Deck 11: Mercury, Venus, and Mars: Terrestrial, yet Unique

Question 1

Which of these planets fits the following description: "a solid, cool surface, with occasional dust clouds and a thin CO₂ atmosphere"?

A)Venus
B)Jupiter
C)Mars
D)Mercury

Answer 1

C

Question 2

A friend who says that he is an astronomer claims that he was outside at midnight a few weeks ago looking at Mercury. What should be your response?

A)"Oh, you must have been in Australia or South America since Mercury can be seen at midnight only from the southern hemisphere."
B)"You must be mistaken, because Mercury NEVER appears in our midnight sky."
C)"Really! Have you just purchased a new telescope? Mercury can be seen at midnight only through a telescope."
D)"Congratulations, you have been fortunate enough to see Mercury on a very rare occasion."

Answer 2

B

Question 3

When Mercury is at greatest elongation it is sometimes at a more favorable position for viewing and sometimes at a less favorable position for viewing. What can change from one occurrence of greatest elongation to the next to cause this difference?

A)the eccentricity of Mercury's orbit
B)the inclination of Mercury's orbit relative to the ecliptic
C)the position of Mercury in its orbit
D)the direction in space of the semimajor axis of Mercury's orbit

Answer 3

C

Question 4

Mercury's orbital period around the Sun is 88 days, and its synodic period (the time from one inferior conjunction to the next) is 116 days. How often do we observe a transit of Mercury across the face of the Sun?

A)It occurs every 88 days.
B)It occurs every 116 days.
C)It occurs much less frequently than once every 116 days because Mercury's orbit is inclined 7° from the plane of the ecliptic.
D)We never see a transit of Mercury because it always crosses the face of the Sun when it is on the opposite side from Earth.

Question 5

When Mercury is at its least value of greatest elongation it is seen 18° from the Earth-Sun line. How long before sunrise (or after sunset) will Mercury be visible at this time?

A)18 minutes
B)a little less than 1 hour
C)2 hours
D)4 hours

Question 6

When Mercury is seen 18° from the Earth-Sun line, it will be visible a little less than 1 hour after sunset. What is the most important value in determining this time?

A)Mercury's rotation period about its axis
B)Mercury's sidereal period
C)Earth's rotation period about its axis
D)Earth's sidereal period

Question 7

Suppose you observe Mercury at each of the following phases and you extrapolate the full angular diameter from the part that you can see. At which phase will the angular diameter appear greatest?

A)full
B)first quarter
C)third quarter
D)crescent

Question 8

Why are there are so few solar transits of Venus across the Sun's face as it revolves in its orbit and passes through inferior conjunction?

A)The orbital plane of Venus is inclined at 3.4° to the ecliptic plane.
B)The synodic period of Venus is very long because of the relative orbits of Earth and Venus.
C)Venus revolves around the Sun in a retrograde direction compared to the other terrestrial planets.
D)Venus rotates on its axis in a retrograde direction compared to the other terrestrial planets.

Question 9

Why does Venus experience fewer transits of the Sun than does Mercury?

A)The orbit of Venus has a larger incline angle to the ecliptic than does the orbit of Mercury.
B)Mercury is closer to the Sun and thus orbits more frequently.
C)The retrograde rotation of Venus inhibits transits of the Sun.
D)The large eccentricity of Venus's orbit results in fewer transits.

Question 10

There are several reasons the surface of Mars is more easily seen from Earth than any other planet's surface. Which of the following is NOT one of those reasons?

A)relative proximity to Earth
B)high mountain ranges casting strong shadows and providing high-contrast images
C)visible high in the sky at midnight when at opposition
D)a thin, almost cloudless atmosphere

Question 11

Mars is best viewed from Earth when it is at opposition, but some occasions are more favorable than others. Why is this?

