1. Hour 5: Planets in Our Solar System -- Histories Compared with Earth Information from Meteorites Earth as a Planet Venus and Mars: Good Planets Gone Bad Tidal heating of Jovian moons - extending the Habitable Zone

2. Take-aways: Meteorites: (1) give age of the solar system, (2) contain organic molecules, and (3) show evidence the solar system formed soon after a nearby supernova explosion Earth is the largest and consequently the most geologically active of the 4 terrestrial planets; is that significant for biological environment ? Earth itself was not “Earth-like” until as recently as 1 Byr ago Venus and Mars were both once more Earth-like, but “went bad” -- Venus as “runaway greenhouse” --- Mars as “runaway refrigerator” Mars had substantial liquid water on its surface during its first billion years - the length of time in which life started on Earth Tidal (gravitational) heating of moons of large planets may extend the Habitable (liquid water) Zone across the solar system

3. Meteorites Chips of asteroids Material for solar system radiometric age Some carry organic matter Some show evidence that formation of the solar system was triggered by a supernova

4. Fig. 19-2d, p.455

5. Shocks Triggering Star Formation Henize 206 (infrared)

6. Earth as a Planet

7. Fig. 17-1, p.380

8. Fig. 17-9, p.394

9. p.384a

10. p.384b

12. Venus and Mars: Good Planets Gone Bad

13. Celestial Profile, p.399

14. Fig. 17-12, p.398

15. Fig. 17-13, p.402

16. Fig. 17-14, p.403

17. Fig. 17-4, p.386

18. Venus Planet originally in Habitable Zone --cool enough for liquid water “Runaway” greenhouse effect Evidence that an entire ocean of water has evaporated Without water, CO2 cannot be removed into crust sediments (Venus atmosphere has same amount of CO2 as Earth crust) This is the eventual fate of the Earth as the Sun’s luminosity continues to rise

19. Mars

20. Celestial Profile, p.405

21. p.401c

22. p.401d

23. p.401e

24. Fig. 17-18c, p.407

25. Fig. 17-20, p.408

26. Fig. 17-17, p.406

27. Fig. 17-16, p.406

28. Fig. 17-21, p.410

29. Mars Planet originally in Habitable Zone -- warm enough for liquid water Low-mass planet with light gravity and little geologic activity slowly lost its atmosphere (and greenhouse warming) Images showing effects of surface water in oldest terrain Rovers find evidence there was once significant amounts of standing water (e.g. lakes)

30. Moons of the Giant Planets -- Tidal Heating Extends Habitable Zone ?

31. Fig. 18-1, p.420

32. Fig. 18-5, p.428

33. Tidal Heating Jupiter’s moons: Io, Europa (also Ganymede and Callisto?) Saturn’s moons Enceladus, Titan

34. Fig. 18-9, p.430

35. Fig. 18-8, p.429

36. Fig. 18-12c, p.436

37. 18CO, p.418

38. Fig. 18-11a, p.432

39. Fig. 18-11b, p.432

40. Fig. 18-11c, p.432

41. Take-aways: Meteorites: (1) give age of the solar system, (2) contain organic molecules, and (3) show evidence the solar system formed soon after a nearby supernova explosion Earth is the largest and consequently the most geologically active of the 4 terrestrial planets; is that significant for biological environment ? Earth itself was not “Earth-like” until as recently as 1 Byr ago Venus and Mars were both once more Earth-like, but “went bad” -- Venus as “runaway greenhouse” --- Mars as “runaway refrigerator” Mars had substantial liquid water on its surface during its first billion years - the length of time in which life started on Earth Tidal (gravitational) heating of moons of large planets may extend the Habitable (liquid water) Zone across the solar system