21st century astronomy the solar system fifth edition test bank chapter 09 by asmacandy

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Chapter 9: Atmospheres of the Terrestrial Planets LEARNING OBJECTIVES 9.1 Atmospheres Change over Time Explain why planets naturally lose their atmosphere. Multiple Choice: 2, 3, 5 Short Answer: Describe the origin of terrestrial planets’ secondary atmospheres. Multiple Choice: 1, 9, 10 Short Answer: Establish why some terrestrial planets do not have secondary atmospheres today. Multiple Choice: 4, 5, 6, 7, 8, 11 9.2 Secondary Atmospheres Evolve Illustrate why planetary mass affects a planet’s ability to retain its atmosphere. Multiple Choice: 12 Describe the atmospheric greenhouse effect. Multiple Choice: 17, 18, 21, 22, 23, 24

Short Answer: Illustrate how greenhouse gases cause the greenhouse effect. Multiple Choice: 14, 19, 20, 25, 26, 29 Short Answer: 9 Compare and contrast the causes for the terrestrial planets to have their current atmospheres. Multiple Choice: 13, 15, 16, 27, 28 Short Answer: 6, 8 9.3 Earth’s Atmosphere Has Detailed Structure Explain how Earth developed an oxygen-rich atmosphere. Multiple Choice: 30, 31, 32, 33, 34, 35, 36, 37, 38, 40, 41, 58 Short Answer: 14 Differentiate the temperature, density, and composition of the different layers of our atmosphere. Multiple Choice: 42, 43, 45, 46, 47, 48, 50, 51, 55 Short Answer: 10, 11, 12, 13, 15, 16, 17, 18, 19 Illustrate how our magnetosphere causes auroras. Multiple Choice: 39, 52 Relate a planet’s rate of rotation to its wind patterns. Multiple Choice: 44, 49, 53, 54, 56 Short Answer: 20 9.4 The Atmospheres of Venus and Mars Differ from Earth’s Describe the atmospheric characteristics of Venus and Mars. Multiple Choice: 59, 62, 63, 67, 69, 70 Characterize the causes for the atmospheric characteristics of Venus and Mars. Multiple Choice: 57, 60, 61, 64, 65 Short Answer: 21, 23, 24, 25 9.5 Greenhouse Gases Affect Global Climates Compare and contrast weather and climate. Short Answer: 26 Explain the different factors that cause climate change on a planet. Multiple Choice: 66 Short Answer: 22, 27, 29, 30 Summarize the evidence that human activity is causing global climate change.

Multiple Choice: 68 Short Answer: 28 Working It Out 9.1 Assess whether a planet will hold onto its atmosphere based on its escape speed at atmospheric temperature. Compute the average molecular speed of atmospheric gas. Short Answer: 2, 4

MULTIPLE CHOICE 1. The major chemical component of the air we breathe today was deposited on Earth primarily via a. volcanic eruptions. b. cometary impacts. c. asteroid impacts. d. chemical reactions in Earth’s oceans. 2. What is the reason Mercury has so little gas in its atmosphere? a. Its mass is small. b. It has a high temperature. c. It is close to the Sun. d. Its escape velocity is low. e. all of the above 3. Why did the terrestrial planets lose the majority of the gas in their primary atmospheres? a. They were too hot and their escape velocities too low to hold onto them. b. The solar wind was too strong and blew these gases off the planets. c. Their high surface temperatures made the gas chemically react with the rock. d. The initial gases were so heavy when the planet differentiated that they sank to the core. 4. Would a nitrogen atom in Venus’s atmosphere, whose temperature is 740 K, eventually escape into outer space? Note that a nitrogen atom has a mass that is 14 times that of a hydrogen atom. Recall that atoms eventually will escape if their average velocity is greater than 1/6 times the escape velocity of the planet. The escape velocity of Venus is 10 km/s. For comparison, a hydrogen atom has an average velocity of 2.5 km/s at a temperature of 300 K. a. The average velocity of nitrogen atoms is 0.4 km/s, and nitrogen does not escape. b. The average velocity of nitrogen atoms is 1.0 km/s, and nitrogen does not escape. c. The average velocity of nitrogen atoms is 1.0 km/s, and nitrogen escapes. d. The average velocity of nitrogen atoms is 4.5 km/s, and nitrogen does not escape. e. The average velocity of nitrogen atoms is 4.5 km/s, and nitrogen escapes. 5. Would water molecules in Venus’s atmosphere, whose temperature is 740 K, eventually escape into outer space? Note that a water molecule has a mass that is 18 times that of a hydrogen atom. The escape velocity of Venus is 10 km/s. For comparison, a hydrogen atom Copyright © 2015 Pearson Canada Inc.

