Exam Questions The Other Terrestrial Planets Chapter 8 14e - Discovering the Universe 14e Test Bank + Answers by Neil F. Comins. DOCX document preview.
Chapter 8: The Other Terrestrial Planets
Section: 8-1
1. Mercury can be seen easily from Earth only
A) during a lunar eclipse, when the sky is sufficiently dark near the Moon, because Mercury is always close to the Moon in the sky.
B) at midnight, when it is high in the sky.
C) just after sunset or just before sunrise.
D) in the winter, when the ecliptic plane is high in the sky at night.
2. Mercury is BEST seen from Earth with the unaided eye at what time of the day?
A) near midday, when it is seen through the least amount of Earth’s atmosphere
B) close to dawn or dusk, when Mercury is at positions of greatest east or west elongation
C) at midnight, when Mercury is at opposition and highest in the sky
D) during the daytime, when Mercury is at superior conjunction
3. Why is Mercury difficult to observe from Earth?
A) Mercury remains close to the Sun in its orbit and is seen in a dark sky only at sunrise or sunset, close to the horizon.
B) Mercury orbits the Sun very rapidly and moves across the sky very quickly.
C) The orbit of Mercury is very elliptical and tilted at a large angle to the ecliptic, and any position on this orbit is visible only at midnight when Mercury is low in the sky.
D) Mercury is a very small object that orbits a long way from the Sun, thereby reflecting little light back to Earth.
4. Why is it relatively difficult to observe details on the surface of Mercury from Earth?
A) The surface of Mercury is always completely covered in clouds.
B) The surface of Mercury appears very bright from reflected ultraviolet sunlight and emitted infrared radiation from its very hot surface.
C) Mercury is a small object that always appears close to the Sun in the sky.
D) Mercury’s orbit always keeps it on the opposite side of the Sun from Earth.
5. Mercury has a very
A) dim magnitude when viewed in the sky.
B) low albedo.
C) large magnetic field.
D) thick atmosphere.
6. The Mariner 10 spacecraft was placed in an elliptical orbit around the Sun, with the period of its orbit twice that of the period of Mercury’s orbit. What is the length of the semimajor axis of Mariner 10’s orbit?
A) 0.48 au
B) 0.61 au
C) 0.39 au
D) 0.0125 au
7. In 2011 a major event in the exploration of Mercury took place, namely
A) sending a radar pulse to bounce off Mercury’s surface.
B) putting the MESSENGER spacecraft in orbit around the planet.
C) a soft, unmanned landing.
D) a manned landing.
8. Mercury’s orbit has a semimajor axis of 0.387 au. How large would the Sun appear to be in the sky (in angular diameter) as seen by someone on Mercury, compared with its angular diameter from Earth?
A) same size because it is the same Sun
B) about 1.5 times larger
C) about 6.25 times larger
D) about 2.5 times larger
9. Which planet MOST resembles the Moon in visible surface features and atmosphere?
A) Mars
B) Venus
C) Uranus
D) Mercury
10. Approximately how many times in 1 Earth year does Mercury go completely around the Sun, as viewed from the distant stars?
A) 4 times
B) 3 times
C) Twice
D) Once
11. How long is 1 solar day (e.g., noon to noon) on Mercury in Earth days?
A) 88 days
B) 1 day
C) 58.7 days
D) 176 days
12. The albedo, or fraction of light reflected from the surface, of Mercury is
A) fairly high, about the same as that of Earth.
B) very low because of its dark rocky surface and absence of an atmosphere.
C) variable and relatively high because of variable cloud cover.
D) very high because of the light color of its surface.
13. Mercury is always much closer to the Sun than Venus is, and yet it never appears brighter than Venus, even at maximum brightness. Explain.
A) We never see more than a small fraction of Mercury’s illuminated surface because of its orbital path relative to that of Earth; hence it always appears dark.
B) Mercury has a thick atmosphere that impedes reflection from its surface and hence appears dark.
C) Mercury has a high albedo, or reflectivity, but it is very small and hence appears relatively dark.
D) Mercury is small, has a dark surface, and has no reflecting clouds.
14. Which of these statements about the similarities of Mercury and Earth’s Moon is NOT true?
A) Both Mercury and the Moon have heavily cratered surfaces.
B) Both Mercury and the Moon have very dark surfaces, or low reflectivity, or albedos.
C) Both Mercury and the Moon have large, circular, and relatively flat basins, or maria, on parts of their surfaces.
D) Mercury and the Moon have no atmospheres.
15. Which one of these features is common to Mercury and the Moon?
A) craters associated with volcanic activity
B) large flat plains dotted with relatively small craters
C) maria filled with solidified basalt and marked with few craters
D) scarps formed when the body shrank
16. The BEST estimate for the time of production of most craters on both Mercury and the Moon is
A) relatively recently, about 4 billion years after planet formation.
B) in the first 800 million years after planet formation.
C) about halfway through their lives, or about 2.3 billion years after planet formation.
D) at a relatively constant rate throughout their lives, up to and including the present day.
17. Mercury, unlike the Moon, has large crater-filled plains rather than maria. The reason is thought to be that
A) Mercury had no large low-lying regions that could be filled in by lava.
B) Mercury’s interior lacks the raw material for lava.
C) because of its large iron core, Mercury has a thinner mantle and therefore has fewer craters produced by volcanoes.
D) Mercury is closer to the Sun and did not receive as many crater-forming impacts as the Moon.
18. Mercury appears from spacecraft photographs to resemble the Moon in its surface features but with one important difference,
A) the presence of extensive plains between craters, in contrast to the surface of the Moon.
B) the presence of retrograde direction of spin compared to most other planets and moons.
C) evidence of active volcanoes on Mercury.
D) the presence of clouds and a measurable and significant atmosphere on Mercury.
19. How has the age of Mercury’s intercrater plains been estimated?
A) from residual radioactivity within the plains compared to areas outside, as measured by the Mariner 10 spacecraft
B) by comparing the albedo of the plains to areas outside because material becomes lighter as it gets older, as it does on the Moon
C) from radioactive dating of rocks returned to Earth by the Mariner 10 spacecraft
D) by comparing the number of craters per unit area within the plains to areas outside
20. Craters on Mercury appear to have been produced by
A) both impacts from objects from space early in the planet’s history and volcanic activity.
B) successive expansion and contraction of the planet’s surface because of intense heating by the Sun and severe cooling during rotation because the craters appear to be in irregular lines across the surface.
C) volcanic eruptions early in the planet’s history.
D) continuous impacts by objects from space throughout the planet's history, including very recently in geological time.
21. Where in the solar system would one find the Caloris Impact Basin?
A) on Jupiter’s outer Galilean satellite, Callisto
B) on Mars
C) on Mercury
D) on the Moon
22. What is the Caloris Basin?
A) lunar mare, on the far side of the Moon
B) volcanic caldera on Mount Maxwell, on Venus
C) large, lowland area on Mars
D) multiringed impact basin on Mercury
23. The Caloris Basin, a huge circular region on Mercury surrounded by rings of mountains, appears to have been produced by
A) the impact of a massive object in the early phases of the planet’s formation, soon after the initial cratering period.
B) successive expansion and contraction of the planet’s surface by intense solar heating and severe cooling as the planet rotated, causing buckling in a similar way to the formation of the North American Rocky Mountains or the South American Andes.
C) wind erosion from huge atmospheric storms, similar to enormous hurricanes on Earth.
D) the eruption of a large and long-lived volcano that formed the mountains in a similar manner to the formation of the Hawaiian Islands on Earth.
24. How do astronomers know that the Caloris Basin on Mercury was formed late in the period of intense bombardment?
A) Radioactive dating of rock samples has fixed the date of formation.
B) The basin contains very few craters.
C) The surface of the basin is much darker than the rest of the planet, suggesting that the surface had not yet been churned over by meteoric impacts.
D) Mountain ranges in the basin are very high because they have not had time to suffer significant erosion.
25. The huge impact of an object that produced the circular Caloris Basin and its ring of mountains on Mercury also produced
A) a very localized region of magnetic field, the only magnetic field possessed by Mercury.
B) melting of permafrost, causing massive floods that produced deep valleys on Mercury’s surface.
C) a pattern of jumbled terrain diametrically opposite the basin, caused by the focused seismic waves from the original impact.
D) a very thick, dusty atmosphere that still obscures the planet’s surface.
26. A distinct area of unusually jumbled, hilly terrain has been found on Mercury. How is this terrain believed to have been formed?
A) by an intense shower of meteoroids near the end of the heavy bombardment era
B) by upwelling of magma while Mercury was still hot enough for its mantle to be tectonically active
C) by the impact of a large comet
D) by seismic waves generated by the Caloris impact
27. When were most of the existing lava plains formed on the surface of Mercury?
A) never—there is no evidence of lava flows on the surface of Mercury
B) when Mercury was first formed, about 4.5 billion years ago
C) near the end of the era of heavy bombardment, about 3.8 billion years ago
D) when the crust wrinkled to form the scarps
28. The Caloris Basin is an immense impact crater on Mercury, which is unusual in that the opposite side of the planet shows jumbled terrain that resulted from shock waves created by the impact. This combination has also been found
A) nowhere else in the solar system.
B) on the Moon.
C) on Earth.
D) on Saturn.
29. The impact that formed the Caloris Basin on Mercury also created intense seismic waves that disrupted the surface of Mercury on the opposite side of the planet. Which other solar system feature is known to have involved a major impact with a similar result?
A) Mare Orientalis on the Moon
B) Hellas Basin on Mars
C) Great Rift Valley on Earth
D) Cleopatra Caldera on Venus
30. What caused the long, meandering scarps (cliffs) that can be seen on Mercury?
A) volcanic eruptions along crustal faults over hot spots in the mantle
B) crustal movement similar to continental drift on Earth, where plates have pressed against one another
C) shrinking and folding of the planet’s surface as it cooled
D) large impacts near the end of the early period of heavy bombardment; the scarps are eroded crater walls
31. The history of Mercury can be summarized as
A) mostly volcanic activity and crustal deformation; the only craters to survive were formed within the last billion years.
B) thin crust forming at first, followed by extensive bombardment, the craters from which were then covered by lava flows that produced extensive lava plains between the remaining craters.
C) early cooling to form a thick crust, with no evidence of volcanism or lava flows at any time.
D) rapid cooling to form a thick crust during the early bombardment, with a few isolated lava flows and very dense cratering everywhere else.
32. Most of the information astronomers have about Mercury’s surface comes from
A) Earth-based telescopic observations.
B) Mariner 10.
C) MESSENGER.
D) landings by robotic spacecraft.
33. What is the major difference between Mariner 10 and MESSENGER?
A) Mariner 10 flew past Mercury several times. MESSENGER went into orbit around the planet.
B) MESSENGER made a soft landing on Mercury, but Mariner 10 only flew by.
