Lecture 20

1. Lecture 20

2. Outline For Today • Venus review • Mars

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

4. Test Quiz Only participate if • If you have free text plan and • don’t mind receiving ads • Eventually I will offer alternatives for others • Soon I will give some sort of credit for these

5. Test Quiz – register for quiz 1 Text to 41411: astr111 1 rweigel You will receive either one or two texts in response Replace with your GMU email name

6. Text one of these to 41411 Quiz 1, Question 1 • Less than 6 hours • Between 6 and 7 hours • Between 7 and 8 hours • Between 8 and 9 hours • Between 9 and 10 hours • More than 10 hours Last night, I slept for 11 11 11 11 11 11

7. Start

8. b c a 12a 12b 12c

9. Suggestion for Taking Notes • Write down first part of question • Write down first part of answer (until unique)

10. The length of one solar day on Venus is 13 • about the same as that on Earth. • much longer than that on Earth. • much shorter than that on Earth, about an hour. • about half as long as that on Earth, about 10 hours. • about one month. 13 13 13 13

11. The length of one solar day on Venus is 13 • about the same as that on Earth. • much longer than that on Earth. • much shorter than that on Earth, about an hour. • about half as long as that on Earth, about 10 hours. • about one month. 13 13 13 13

12. If an observer says it is noon in at point D, what time is it for the observer at point B if the planet has an orbital period of 100 days and a rotational period (protograde) of 100 days? • Noon • Dawn • Dusk • Midnight • 9:00 am C B D 14 14 A 14 14 14

13. If an observer says it is noon in at point D, what time is it for the observer at point B if the planet has an orbital period of 100 days and a rotational period (protograde) of 100 days? • Noon • Dawn • Dusk • Midnight • 9:00 am C B D 14 14 A 14 14 14

14. Tectonic activity on Venus differs from that on Earth in that • A) active crustal deformation appears to be completely absent. • B) the lithosphere appears to be softer or more plastic and cannot support the creation and motion of solid plates. • C) the lithosphere appears to be cooler and thicker and is therefore too rigid to break up into moving plates. • D) mantle convection appears to be more vigorous and has broken the lithosphere into a multitude of small plates instead of a few large ones.

15. Tectonic activity on Venus differs from that on Earth in that • A) active crustal deformation appears to be completely absent. • B) the lithosphere appears to be softer or more plastic and cannot support the creation and motion of solid plates. • C) the lithosphere appears to be cooler and thicker and is therefore too rigid to break up into moving plates. • D) mantle convection appears to be more vigorous and has broken the lithosphere into a multitude of small plates instead of a few large ones.

16. The so-called greenhouse effect, which produces very high temperatures on the surface of Venus, is • A) the absorption by the CO2 gas of the planet's atmosphere of infrared radiation emitted by its surface. • B) the absorption of solar visible radiation by the CO2 gas of the Venusian atmosphere, thereby heating this gas. • C) the trapping of hot gases ejected by continuously active volcanoes under the dense cloud cover. • D) due to the loss of ozone about its poles. • E) the melting of its polar ice caps.

17. The so-called greenhouse effect, which produces very high temperatures on the surface of Venus, is • A) the absorption by the CO2 gas of the planet's atmosphere of infrared radiation emitted by its surface. • B) the absorption of solar visible radiation by the CO2 gas of the Venusian atmosphere, thereby heating this gas. • C) the trapping of hot gases ejected by continuously active volcanoes under the dense cloud cover. • D) due to the loss of ozone about its poles. • E) the melting of its polar ice caps.

18. Why is the surface of Venus hotter than that of Mercury, even though Mercury is much closer to the Sun? • A) Chemical reactions within the thick clouds and dense atmosphere are continuously supplying heat to the surface. • B) Continuous volcanic activity releases large quantities of hot lava onto the surface. • C) Venus rotates rapidly, thereby ensuring that its entire surface is being heated regularly and uniformly. • D) The thick CO2 atmosphere prevents re-emission into space of the heat absorbed from sunlight. • E) Mercury has a lower albedo.

