPL


~100 km thick

Ocean vs. Ice - Magnetometer•Europan induced magnetic field•Varies in direction + strength to

Jupiter’s magnetic field



NASA/JPL


~100 km thick


Jupiter’s magnetic field•Requires near-surface, global,

electrically conducting layer



NASA/JPL


~100 km thick


Jupiter’s magnetic field•Requires near-surface, global,

electrically conducting layer•Requires nearly complete

spherical shell Anderson et. al., 1998Kivelson et. al., 2000Zimmer et. al., 2000

Tidal Heating & Volcanism on Galilean Satellites

• Flexing of tidal bulge produce internal dissipation of energy • Tidal bulge height varies with

distance from Jupiter• ⇑ eccentricity = ⇑ variability

NASA/JPL

NASA/JPL

Tidal Heating & Volcanism on Galilean Satellites

• Flexing of tidal bulge produce internal dissipation of energy • Tidal bulge height varies with

distance from Jupiter• ⇑ eccentricity = ⇑ variability

NASA/JPL

NASA/JPL

• Europa ~1.6X further, ~2.5X eccentricity of Io

Modeled Heat Flow ≈ 200-300 mW m-2 (McKinnon & Shock, 2001)

Tidal Heating & Europan Seafloor Volcanism and Hydrothermal Systems?

Thin Ice Shell Thick Ice Shell

NASA/ESA

Europan Surface Composition:Galileo’s Near-Infrared Mapping Spectrometer

McCord et. al., 1999; Carlson et. al., 1999NASA/JPL


•Water Ice



•Water Ice•Hydrated Salts?•Mg-SO4-hydrates• Na-Mg-SO4-hydrates• Na-CO3-hydrates• Na-SO4-hydrates



•Water Ice•Hydrated Salts?•Mg-SO4-hydrates• Na-Mg-SO4-hydrates• Na-CO3-hydrates• Na-SO4-hydrates•Hydrated Sulfuric Acid?


NIMSend-members

H2SO4•nH2O

NIMS-hydrateH2SO4•8H2O


•Water Ice•Hydrated Salts?•Mg-SO4-hydrates• Na-Mg-SO4-hydrates• Na-CO3-hydrates• Na-SO4-hydrates•Hydrated Sulfuric Acid?•Minor SO2, H2O2, CO2


NIMSend-members

H2SO4•nH2O

NIMS-hydrateH2SO4•8H2O


•Water Ice•Hydrated Salts?•Mg-SO4-hydrates• Na-Mg-SO4-hydrates• Na-CO3-hydrates• Na-SO4-hydrates•Hydrated Sulfuric Acid?•Minor SO2, H2O2, CO2

NASA/JPL-Caltech

BLUE = more saltsYELLOW-ORANGE = more ice

Europan Surface GeologyLimited impact craters indicate young surface age

Pwyll Crater ~26 km wide

Tyre Impact Scar ~140 km wide

NASA/JPL/ASU

Europan Surface GeologyRidge Plains & “Double ridges”

0.2-4 km wide, 200-350 m tall, 10-1000 km long

Ridge ~2.6 km wide ~300 m highImage 14 x 17 km

Image 20 x 20 km NASA/JPLGreeley et. al., 2000

Europan Surface GeologyRidge Plains & “Double ridges”

0.2-4 km wide, 200-350 m tall, 10-1000 km long

NASA/JPL/DLR

Europan Surface GeologyBands - multiple parallel lines little topographic expression

NASA/JPL/ASU

Astypaleae Linea fault >800 km longImage 24 x 16 km

Europan Surface GeologyChaotic Terrains - “Rafted” iceberg-like blocks

Conamara ChaosImage 70 x 30 km

NASA/JPL/ASU

Europa Technical Challenges

1. Drilling through km’s (?) of ice2. Jovian radiation3. Others

Picture: NASA JPL

Yeah, right!

Drill Baby Drill!

• Using existing technology, a small (10 inch diameter) heated-drill could drill an estimated 10 cm/day. • Even most hopeful estimates put thickness of

ice crust at 10km. • Time required to drill 10km = 100000 days.

Not very feasible!

Drilling Dillema

• Solution: Don’t drill (all the way)• Small drill arm could drill several cm’s• Pristine samples of Europan ice

Jovian Radiation: Overview• Jupiter magnetic field 20,000x Earth magnetic

field.• Radiation source from charged particles in

Jupiters mag. field.• Europa orbit annual radiation dose 3 million x

human annual dose.• Europan surface dose halved.