A)Mars has an elliptical orbit, and favorable oppositions occur when Mars is near perihelion in its orbit, and hence closest to Earth.
B)Mars has an elliptical orbit, and favorable oppositions occur when Mars is near aphelion in its orbit, and hence closest to Earth.
C)Mars's orbit is inclined at a significant angle to the ecliptic, so favorable oppositions occur when it is crossing the ecliptic plane while near opposition.
D)Even though Mars moves in a circular orbit, the orbit of Earth is elliptical, and so favorable oppositions occur when Earth is near perihelion.

Question 12

We have seen that our best Earth-bound views of Mercury and Venus occur when these planets are at their greatest elongations. Where is Mars when we have our best Earth-bound view of it?

A)greatest western elongation
B)greatest eastern elongation
C)conjunction
D)opposition

Question 13

When we view Mars at its most favorable opposition, a Martian would view Earth at:

A)most favorable opposition.
B)least favorable opposition.
C)superior conjunction.
D)inferior conjunction.

Question 14

How was Mercury's unusual spin-orbit coupling discovered?

A)Earth-based telescopes watched the movement of surface features on Mercury as it rotated.
B)It was determined by watching the phases of Mercury as observed from Earth.
C)It was not observed until a spacecraft was put into a permanent orbit around Mercury.
D)Radar waves were bounced off Mercury from an Earth-based radio telescope, and the Doppler shift of the reflections was measured.

Question 15

To what does the phrase "synchronous rotation" for an astronomical object (e.g., planet or moon) refer?

A)It has a rotation rate that is precisely maintained (e.g., 23 h 56 m 4.096 s for Earth).
B)For an object in an elliptical orbit, the rotation rate increases and decreases to match the changes in its orbital speed.
C)It completes precisely one rotation around its own axis for every orbit (1-to-1 spin-orbit coupling).
D)It has any rotation period that is in simple proportion to its orbital period (1-to-1 spin-orbit coupling, 3-to-2 spin-orbit coupling, etc.).

Question 16

The reason the temperature on the dark side of Mercury is warmer than originally expected is that:

A)Mercury's large iron core conducts heat through the planet.
B)Mercury does not rotate synchronously with its orbital period.
C)several very active volcanoes on Mercury, produced by tidal stresses from the Sun, produce excess heat.
D)winds in Mercury's tenuous atmosphere carry heat from the daytime side to the night side.

Question 17

If you are 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)? (See Figure 11-3.)
​
​

A)It is noon.
B)It could be any time, because Mercury rotates independently of its revolution.
C)It is midnight.
D)It is just after sunset.

Question 18

If you are on Mercury and the time is noon (Sun directly overhead), how many times will Mercury rotate on its axis before the Sun is again directly overhead? (See Figure 11-3.)
​
​

A)one
B)two
C)three
D)58 2/3

Question 19

Mercury obeys Kepler's third law a³/T² = 1. What is T in this equation?

A)Mercury's synodic period (in days)
B)Mercury's synodic period (in years)
C)Mercury's sidereal period (in days)
D)Mercury's sidereal period (in years)

Question 20

Mercury rotates once on its axis with respect to the distant stars in 58 2/3 days and has a sidereal period of 88 days. A star is overhead to an observer on Mercury at midnight. How many times will Mercury orbit the Sun before this star is again directly over the observer's head at midnight? (Draw a diagram to help with this exercise.)

A)It will never again reach this specific position.
B)one
C)two
D)three

Question 21

Of the facts listed below, three contribute to the unusual 3-to-2 spin-orbit coupling of Mercury's motion. Which one does NOT contribute?

A)The gravitational attraction between two masses decreases as the distance between the two masses increases.
B)Mercury's orbit is inclined at an unusually large angle to the ecliptic.
C)Mercury's orbit has an unusually large eccentricity.
D)Mercury is slightly oblong rather than perfectly round.

Question 22

The one terrestrial planet that rotates in the "wrong" direction (opposite to the planet's direction of revolution around the Sun) is:

A)Mars.
B)Earth.
C)Venus.
D)Mercury.