C) The two spacecraft were essentially identical, except that Mariner 10 landed on the daylight side of the planet and MESSENGER landed on the night side.
D) Mariner 10 was a failed mission. It crashed into Mercury. MESSENGER conducted a successful flyby.
Section: 8-2
34. Earth’s average density (5520 kg/m3) is slightly higher than that of Mercury (5430 kg/m3) because
A) Earth has a larger iron core in proportion to its size than Mercury has.
B) Earth is more massive than Mercury and has therefore become more compressed, gravitationally.
C) Mercury’s interior has expanded slightly because of radioactive heating, reducing its density since its formation.
D) Earth has a denser atmosphere than Mercury has.
35. The planet with the highest overall density is
A) Mercury.
B) Venus.
C) Earth.
D) Mars.
36. Mercury can be characterized as having
A) a Moonlike surface and an Earthlike interior.
B) both a surface and an interior like that of Earth’s Moon.
C) an Earthlike surface and a Moonlike interior.
D) a surface and an interior nothing like either the Moon or Earth.
37. Mercury’s iron core takes up approximately what fraction of the mass of the planet?
A) about 32 percent, very similar to that of Earth
B) greater than 95 percent
C) about 60 percent
D) about 10 percent
38. The density of Mercury is about the same as that of Earth, but Mercury contains a larger proportion of iron. How is this possible?
A) The iron in Mercury’s core is accompanied by a very low-density crust. The average density is thus comparable to the density of Earth.
B) The inner core of Mercury is hollow, thus reducing the overall density much below that of iron.
C) Mercury has only 1/18 Earth’s mass. Thus, it must be composed of heavier materials (like iron) in order to match Earth’s density.
D) Earth contains, proportionally, a smaller volume of iron, but because of Earth’s greater mass, Earth’s iron has been compressed to a higher density than the iron on Mercury.
39. Mercury has a higher proportion of iron in its makeup than does Earth. So how does Mercury’s density compare to Earth’s density?
A) Mercury must have the higher density.
B) Earth has the greater density because larger masses always have greater densities.
C) Mercury has the smaller density because the non-iron portion of its makeup is very light, porous materials that more than compensate for the greater proportion of iron.
D) Earth has the greater density because Earth’s iron is more dense than Mercury’s iron, thanks to the greater pressure experienced at the core of Earth compared to that at Mercury’s core.
40. Mercury’s average density and the fact that it has a (weak) magnetic field lead to the conclusion that its central core is probably composed of
A) solid rocks of relatively low density.
B) solid and/or molten iron.
C) ices of water and methane.
D) molten rock.
41. “This planet has a large iron core, a heavily cratered surface, and no atmosphere.” Which planet in Earth’ solar system fits this description?
A) Mars
B) Neptune
C) Mercury
D) Earth
42. Mercury is unique among the inner planets in having
A) one hemisphere with many craters and few volcanoes and the other hemisphere with few craters and many volcanoes.
B) extensive volcanic activity and crustal deformation over most of its history but no evidence of plate tectonics.
C) no evidence of an iron core.
D) an iron core that occupies almost half its volume.
43. Many planetary scientists believe Mercury suffered a major collision early in the history of the solar system. How could such a collision explain some of Mercury’s peculiar properties?
A) Mercury’s original core, along with a relatively thin mantle, formed the present Mercury. The remaining material was deflected out into the inner solar system.
B) The impactor, a large iron meteorite, was absorbed by Mercury, enhancing its iron core.
C) Mercury’s original core, plus a very thin mantle, formed the present Mercury. The remaining material formed Vulcan, the small planet inside Mercury’s orbit.
D) The result was dense Mercury and non-dense Venus.
44. The interior of Mercury contains
A) significant amounts of water as permafrost because occasional melting has produced deep water-formed valleys that crisscross the planet’s surface.
B) mostly ices and very low-density material because the planet’s average density is close to that of water.
C) an iron core that occupies a large fraction of the volume of the overall planet and produces a magnetic field.
D) very little iron, in contrast to Earth, and so the planet has no magnetic field.
45. The internal structure of Mercury is a
A) dense iron core taking up almost half the volume of the planet and a rocky mantle surrounding the core.
B) rocky core with a liquid (or perhaps frozen) water mantle and icy surface.
C) thick rocky mantle taking up most of the volume of the planet, overlaying a small but dense iron core.
D) rocky core surrounded by liquid metallic hydrogen and a hydrogen-helium atmosphere.
46. Which physical feature of the planet Mercury interacts with solar wind particles near the planet?
A) stream of ionized atoms, heated by the intense sunlight, that are emitted continuously by the planet
B) dense, ionized atmosphere surrounding the planet
C) magnetic field that, like Earth’s, produces a magnetosphere surrounding the planet
D) Mercury’s gravitational field
47. When the solar wind (mostly protons and electrons, emitted continuously at relatively high speeds by the Sun) approaches Mercury, it
A) is deflected around the planet by the magnetic field.
B) is absorbed and stopped by the atmosphere of the planet.
C) hits the surface directly, causing heat and a continuous fluorescent glow.
D) is repelled by the high electrostatic charge on the planet.
48. Compared with that of Earth, Mercury’s magnetic field is
A) weak but clearly present.
B) below the limit of detection and therefore still needs confirmation.
C) similar in strength.
D) much more powerful.
49. Both Mercury and Earth have global magnetic fields. Compared to Earth, which feature is Mercury known to lack that is thought necessary for generating a STRONG field?
A) Mercury does not lack any such feature.
B) large iron core
C) rapid planetary rotation
D) molten iron core
50. What is the observed feature that suggests that Mercury’s iron core is at least partly molten?
A) presence of a global magnetic field
B) background sloshing sound in radio transmissions sent back by the Mariner 10 spacecraft
C) irregularities in Mercury’s rotation rate
D) extensive lava flows near the regions of greatest tidal stress, such as the Caloris Basin
Section: 8-3
51. Mercury rotates once in 59 days with respect to the distant stars and has a sidereal period of 88 days. If a star is seen to be overhead to an observer on Mercury at midnight on a particular day, how many times will Mercury orbit the Sun before this star is again above the observer’s head in a nighttime sky?
A) 3 times
B) twice
C) It will never again reach this specific position.
D) once
52. How many times does Mercury rotate with respect to the Sun in one sidereal orbital period?
A) many times because Mercury rotates rapidly
B) once
C) 1
times
D) twice
53. If one is on Mercury and the time is noon (Sun directly overhead), what time of day will it be 1 Mercurian year later (after Mercury has orbited the Sun once)?
A) just after sunset
B) any time because Mercury rotates independently of its revolution
C) noon
D) midnight
54. What is the relationship between Mercury’s rotation about its axis (measured relative to the distant stars) and its revolution around the Sun
A) Mercury rotates once for every 3 revolutions around the Sun.
B) Mercury rotates exactly once during each revolution around the Sun.
C) Mercury rotates approximately 88 times during each revolution around the Sun.
D) Mercury rotates 3 times for every 2 revolutions around the Sun.
55. How many times does Mercury rotate around its axis with respect to the distant stars in one orbit around the Sun?
A) 1
times
B) 3 times
C) 2/3 times
D) twice
56. In one orbit around the Sun, Mercury rotates around its axis how many times?
A) twice
B) 3 times
C) 1
times
D) once, in a synchronous orbit
57. How does Mercury rotate, relative to the Sun?
A) Mercury rotates relatively quickly, so that a solar day (from sunrise to the next sunrise) on Mercury is just a bit shorter than on Earth.
B) Mercury rotates in a retrograde direction; consequently, the Sun rises in the west each day and sets in the east.
C) Mercury turns the same side (Caloris Basin) toward the Sun at all times, much as the Moon turns the same side toward Earth.
D) Mercury alternately turns one side (Caloris Basin) toward the Sun at one perihelion and the opposite side toward the Sun at the next perihelion.
58. Why has Mercury become locked into a 3-to-2 spin orbit coupling instead of a 1-to-1 coupling like the Moon around Earth?
A) Mercury feels a stronger gravitational pull from the more massive Sun than the Moon does from Earth, so its rotation became locked on the Sun before it had slowed enough for a 1-to-1 lock.
B) Mercury’s orbit is very eccentric, so its orbital speed varies while its rotation rate remains constant, preventing a 1-to-1 lock.
C) Mercury’s rotation rate is still slowing down, and the apparent 3-to-2 lock is actually just coincidence.
D) Mercury’s orbit is highly inclined (tipped up at an angle to the orbits of the other planets), so the Sun sometimes pulls more on Mercury’s north pole and sometimes more on its south pole.
59. If one was watching the sunrise on Mercury when Mercury was near perihelion, what would they see?
A) The Sun would rise slowly, gradually speed up over a period of a few days, then slow down again.
B) The Sun would rise, cross the sky, and set again, all in a few days, then spend the rest of Mercury’s “year” below the horizon.
C) The Sun would rise, stop, turn back toward the east, stop, and then continue westward.
D) The Sun would rise, slowly come to a standstill, then start rising again.
60. Suppose Mercury had oceans. What would be the length of time between successive high tides?
A) Mercury does not have a moon, so it does not have tides.
B) 58.7 days
C) 88 days
D) 176 days
61. Suppose Mercury had 5-to-3 spin-orbit coupling and that its sidereal period remained 88 days, as now. What would be the time from noon to noon on Mercury, in days?
A) 88
B) 147
C) 264
D) 440
62. Suppose Mercury had 5-to-3 spin-orbit coupling and that its sidereal period remained 88 days, as now. An observer sees the Sun directly overhead in the Mercurian sky and then observes again from the same location 88 days later. Where will the Sun be in the sky? (Mercury, like Earth, rotates toward the east.)
A) below the eastern horizon
B) below the western horizon
C) directly overhead again
D) directly on the opposite side of the planet
63. When Mariner 10 passed by Mercury, the Caloris Basin was crossed by the terminator line. Which statement correctly evaluates this situation?
A) This is not surprising because the Caloris Basin is so large that the terminator line always crosses part of it.
B) This is not surprising. Because of Mercury’s synchronous rotation orbit, the terminator line does not move across the face of the planet, and it lies perpetually on the Caloris Basin.
C) Because of Mercury’s 3-to-2 spin-orbit coupling the terminator line moves slowly across the face of Mercury. When Mariner 10 flew by it happened to lie across the Caloris Basin.
D) There is a direct correlation between the Caloris Basin and Mercury’s unusual rotation. This unusual rotation occurs because of the bulge on Mercury—and this was caused by the impact that produced the Caloris Basin. So, it is not surprising that the terminator line was found across the Caloris Basin.
64. Recent radar observations of Mercury have suggested that Mercury may
A) have one or more tectonic rift valleys.
B) have ice at its north and south poles.
C) have geologically recent lava flows on the side that was not photographed by Mariner 10.
