1. Lecture 19

2. Outline Discuss Quiz Mercury Venus

3. Outline For Rest of Semester Oct. 29 th Chapter 9 (Earth) Nov 3 rd and 5 th Chapter 9 and Chapter 10 (Earth and Moon) Nov. 10 th and 12 th Chapter 11 (Mars, Venus, and Mercury) Nov. 17 th and 19 th Chapter 12 (Jupiter and Saturn) Nov 24 th Chapter 13 (Uranus and Neptune) Nov 26 th Thanksgiving Dec. 1 st - Exam 3 Dec. 3 rd – Chapter 14 (Pluto, and the Kuiper Belt) Dec. 8 th and 10 th – Chapter 7 and 8 (Comparative Planetology I and II) Tuesday December 15 th (7:30 am – 10:15 am) Final Exam No Reading days are scheduled this semester Exam Period begins at 7:30 a.m. on Monday, December 14 and ends on December 21

4. Mercury

5. Observations Observing Mercury –What are best conditions to observe? Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Craters –How similar to the moon –How different Unexpected magnetic field –Why unexpected –How measured

7. Observations Observing Mercury –What are best conditions to observe Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Craters –How similar to the moon –How different Unexpected magnetic field –Why unexpected –How measured

8. No-name rotation

9. synchronous rotation 1-to-1 spin-orbit coupling

10. The Moon’s rotation always keeps the same face toward the Earth due to synchronous rotation

11. Mercury’s orbital period is 88 days Mercury’s rotation period is 58 days A B C D Draw ball and arrow at A, B, C, D

12. Mercury’s orbital period is 88 days Mercury’s rotation period is 58 days A B C D Draw ball and arrow at A, B, C, D A few days later …

13. Mercury’s orbital period is 88 days Mercury’s rotation period is 58 days A B C D Draw ball and arrow at A, B, C, D 88/4 = 22 days to get to A 22/58 = 0.375

14. Mercury’s orbital period is 88 days Mercury’s rotation period is 58.6 days A B C D Draw ball and arrow at A, B, C, D 88/4 = 22 days to get to A 22/58 = 0.375 First move into position in orbit. Then rotate around Mercury’s axis.

15. Mercury’s orbital period is 88 days Mercury’s rotation period is 58 days A B C D Draw ball and arrow at A, B, C, D 88/4 = 22 days to get to A 22/58 = 0.375 D 0.375 of a full turn

16. Mercury’s orbital period is 88 days Mercury’s rotation period is 58 days A B C D Draw ball and arrow at A, B, C, D 88/4 = 22 days to get to A 22/58 = 0.375 D

17. Planet’s orbital period is 90 days Planet’s rotation period is 60 days A B C D

18. Planet’s orbital period is 200 days Planet’s rotation period is 200 days (retrograde) A B C D

19. Animation

22. ? ?

24. Observations Observing Mercury –What are best conditions to observe Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Craters –How similar to the moon –How different Unexpected magnetic field –Why unexpected –How measured

25. Heavily cratered surface Less dense cratering than moon Gently rolling plains Scarps No evidence of tectonics

26. Note how much more densely the craters occur on the moon’s surface.

27. Scarps are cliffs This one is more than a km high They probably formed as the planet cooled and shrank

28. Animation

29. The Caloris Basin is evidence of a large impact

30. The seismic waves from the impact that caused the Caloris Basin caused this deformation on the opposite side of Mercury

31. Observations Observing Mercury –What are best conditions to observe Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Craters –How similar to the moon –How different Unexpected magnetic field –Why unexpected –How measured

32. Questions It is relatively difficult to observe details on the surface of Mercury from Earth because –A) detail is obscured by bright glows from hot regions of molten surface heated by the intense sunlight. –B) its orbit always keeps it on the opposite side of the Sun from Earth. –C) it is a small object that always appears close to the Sun in the sky. –D) its surface is always completely covered in clouds.

33. Questions The reason the temperature on the dark side of Mercury is warmer than originally expected is that –A) Mercury's large iron core conducts heat through the planet. –B) Mercury does not rotate synchronously with its orbital period. –C) several very active volcanoes on Mercury, produced by tidal stresses from the Sun, produce excess heat. –D) winds in Mercury's tenuous atmosphere carry heat from the daytime side to the night side.

34. Questions What is believed to be the cause of the long, meandering scarps (cliffs) observed on Mercury? –A) shrinkage of the planet as Mercury cooled –B) large impacts near the end of the early period of heavy bombardment –C) volcanic eruptions along crustal faults over hot spots in the mantle –D) crustal movement due to convection in the mantle, similar to continental drift on Earth but to a much smaller extent

35. Outline For Today Discuss Quiz Mercury Venus Mars

36. Interesting facts Mariner 2 visited in 1962 Venus Express – recently arrived

37. Observations Observing Venus –What are best conditions to observe? Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Craters –How similar to the moon –How different Unexpected magnetic field –Why unexpected –How measured

40. Observations Observing Venus –What are best conditions to observe? Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Climate –Runaway greenhouse effect Surface

41. Venus’s rotation is slow and retrograde (“retro”)

42. No-name rotation

43. synchronous rotation

44. Mercury’s orbital period is 88 days Mercury’s rotation period is 58 days A B C D 88/4 = 22 days to get to A 0.375 of a turn 0.75 of a full turn 1.125 turns 1.5 turns A

45. Venus’s orbital period is 224 days Venus’s rotation period is 243 days (retrograde) A B C D Draw ball and arrow at A, B, C, D How long is Venus’s day?

46. Observations Observing Venus –What are best conditions to observe? Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Surface Climate –Runaway greenhouse effect

47. The surface of Venus shows no evidence of plate tectonics The surface of Venus is surprisingly flat, mostly covered with gently rolling hills There are a few major highlands and several large volcanoes The surface of Venus shows no evidence of the motion of large crustal plates, which plays a major role in shaping the Earth’s surface

50. Volcanic eruptions are probably responsible for Venus’s clouds Venus’s clouds consist of droplets of concentrated sulfuric acid Active volcanoes on Venus may be a continual source of this sulfurous material

53. Observations Observing Venus –What are best conditions to observe? Unusual spin –How suspected to be unusual –Why unusual –How verified –How to make a guess that will make you famous Surface Climate –Runaway greenhouse effect

54. Climate on Venus followed a different evolutionary path from that on Earth Venus’s high temperature is caused by the greenhouse effect, as the dense carbon dioxide atmosphere traps and retains energy from sunlight. The early atmosphere of Venus contained substantial amounts of water vapor This caused a runaway greenhouse effect that evaporated Venus’s oceans and drove carbon dioxide out of the rocks and into the atmosphere

55. Climate on Venus followed a different evolutionary path from that on Earth Almost all of the water vapor was eventually lost by the action of ultraviolet radiation on the upper atmosphere. The Earth has roughly as much carbon dioxide as Venus, but it has been dissolved in the Earth’s oceans and chemically bound into its rocks

56. Runaway Greenhouse Effect