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has an average velocity of 2.5 km/s at a temperature of 300 K. a. No, the average velocity of water molecules is 0.9 km/s. b. Yes, the average velocity of water molecules is 0.9 km/s. c. Yes, the average velocity of water molecules is 2.1 km/s. d. No, the average velocity of water molecules is 2.1 km/s. e. Yes, the average velocity of water molecules is 19 km/s. 6. If sunlight broke up water molecules in Venus’s atmosphere, would the hydrogen atoms escape into outer space? Note that Venus’s temperature is 740 K. Recall that gas eventually will escape if the average velocity of its atoms is greater than 1/6 times the escape velocity of the planet. The escape velocity of Venus is 10 km/s. a. No, the average velocity of hydrogen atoms would be 0.8 km/s. b. No, the average velocity of hydrogen atoms would be 3.9 km/s. c. Yes, the average velocity of hydrogen atoms would be 3.9 km/s. d. Yes, the average velocity of hydrogen atoms would be 25 km/s. e. No, the average velocity of hydrogen atoms would be 25 km/s.

7. If an average hydrogen atom in Earth’s atmosphere has a velocity of 2.5 km/s, what would be the average velocity of an oxygen molecule in Earth’s atmosphere? Note that the atomic mass of an oxygen atom is 16 times that of a hydrogen atom. a. 0.16 km/s b. 2.5 km/s c. 0.62 km/s d. 0.44 km/s e. 0.25 km/s 8. A gas eventually will escape from a planet’s atmosphere if the average velocity of the atoms exceeds 1/6 times the escape velocity of the planet. If the average velocity of water vapor in Venus’s atmosphere is 0.9 km/s, would it eventually escape into outer space? Note that Venus’s mass is 5 × 1024 kg, and its radius is 6,050 km. a. Water vapor would escape because 1/6 times the escape velocity is 0.51 km/s. b. Water vapor would not escape because 1/6 times the escape velocity is 1.7 km/s. c. Water vapor would escape because 1/6 times the escape velocity is 0.42 km/s. d. Water vapor would not escape because 1/6 times the escape velocity is 2.6 km/s. e. Water vapor would escape because 1/6 times the escape velocity is 1.3 km/s. 9. Which of the following processes did not contribute gas to Earth’s secondary atmosphere? a. volcanism b. accretion c. oxidation d. comet impacts e. All of the above contributed gases to Earth’s secondary atmosphere. 10. The nitrogen in Earth’s atmosphere primarily came from a. ammonia delivered by comet impacts. b. photosynthesis done by algae and plants. c. oxidation of silicate-rich minerals. d. rock delivered by asteroid impacts. e. its primary atmosphere. 11. Based solely on mass and distance from the Sun, which of the following terrestrial planets would you expect to retain the densest secondary atmosphere? a. Mercury b. Venus c. Mars

d. the Moon e. Earth 12. Which molecule moves with the fastest average speed while being bound in Earth’s atmosphere in thermal equilibrium? a. Water, H2O (atomic mass = 18) b. Carbon dioxide, CO2 (atomic mass = 44) c. Nitrogen (atomic mass = 28) d. Oxygen (atomic mass = 32) 13.