D) not be precisely locked into its hypothesized 3-to-2 spin-orbit coupling.
65. How was water ice discovered near Mercury’s poles?
A) by studying reflections of radio waves sent to Mercury from Earth
B) visually by cameras aboard Mariner 10
C) by a surface rover sent out by MESSENGER
D) visually from the Hubble Space Telescope
66. Which unexpected chemical compound has recently been discovered on Mercury?
A) nitrogen dioxide in Mercury’s upper atmosphere
B) cyanide, poisonous to humans, in the troposphere
C) ammonia, escaping from fissures in the Caloris Basin
D) water ice at the north and south poles
67. Where has water ice been found on Mercury?
A) nowhere
B) suspended as microscopic crystals in the stratosphere
C) in permanently shadowed crater floors at the north and south poles
D) in deep fissures on the night side
68. How is water ice able to remain on the surface of Mercury, despite the planet’s close proximity to the Sun?
A) The water ice is continuously replenished by condensation of water vapor from volcanoes.
B) The water ice is continuously replenished by fresh impacts from comets.
C) The water ice exists as permafrost below the thermally insulating surface and is exposed only by occasional impacts.
D) The water ice is permanently shielded from the Sun by crater walls at the north and south poles.
69. The source of the water found in the form of ice near Mercury’s north and south poles is
A) comet impacts.
B) unknown at the present time.
C) rainfall early in Mercury's history, when the planet had a dense atmosphere.
D) a former global ocean, now almost entirely evaporated and lost to space.
Section: 8-4
70. “This planet has a solid, cratered surface, which is alternately very hot and very cold, and it has no permanent atmosphere.” Which of the planets fits this description?
A) Venus
B) Mercury
C) Jupiter
D) Mars
71. Mercury’s atmosphere consists mostly of
A) sulfur dioxide and hydrogen sulfide from volcanoes.
B) carbon dioxide.
C) nitrogen and oxygen, with traces of carbon dioxide and argon.
D) hydrogen, helium, potassium, sodium, and oxygen.
72. Mercury’s atmosphere is
A) almost nonexistent.
B) relatively dense, composed mostly of nitrogen (80 percent) and oxygen (20 percent).
C) very thin, made up of sulfur dioxide and hydrogen sulfide from volcanoes.
D) relatively thin, composed of carbon dioxide with small quantities of nitrogen and argon.
73. What do most astronomers believe is the source of the minute amount of oxygen in Mercury’s atmosphere?
A) sublimation of water molecules from ice at the poles
B) ions captured from the solar wind
C) decay of sulfur dioxide ejected from volcanic eruptions
D) bacterial activity in a permafrost layer below the surface
74. Because Mercury has no appreciable atmosphere, its surface shows extreme temperature changes between night and day, with a range of about
A) 600 K.
B) 900 K.
C) 20 K.
D) 60 K.
75. There are traces of oxygen in Mercury’s atmosphere. The source of this is believed to be
A) the sublimation of polar ice.
B) the remnants of the primordial solar nebula.
C) outgassing from within the planet.
D) a continual rain of ice-coated cometary fragments into the atmosphere of Mercury.
76. How do planetary scientists explain the small amounts of hydrogen and helium in Mercury’s atmosphere?
A) Mercury’s large iron core has allowed it to retain these light gases from its primordial atmosphere.
B) They have escaped from the Sun and drifted to Mercury. Mercury does not retain them, but they are continually replenished from the Sun.
C) They are outgassed from Mercury’s active volcanoes.
D) The hydrogen at least is formed when the Sun’s intense ultraviolet radiation breaks apart the hydrocarbons on Mercury’s surface.
77. The highest daytime temperature reached on the surface of Mercury is
A) 961°C, high enough to melt silver.
B) 430°C, high enough to melt lead and tin.
C) 0°C, high enough to melt water ice.
D) 100°C, high enough to boil water.
78. Temperatures on the surface of Mercury are seen to fluctuate between very cold 100 K (–173°C) and extremely hot 700 K (427°C). What does this measurement indicate about conditions on Mercury?
A) Mercury has a very elliptical orbit, and varying distance from the Sun produces these large temperature fluctuations because intensity varies as the inverse square of the distance from the Sun.
B) The planet has an atmosphere in which the greenhouse effect captures solar radiation to heat the sunlit hemisphere of the planet.
C) The planet is close to the Sun, has no atmosphere to maintain heat from the Sun, and is rotating slowly.
D) Erupting volcanoes occasionally heat the planet’s surface to extreme temperatures.
79. The highest temperature on Mercury is 700 K, which is 50 K LESS than the highest temperature on Venus. How, then, can Mercury experience the greatest temperature range in the solar system? Which of these does NOT contribute to this great range of temperature?
A) Mercury has no significant atmosphere to retain heat on its night side.
B) Mercury has no greenhouse gases to keep the planet warm at night.
C) The ice near the poles contributes to the very cold night temperature.
D) Mercury has a slow rotation rate, which allows it to cool off easily on the night side.
80. Tomorrow’s weather forecast for the Caloris Basin on Mercury’s equator is
A) overcast, light winds, occasional acid rain.
B) hot and humid by mid-afternoon; cooling to near freezing overnight.
C) sunny with scattered clouds, possible afternoon dust storms.
D) lead and zinc melting by noon; temperatures well below freezing overnight.
Section: 8-5
81. On the basis of its appearance and general properties, which planetary body could be described as Earth’s twin?
A) Mars; somewhat smaller but with a similar surface, a thin atmosphere, and clouds
B) Moon; somewhat smaller but having the same average density and geology
C) Pluto; similar size and density, a large moon, and probably life on its surface
D) Venus; about the same mass and diameter, dense atmosphere, and cloud-shrouded
82. Which of these physical properties of Venus are very similar in value to those of Earth?
A) mass and radius and hence average density and surface gravity
B) rotation rate around its axis and length of solar day
C) temperatures of surface and atmosphere
D) magnetic field and magnetosphere
83. Which of these has NOT been observed on Venus?
A) lightning
B) active volcanoes
C) perpetual haze and fog at the surface
D) perpetual yellowish cloud cover
84. When Venus is at its brightest as seen from Earth (near greatest elongation), it is
A) the brightest celestial object in the sky other than the Sun and the Moon.
B) just bright enough to be seen with the unaided eye if one knows exactly where to look for it.
C) brighter than the full Moon, but not as bright as the Sun.
D) too faint to see without binoculars or a telescope.
85. Venus appears to be very bright as viewed from Earth at certain times because
A) its rocky surface is shiny, like the surface of new volcanic lava.
B) it is glowing from the heat of its surface, where the temperature is 750 K.
C) it is covered by very reflective clouds.
D) even though its surface is very dark, it is relatively close to the Sun.
86. At greatest elongation, the Earth–Venus line makes an angle with the Sun–Venus line that is
A) nearly 180°.
B) 90°.
C) 0°.
D) an acute angle, less than 90°.
87. “This planet has a very hot solid surface, it is cloud-shrouded, and it has a dense carbon dioxide atmosphere.” Which of the planets fits this description?
A) Jupiter
B) Mars
C) Mercury
D) Venus
88. An Earth-based telescopic view of Venus shows
A) a crater-covered surface of reddish color.
B) evidence of ice-covered polar caps and huge dust storms.
C) a smooth, dark surface with few mountain ranges.
D) a completely cloud-shrouded planet.
89. The surface pressure of the atmosphere of Venus compared with the surface pressure of the atmosphere of Earth is
A) about the same.
B) extremely small.
C) about 1/100 atmosphere.
D) about 90 atmospheres.
90. The conditions on the surface of Venus are
A) no atmosphere, hence very variable temperatures under direct sunlight.
B) a low-pressure, low-temperature, carbon dioxide atmosphere.
C) a high-pressure, high-temperature, carbon dioxide atmosphere.
D) a dense atmosphere of methane, ammonia, and water at a low temperature.
91. Clouds extend above the surface of Venus to a maximum altitude of
A) thousands of kilometers.
B) almost 70 km.
C) zero because there are no clouds on Venus.
D) just over 20 km.
92. The cloud structure in the atmosphere of Venus can be described as
A) a clear layer at the surface, a haze layer above it, a thick layer of permanent clouds, and then more haze.
B) a permanent and thick cloud layer, extending almost to ground level.
C) isolated clouds forming and dissipating all the time, with clear sky between them.
D) mostly clear sky with occasional thin, high clouds and dust.
93. The lower atmosphere of Venus near the surface can be described as
A) clear.
B) foggy.
C) very dusty.
D) absent (Venus has almost no atmosphere!).
94. An observer is on the surface of Venus (suitably protected). Looking about, what kind of weather will the observer see?
A) The air is filled with fog and haze, no matter which direction one looks.
B) The surface is fogged over, but if a break in this surface layer could be found, one would see that the atmosphere is clear above it. If it were night, the obseerver could see the stars through a break in this surface layer.
C) If the observer is within about 30 degrees of the equator, the atmosphere will be perfectly clear. North or south of this, the atmosphere will be an unbroken layer of clouds.
D) Near the surface the air is clear, but looking up the observer will see a solid bank of clouds extending from horizon to horizon.
95. The sulfuric acid clouds on Venus
A) are confined to a layer about 60 km above the planet’s surface and cover the whole planet.
B) extend from the surface to a height of 70 km and cover the whole planet.
C) are confined to a layer just above the surface about 1 km thick and completely opaque, rendering the surface invisible from above.
D) are in a layer about 70 km above the planet’s surface but are patchy, so the surface can be seen occasionally from above.
96. The clouds in the atmosphere of Venus consist primarily of
A) dust particles.
B) droplets of carbon dioxide.
C) water.
D) droplets of sulfuric acid.
97. The MOST likely source for the sulfur compounds in the clouds above the surface of Venus appears to be
A) intense wind storms that have carried surface dust high into the atmosphere.
B) meteoritic material that burned up as it fell into the Venusian atmosphere.
C) recent eruptions of volcanoes, spewing gases and dust high into the atmosphere.
D) the solar wind, having been captured by the intense magnetic field of the planet.
98. One chemical element that plays a major role in the coloring and chemistry of the Venusian atmosphere and clouds, and is suspected of coming from volcanic eruptions, is
A) nitrogen (as gas), nitric oxide, and nitric acid droplets.
B) chlorine (as gas), hydrogen chloride, and hydrochloric acid droplets.
C) iron (as red dust), iron oxides, and iron sulfides.
D) sulfur (as dust), sulfur dioxide, and sulfuric acid droplets.
99. Which particular chemical associated with volcanic emissions exists in short-lived compounds but has been detected on Venus, indicating the possibility of active volcanoes on that plaent at the present time?
A) sulfur and sulfur compounds
B) silicon and silicate dusts
C) ammonia and methane gases
D) carbon in carbon dioxide and carbon oxide
100. Why do planetary scientists believe there are active volcanoes on Venus?
A) Images from the Russian Venera lander show a volcanic plume.