Question 23

The rotation rate of the planet Venus was first determined by measuring:

A)the time delay of radio pulses after reflection from the planet's surface.
B)the Doppler shift in radio waves reflected from the planet's surface.
C)photography from the Hubble Space Telescope at infrared wavelengths that penetrate the planet's clouds.
D)sequential photography of Venus from Earth.

Question 24

An explanation for the retrograde rotation (in a direction opposite to that of most other planets) of Venus that has received serious consideration is the:

A)frictional drag of its very dense atmosphere on the rotating planet throughout its history.
B)uneven pull of the Sun's gravitation due to the oblate shape of the Sun.
C)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.
D)combined gravitational effects of its neighboring planets, Mercury and Earth.

Question 25

If one were on the planet Venus viewing the Sun through the clouds, where would the Sun appear to rise as Venus rotated?

A)The Sun would rise in the east.
B)The Sun would rise in the north, because the spin axis of Venus is parallel to the plane of its orbit.
C)The Sun would not rise or set because Venus rotates synchronously, keeping one side always toward the Sun.
D)The Sun would rise in the west.

Question 26

What was required to obtain a visible-light image of the surface of Venus?

A)building a bigger visible-light Earth-based telescope
B)sending a visible-light telescope into orbit around Venus
C)sending an unmanned lander to the surface of Venus
D)sending a manned lander to the surface of Venus

Question 27

The tilt of the spin axis of Mars to the perpendicular to its orbital plane:

A)varies rapidly through the Martian year.
B)is 90°.
C)is 0°.
D)is very similar to that of Earth.

Question 28

In view of Mars's tilted angle of rotation at 25° to the ecliptic, its very similar rotation period to that of Earth (24 h, 37 min), and its orbital period of nearly 2 years, what will be the seasonal variations on Mars, compared to those upon Earth?

A)very similar seasonal variations, but each season lasting about half as long as those upon Earth because of the different orbital periods
B)very similar seasonal variations, including seasons lasting about as long as those upon Earth because of the similar rotation rates of the two planets
C)very similar seasonal variations, but with each season lasting twice as long as Earth's seasons
D)much smaller seasonal variations than Earth's seasonal variations because of Mars's distance from the Sun, each season lasting about twice as long as those upon Earth

Question 29

When do scientists think the Caloris Basin was formed, and why do they think this?

A)It must have been formed early in Mercury's history, because it is overlapped by many other craters, some of them quite large.
B)It must have been formed early in Mercury's history, because the shock wave that created the jumbled terrain on the opposite side of the planet could only pass through Mercury when it was in a semi-molten state.
C)It must have been formed about the middle of the Heavy Bombardment period, because the crater density within the basin is only about half the average crater density for Mercury.
D)It must have been formed at the end of the Heavy Bombardment period, because the crater density in the basin is very low compared to the average crater density for Mercury.

Question 30

The central core of Mercury is probably composed of:

A)molten rock.
B)solid rocks of relatively low density.
C)ices of H₂O and CH₄.
D)solid and/or molten iron.

Question 31

To explain the large iron core of Mercury, one theory suggests that as Mercury was forming as a planet it was struck by a large planetesimal, stripping away the mantle and leaving the iron core. This theory has the advantage because it also helps to explain Mercury's:

A)3-to-2 spin-orbit coupling.
B)highly elliptic orbit.
C)Caloris Basin.
D)slow rotation rate.

Question 32

Mercury's magnetic field, compared with that of Earth, is:

A)of equivalent strength.
B)weak, but strong enough to deflect the solar wind.
C)extremely weak, so it cannot prevent the solar wind from hitting the surface of Mercury.
D)much more powerful.

Question 33

What can we say about the abundance of volatile materials on Mercury?

A)The observed abundance of volatile materials is low. This is consistent with Mercury's formation close to the Sun, where volatile materials would be "boiled out" of the solar system.
B)The observed abundance of volatile materials is low. This is consistent with a large planetesimal striking Mercury and taking away the outer mantle-the usual explanation for Mercury's large iron core.
C)The observed abundance of volatile materials is low. This is consistent with the outer mantle of Mercury being stripped away in just a few minutes due to a large impact.
D)The observed abundance of volatile materials is high. This is inconsistent with Mercury's formation close to the Sun.