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e. Hydrogen, H2 (atomic mass = 2) Earth has roughly _________ times more atmospheric pressure than Mars and _________ times less than Venus. a. 10; 10 b. 200; 100 c. 2,000; 2 d. 2; 10 e. 1,000; 200 If the carbon dioxide in Earth’s rocks were suddenly released into its atmosphere, what would happen? a. It would rapidly escape into space. b. It would dissociate into carbon and oxygen. c. It would collect as ice on the north and south poles. d. It would cause a runaway greenhouse effect. The presence of gases such as carbon dioxide and water vapor in a planet’s atmosphere is direct evidence of _________ in a planet’s history. a. high surface temperatures b. volcanic activity c. cometary impacts d. a lack of asteroid impacts e. the greenhouse effect The terrestrial planets, ranked in order of decreasing atmospheric density, are a. Venus, Earth, Mars, Mercury b. Venus, Mars, Earth, Mercury c. Mercury, Mars, Earth, Venus d. Mars, Venus, Mercury, Earth The main greenhouse gases in the atmosphere of the terrestrial planets are a. oxygen and nitrogen. b. methane and ozone. c. carbon dioxide and water vapor. d. hydrogen and helium. e. methane and ammonia. Earth releases the energy it receives from the Sun by emitting _________ radiation. a. infrared b. visible c. ultraviolet (UV) d. radio e. microwave In the absence of a greenhouse effect, what would happen to Earth’s oceans? a. They would evaporate. b. They would freeze over. c. They would be rapidly absorbed into the surface rocks. d. They would dissociate into ozone and hydrogen. What makes carbon dioxide a highly effective greenhouse gas? a. It easily absorbs UV radiation.

b. It easily absorbs visible light. c. It easily absorbs infrared radiation. d. It easily reacts chemically with rock. e. It easily photodissociates in the upper atmosphere. 21. The greenhouse effect raises Earth’s surface temperature by roughly a. 0 K. b. 0.35 K. c. 3.5 K. d. 35 K. e. 350 K. 22. The greenhouse effect is the a. trapping of infrared radiation by the atmosphere. b. accentuated growth of plants near the equator, compared to other regions. c. capturing of visible and UV radiation from the Sun the atmosphere. d. shielding of life-forms from solar UV radiation by the ozone layer.

23. If it were not for the greenhouse effect on Earth, a. there would be no liquid water on Earth. b. life as we know it would not have developed on Earth. c. it would be a much colder planet. d. there would be no oxygen in Earth’s atmosphere. e. All of the above are results of the greenhouse effect. 24. If water vapor were released from Venus’s surface because of tectonic activity into its upper atmosphere, what would most likely happen to it? a. The water vapor would relieve the greenhouse effect and decrease Venus’s surface temperature. b. Water droplets would condense into rain and form lakes on Venus’s surface. c. The water vapor would chemically react with carbon dioxide and form acid rain. d. UV light would break apart the water molecules, and the hydrogen would be lost into space. e. It would rise into the atmosphere and form hurricane-like storms. 25. When learning about light, we predicted that Venus should have a temperature of 250 K based on its albedo and distance from the Sun. Why is Venus’s observed average surface temperature equal to 740 K, which is hot enough to melt lead? a. Venus has slow, retrograde rotation, and its seasons are very long. b. Venus has many active volcanoes that release heat into its atmosphere. c. Venus has a very thin atmosphere, and more sunlight falls onto its surface. d. Venus has a strong greenhouse effect. e. Venus has a highly eccentric orbit and is sometimes much closer to the Sun than other times. 26. In the absence of the greenhouse effect, the water on the surface of Earth would a. escape into outer space. b. remain in liquid form. c. vaporize and form clouds in the atmosphere. d. freeze. e. be absorbed into rocks. 27. By examining the following three images, what can you conclude? a. Venus is covered with clouds. b. Earth has a large amount of liquid water. c. Some form of ice does exist on Mars, but it does not have large amounts of liquid water. d. The planets in order from the least to most dense atmospheres are Venus, Earth, and Mars. e. all of the above