Jovian Radiation: Effects• Damage to electronics from electrostatic

discharge.• Parasitic currents.• Spurious noise introduced to detectors/

sensors.

Source: NASA-ESA Outer Planet Mission Study

Jovian Radiation: Mitigation Orbit

•2.9Mrad in orbit around Europa.•Protect orbiter/lander with Al-shielding and rad-hardened parts.•Minimize radiation exposure by special positioning of orbit.

Surface•Surface landing: Radiation halved.

Source: NASA-ESA Outer Planet Mission Study

Above: Shielded circuitry part of the ESA Planck satellite.

Source: www.cryoconnect.com

Other Challenges• Europan orbiter/lander must

regulate temperature.• Landing on body with no

atmosphere, can’t parachute!• Periodic communication

blackouts due to orbit. • Sterilizing orbiter/lander.

Russian Space Agency Europa Lander concept.Source: http://arc.iki.rssi.ru/conf/2009elw/presentations/

Ethical Issues

• Nuclear power source

• Contamination of Europa–Leaving equipment on surface and in ocean–Introducing non-native life from Earth

Nuclear Power

• Weight efficient• Hazard to human health–Accident in construction–Failure in launch–Nuclear waste from enrichment

• Convince the public

Why prevent contamination?

• Terrestrial life taints currently pristine Europa–"false positives"–Safe guard future scientific exploration of Europa

and its biological potential–Protect possible native Europan life–Required under UN Treaty on Principles Governing

the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies

Task Group on the Forward Contamination of Europa

• Commission on Physical Sciences, Mathematics, and Applications (Space Studies Board)• Produced "Preventing the Forward

Contamination of Europa" in 2000• David Stahl, Northwestern University

Task Group Findings• NASA requirements for contamination

prevention efforts based on likelihood of body harboring life• Current requirements are satisfactory–Isopropyl alcohol, hydrogen peroxide, dry heating,

clean room assembly, bioload tests, final sterilization by Jupiter's radiation

• Recommended studies to define issues–Clean room practices, bioload assay methods,

radiation resistant microbes, autotroph detection

Task Group Disagreement

• Majority: bioload reduced so that probability of contaminating viable terrestrial organism is 10e-4

• Minority: less stringent requirements (Viking-level cleaning)–No reason for enhanced policies–Radiation will kill, life will not survive and multiply

in Europan ocean

Mission Objectives

• Characteristics of ice and salts

• Characteristics of sub-surface ocean

• Internal structure

• Life?

Ice

• Chemical Composition• Surface water• Chemistry –Is life even possible?

• Physical characteristics–Thickness–Mid-ocean ridge?

Ocean

• Chemical Composition• Depth• Relation to the interior• Ice-ocean exchange and

relationship

Formation of surface processes

• Smokers• Hydrothermal vents• Physical Characteristics• Try to find a site for

future exploration–Possible thin spot for

drilling

Radiation, Gravity, Magnetism•Effects of extreme radiation due to Jupiter•Tidal bulges from gravitational pull•Presence of a magnetic field

Life

• Is life even possible on Europa?–Are there hydrothermal vents?–If not, is life likely to be found?

• Should we continue the search in the ocean?–Should we find a thin section of ice and drill?

• Would we even recognize if we found life?

Equipment

• Orbiter–Map Europa’s surface–Characterize ocean–Relay information

Orbiter instruments:• Magnetometer• Laser altimeter• Radio Science• Ice Penetrating Radar•VIS-IR Imaging Spectrometer•UV Spectrometer•Ion and Neutral Mass Spectrometer•Thermal Instrument• Narrow Angle Camera• Wide Angle Camera and Medium Angle Camera•Magnetometer • Particle and Plasma Instrument

Nasa/JPL

Equipment

• Surface lander–Sample the ice (drill a few centimeters)–Deploy seismometer–Ocean depth–Ice thickness

Budget & Time LineJEO Phase A-F lifecycle NASA: $4 billionJGO Phase A-F lifecycle ESA: 650€ million

The Family Portrait: Galilean Satellites

mission to europa - northwestern universitylunar.earth.northwestern.edu/courses/351/europa.pdf ·...

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