Question 34

What can be said about the presence of water on Venus?

A)The Venera lander first sampled the atmosphere and found abundant water vapor there.
B)Mariner 2 monitored the 1.35-cm line, which is absorbed by water. Little 1.35-cm radiation was absorbed, thus suggesting little or no water.
C)Mariner 2 monitored the 1.35-cm line, which is absorbed by water. Little 1.35-cm radiation was detected, suggesting it was absorbed by water vapor in the atmosphere.
D)Radio waves from Earth, bounced off of Venus, were used to measure the rotation rate of Venus. The same radio wave detector observed the radio waves associated with water, thus suggesting abundant water on Venus.

Question 35

The surface temperature of Venus was first measured by:

A)direct temperature measurement at the planet's surface by the Soviet lander Venera 7.
B)infrared emission from the lower atmosphere of Venus by astronomers at the Canada-France-Hawaii telescope on Mauna Kea.
C)radio emission from the planet's surface by the Arecibo radio telescope in Puerto Rico.
D)microwave emission from the planet's surface by the American spacecraft Mariner 2.

Question 36

The Venera series of spacecraft landed on which planet or moon?

A)Mercury
B)Venus
C)Mars
D)Earth's Moon

Question 37

To measure the surface temperature of Venus, Mariner 2 measured emissions with wavelengths of 1.35 cm and 1.9 cm. The temperature of Venus is 730 K. What is the peak wavelength in the emission spectrum of Venus?

A)1.35 cm
B)1.9 cm
C)4
? m
D)6 nm

Question 38

How did optical illusion mislead early visual observers of Mars?

A)Apparent movement of surface features, because of fluctuations in images when viewed through Earth's atmosphere, were interpreted as evidence for moving life-forms or Martians.
B)Volcano and rock structures were seen as eye shaped and face like and were interpreted as having been made by intelligent beings to indicate their presence.
C)Moving areas of obscured detail on the planet were interpreted as massive flash floods rather than dust storms.
D)Chance alignments of faint, dark features looked like canals whereas darker areas, when viewed against the orange-red surface, were interpreted as vegetation.

Question 39

Observers in the nineteenth century reported seeing many straight-line features crisscrossing the surface of Mars, and these were interpreted as canals constructed by intelligent beings. What is the most likely present-day explanation for these observations?

A)stationary linear cloud formations (mountain lee wave clouds) and weather fronts, rotating with the planet
B)optical illusions caused by vague shadings on the planet surface
C)rifts at the boundaries of geological tectonic plates
D)lines of volcanoes similar to those of the Hawaiian Islands on Earth

Question 40

The dark markings near the equator of Mars show seasonal variations because of:

A)changes in coverage of rocks by CO₂ ice as the temperature varies from above to below the freezing point of CO₂.
B)changes in the growth of vegetation.
C)changes in the flow of water released from permafrost by sunlight.
D)variations in the dust coverage of the surface.

Question 41

What effect causes the seasonal variation in color and shading of parts of the Martian surface?

A)changes in dust covering in response to wind storms
B)changes in the fluorescent glow caused by the varying intensity of solar UV radiation
C)growth and decay of vegetation
D)moisture falling as light rain, dampening the surface

Question 42

The dark, seasonal markings on Mars that grow in the spring and fade in the autumn are believed to result from:

A)microbial activity in the soil (or regolith).
B)lighting effects that vary as the angle of the Sun changes with the seasons.
C)dust being blown by winds, alternately covering and uncovering dark rocks.
D)plant life.