28. Like Mars and Venus, Earth originally had a significant amount of carbon dioxide in its atmosphere. Where is the majority of the carbon now? a. It has escaped into outer space. b. It is bound up in the plant life on Earth. c. It is bound up in rocks. d. It is dissolved into the oceans. e. It is still in the atmosphere in the form of complex molecules. 29. Venus and Earth probably formed with similar amounts of carbon dioxide in their secondary atmospheres. Which of the following is true? a. The majority of Earth’s carbon dioxide escaped into space because of its hotter temperature, whereas Venus’s carbon dioxide remains gravitationally bound to Venus. b. The majority of Earth’s carbon is now bound up in rock, whereas Venus’s remains in its atmosphere. c. Earth lost more of its secondary atmosphere because it was bombarded by more planetesimals than Venus. d. The majority of Earth’s carbon was absorbed by plants during photosynthesis. e. Earth and Venus still have equal amounts of carbon dioxide in their atmospheres. 30. The major difference in the composition of Earth’s atmosphere compared to the atmospheres of Venus and Mars is a direct consequence of a. life on Earth. b. Earth’s plate tectonics. c. differences in the greenhouse effect. d. the presence of liquid water. e. differing distances from the Sun. 31. According to the following figure, about how long ago did oxygen reach its current abundance in Earth’s atmosphere? a. 3 billion years ago b. 1 billion years ago c. 0.5 billion years ago d. 0.25 billion years ago e. 0.1 billion years ago 32. How does the fraction of oxygen in Earth’s atmosphere today compare to what it was 3 billion years ago? a. It has significantly declined. b. It has significantly increased. c. It kept increasing up to 2 billion years ago but has been declining ever since. d. It hasn’t changed. 33. The best way to use a telescope to look for life on other planets is to a. search for absorption from nitrogen in their atmospheres. b. search for absorption from oxygen in their atmospheres. c. search for emission lines from water vapor in their atmospheres. d. search for carbon dioxide on their moons. 34. _________ in our atmosphere is a direct consequence of the emergence of life. a. Carbon dioxide b. Water vapor c. Nitrogen d. Oxygen e. Helium 35. If photosynthesis were to disappear on Earth, a. the atmosphere would become less dense. b. oxygen would disappear from the atmosphere. c. the atmosphere would become hotter. d. nitrogen would disappear from the atmosphere. e. the amount of water vapor in the atmosphere would decrease.

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36. By approximately _________ years ago, _________ had produced oxygen in enough amounts to be a significant fraction in Earth’s atmosphere. a. 100 million; trees and plants b. 1 billion; trees and plants c. 250 million; bacteria and algae d. 2.5 billion; bacteria and algae e. 2,000; animals and humans 37. Approximately how long after the Solar System formed did it take for oxygen to get to within 80 percent of its present abundance in Earth’s atmosphere? a. 4 billion years b. 1 billion years c. 400 million years d. 1 million years e. Oxygen was always a primary component of Earth’s atmosphere.

