1. Lecture 11: Beyond Mars - the World of Solar System Planets & their Moons: Europa, Titan, Enceladus 1.Giant planets vs. Earth-like planets 2.Life beyond the habitable zone (HZ) 3.Beyond the HZ - Europa. 4.Beyond the HZ - Enceladus. 5.Beyond the HZ - Titan.

2. The Giant Planets

5. 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

6. Beyond the HZ: Europa

7. What is on Europa’s surface ? Blue: pure water; Red: ice covered with dust veneer (Galileo orbiter)

8. Beyond the HZ: Europa ‘Icebergs’ on Europa: Many pieces are a few kilometers in size; 70km x 30km area (Galileo orbiter)

9. Beyond the HZ: Europa (Galileo orbiter)

10. Beyond the HZ: Europa The inferred interior with two possible upper layers: Warm ‘slush’ Liquid ocean

11. Beyond the HZ: Europa There are a couple of developed NASA proposals to explore Europa’s ocean; this artist conception is from one of them called ‘ICEPICK’

12. Beyond the HZ: Europa Measuring the ocean’s depth and the thickness of the ice crust. The Europa orbiter will make sensitive gravimetric measurements by recording very slight changes in its orbit. (NASA project) (J. Lunine 2005)

13. Beyond the HZ: Enceladus Picture of Enceladus in front of Saturn and its rings (Cassini mission, March 2006):

14. Beyond the HZ: Enceladus

21. Beyond the HZ: Titan

22. Titan properties 50% silicates, 50% ices; probably differentiated Atmosphere is >90% N 2 and 2-5% CH 4 T s = 94K, P s = 1.5 bar : Titan :: : Earth Liquid CH 4 & Water ice Liquid H 2 O & Silicate rock Near triple point Similar mechanical strength

23. Methane rainfall? Evidence of atmospheric convection –Transient clouds near summer pole Short cloud lifetimes (hours)  CH 4 rainfall? Roe et al. [2002]

24. ~5 km ESA/NASA/U. Arizona Images from Huygens Descent Imager/Spectral Radiometer

25. NASA/JPL/U. Arizona Dendritic networks are valleys

26. ~10 cm Tomasko et al., 2006 Image taken by the Huygens probe at its landing site Titan landscape

27. Rain on Titan: Dendritic valleys near Huygens landing site were probably eroded mechanically by CH 4 runoff Earth-like precipitation rates are required to mobilize sediment of the size observed at landing site

29. Lakes and channels on Titan!

30. Main points to take home: 1)The Solar System planets: orbits and relative sizes 2)The Habitable Zone generalized: other sources of heating - internal & tidal 3)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 N 2 and CH 4 - evidence for CH 4 rain and lakes - complex organic chemistry