B) Radar evidence from the Magellan orbiter shows fresh basalt on the surface.
C) Radar mapping has indicated a boundary line between tectonic plates, and such boundaries always include volcanic activity.
D) The amount of short-lived sulfur compounds detected in the atmosphere of Venus implies regular replenishment.
101. Which of these does NOT describe an argument in favor of the presence of active volcanoes on Venus at the present time?
A) There has been confirmed observation of lightning in Venus’s atmosphere.
B) There has been confirmed observation of hot spots in rift valleys on Venus’s surface.
C) There has been confirmed observation of natural radioactivity on Venus’s surface.
D) There has been confirmed observation of short-lived sulfur compounds in Venus’s atmosphere.
102. Spacecraft from which country or countries have landed on the surface of Venus?
A) United States and former Soviet Union
B) No country has yet successfully landed spacecraft on the surface of Venus.
C) United States
D) former Soviet Union
103. Why did the Soviet spacecraft survive for only a few minutes on the Venusian surface?
A) It landed in very rugged terrain and was not able to land upright, and it became damaged when it toppled over.
B) It landed very fast because there was insufficient atmosphere to slow down its descent.
C) It was attacked and destroyed by native inhabitants, but the space agency is not telling the world.
D) The conditions of extreme pressure, corrosive atmosphere, and high temperatures severely damaged it.
104. The severe atmospheric conditions that quickly destroyed spacecraft that soft-landed on the surface of Venus were
A) very low temperatures, a near vacuum, and corrosive alkaline clouds and mist.
B) high temperatures, high pressures, and corrosive acid clouds and mist.
C) high temperatures, low atmospheric pressure, and intense UV radiation from the Sun.
D) intense sunlight, including UV radiation, very high pressures, and very low temperatures.
105. The highest temperature in the Venusian atmosphere occurs where?
A) in the clear atmospheric layers below the cloud level, at an altitude of about 30 km
B) at the planet’s surface
C) at the height of the thickest clouds, 48–52 km, where infrared absorption is highest
D) at the cloud tops, which are heated by sunlight
106. The temperature in the atmosphere of Venus
A) has a complicated structure reaching several maxima and minima at various altitudes.
B) increases smoothly with increasing altitude.
C) is almost constant with altitude.
D) decreases smoothly with increasing altitude.
107. The temperature in the atmosphere of Venus has its maximum value
A) at the top of the atmosphere—closest to the Sun.
B) at the top of the cloud layer.
C) at the bottom of the cloud layer.
D) on the ground.
108. There are many reasons why a multiday hiking trip on foot across Aphrodite Terra on Venus would not be advisable, at least not without suitable protection. Which of these conditions would NOT be a concern?
A) corrosive mists in the atmosphere
B) very cold nighttime temperatures
C) predominantly carbon dioxide atmosphere
D) no water
109. Which planet is the hottest one in the solar system, measured at the surface?
A) Earth
B) Mars
C) Venus
D) Mercury
110. When Venus is seen at inferior conjunction, a ring of light is seen around it. What does this ring tell astronomers about Venus?
A) The Venusian atmosphere is so hot that it glows, even on its dark side.
B) Venus has auroral displays like those on Earth, which extend over the whole planet.
C) Venus is very massive because the gravitational field of Venus is sufficient to bend sunlight around the planet toward Earth.
D) Venus has a thick atmosphere that scatters sunlight toward Earth.
111. Tomorrow’s weather report for Venus would be
A) overcast and very hot.
B) cold and clear.
C) snow.
D) hot and humid, with clear skies.
112. The surface temperature of Venus has been found by radio observations and by remote exploration by spacecraft to be approximately
A) 300 K.
B) 750 K.
C) 273 K.
D) 110 K.
Section: 8-6
113. The mechanism of the “greenhouse effect,” which has resulted in very high temperatures on the surface of Venus (and moderate temperatures on Earth), can be described as solar
A) UV and visible radiation heating the planet surface, the infrared emissions of which are trapped by carbon dioxide in the atmosphere.
B) UV and visible radiation entering the clouds and triggering chemical reactions in the carbon dioxide and sulfur compounds, the released energy then heating the atmosphere.
C) UV and visible radiation being absorbed by the carbon dioxide of the atmosphere, thereby heating it.
D) infrared radiation heating the planet surface that then emits visible and UV radiation that is trapped by carbon dioxide in the atmosphere.
114. Consider two planets, identical except that one has an atmosphere rich in carbon dioxide and the other has no atmosphere, both at the same distance from their star. What will be true in comparing these planets?
A) The planet with the atmosphere will have a higher surface temperature.
B) The planet with the atmosphere will only gain energy from the star, while the other will only reflect energy.
C) The planet with the atmosphere will have the lower albedo.
D) The planet with the atmosphere will give out more radiant energy than it receives from its star.
115. Some radiant energy “leaks” through the cloud layers of Venus and escapes into space. How much energy is this?
A) less than the amount of radiant energy absorbed by Venus
B) just enough to balance the amount of radiant energy absorbed by Venus
C) more than the amount of radiant energy absorbed by Venus
D) considerably more on the night side of Venus than on the day side
116. The main reason for the very high temperature (750 K) on the surface of the planet Venus is thought to be
A) chemical reactions between constituents of the atmosphere, particularly sulfuric acid.
B) radiation from hot lava, produced by intense and continuous volcanic action.
C) continuous bombardment of the surface by solar wind particles and meteoroids.
D) absorption of visible radiation by the Venusian surface and the subsequent trapping of infrared radiation emitted by the surface, by the atmosphere, and clouds.
117. The component of Venus’s atmosphere that is responsible for the excess heating, caused by the greenhouse effect, is
A) water vapor.
B) nitrogen.
C) carbon dioxide.
D) sulfuric acid droplets.
118. What is the main reason that the greenhouse effect has been much more effective in raising the surface temperature on Venus than in raising the surface temperature on Earth?
A) The solar wind, the major cause of heating in the greenhouse effect, is far more intense at Venus’s distance from the Sun, and Venus has no magnetic field to deflect this solar wind.
B) Carbon dioxide, which traps heat from the planet’s surface, is the major component in the very dense Venusian atmosphere, while it is only a minor constituent of Earth’s.
C) The oceans on Earth have acted as a thermostat in absorbing much of the heat that would otherwise have raised Earth’s temperature significantly.
D) The surface of Venus is much more effective than the surface of Earth in absorbing solar visible and UV radiation.
119. Why is the surface of Venus hotter than that of Mercury, even though Mercury is much closer to the Sun?
A) Venus experiences continuous volcanic activity and the release of hot lava onto the surface.
B) The thick carbon dioxide atmosphere of Venus has prevented re-emission into space of the heat absorbed from sunlight.
C) Chemical reactions within the thick clouds and dense atmosphere of Venus are continuously supplying heat to the surface.
D) Venus rotates rapidly, which ensures that its entire surface is being heated regularly and uniformly.
120. Which of these correctly explains why Venus has a higher surface temperature than Mercury.
A) Venus is closer to the Sun than Mercury is.
B) Venus has a dense atmosphere of carbon dioxide.
C) Venus is still contracting gravitationally and thus giving out more radiant energy than it receives.
D) Venus has a higher albedo (reflectance) than Mercury.
121. Water was once much more abundant on Venus than it is now. Where did this ancient water go?
A) It evaporated into space.
B) It is locked up in rocks on the surface.
C) It is in underground reservoirs.
D) It forms the cloud layers.
Section: 8-7
122. The length of a solar “day” (time between successive sunrises) on Venus is about
A) 117 days.
B) 88 days.
C) 243 days.
D) 224 days.
123. Compared with the length of a solar day (time between successive sunrises) on Earth, the length of one solar “day” on Venus is
A) about the same.
B) much shorter, about 1 hour.
C) about half as long, about 10 hours.
D) significantly longer.
124. Spacecraft measurements indicate that the surface of Venus is dominated by
A) sandstone, a sedimentary rock formed on Venus by sand grains deposited by wind.
B) granite, a plutonic rock formed when lava solidifies deep below the surface.
C) basalt, a volcanic rock formed when lava solidifies on the surface.
D) schist, a metamorphic rock formed by the deformation of other rocks by pressure and heat.
125. Which of these does NOT characterize the rotational and orbital motion of Venus?
A) retrograde rotation around its axis
B) retrograde orbital motion
C) rotation axis lying almost in its orbital plane
D) sidereal rotation period longer than its orbital period
126. Which spacecraft and technique has given planetary scientists the most extensive information about the overall surface of Venus?
A) photography from the space shuttle at UV wavelengths that can penetrate the Venusian clouds
B) photography by the four Viking spacecraft (two landers and two orbiters)
C) photography by the Venera landers of the former Soviet Union
D) radar mapping by the Magellan orbiter
127. The surface features and overall topology of Venus have been determined primarily by
A) balloon-borne spacecraft, launched into the Venusian atmosphere by spacecraft.
B) surface lander vehicles that have explored the surface thoroughly.
C) visible and UV photography from the space shuttle.
D) radar methods from Venus-orbiting spacecraft, measuring radio echoes from the surface.
128. The overall geography of the Venusian surface has been determined largely by
A) photography from orbiting spacecraft in long elliptical orbits in order to descend below the clouds during part of their orbits.
B) robotic spacecraft that landed on the surface.
C) radar techniques from orbiting spacecraft.
D) visible-light photography.
129. The BEST images of the overall topography of Venus have been produced by
A) imaging cameras on board two spacecraft that soft-landed on the surface of Venus.
B) reflection of radio waves from the surface by an orbiting spacecraft.
C) photography from the Hubble Space Telescope at UV wavelengths to which the Venus atmosphere and clouds are transparent.
D) visible wavelength images from cameras on board an orbiting spacecraft.
130. Which of these hypotheses has NOT been proposed as a mechanism for resurfacing Venus (and periodically eradication of the craters)?
A) continual tectonic plate activity much like Earth
B) volcanism caused by mantle convection heated by radioactive decay
C) episodic tectonic activity following the cracking of the surface
D) episodic global crustal melting
131. A radar mapping satellite named Magellan orbited which planet in the early 1990s?
A) Mars
B) Venus
C) Moon
D) Mercury
132. In the mapping of Venus by the orbiting Magellan spacecraft, what parameter was measured by the sensors in order to produce three-dimensional maps of the planet’s surface?
A) precise photographs of the extreme limb of the planet, taken at UV wavelengths to which the atmosphere is transparent, that showed detailed profiles of the planet’s surface
B) time delay of the return of reflected radio waves
C) wavelength and hence Doppler shift of reflected radio waves
D) pairs of photographs taken from different angles that were then combined stereoscopically to produce contour maps
133. Radar observations are used from Venus-orbiting spacecraft to evaluate mountain heights by measuring the time difference between echoes from mountain peaks and from the surrounding plains. In this technique, what would be the time difference for signals reflected from Maxwell Montes, which rises 12 km above the plain? (Think about the geometry and total path length.)