38. For the first 1 billion years of Earth’s evolution, the fraction of oxygen in its atmosphere was approximately a. zero. b. half of what it is today. c. 2 times what it is today. d. 10 times what it is today. e. the same as it is today. 39. Why are auroras produced only near the northern and southern magnetic poles of a planet? a. Those are the locations where the atmosphere is thinner, letting particles penetrate. b. The poles are pointing toward the Sun, so they receive more solar wind particles. c. The oxygen atoms responsible for auroral emission only exist near the poles. d. Charged particles are forced to flow along Earth’s magnetic field lines, which come out of Earth’s poles. 40. According to the figure below, approximately how many years ago did oxygen finally get to half its current abundance in Earth’s atmosphere? a. 3 billion years ago b. 1 billion years ago c. 0.6 billion years ago d. 0.25 billion years ago e. 0.1 billion years ago 41. If you found absorption from _________ in the spectrum of a planet, you could conclude that it might contain some form of life. a. oxygen b. methane c. water vapor d. oxygen, methane, or water vapor 42. Without the ozone layer, life on Earth would be in danger from increased levels of _________ radiation. a. UV b. X-ray c. gamma ray d. infrared e. microwave 43. According to the following figure, the different layers of Earth’s atmosphere are defined by a. how the temperature varies with altitude. b. how the pressure varies with altitude. c. how the density varies with altitude.

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d. different temperature ranges. e. different pressure ranges. 44. The planet-wide flow of air from Earth’s equator to the colder poles is called Hadley circulation. An example of this effect is also seen a. on Mars b. on Mercury c. on Venus d. nowhere else in the solar system 45. According to the way the layers of Earth’s atmosphere are defined in the following figures, the atmosphere of Venus has only _________ distinct layer(s). a. one b. two c. three d. four e. five

46. All weather and wind on Earth are a result of convection in the a. troposphere. b. stratosphere. c. mesosphere. d. ionosphere. e. thermosphere. 47. According to the following figure, as you increase in altitude in Earth’s lower atmosphere, the atmospheric pressure ________ dramatically at a(n) _________ rate. a. increases; increasing b. increases; decreasing c. decreases; decreasing d. decreases; increasing e. decreases; constant 48. The only two layers of Earth’s atmosphere that have temperature gradients that allow convection to take place are a. the troposphere and the thermosphere. b. the mesosphere and the stratosphere. c. the thermosphere and the stratosphere. d. the troposphere and the mesosphere. e. the troposphere and the stratosphere. 49. Winds are generated on Earth primarily because of a. strong updrafts from the equator and air sinking near the poles. b. uneven heating of the surface and rotation of the planet. c. water condensation onto mountains. d. hot air rising and cool air sinking. 50. Heating from _________ causes the top of Earth’s stratosphere to be warmer than the bottom. a. higher-energy particles in the solar wind b. convection c. the ozone layer absorbing UV light d. charged particles trapped by magnetic fields e. the greenhouse effect 51. The shape of Earth’s magnetosphere is modified by a. the Moon’s tidal force. b. the solar wind. c. Earth’s own gravity. d. asymmetries in the shape of Earth’s core.

e. Earth’s elliptical orbit. 52. Auroras are caused by a. gases fluorescing in the atmosphere because of collisions with solar wind particles. b. the magnetosphere of Earth touching its atmosphere. c. the ozone layer being destroyed by UV light. d. a product of the atmospheric greenhouse effect. e. scattering of sunlight from particles in Earth’s stratosphere. 53. In the Southern Hemisphere, hurricanes _________ compared to hurricanes in the Northern Hemisphere because of the Coriolis effect. a. rotate in the same direction b. rotate in the opposite direction c. move from east to west d. have larger wind speeds e. cause more damage

54. What is the main reason Hadley circulation in a planet’s atmosphere breaks up into zonal winds? a. convection driven by solar heating b. heating from the solar wind c. hurricanes developing along the planet’s equator d. a planet’s rapid rotation e. heating from the greenhouse effect 55. Runaway convection in Earth’s atmosphere can lead to a. snow. b. destruction of ozone. c. auroras. d. acid rain. e. violent storms. 56. Hurricanes are powered by a. Hadley circulation. b. the Coriolis effect. c. the heat of vaporization of water. d. electrical conductivity of water. e. the greenhouse effect. 57. Given the thickness and chemical composition of Venus’s atmosphere, by how much would you expect its average surface temperature to change between day and night? a. There should be almost no change in temperature. b. by tens of K (like Earth) c. by hundreds of K (like Mercury) d. The answer depends on where Venus is in its orbit around the Sun. 58. Earth’s sky is blue because a. blue light from the sun is more readily scattered by molecules in the atmosphere than red light. b. of reflected light from the oceans. c. red light from the sun is more readily scattered by molecules in the atmosphere than blue light. d. molecules that make up Earth’s atmosphere radiate preferentially at blue wavelengths. e. the Sun radiates more blue light than other wavelengths. 59. Which of the following is not a consequence of the high thickness and peculiar composition of Venus’s atmosphere? a. We cannot see down to its surface in visible light. b. Its surface is very smooth.