Question 43

One nineteenth-century observation, which convinced many of the existence of at least plant life on Mars, was the behavior of the polar caps and the dark areas. This means that the:

A)northern polar cap grows during the northern winter while the dark patches in the northern hemisphere turn white, suggesting that they become ice covered.
B)northern polar cap grows during the northern winter while the dark areas in the northern hemisphere begin to radiate in the ultraviolet and infrared.
C)polar caps are connected to each other by a network of canals.
D)dark areas in the northern hemisphere grow during the northern summer as the northern polar cap recedes.

Question 44

What can you determine from the topographic map of Mars in Figure 11-17?
​
​

A)The northern (upper) half is covered by an ocean.
B)The northern hemisphere is younger.
C)The northern hemisphere is older.
D)The entire southern hemisphere is at a higher elevation than the average elevation for Mars.

Question 45

One of the striking features of the overall surface of Mars is the:

A)two very distinct hemispheres, one of them lower and smoother than its counterpart and almost free of craters.
B)presence of active volcanoes and lava flows over the whole surface, including near to the poles, where these flows melt the icecaps regularly.
C)remarkable similarity of surface features across the whole of the planet, including uniform distribution of craters and ancient river valleys.
D)uniform distribution of water-ice frost over the whole surface, hidden in the shade of rocks, both winter and summer.

Question 46

Judging by the density of craters, which of the following lists the planets according to the age of the surface from youngest to oldest?

A)Earth, Venus, and Mercury
B)Earth, Mercury, and Venus
C)Venus, Earth, and Mercury
D)Mercury, Venus, and Earth

Question 47

At the present time, how many tectonic plates does Mars have?

A)zero
B)one
C)two
D)five

Question 48

The thickness of the crust of Mars has been measured to be different under two different hemispheres. How was this measurement made?

A)by radar measurements from an orbiting spacecraft, detecting radar waves reflecting back from the interface between crust and mantle on Mars
B)by drilling from Mars lander spacecraft into the crust of the planet, down to the mantle
C)by measuring the effect of slight differences in gravitational field upon the motion of a spacecraft orbiting Mars
D)by a seismology from the Mars landers, detecting the waves generated by Martian "earthquakes" as they passed through Mars

Question 49

What evidence exists of volcanic activity on Venus?

A)There is no evidence.
B)There is only the evidence of lava flows, which suggests active volcanoes as recently as 10 million years ago.
C)In addition to old lava flows scientists have measured variability of sulfur compounds during the past half century. This suggests active volcanoes now.
D)One of the Venera landers photographed a volcano in the act of erupting.

Question 50

Venus and Earth are about the same size, yet they have only one of the following characteristics in common. Which one?

A)evidence of planet-wide plate tectonics
B)volcanic activity
C)a planet-wide magnetic field
D)an atmosphere made up predominantly of greenhouse gases

Question 51

The surface of the planet Venus:

A)has several large volcanoes, but no extensive ridged or mountainous regions.
B)shows long mountain ranges similar to the Rockies and Andes ranges and the mid-ocean ridges on Earth.
C)has ridged and mountainous regions but no long, connected mountain ranges like the mid-ocean ridges on Earth.
D)is very smooth, with no mountains.

Question 52

Tectonic activity on Venus is characterized by:

A)large-scale convection currents in the mantle, which push several hard, lithospheric plates around on the surface.
B)constant resurfacing of the crust by lava floods, without separately identifiable upward and downward-flowing magma currents in the mantle.
C)a cool, solid mantle that has not driven any crustal deformation for the last 3.2 billion years.
D)hot-spot volcanism and localized regions of downwelling magma.

Question 53

Does Mars have a planet-wide magnetic field?

A)Yes, it does.
B)No, because the rotation rate is too slow to produce the necessary electric currents.
C)No, because the core is solid, not liquid.
D)No, because the core, although a liquid mixture of iron and sulfur, does not support electric currents.

Question 54

The magnetic field of Mars, compared to that of Earth, is:

A)nonexistent anywhere on the planet.
B)very similar in strength and orientation, its north-south axis being almost along the planet's spin axis.
C)localized and very weak.
D)much stronger, but with its north-south axis lying in the equatorial plane, the north pole coinciding with the large volcano, Olympus Mons.