A) 80 ns, or 8 10–8 s
B) 800 ns, or 8 10–7 s
C) 80 ms, or 8 10–2 s
D) 80 s, or 8 10–5 s
134. The geology and geography of the surface of Venus is BEST described as
A) volcanoes and volcanic uplifts in the northern hemisphere and cratered plains in the southern hemisphere.
B) colliding surface plates with long mountain chains, rift valleys, and deep subduction trenches.
C) heavily cratered, with no major volcanoes or lava flows.
D) mostly volcanic plains, with two continent-sized uplands and a number of large volcanoes.
135. Compared with the surface of Earth, the surface of Venus is
A) very smooth and flat, with no mountains or structure.
B) extremely rugged, with deep valleys and many high volcanic mountains.
C) completely covered with innumerable, overlapping craters and old crater walls, which constitute mountain ranges.
D) almost completely flat and relatively smooth, except for two high volcanic mountain ranges.
136. How many raised areas that look like continents are seen on Venus?
A) one
B) several
C) none
D) two
137. On a topographical map of Venus, how many large “continents” of high ground rise above the flat plains?
A) none
B) one
C) two
D) seven
138. What is so special about Aphrodite Terra and Ishtar Terra on Venus that they are distinguished as being continents?
A) They are the only regions on the planet that are not flat plains of basalt.
B) They are symmetrically located around the north and south polar regions of Venus.
C) They are highlands with average elevations significantly above the average elevation for the planet.
D) They are surrounded by dry basins that, it is thought, were once filled with water.
139. What is the highest mountain on Venus called?
A) Olympus Mons
B) Ishtar Terra
C) Maxwell Montes
D) Alpha Regio
140. The MOST common surface features on Venus are
A) impact craters.
B) ancient river valleys and huge flood plains.
C) evidence of plate tectonic motion, including long mountain ranges and subduction troughs.
D) volcanoes and lava flows.
141. The surface of Venus
A) shows long mountain ranges similar to the Rockies/Andes ranges and the mid-oceanic ridges on Earth.
B) is very smooth, with no mountains or mountain ranges.
C) has several large individual volcanoes on a smooth plain but no extensive ridged or mountainous regions.
D) has two elevated mountainous regions rising above a smooth plain but no long, connected mountain ranges such as are seen on Earth.
142. Observations of tectonic activity differ on Venus and on Earth. A reasonable explanation is that on Venus
A) the crust appears to be thicker and is therefore too rigid to break up into moving plates.
B) the surface is broken into only two plates, divided by a line at an angle to the equator.
C) the crust appears to be thinner and weaker and cannot support the creation and motion of solid 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.
143. The reason that very few impact craters are seen on Venus compared with the Moon is believed to be that
A) Venus formed closer to the Sun than the Moon did, where the cratering rate was much lower.
B) due to rainfall and wind, all but the most recent craters have eroded away.
C) lava flows and surface melting have covered all but the most recent craters.
D) the surface of Venus has been subducted down into the planet several times in its history, thereby removing evidence of impacts.
144. How does the number of impact craters seen on Venus compare with the number seen on Mercury and the Moon, both of which are significantly smaller than Venus?
A) Venus has more than either Mercury or the Moon.
B) Venus has more than the Moon but fewer than Mercury.
C) Venus has more than Mercury but fewer than the Moon.
D) Venus has fewer than either Mercury or the Moon.
145. The reason there are very few impact craters on the surface of Venus compared with the surfaces of Mercury and Mars is thought to be that
A) wind erosion from the dense atmosphere of Venus and chemical action from its corrosive clouds and mist have destroyed most craters.
B) the thick atmosphere of Venus has protected it from most incoming objects, and the surface has melted periodically to obliterate old craters.
C) plate tectonic motions have recycled the surface of Venus several times since the main bombardment of the planetary system occurred.
D) ocean waters that covered Venus at earlier times washed away any evidence of cratering.
146. The average age of the surface of Venus has been determined primarily from
A) the number of impact craters per unit area of surface.
B) the amount of weathering of lava flows imaged by the Magellan radar mapper.
C) soil analysis by Russian landers.
D) radio-isotope analysis of rocks brought back from Venus by space probes.
147. Venus has
A) a very powerful magnetic field.
B) no permanent magnetic field at all.
C) a weak magnetic field, about 1/100 of Earth’s field strength.
D) a magnetic field about the strength of that of Earth.
148. Spacecraft measurements near Venus indicate that the planet has
A) a very powerful magnetic field, much stronger than that of Earth.
B) a magnetic field that varies in concert with the 11-year solar activity cycle and is linked to it via the solar wind.
C) no permanent planetwide magnetic field.
D) a variable planetwide magnetic field like Earth.
149. The one terrestrial planet that rotates in the “wrong” way (opposite to the rotation of most other planets and to the planet’s revolutionary direction) is
A) Mars.
B) Earth.
C) Mercury.
D) Venus.
150. Which of these planets rotates on its axis in a retrograde fashion, opposite to that of most of the planets and opposite to the direction of revolution of the planets?
A) Mercury
B) Venus
C) Saturn
D) the Moon
151. An observer on the surface of Venus looking upward during the daytime would be likely to see
A) a solid cloud deck, with the Sun moving from east to west.
B) scattered, billowy clouds with clear sky between them and the Sun moving from west to east.
C) thin, high clouds near mountains or otherwise clear skies and the Sun moving from east to west.
D) a solid cloud deck, with the Sun moving from west to east.
152. Venus rotates
A) “locked in” to the Sun, maintaining one side toward it at all times in synchronous rotation.
B) in the same direction as Earth but very rapidly (in a few hours).
C) in the same direction as Earth but very slowly.
D) in the opposite direction from Earth but very slowly.
153. Where would the Sun appear to rise on Venus if one could see through the clouds?
A) in the north because Venus has its spin axis parallel to the plane of its orbit
B) in the west
C) in the east
D) The Sun would not rise or set because Venus rotates synchronously, always keeping one side toward the Sun.
154. The MOST plausible explanation for the retrograde rotation (rotation in a direction opposite that of most other planets) of Venus is the
A) frictional slowing down and eventual reversal of Venus’s rotation by tidal forces at a time when the planet had deep oceans over its surface.
B) frictional drag of its very dense atmosphere on the rotating planet throughout its history.
C) combined gravitational effects of its neighboring planets, Mercury and Earth.
D) impact of a massive object on it early in its history.
Section: 8-8
155. Both impact craters and dormant volcanoes have been found on Mars. Where are they?
A) The northern hemisphere contains most of the craters and most of the volcanoes.
B) The southern hemisphere contains most of the craters and most of the volcanoes.
C) The northern hemisphere contains most of the volcanoes, whereas most of the craters are found in the southern hemisphere.
D) The southern hemisphere contains most of the volcanoes, whereas most of the craters are found in the northern hemisphere.
156. Mars has one hemisphere that is at a higher elevation than the other. In this way, it is similar to
A) Earth.
B) the Moon.
C) Mercury.
D) Venus.
157. Mars has a period and direction of rotation that are
A) a little longer than 24 hours and in the same direction as Earth.
B) 687 days (1 Martian year) because Mars always turns the same face toward the Sun.
C) just less than 10 hours and in the same direction as Earth.
D) about 240 days and in the opposite direction as Earth (retrograde rotation).
158. The mass of Mars is 11 percent of Earth’s mass, while its radius is half of Earth’s radius. What do these figures suggest for the density of Mars?
A) The density of Mars is less than the density of Earth.
B) The density of Mars is the same as the density of Earth.
C) The density of Mars is greater than the density of Earth.
D) Not enough information is given to compare the densities of Mars and Earth.
159. In which of these physical characteristics are Earth and Mars MOST similar to each other?
A) total mass
B) number of moons
C) length of solar day
D) planetary diameter
160. In what way did optical illusion mislead earlier visual observers of Mars?
A) Chance alignments of faint dark features looked like manufactured canals, and variable dark areas near the equator were interpreted as vegetation.
B) Moving areas of obscured detail on the planet were interpreted as massive flash floods rather than dust storms.
C) Apparent movement of surface features due to seeing fluctuations of images when viewed through Earth’s atmosphere were interpreted as evidence of movement of life-forms, or Martians.
D) Volcano structures were seen as eye-shaped images and were interpreted as having been made by intelligent beings to indicate their presence on Mars.
161. Observers in the nineteenth century reported seeing many straight-line features crisscrossing the surface of Mars and interpreted them to be canals constructed by intelligent beings. What is the MOST likely present-day explanation for these observations?
A) The lines were rifts in the Martian surface at the boundaries of geological tectonic plates.
B) The lines were linear, stationary cloud formations (mountain lee wave clouds) and weather fronts moving around with the planet.
C) The lines were optical illusions caused by vague shadings on the planet’s surface.
D) The lines were groups of dark volcanoes similar to those of the Hawaiian Islands on Earth.
162. What observations of the Martian surface led Lowell to the conclusion that intelligent life-forms existed on Mars?
A) melting icecaps, a network of linear features that look like canals, and varying dark surface markings assumed to be vegetation
B) geometrical structures and patterns that are apparently the remains of buildings and cities
C) sculpted mountains in the shape of humanoid heads, obviously carved to announce the presence of intelligent life to distant observers
D) lakes and rivers of water flowing from polar ice caps and detected by strong specular reflection of sunlight
163. The so-called “canals” that Schiaparelli and Lowell reported seeing on the surface of Mars were actually
A) the remnants of the walls of ancient craters that have been eroded by winds and dust over Mars’s history.
B) river valleys caused by massive floods early in Mars’s history.
C) lines of volcanoes along faults in the Martian surface.
D) optical illusions.
164. Which of these statements BEST characterizes the surface of the planet Mars?
A) The surface of Mars is continuously resurfaced by ongoing volcanic activity; consequently, there are almost no visible impact craters.
B) All the big volcanoes are in the northern hemisphere of Mars, and most of the craters are in the southern hemisphere.
C) Eighty percent of the surface of Mars is rolling plains, with a number of major volcanoes and only two continent-sized uplands.
D) On Mars there are several moving lithospheric plates rimmed by long mountain chains, deep subduction trenches, and several large rift valleys.
165. The overall geography of Mars can BEST be summarized as
A) moving lithospheric plates whose motions have produced long folded mountain chains, deep subduction trenches, and several large rift valleys.
B) mostly rolling plains, with several volcanoes on top of two continent-sized uplands.
C) smooth plains where continuous resurfacing by ongoing volcanic activity has hidden older impact craters and other details.
D) major volcanoes in the northern hemisphere and extensively cratered plains in the southern hemisphere, separated by one major valley system.