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c. Venus looks highly reflective. d. The surface pressure is 100 times higher than on Earth’s surface. Venus rotates so rapidly that the dominant form of atmospheric circulation is powered by a. winds moving from its equator to its poles. b. heated air escaping from its volcanoes moving along the equator. c. winds moving from its poles to its equator. d. heated air escaping from active tectonic plates. The absence of oxygen on Mars means that it has very little a. carbon dioxide. b. methane. c. ozone. d. helium. When the Martian springtime arrives and the daytime temperature reaches 20°C, what occurs? a. Water melts and forms large pools of liquid. b. The polar ice caps disappear. c. Large planet-wide dust storms. d. The entire planet changes color. The exospheres of the Moon and Mercury differ from the atmospheres of Venus, Earth and Mars in that a. they are made of a very thin layer of carbon dioxide. b. they are made of a thick layer of water vapor. c. they extend much farther from the rocky surface. d. they are made of a thin layer of light atoms such as helium, sodium, and argon. Venus has an unusual rotation rate because a. it is very slow. b. it is very slow and retrograde. c. its obliquity is 90 degrees. d. it is very fast. e. it is very fast and retrograde.

65. Venus’s surface temperature is fairly uniform from the equator to the poles because a. Venus rotates very rapidly, which causes strong zonal winds. b. Venus is covered by a thick cloud layer that absorbs most of the sunlight that falls on it. c. the carbon dioxide in Venus’s atmosphere efficiently emits infrared radiation. d. Venus rotates slowly so Coriolis forces do not disrupt Hadley circulation. e. Venus’s orbit is nearly perfectly circular. 66. Each halogen atom, such as chlorine, fluorine, and bromine, in Earth’s atmosphere contributes to a. the production of carbon dioxide. b. the production of acid rain. c. the destruction of ozone over decades and centuries. d. the destruction of water in the upper atmosphere. 67. Humans cannot survive on the surface of Mars for long periods of time because a. there is not enough oxygen in the atmosphere. b. the range in temperature between day and night is too large. c. the flux of UV radiation reaching the surface is too high. d. the atmospheric pressure would be too low. e. all of the above 68. The amount of carbon dioxide in Earth’s atmosphere has been increasing over the last 50 years because of a. global warming. b. the growth of the ozone hole. c. the burning of fossil fuels.

d. increased energy output from the Sun. e. increased magnetic activity in the Sun. 69. When frozen water on the surface of Mars heats up during summer time, the water a. melts and forms liquid pools on the surface. b. boils off the surface and escapes into outer space. c. sublimates and goes directly into the gaseous phase. d. remains frozen because the temperature remains below the freezing point. e. melts and creates flowing rivers that erode the landscape. 70. Global temperature variations on Earth driven by the Milankovitch cycle differ from those driven by the anthropogenic greenhouse effect in that a. they are very small in magnitude, less than 1°C. b. they occur at irregular time intervals. c. they are driven by volcanic activity. d. they occur over much longer time scales (thousands of years). e. they are driven by emissions of methane gas rather than carbon dioxide.