19. Why is the surface of Venus hotter than that of Mercury, even though Mercury is much closer to the Sun? • A) Chemical reactions within the thick clouds and dense atmosphere are continuously supplying heat to the surface. • B) Continuous volcanic activity releases large quantities of hot lava onto the surface. • C) Venus rotates rapidly, thereby ensuring that its entire surface is being heated regularly and uniformly. • D) The thick CO2 atmosphere prevents re-emission into space of the heat absorbed from sunlight. • E) Mercury has a lower albedo.

20. Outline For Today • Venus review • Mars

21. Observations • Observing Mars • Moons • Surface • Atmosphere

22. Orbital period of 1.5 years Orbital period of 1 years

23. Orbital period of 1.5 years Orbital period of 1 years How long will it take to get into this configuration again? • 1 year • 1.5 years • 2 years • 3 years • 3.5 year • 4.25 years 15 15 15 15 15 15

25. Earth-based observations of Mars are best made during favorable oppositions The best Earth-based views of Mars are obtained when Mars is simultaneously at opposition and near perihelion

26. Observations • Observing Mars • Moons • Surface • Atmosphere

27. The two Martian moons resemble asteroids • Mars has two small, football-shaped satellites that move in orbits close to the surface of the planet • They may be captured asteroids or may have formed in orbit around Mars out of solar system debris

28. Observations • Observing Mars • Moons • Surface • Atmosphere

29. Earth-based Observations • A solar day on Mars is nearly the same length as on Earth • Mars has polar caps that expand and shrink with the seasons • The Martian surface undergoes seasonal color changes

30. Landers have explored the surface of Mars

31. Unmanned spacecraft found craters, volcanoes, and canyons on Mars • The Martian surface has numerous craters, several huge volcanoes, a vast rift valley, and dried-up riverbeds— but no canals • Martian volcanoes and the Valles Marineris rift valley were formed by upwelling plumes of magma in the mantle

32. Olympus Mons

33. For reasons that are not understood, the chemical composition of ancient Martian lava is different from that of more recent lava • Mars has no planet wide magnetic field at present but may have had one in the ancient past

34. The heavily cratered southern highlands are older and about 5 km higher in elevation than the smooth northern lowlands • The origin of this crustal dichotomy is not completely understood

35. Surface features indicate that water once flowed on Mars • Flash-flood features and dried riverbeds on the Martian surface indicate that water has flowed on Mars at least occasionally • No liquid water can exist on the Martian surface today

38. Polar Ice Caps • Mars’s polar caps contain frozen water, a layer of permafrost may exist below the Martian regolith, and there may be liquid water beneath the surface • The Martian polar caps expand in winter as a thin layer of frozen carbon dioxide (dry ice) is deposited from the atmosphere

41. Earth and Mars began with similar atmospheres that evolved very differently • Mars’s primordial atmosphere may have been thicker and warmer than the present-day atmosphere • It is unclear whether it contained enough carbon dioxide and water vapor to support a greenhouse effect that would permit liquid water to exist on the planet’s surface • The present Martian atmosphere is composed mostly of carbon dioxide • The atmospheric pressure on the surface is less than 1% that of the Earth and shows seasonal variations as carbon dioxide freezes onto and evaporates from the poles

42. Clouds Above Mars’ Mountains

43. Observations • Observing Mars • Moons • Surface • Atmosphere

44. Earth’s Atmosphere

45. Mars Atmosphere

46. The Martian atmosphere changes dramatically with the seasons • Great dust storms sometimes blanket Mars • Fine-grained dust in its atmosphere gives the Martian sky a pinkish-orange tint • Seasonal winds blow dust across the face of Mars, covering and uncovering the underlying surface material and causing seasonal color changes

48. Afternoon dust devils help to transport dust from place to place

49. What causes the seasons on Mars? • A) its elliptical orbit. • B) its spin axis being tilted with respect to its orbital plane. • C) its day being about 24 hours in length. • D) its year being about 700 days in length. • E) its distance from the sun varies in its orbit.

50. What causes the seasons on Mars? • A) its elliptical orbit. • B) its spin axis being tilted with respect to its orbital plane. • C) its day being about 24 hours in length. • D) its year being about 700 days in length. • E) its distance from the sun varies in its orbit.