166. Where are MOST of the extinct volcanoes located on Mars?
A) along the bottom of the deep valley Valles Marineris, which was originally formed by enormous geological stresses
B) in the northern hemisphere
C) around the southern polar cap
D) in a line along the equator, the line of maximum tidal stress on the planet
167. The Martian valley Valles Marineris is shown in Figure 8-27 of the text. How long is this valley in terms of Earth distances?
A) half the length of Earth’s equator, about 20,000 km
B) about 50 km, a significant distance on this small planet
C) a few hundred kilometers—New York to Washington, DC
D) the full width of the North American continent at midlatitudes—a few thousand kilometers
168. Which of these is NOT a legitimate reason to believe that the northern hemisphere of Mars has experienced more geologic activity than the southern hemisphere?
A) Most of the Martian craters are in the southern hemisphere.
B) Most of the Martian volcanoes are in the northern hemisphere.
C) The Martian magnetic field is oriented north to south, opposite Earth’s magnetic field.
D) The southern hemisphere has a higher elevation than the northern hemisphere.
169. Where in the planetary system is the massive extinct supervolcano Olympus Mons?
A) on the mountain range Ishtar Terra on Venus
B) on Earth
C) on Mars
D) on Io, one of the moons of Jupiter
170. Olympus Mons is a
A) long-lived anticyclone, or spot, on Jupiter.
B) valley on the Moon.
C) mountain on Venus.
D) volcano on Mars.
171. Which of these features was NOT found on Mars when spacecraft finally visited the planet?
A) deep, winding canyons
B) straight canals
C) extinct volcanoes
D) craters
172. Which of these is one reason there are no volcanoes on Earth anywhere near the size of Olympus Mons?
A) Mars’s smaller gravity caused lava to flow more slowly, building up thicker layers as it cooled.
B) Because Mars is smaller than Earth, it retained its interior heat longer and allowed volcanic activity for a longer time.
C) Because of tectonic activity on Earth, volcanoes are subducted too quickly to become large.
D) Because of colder temperatures on Mars, lava solidified more quickly before it had time to move far from the volcanic cone.
Section: 8-9
173. What is the “face” on Mars?
A) natural rock formation that looks like a face in the right light
B) small carved portrait placed on the Martian surface by one of the Viking landers
C) sculpted hill carved either by a long-dead Martian civilization or by visiting aliens
D) natural arrangement of volcanoes and lava plains that gives the appearance of a face when viewed from Earth
174. What did the 1998 spacecraft Mars Orbiter find when it looked at the “face” on Mars?
A) The orbiter found that the face had two noses, showing that it had been carved by a nonhuman sculptor.
B) The orbiter found that the shifting sands had uncovered two other, smaller faces on either side of it.
C) The orbiter found nothing—the face and the rocks around it were either gone or buried by sand.
D) The orbiter showed the face to be a natural rock formation.
175. In 1976 the Viking 1 orbiter imaged what appeared to be a humanlike face on Mars. Images taken by Mars Global Surveyor in 1998 did not show any evidence for a face. Which of these did NOT contribute to this difference?
A) a different camera angle
B) the washing away of some of the original features by running water
C) the eroding away of some of the original features by winds
D) improved camera technology
Section: 8-10
176. A caldera is a
A) crater formed by collapse at the summit of a volcano.
B) valley formed by the separation of two crustal plates.
C) long, sinuous valley carved by the flow of molten rock.
D) depression formed by the impact of an asteroid on a planetary surface.
177. Which of these statements appears to be true for Mars?
A) Plate tectonics has had little or no effect other than perhaps in the earliest times because Mars is small and cooled more rapidly than Earth so that a thick, solid crust formed.
B) Plate tectonics is only just beginning and will be important in the distant future because geologic processes happen more slowly on a small planet.
C) The oppressive heat on Mars has kept the planet’s crust thin and prevented the onset of plate tectonics.
D) Plate tectonics is the dominant process creating large-scale surface features such as mountain ranges and volcanoes.
178. Tectonic plate activity is believed to have been present on Mars billions of years ago. Which of these is NOT consistent with such plate activity on the early Mars?
A) a stronger magnetic field
B) a more molten interior
C) more giant volcanoes like Olympus Mons
D) more long chains of volcanoes
179. Which of these is NOT a sign of former tectonic activity that has been found on Mars?
A) the Valles Marineris
B) interlocked magnetic fields along extended regions
C) remnants of global magnetism
D) long lines of dormant volcanoes marking ancient plate boundaries
180. What evidence is there that plate tectonics may have occurred in very early times on Mars?
A) Magnetic fields at the surface of Mars show interlocking patterns similar to those in regions where plates are separating on Earth.
B) There are several highly eroded systems of folded mountain ranges and linear troughs on Mars, similar to regions of plate collision on Earth.
C) “Fossilized” rift valleys have been discovered by ground-penetrating radar under the blanket of dust and lava of Mars’s surface.
D) Interconnecting patterns of strike-slip faults in the volcanic northern hemisphere of Mars are similar to those where tectonic plates are sliding past each other on Earth.
181. What evidence is there that Mars may have had an internal magnetic dynamo in its youth?
A) Phobos and Deimos, the two moons of Mars, show residual radioactivity, as if they had orbited through the high-energy charged particles of a former Martian magnetosphere.
B) There is no evidence that Mars has ever had an internal magnetic dynamo.
C) “Fossilized” regions of opposite magnetic polarity have been found near Mars’s north and south geographic poles.
D) Magnetic fields at the surface of Mars show interlocking patterns similar to those produced on Earth by magnetic reversals in Earth’s internal dynamo.
182. Hot-spot volcanism is a process that
A) produces gigantic volcanoes on Venus and Mars and chains of smaller volcanoes on Earth (e.g., the Hawaiian Islands).
B) produces dome-shaped rises on Venus and Mars and mid-ocean ridges on Earth (e.g., the Mid-Atlantic Ridge).
C) produces large rift valleys on Mars, Venus, and Earth (e.g., the Great Rift Valley of Africa).
D) does not operate on Venus or Mars but produces folded mountain chains and subduction zones on Earth (e.g., along the west coasts of North America and South America).
183. The major volcanoes on Mars have formed
A) in mountain belts where the planet’s surface is being stressed as it is bent and subducted back into the mantle.
B) where shrinkage of the crust during cooling early in the planet’s history has wrinkled the surface.
C) on long, interconnected ridges where magma, rising from the mantle, is pushing the crust apart.
D) over individual stationary hot spots in the underlying molten mantle.
184. In what way was the production of the major volcanoes on Mars similar to the production of the Hawaiian Islands on Earth?
A) The major volcanoes on Mars and the Hawaiian Islands were both produced by the collision of an oceanic plate with a continental plate.
B) The major volcanoes on Mars and the Hawaiian Islands were both produced by hot-spot volcanism resulting from the upflow of heat from below.
C) The major volcanoes on Mars and the Hawaiian Islands were both produced by upwelling magma along a boundary where two plates are separating.
D) The major volcanoes on Mars and the Hawaiian Islands were both produced by shattering of the crust by a major impact and the consequent release of subsurface magma.
185. In what way was the production of the major volcanoes on Mars different from the production of the Hawaiian Islands on Earth?
A) The Martian volcanoes formed while Mars was still completely molten, whereas the Hawaiian Islands formed recently, after Earth’s crust had solidified.
B) The Martian volcanoes formed in crust that was stationary over an underlying hot spot, whereas the Hawaiian Islands formed in crust that was moving over an underlying hot spot.
C) The Martian volcanoes formed through crustal shattering by a major impact, whereas the Hawaiian Islands formed by volcanic action over an underlying hot spot in Earth’s upper mantle.
D) The Martian volcanoes formed in crust that was moving over an underlying hot spot, whereas the Hawaiian Islands formed along a boundary between two crustal plates.
186. Two observed features on Mars appear to lead to contrary geological conclusions—the appearance of massive, solitary volcanoes, apparently caused by hot spots under the planet’s surface, and the discovery of a long, deep rift valley across the planet. Why are the two features a contradiction?
A) Volcanoes suggest a molten inner planet, whereas a rift valley suggests the presence of a solid core.
B) Massive volcanoes should have covered the planet’s surface, including the valley, with dust and ash, but the valley remains as a major feature.
C) Ancient volcanoes show no sign of erosion by water, whereas the valley suggests prolonged rainfall and erosion.
D) Single massive volcanoes indicate hot-spot volcanism with no plate tectonic motion, whereas a rift valley suggests otherwise.
187. On which object would one find the great valley system Valles Marineris?
A) Venus
B) Mars
C) Moon
D) Callisto (one of the large satellites of Jupiter)
188. What is the Valles Marineris?
A) large rift valley system associated with the great volcanoes on Mars
B) long scarp-and-trough system in the lava plains of Mercury
C) system of deep trenches bordering Aphrodite Terra on Venus
D) system of tectonic faults on the Jovian satellite Ganymede
189. Which of these statements BEST describes the current understanding of the Valles Marineris?
A) The valley system appears to have been carved almost entirely by water flowing toward the lowlands from the geological rise near Olympus Mons.
B) The valley system appears to be a set of parallel subduction trenches along the boundary where the northern lowlands are colliding with the southern highlands.
C) The valley system appears to have formed entirely by cracking and faulting of the Martian surface, without noticeable intervention of erosion by water.
D) One side of the valley system formed primarily by cracking and faulting of the Martian surface, but some valleys at the eastern end appear to have been carved by water.
190. The spacecraft that has provided the MOST detailed understanding of the Martian surface to date is
A) Mars Global Surveyor.
B) Viking.
C) Mars Pathfinder.
D) Magellan.
191. Why have astronomers come to believe that large bodies of liquid water, if they exist on Mars, must be deep beneath the surface?
A) The Martian magnetic field appears to be generated by large bodies of water (containing dissolved minerals to make them electrical conductors) moving deep within the planet.
B) No signs of liquid water, past or present, have been found on the surface.
C) The surface of Mars does not buckle under the weight of its northern polar cap and is thus much thicker than previously thought.
D) The low water content of the basalt near Mars’s large volcanoes suggests a deficit of water immediately below the surface.
192. Earth has buckled slightly under the weight of its northern polar cap. Mars has not similarly deformed in response to its northern polar cap. This suggests that
A) the crust and upper mantle must be thicker than those of Earth.
B) any liquid water under the planet’s surface must be very near the surface.
C) any life under the planet’s surface must be very near the surface.
D) the poles must be 100 percent carbon dioxide ice rather than the more dense water ice.
193. The Martian magnetic field is
A) nonexistent—no spacecraft has ever detected a magnetic field on Mars.
B) much stronger and more extensive than Earth’s magnetic field.
C) weak and localized, not at all like the global magnetic field of Earth.
D) comparable to Earth’s magnetic field.
194. The Martian magnetic field
A) is confined to the planet’s interior by its thick crust.