SHORT ANSWER 1. The primary atmospheres of the terrestrial planets formed from hydrogen and helium. Why? What happened to this gas? 2. A gas eventually will escape from a planet’s atmosphere if the average velocity of its atoms exceeds 1/6 times the escape velocity of the planet. If the average velocity of water vapor in Venus’s atmosphere is 0.5 km/s, what would be the average velocity of a single hydrogen atom? If Venus’s escape velocity is 11 km/s, will hydrogen atoms eventually escape? 3. Most of Earth’s present-day atmosphere comes from a combination of what three sources? 4. If the average CO2 molecule in Venus’s atmosphere has a velocity of 0.6 km/s, what would be the velocity for a hydrogen atom in Venus’s atmosphere? Note the mass of a CO2 molecule is 44 times that of a hydrogen atom. 5. What is the origin of Earth’s water? 6. List the three planets shown in the following images in order of decreasing surface temperature, and cite evidence that can be seen in the images that supports your choice. 7. What is the greenhouse effect? 8. Where is most of Earth’s supply of carbon dioxide today? 9. Describe how the closer location of Venus to the Sun compared to Earth led to the runaway greenhouse effect observed on Venus today. 10. Earth’s atmosphere is a (seemingly) enormous blanket roughly 250 km thick. What percentage of Earth’s radius, which is 6,400 km, does this represent? How does it compare to the average depth of the oceans, which is 3 km?

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11. If there is 1E4 kg of air above every square meter of the surface of Earth, and Earth is modeled as a sphere of radius 6.4 × 106 m, what is the mass of Earth’s atmosphere, and what fraction is it of the total mass of Earth? Show your calculation. 12. Suppose you go out hiking in the snow on a mountaintop on a cold winter day when the temperature outside is 0°C = 273 K and the pressure is 0.75 bar. If you brought along a package of potato chips that was sealed at sea level when the temperature was 24°C = 297 K, what would have happened to the volume of the bag of chips? By how much will the volume have changed? 13. You take a sealed plastic bag of snacks onto an airline flight where the atmospheric pressure is reduced to 0.8 bar, but the cabin is heated so that the temperature is approximately the same as when you sealed the bag. What will happen to the volume of the bag? By how much will it have changed? 14. According to the following figure, about how long ago did oxygen first appear in Earth’s atmosphere? About how long ago did oxygen reach 50 percent of its current abundance in Earth’s atmosphere? 15. Describe the process(es) responsible for producing rain. 16. Over the last century, why has the ozone hole over Earth grown larger? How long might it take to revert to its former state? 17. Give two reasons why the atmosphere of Earth is warmer near the surface than at higher elevations. 18. Why does the temperature decrease as you go higher up in altitude in the troposphere on Earth? 19. In the stratosphere of Earth’s atmosphere, how does the temperature vary with increasing altitude, and what causes this variation? 20. The global winds on Earth are the result of a combination of what three things? 21. If sunlight cannot penetrate Venus’s cloud layer efficiently, why does the temperature of the planet remain so high? 22. Carbon dioxide levels in Earth’s atmosphere have been rising by about 4 percent per decade because of the use of fossil fuels. If this trend continues, what could happen to Earth? 23. On Mars, water could exist in what form(s): solid, liquid, or gas? How does this vary with the seasons on Mars? Why are the seasonal variations on Mars different in its northern and

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southern hemispheres? 24. Give three reasons why we believe Venus may currently have active volcanoes. 25. Describe how a weak magnetic field on Mars may lead to loss of its atmosphere over time. 26. How does climate differ from weather? 27. The obliquity of Earth’s rotation axis has remained stable at 23 degrees over its history, whereas that of Mars is believed to have varied from 13 to 40 degrees. Why? 28. Although Earth is known to exhibit long-term natural variations in temperature, scientists are nearly unanimous in believing that the recent rise in temperature is due to human industrial activity. Why? 29. What factors drive the long-term periodic variations in Earth’s average temperature (known as the Milankovitch cycle)? 30. Describe the factors influencing the climate on Earth.

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