Lecture 11: Beyond Mars - the World of Solar System Planets & their Moons: Europa, Titan, Enceladus

1. Giant planets vs. Earth-like planets2. Life beyond the habitable zone (HZ)3. Beyond the HZ - Europa.4. Beyond the HZ - Enceladus.5. Beyond the HZ - Titan.

The Giant Planets

The Giant Planets

The Giant Planets

Beyond the HZ:

Radiant heating from a parent star is not the only way to provide an energy source:

(1) Planetary interiors: radioactive & core heat Deep Biosphere Lab (Sweden): hyperthermophiles at depths of ~ 6 km (80 C).

(2) Tidal heating

Beyond the HZ: Europa

Beyond the HZ: Europa

What is on Europa’s surface ?

Blue: pure water;Red: ice covered with dust veneer

(Galileo orbiter)

Beyond the HZ: Europa

‘Icebergs’ on Europa:

Many pieces are a fewkilometers in size;

70km x 30km area

(Galileo orbiter)

Beyond the HZ: Europa

(Galileo orbiter)

Beyond the HZ: EuropaThe inferred interior with two possible upper layers:

Warm ‘slush’

Liquid ocean

Beyond the HZ: Europa

There are a couple ofdeveloped NASA proposals toexplore Europa’s ocean;

this artist conception is fromone of them called ‘ICEPICK’

Beyond the HZ: Europa

Measuring the ocean’sdepth and the thickness ofthe ice crust.The Europa orbiter will makesensitive gravimetricmeasurements by recordingvery slight changes in itsorbit. (NASA project)

(J. Lunine 2005)

Beyond the HZ: Enceladus

Picture of Enceladus in front ofSaturn and its rings(Cassini mission, March 2006):

Beyond the HZ: Enceladus

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Beyond the HZ: Enceladus

Beyond the HZ: Enceladus

Beyond the HZ: Enceladus

Beyond the HZ: Titan

Titan properties

• 50% silicates, 50% ices; probably differentiated

• Atmosphere is >90% N2 and 2-5% CH4

• Ts= 94K, Ps= 1.5 bar

: Titan :: : EarthLiquid CH4

& Water ice

Liquid H2O &

Silicate rock

Near triple point

Similar mechanical strength

Methane rainfall?

• Evidence of atmospheric convection– Transient clouds near summer pole

• Short cloud lifetimes (hours) CH4 rainfall?

Roe et al. [2002]

~5 kmESA/NASA/U. Arizona

Images from Huygens Descent Imager/Spectral Radiometer

NASA/JPL/U. Arizona

Dendritic networks are valleys

~10 cm

Tomasko et al., 2006

• Image taken by the Huygens probe at its landing site

Titan landscape

Rain on Titan:

• Dendritic valleys near Huygens landing site were probably eroded mechanically by CH4 runoff

• Earth-like precipitation rates are required to mobilize sediment of the size observed at landing site

Lakes and channels on Titan!

Main points to take home:1) The Solar System planets: orbits and

relative sizes2) The Habitable Zone generalized: other

sources of heating - internal & tidal3) Europa: water ocean under solid ice

crust - tidal heating;4) Enceladus: geysers - water from

hydrothermal circulation under ice crust - tidal heating;

5) Titan: thick atmosphere of N2 and CH4 - evidence for CH4 rain and lakes - complex organic chemistry