B) has a tail pointing away from the Sun, formed by the solar wind.
C) has the same shape as Earth’s but is significantly weaker.
D) is comparable in shape and intensity to Earth’s magnetic field.
195. Which of these correctly describes aurorae on Mars?
A) The aurorae last only a few seconds and are the direct result of solar wind particles impacting atoms and molecules in Mars’s atmosphere.
B) The aurorae are formed when solar storms interact with the powerful magnetic field surrounding Jupiter.
C) The aurorae are formed by the same mechanism as Earth’s, but they are weaker because Mars lacks a strong magnetic field.
D) Mars does not have aurorae because it lacks a magnetic field.
196. The origin of the Martian magnetic field appears to be
A) magnetic material deposited by impacts of iron meteorites.
B) an electric dynamo still operating in the small Martian core.
C) convection of molten, iron-rich lava in the Martian mantle.
D) remnant magnetism from an earlier global magnetic field when Mars was young.
Section: 8-11
197. The distinctive red color of Mars is probably caused by
A) progressive reddening of sunlight as it traverses the interplanetary dust between the Sun and Mars and then Mars and Earth.
B) red dust that is suspended high above the surface by winds and filters the sunlight.
C) the scattering of blue sunlight out of the optical beam by dust in the atmosphere, similar to sunsets on Earth.
D) iron oxides or rust in the soil.
198. The reddish color of Mars is probably due to
A) the glow from the very high temperature surface on the sunlit parts of Mars.
B) iron oxides such as rust.
C) vegetation turning red in the Martian autumn.
D) sulfur compounds thrown out by active volcanoes.
199. The dominant component of the soil on Mars is probably
A) sedimentary rocks laid down by massive floods early in Mars’s history.
B) volcanic ash from eruptions in recent geological times.
C) basaltic lava pulverized by meteoritic bombardment.
D) iron oxides.
200. What is the material that produces the distinct red color of Mars?
A) scattered sunlight from very fine dust, similar to sunset effects on Earth
B) rust, or iron oxides
C) carbon dioxide because it absorbs blue and green light preferentially
D) red-colored vegetation that seems to fluctuate seasonally, particularly near the equator
201. Craters on Mars have flatter bottoms and their rims appear to be more worn down than those on either Earth’s Moon or Mercury. What has caused this wear?
A) breakdown of the rocks by the extreme temperature variations between day and night
B) erosion by the seasonal fall and subsequent melting of carbon dioxide snow
C) erosion by wind and infilling by dust storms
D) erosion by rainfall, now and in the past
202. What is a Martian dust devil?
A) a line of sand dunes marking the edge of an ancient tectonic plate
B) the name given to one of the humanlike forms imaged on Mars in the 1970s
C) a natural whirlwind on the planet’s surface
D) the name given to a possible fossil found in a dust-filled meteorite from Mars
203. Which of these features has NOT been seen or detected on Mars?
A) polar ice caps
B) dust storms
C) active volcanoes
D) erosion of surface features
204. Mars’s atmosphere contains no water vapor. Why is this?
A) Mars’s gravity is too weak to retain water vapor on the planet.
B) The temperature of Mars is too high for water vapor to be retained on the planet.
C) There has never been any liquid water on the surface of Mars.
D) Mars was formed outside the region of the solar nebula where water vapor was stable.
205. The gas that is the major constituent of the atmospheres of Venus and Mars and a minor constituent of Earth’s atmosphere is
A) oxygen.
B) water.
C) carbon dioxide.
D) nitrogen.
206. Seasons on Mars last nearly twice as long as those on Earth because
A) Mars’s tilt on its axis is nearly twice the angle of Earth’s tilt.
B) Mars takes nearly twice as long to rotate on its axis as Earth does.
C) Mars takes nearly twice as long to orbit the Sun as Earth does.
D) Mars is nearly twice as far from the Sun as Earth is.
207. “This planet has a cool, solid surface, a thin carbon dioxide atmosphere, and occasional dust clouds.” Which planet fits this description?
A) Mercury
B) Venus
C) Jupiter
D) Mars
208. What is the major constituent of the atmosphere of Mars?
A) CO2 (carbon dioxide)
B) CH4 (methane or natural gas)
C) H2O (water vapor)
D) H2 (hydrogen)
209. The tilt of the equator of Mars to its orbital plane
A) varies periodically through the Martian year.
B) is 0°.
C) is 90°.
D) is very similar to that of Earth, about 25°.
210. The equator of Mars is tilted with respect to its orbital plane, so Mars
A) shows similar seasons to Earth, each lasting about twice the length of those on Earth.
B) experiences very long (20-year) seasonal variations.
C) occasionally experiences small seasonal variations.
D) shows no seasonal variation at all.
211. Earth and Mars each has about the same tilt of its spin axis with respect to its orbital plane. Earth experiences precession, which causes the DIRECTION of its spin axis to change slowly over time, but the ANGLE of tilt stays relatively constant. By contrast, the ANGLE of tilt of Mars’s spin axis is NOT expected to be stable over long periods of time. Which of these is a potential explanation for this?
A) Mars is a smaller planet, and smaller planets are all unstable in this manner.
B) Spin axes are stabilized by magnetism. Earth has a strong magnetic field and Mars has none.
C) Spin axes are stabilized by the presence of a large moon. Earth has one and Mars has none.
D) Mars was struck by a large object early in its history, accounting for the difference in its hemispheres. One aftereffect of this collision is a long-term instability in its spin direction.
212. Mars experiences similar seasonal changes to those on Earth because
A) it has about the same shape of elliptical orbit as Earth, which produces similar changes in solar radiation intensity as the planet orbits the Sun.
B) its spin axis is tilted at about the same angle to its orbital plane as is Earth’s axis.
C) the length of its day is very close to the length of an Earth day.
D) the length of its year is very close to that of Earth.
213. Which of these properties of Earth and Mars are very similar?
A) length of solar day and inclination of equator to the ecliptic
B) length of solar day and diameter
C) planet diameter and inclination of equator to the ecliptic plane
D) orbital period and length of solar day
214. A major feature of the atmosphere of Mars is
A) very dense clouds shrouding most of the planet.
B) very high temperatures and pressures.
C) occasional strong winds and dust storms.
D) a chemical mixture very similar to that of Earth.
215. Atmospheric pressure at the surface of Mars compared with atmospheric pressure at Earth’s surface is
A) about 90 times greater.
B) less than 1/100.
C) extremely small (less than 1 millionth).
D) about the same.
216. Which of these processes did NOT contribute to Mars losing its atmosphere about two billion years ago?
A) stripping by the solar wind
B) the breakup of molecules by solar ultraviolet radiation
C) some gases freezing and being buried under the surface
D) the greenhouse effect
217. There are many reasons why a multiday hiking trip on foot through the Valles Marineris on Mars would not be advisable, at least not without suitable protection. Which of these conditions would NOT be a concern?
A) possibility of dust storms
B) predominantly carbon dioxide atmosphere
C) high levels of ultraviolet radiation
D) oppressively high atmospheric pressure
Section: 8-12
218. On which planet have planetary scientists observed prominent but variable ice caps?
A) Mercury
B) Mars
C) Venus
D) Moon
219. How have planetary scientists obtained samples of Martian rocks?
A) Astronauts have collected rocks and returned them to Earth.
B) Scientists have not yet been able to obtain any Martian rocks.
C) Rocks were blasted off Mars by impacts and landed on Earth as meteorites.
D) A robotic rover collected rocks for return by its lander.
220. The SNC meteorites are
A) granitic rocks from Venus formed by solidification of a molten crust.
B) rocks from Mars containing water-soaked clay.
C) basaltic rocks from the Moon made up of solidified lava.
D) carbonaceous chondrites from the asteroid belt containing naturally occurring amino acids
221. Scientists have now examined rocks that came from Mars in their laboratories on Earth because
A) an orbiting spacecraft scooped up Martian dust during its passage by Mars and then returned to Earth.
B) several meteorites are now thought to have been knocked off Mars and fallen to Earth.
C) spacecraft have been to the surface of Mars and have returned with samples of Martian rocks and soil.
D) a large impact that occurred on the Martian surface early in its history created a vast dust cloud through which Earth passes once per year, and samples of this dust have now been collected by the space shuttle.
222. Why do planetary scientists believe the SNC meteorites came from Mars?
A) They were brought back by the return voyage of the Mars Pathfinder mission.
B) Their fall to Earth was tracked by radar, so it was possible to reconstruct their trajectories.
C) Radioactive minerals in the rocks allows them to be dated from approximately the same time as similar layers on Mars.
D) Their chemistries are similar to rocks from Mars’s surface, and they contain trace gases that match Martian atmospheric samples.
223. In view of the present surface and atmospheric conditions on Mars, why would there be no liquid water on its surface?
A) The water would all be frozen, given the prevailing day and night temperatures.
B) The very low atmospheric pressure would allow the water to boil and evaporate rapidly.
C) Water would have reacted chemically with the surface rocks.
D) The UV radiation from the Sun would have dissociated the water molecules into hydrogen (which would leave the planet) and oxygen (which is still present).
224. The “snow” that occasionally falls in and near the polar regions of Mars consists of
A) water ice.
B) frozen sulfuric acid droplets.
C) very fine white dust, disturbed occasionally by fierce wind storms.
D) carbon dioxide ice.
225. The polar caps on Mars are MOST likely made up of
A) volcanic outflows of light-colored lava and dust similar to that produced by Earth-based volcanoes (such as Mount St. Helens).
B) sulfur dioxide and sulfur compounds.
C) light-colored dust, blown there by the Martian dust storms.
D) water and carbon dioxide ices.
226. The polar caps on Mars are now known to consist of
A) methane (CH4), ammonia (NH3), and water (H2O) ices, whose relative abundances vary with the seasons.
B) a combination of carbon dioxide (CO2) ice and water (H2O) ice.
C) only carbon dioxide (CO2) ice, which is very volatile and melts easily.
D) only water (H2O) ice, which does not melt easily and survives the summer heat.
227. On which planetary body can distinct evidence be seen for the flow of water at an earlier time?
A) Mars
B) Earth’s Moon
C) Venus
D) Titan, the moon of Saturn
228. What significant evidence is there for the idea that large quantities of water once flowed on the planet Mars?
A) network of relatively straight canals linking polar and equatorial regions
B) clouds and frost that formed above and around the Viking spacecraft
C) frozen, dust-covered lakes inside ancient craters
D) winding channels resembling riverbeds carved into Mars’s surface
229. Which of these is NOT one of the known locations of water on Mars?
A) flowing in river valleys
B) in polar ice caps
C) as water vapor in the atmosphere and as clouds
D) in permafrost below the surface
230. Where has water been definitively detected on Mars?
A) as a liquid flowing along the numerous flood valleys and meandering stream beds
B) only as aospheric water vapor, never condensing out as clouds, liquid water, or solid ice
C) in permafrost and polar ice caps and as water vapor in the atmosphere
D) as a liquid in undersurface lakes and rivers
231. Which of these is true of Mars?
A) Linear canals, apparently built to carry water for irrigation, crisscross the planet.