Question 55

All of the following are characteristics usually associated with a planet-wide magnetic field. Which one does Mars lack?

A)some liquid in the core
B)some solid in the core
C)some electrically conducting material in the core
D)a relatively rapid rotation rate

Question 56

The clouds in the atmosphere of Venus consist primarily of:

A)dust particles.
B)droplets of liquid methane and ammonia.
C)droplets of H₂SO₄ or sulfuric acid.
D)H₂O.

Question 57

The atmosphere of Venus immediately above the surface of the planet, as discovered by the Venera spacecraft, can BEST be described as:

A)very dense, corrosive, and opaque clouds.
B)quite dusty.
C)very clear.
D)foggy.

Question 58

What phenomenon causes the V-shaped patterns that are a prominent feature on Venus?

A)circulation patterns of winds in clouds around the north pole of the planet, which points toward Earth once every synodic period of Venus
B)clouds blown by strong winds, dividing into north and south components around Maxwell Montes, the high mountain on the Ishtar Terra range
C)patterns in the sulfur dust storms on the surface of Venus
D)strong winds blowing from east to west, combining with north-south convection currents at cloud altitudes

Question 59

The relative rotation patterns of the Venusian atmosphere and Venus itself are:

A)fast (4 days) retrograde rotation of planet and slow (243 days) retrograde rotation of the upper cloud bank.
B)slow (243 days) prograde or direct planetary rotation and fast (4 days) retrograde rotation of the cloud tops.
C)slow (243 days) retrograde rotation of planet and rapid (4 days) retrograde rotation of upper atmospheric clouds.
D)no rotation of Venus itself, but atmospheric cloud tops rotate slowly (243 days) in a retrograde direction.

Question 60

Why did the Venera series of spacecraft survive for only a few minutes on Venus's surface?

A)They landed very fast because there was insufficient atmosphere to slow down their descent.
B)Conditions of extreme pressure, corrosive atmosphere, and high temperatures caused severe damage.
C)They were attacked and destroyed by native inhabitants, but the space agency is not telling the world of this.
D)They landed in very rugged terrain and were not able to land upright; they became damaged when they toppled over.

Question 61

The circulation pattern in Venus's atmosphere consists of:

A)one main convection cell in each of the northern and southern hemispheres, which extends from the equator almost to the poles and drives weaker cells above and below it.
B)three cells in each of the northern and southern hemispheres, resulting from upwelling at the equator combined with the Coriolis force due to the planet's rotation.
C)one main convection cell extending across the equator from near the pole in the "summer" hemisphere to subtropical latitudes in the "winter" hemisphere.
D)several individual convection cells in regions where the time of day is noon to late afternoon, moving around the planet to keep pace with the Sun as Venus rotates.

Question 62

What is the difference in temperature between the equator and the poles on Venus?

A)large but less than on Earth, because a very dense atmosphere on Venus conducts heat more efficiently than does our own atmosphere
B)almost none, because of a very efficient pattern of circulation in Venus's atmosphere
C)much larger than on Earth, because Venus lacks an ocean. On Earth, ocean currents such as the Gulf Stream transport heat from the equator to the poles.
D)extreme, because of a lack of any appreciable atmosphere on Venus results in extreme solar heating at the equator and uninhibited heat loss at the poles

Question 63

Why can permanent liquid water not exist on Mars today?

A)Both atmospheric pressure and surface temperature are too low, and any water would be in the form of ice or vapor.
B)The surface of Mars is too porous to allow water to remain on the surface.
C)Water would react with the CO₂ in the atmosphere to form carbonic acid, which would react quickly with the rocks on Mars to destroy the water.
D)Surface temperatures are too high, since at the low Martian atmospheric pressure, water would just boil away at the present Martian temperatures.

Question 64

The composition of the polar ice caps of Mars has been determined by each of the following methods EXCEPT one. Which one has NOT been used?

