Chapter 6 The Terrestrial Planets

1. Chapter 6The Terrestrial Planets

2. Chapter 6The Terrestrial Planets

3. Units of Chapter 6 Orbital and Physical Properties Rotation Rates Atmospheres The Surface of Mercury The Surface of Venus The Surface of Mars Internal Structure and Geological History Atmospheric Evolution on Earth, Venus, and Mars

4. Sputnik 1

5. Question 1 Which of the following inner solar system bodies has the largest volcanoes? a) Mercury b) Venus c) Earth d) Mars e) Moon

6. Question 1 Which of the following inner solar system bodies has the largest volcanoes? a) Mercury b) Venus c) Earth d) Mars e) Moon Mars’ largest volcano, Olympus Mons, rises more than 25 km (75,000 ft) above the surrounding plains.

7. Orbital and Physical Properties The orbits of Venus and Mercury show that these planets never appear far from the Sun.

8. Orbital and Physical Properties The terrestrial planets have similar densities and roughly similar sizes, but their rotation periods, surface temperatures, and atmospheric pressures vary widely.

9. Rotation Rates Mercury can be difficult to image from Earth; rotation rates can be measured by radar.

10. Rotation Rates Mercury was long thought to be tidally locked to the Sun; measurements in 1965 showed this to be false. Rather, Mercury’s day and year are in a3:2 resonance; Mercury rotates three times while going around the Sun twice.

11. Rotation Rates Mars Venus -243 days 1.03 days

12. Rotation Rates All the planets rotate in a prograde direction, except Venus, which is retrograde.

13. Question 2 a) Mercury b) Venus c) Earth d) Moon e) Mars Which of the following inner solar system bodies has the densest atmosphere?

14. Question 2 a) Mercury b) Venus c) Earth d) Moon e) Mars Which of the following inner solar system bodies has the densest atmosphere? Venus’ atmosphere has a pressure about 90 times larger than Earth’s. Many of its surface features are affected by this immense pressure.

15. Atmospheres Mercury has no detectable atmosphere; it is too hot, too small, and too close to the Sun. Venus has an extremely dense atmosphere. The outer clouds are similar in temperature to Earth, and it was once thought that Venus was a “jungle” planet. We now know that its surface is hotter than Mercury’s, hot enough to melt lead. The atmosphere of Mars is similar to Earth in composition, but very thin.

16. Question 3 a) nitrogen b) hydrogen c) carbon dioxide d) oxygen e) sulfuric acid The greenhouse effect on Venus is due to ______ in its atmosphere.

17. Question 3 a) nitrogen b) hydrogen c) carbon dioxide d) oxygen e) sulfuric acid The greenhouse effect on Venus is due to ______ in its atmosphere. Venus’ atmosphere is over 96% CO2, resulting in a surface temperature exceeding 900 °F.

18. Question 4 a) the Moon’s far side b) Venus’ polar regions c) Earth’s deserts d) the Moon’s near side e) Mars’ deserts Mercury’s surface most resembles which of these?

19. Both Mercury and the Moon’s far side are heavily cratered. Question 4 a) the Moon’s far side b) Venus’ polar regions c) Earth’s deserts d) the Moon’s near side e) Mars’ deserts Mercury’s surface most resembles which of these?

20. The Surface of Mercury Mercurycannot be imaged well from Earth; best pictures are from Messenger. Crateringon Mercury is similar to that on the Moon.

21. Messenger Selected 1999 Launched 2004 Orbit insertion 2011 $446 Billion 5 Billion miles

23. Question 5 a) it always appears only half lit. b) it is never more than 28° from the Sun. c) its elliptical orbit causes it to change speed unpredictably. d) its surface reflects too little sunlight. e) its surface does not allow radar to bounce back to Earth. Mercury is very hard to observe from Earth because

24. Question 5 a) it always appears only half lit. b) it is never more than 28° from the Sun. c) its elliptical orbit causes it to change speed unpredictably. d) its surface reflects too little sunlight. e) its surface does not allow radar to bounce back to Earth. Mercury is very hard to observe from Earth because Mercury’s inner orbit keeps it close to the Sun, visible only for an hour or two before sunrise or after sunset.

25. The Surface of Mercury Some distinctive features: Scarp(cliff), several hundred km long and up to 3 km high, thought to be formed as the planet cooled and shrank.

26. The Surface of Mercury Caloris Basin, very large impact feature; ringed by concentric mountain ranges

27. Question 6 a) it is so close to the Sun. b) its surface rocks don’t retain heat. c) it spins too fast to cool down. d) Mercury’s axis has no tilt; its equator receives direct sunlight. e) it has no atmosphere to moderate temperatures over the globe. Mercury has extreme high and low temperatures between night and day because

28. Question 6 a) it is so close to the Sun. b) its surface rocks don’t retain heat. c) it spins too fast to cool down. d) Mercury’s axis has no tilt; its equator receives direct sunlight. e) it has no atmosphere to moderate temperatures over the globe. Mercury has extreme high and low temperatures between night and day because Mercury’s very high sunlit surface temperature of 700 K, and low mass, explain why it has no atmosphere.

29. The Surface of Venus This map of the surface features of Venus is on the same scale as the Earth map below it.

30. The Surface of Venus Venus as a globe, imaged by Magellan launched from STS-30 in 1989. 730 k = HOT! 855 F 90 atm Sulfuric acid rain

31. Question 7 a) many impact craters of all sizes. b) shield volcanoes. c) a continent-sized plateau. d) huge circular volcanic coronae. e) lava domes. Venus’ surface shows all of the following EXCEPT

32. Question 7 a) many impact craters of all sizes. b) shield volcanoes. c) a continent-sized plateau. d) huge circular volcanic coronae. e) lava domes. Venus’ surface shows all of the following EXCEPT Venus’ thick atmosphere shields the planet from smaller meteor impacts.

33. The Surface of Venus Top: Lava domes on Venus (L), and a computer reconstruction (R) Bottom: the volcano Gula Mons

34. The Surface of Venus Venus corona, with lava domes Fly by

35. The Surface of Venus A photograph of the surface, from the Venera lander. Russia sent more than 16 probes.

36. Photography on Venus

37. Venera - USSR

38. The Surface of Venus Impact craters. Left: multiple-impact crater Above: Mead, Venus’s largest impact crater

39. Mars

40. The Surface of Mars Major feature: Tharsis bulge, size of North America and 10 km above surroundings Minimal cratering; youngest surface on Mars

41. Viking I & II 1976

42. Viking 1976

43. The Surface of Mars • Northern hemisphere (left) is rolling volcanic terrain. • Southern hemisphere (right) is heavily cratered highlands; average altitude 5 km above northern. • Assumption is that northern surface is younger than southern. • Means that northern hemisphere must have been lowered in elevation and then flooded with lava. Fly by

44. The Surface of Mars This map shows the main surface features of Mars. There is no evidence for plate tectonics.

45. The Surface of Mars Mars has largest volcano in Solar System; Olympus Mons: • 700 km diameter at base • 25 km high • Caldera 80 km in diameter Three other Martian volcanoes are only slightly smaller.

46. The Surface of Mars Was there running water on Mars? Runoff channels resemble those on Earth. Left: Mars Right: Earth

47. The Surface of Mars No evidence of connected river system; features probably due to flash floods

48. The Surface of Mars This feature may be an ancient river delta. Or it may be something entirely different. Okavango

49. 6.6 The Surface of Mars Much of northern hemisphere may have been ocean.

50. The Surface of Mars Impact craters less than 5 km across have mostly been eroded away. Analysis of craters allows estimation of age of surface. Crater on right was made when surface was liquid.