giant planets vs. earth-like planets life beyond the habitable zone (hz) beyond the hz - europa
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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
QuickTime™ and aPNG decompressor
are needed to see this picture.
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
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