lecture 11: beyond mars - the world of solar system planets & their moons: europa, titan,...

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

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


What is on Europa’s surface ?

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

(Galileo orbiter)


‘Icebergs’ on Europa:

Many pieces are a fewkilometers in size;

70km x 30km area

(Galileo orbiter)


(Galileo orbiter)

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

Warm ‘slush’

Liquid ocean


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

this artist conception is fromone of them called ‘ICEPICK’


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):

QuickTime™ and aPNG decompressor

are needed to see this picture.

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 km

ESA/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

lecture 11: beyond mars - the world of solar system planets & their moons: europa, titan,...

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