B) Water can be seen in the bottoms of river valleys on spacecraft photographs.
C) Mars has dry riverbeds but no liquid water on its surface at the present time.
D) There is no evidence of water ever having been on Mars.
232. Which of these signatures of water is NOT seen on Mars?
A) evidence of permafrost under the Martian surface
B) meltwater pools at the edges of the polar caps
C) water ice (as opposed to carbon dioxide ice) in the polar caps
D) occasional clouds around the large volcanoes
233. Which of these conditions would NOT be in a weather report from Mars, in view of the present atmospheric conditions on the planet?
A) dry and windy with blowing and drifting dust
B) dry-ice snow
C) clear and cold
D) rain tapering to intermittent showers by noon
234. Evidence of past water on Mars comes from each of these EXCEPT
A) polygon-shaped cracks in rocks.
B) dried-up lakebeds and riverbeds.
C) the presence of small, round hematite rocks.
D) observation of water-rich bodies striking the planet, implying more of them did so in the past.
235. Rover Opportunity discovered Martian rocks with polygon-shaped cracks. One theory is that an impact released water from the Martian soil to flood these rocks. Water seeped into the rocks, froze, and caused the cracks. This explanation requires large amounts of water for several reasons. Which of these is NOT one of these reasons?
A) The surface temperature on Mars is always below the freezing point of water.
B) Much of the water thus liberated would be vaporized by the impact.
C) Liquid water on the surface of Mars would vaporize because of the low pressure.
D) Such rocks have been discovered at widespread locations on Mars.
236. Mars rovers have uncovered lava rocks containing olivine and pyroxene. What conclusion has been drawn from this?
A) These rocks dissolve quickly in water, thus Mars must have been dry for several billion years.
B) These rocks contain water, so the surface must have been submerged at some time during the last billon years.
C) These rocks contain microfossils that might be the remnants of living organisms. This greatly increases expectations of past life on Mars.
D) These rocks form at high temperature, suggesting that Mars formed closer to the Sun than it is now.
237. What is the strongest evidence for liquid water flowing on Mars today?
A) the continued erosion of some riverbeds
B) brown lines on some surface features believed to be salt deposits from water flows
C) seasonal channels feeding meltwater pools near the polar ice caps
D) There is no such evidence; water does not appear to be flowing on Mars at present.
Section: 8-13
238. Where in the solar system did the Viking spacecraft land?
A) on Europa, one of the moons of Jupiter
B) on Venus
C) on Mars
D) on Earth’s Moon
239. Viking 1 and Viking 2, the planet-exploring spacecraft, were sent to which planet?
A) Mars
B) Jupiter
C) Venus
D) Mercury
240. Experiments carried out to detect life on another world were performed by the
A) Apollo astronauts.
B) Venera landers.
C) Galileo spacecraft.
D) Viking landers.
241. On which of these planets have experiments been carried out to search for life-forms or evidence of life?
A) Venus
B) Mars
C) Mercury
D) Jupiter
242. The exploratory life-sciences experiments aboard the Viking spacecraft landers found evidence of
A) a very sterile environment in which life could not have existed and a very chemically inert soil, reacting with almost no reagents.
B) primitive life-forms such as elementary bacteria that should not be a hazard when humans explore Mars.
C) very reactive chemistry in the Martian surface rocks, but no evidence of life or remnants of life-forms.
D) primitive life-forms that had existed on Mars earlier in its history but had not survived.
243. What were the results of the life-sciences experiments aboard the Viking landers?
A) strong reactions releasing oxygen from apparent biological causes (e.g., bacteria)
B) none at all; the Martian soil is completely chemically inert and biologically sterile.
C) strong reactions releasing oxygen but from nonbiological causes
D) slight fizzing due to released carbon dioxide but very little else
244. Several aspects of Mars render it hostile to life on the planet. Which of these components is NOT one of these factors?
A) solar UV radiation, which is not absorbed by the thin atmosphere
B) sulfuric acid droplets in the atmosphere
C) hydrogen peroxide in the soil
D) ozone in the atmosphere produced by solar UV light
245. Where did some scientists claim that they have found direct evidence for life, either contemporary or ancient, beyond Earth that has since been disproven?
A) in spectra of the dark deposits along fissures in the ice of Jupiter’s satellite Europa
B) in “orange soil” found on the Moon
C) in the “soil” (regolith) at the Viking 2 landing site on Mars
D) in meteorites composed of ancient Martian rock
246. What evidence have some scientists claimed for ancient life on Mars (although the hypothesis has been strongly disputed by many other scientists)?
A) an apparent thumbprint on a rock at the Mars Pathfinder landing site
B) peroxides in the “soil” (regolith) found by experiments on the Viking landers
C) microscopic features in a Martian meteorite similar to biologically generated features on Earth
D) calcium carbonate deposits similar to seashells in a sample of Martian limestone
247. The unstable chemicals dissolved in the Martian regolith suggest that the amount of ultraviolet radiation reaching the surface of Mars is much greater than the amount reaching the surface of Earth. The Martian atmosphere lacks which constituent in sufficient quantities to absorb incoming ultraviolet radiation?
A) Oxygen
B) Ozone
C) carbon dioxide
D) Nitrogen
248. What role has methane played in the search for life on Mars?
A) Methane destroys simple life-forms, so the existence of methane precludes the existence of simple life-forms on Mars.
B) Methane is produced by life-forms, so the search for methane being released from under the Martian surface—so far unsuccessful—continues.
C) Sunlight breaks down methane within a few centuries. The presence of methane on Mars suggests that it is being renewed continually, perhaps by living organisms.
D) So far methane has played no role in the search for life on Mars.
Section: 8-14
249. The Moon raises tidal bulges on Earth and as a consequence is being pulled gradually away from Earth. Phobos raises tidal bulges on Mars and as a consequence is being pulled gradually toward Mars. Why this difference?
A) Phobos orbits Mars with a shorter period than Mars itself rotates.
B) Phobos is in a polar orbit rather than an equatorial orbit.
C) Phobos is in a retrograde orbit.
D) Phobos is in a highly eccentric orbit.
250. Phobos orbits Mars in a prograde orbit with a period less than the rotational period of Mars itself. What consequence follows from this?
A) Phobos rises in the west and sets in the east.
B) Phobos rises in the east and sets in the west.
C) Phobos is in a stationary orbit, always over the same point on Mars.
D) The situation described violates Kepler’s third law: the farther out an orbit, the longer its period.
251. Phobos and Deimos are moons of which planet?
A) Jupiter
B) Venus
C) Uranus
D) Mars
252. When were the two moons of Mars, Phobos and Deimos, discovered?
A) 1746
B) 1610
C) 1877
D) 1930
253. The moons of Mars are
A) ice-covered, approximately spherical, but flattened by rapid rotation.
B) spherical and have active volcanoes on their surfaces.
C) spherical and smooth-surfaced (no visible craters or volcanoes).
D) irregularly shaped, cratered, and grooved.
254. The shapes and sizes of the two moons of Mars are
A) spherical and quite large compared to the planet, about 1000 km in diameter, similar to the largest asteroid.
B) almost spherical but very small, only 10 and 30 km in diameter, respectively.
C) irregular, but quite large compared to the planet, between 500 and 1500 km across.
D) irregular in shape and very small, only several tens of kilometers across.
255. The Martian moon Phobos orbits near the equatorial plane of Mars in just over 7.5 hours in the same direction as the planet rotation. How then would one see Phobos move across the Martian sky from the surface of the planet?
A) Phobos would rise in the west, move rapidly across the sky, and set in the east, and it would do so only once per Martian day.
B) Phobos would rise in the east, move rapidly across the sky, set in the west, and appear several times per Martian day.
C) Phobos would remain almost stationary in the sky, in almost synchronous orbit, because its period is close to Mars’s rotation period.
D) Phobos would rise in the west, move rapidly across the sky, set in the east, and appear several times per Martian day.
Section: 8-15
256. According to modern dynamo theory, the production of a planetwide magnetic field around a terrestrial-type planet appears to require
A) rapid rotation and a molten metallic core.
B) a permanently magnetized solid metallic core.
C) a molten metallic core, with or without rotation.
D) rapid rotation and a metallic core, either solid or molten.
257. A global magnetic field generated from inside the planet is found around which terrestrial planet or planets?
A) Mercury, Venus, Earth, and Mars
B) Mercury and Earth
C) Mercury, Earth, and Mars
D) only Earth
258. An atmosphere containing a significant amount of oxygen is found around which terrestrial planet or planets?
A) Mercury, Venus, Earth, and Mars
B) Mercury and Earth
C) Mercury, Earth, and Mars
D) only Earth
259. If one characterizes the age of a surface by the age of the oldest feature that has been dated there, then the ages of these surfaces are, from youngest to oldest,
A) Venus, Mars, and the Moon.
B) Earth, Mars, and the Moon.
C) Earth, the Moon, and Mars.
D) Mars, the Moon, and Earth.
260. Which of these craters are the youngest?
A) oldest craters on Mercury
B) oldest craters on Venus
C) oldest craters on the Moon
D) oldest craters on Mars
261. The MOST heavily cratered planet in the solar system is
A) Mercury.
B) Venus.
C) Earth.
D) Mars.
262. Which of these properties do the terrestrial planets, Mercury, Venus, Earth, and Mars, have in common?
A) The terrestrial planets all orbit the Sun in a year or less.
B) The terrestrial planets all have solid surfaces.
C) The terrestrial planets are all cloud-covered.
D) The terrestrial planets all have very dense atmospheres.
263. The inner planets, in order of increasing planetary radius, are
A) Mercury, Venus, Earth, and Mars.
B) Mercury, Mars, Venus, and Earth.
C) Mercury, Earth, Venus, and Mars.
D) Mercury, Venus, Mars, and Earth.
264. The approximate pressures of the atmospheres at the surfaces of Mercury, Venus, and Mars, in terms of the pressure at the surface of Earth (known as 1 atmosphere), are, respectively,
A) 0; about 10 atmospheres; 1/10 atmosphere.
B) 1/100 atmosphere; almost 100 atmospheres; 1/10 atmosphere.
C) 1/10 atmosphere; almost 100 atmospheres; 1/10 atmosphere.
D) 0; almost 100 atmospheres; 1/100 atmosphere.
265. Which of these aspects is the MOST similar across all of the terrestrial planets?
A) All four terrestrial planets have permanent global magnetic fields.
B) All four terrestrial planets have strong day-night temperature variations.
C) All four terrestrial planets have an iron core, rocky mantle, and crust composed of lighter elements.
D) The four terrestrial planets have similar counts of craters per square mile on their surfaces.