A)the soft landing of an unmanned space craft at the north pole
B)measuring from orbit the spectrum of sunlight reflected from the poles
C)measuring from orbit the temperature at the poles
D)using infrared cameras to probe the spectrum of the lower layers of the caps

Question 65

The northern Martian polar cap decreases in size during the northern Martian summer but does not completely disappear. What is the explanation for this?

A)The polar cap is composed entirely of solid carbon dioxide (dry ice).
B)The polar cap is composed partially of water ice.
C)Streams on the surface constantly keep the northern polar cap supplied with water during the summer.
D)The Martian atmosphere can hold only so much water vapor from the melting ice cap before the atmosphere becomes saturated.

Question 66

The initial and very rapid recession of the edge of the white polar cap region toward the poles in springtime is caused by:

A)the melting and evaporation of CO₂ ice.
B)the increased growth of vegetation toward the poles from mid latitudes.
C)the change in color of the rocks by photochemical action, similar to bleaching.
D)the melting of H₂O ice and subsequent runoff of water.

Question 67

Mars Odyssey was unsuccessful in detecting evidence of large bodies of frozen water well below the Martian surface. This is not surprising because:

A)the neutrons it was detecting can only escape from the top meter or so of the ground.
B)volcanic activity suggests it is too hot below the surface for frozen water to exist.
C)the lack of tectonic activity suggests that the crust of Mars is very solid with no possibility of water penetration in the past.
D)the spectral signature of H₂O, which Mars Odyssey was detecting, can only escape from the top few centimeters of the soil.

Question 68

The methane content of Mars's atmosphere is not constant but variable. All of the following processes could be responsible EXCEPT one. Which does NOT produce methane?

A)volcanic activity
B)dust devils
C)microbes
D)small meteorites exposed to ultraviolet radiation

Question 69

The "snow" that occasionally falls upon Mars and covers the bottoms of craters is most probably made of:

A)very fine white dust, disturbed occasionally by fierce wind storms.
B)carbon dioxide ice.
C)water ice.
D)frozen sulfuric acid droplets.

Question 70

In 2012, snow was observed falling above the south pole of Mars. This snow was composed of:

A)water.
B)carbon dioxide.
C)methane.
D)ammonia.

Question 71

On Mars, the air pressure varies much more from one season to another than it does on Earth. Why is this?

A)Seasonal dust storms on Mars blanket the entire planet, increasing the weight of the atmosphere.
B)Because the atmosphere of Mars is so thin, water vapor condensing on the polar ice caps in winter removes a much larger fraction of the atmosphere than on Earth.
C)Because of the low density of the atmosphere, solar heating has a much larger effect on Mars than on Earth.
D)On Mars, much of the CO₂, the major constituent of the atmosphere, condenses out to the surface as snow. This gas is only a minor constituent in Earth's atmosphere.

Question 72

What do we understand about the presence of H₂O on Venus?

A)There has probably never been a significant amount of water on Venus.
B)In the past, the atmosphere of Venus held significant amounts of water vapor, but it has always been too hot for liquid water to exist on the surface.
C)Oceans of liquid water once existed on the surface, but these evaporated and the water vapor was dissociated by ultraviolet radiation from the Sun.
D)Oceans of liquid water once existed, but this water is now locked up in various rocks on the surface.

Question 73

For hundreds of millions of years the surface of Venus, it is believed, was hot and humid, with the pressure of its thick water vapor-dominated atmosphere large enough to prevent liquid water from boiling away. What happened to disturb this equilibrium, raise the temperature, and boil away the liquid water?

A)Radioactivity in minerals in the mantle raised the surface temperature.
B)Bombardment by heavy impactors raised the surface temperature.
C)The Sun got hotter.
D)Friction with the dense atmosphere slowed the rotation of Venus so that the Sun was able to raise the temperature of the daytime hemisphere well above the boiling point.

Question 74

On both Earth and Venus some sulfur dioxide is removed from the atmosphere to be locked up in various rocks and minerals. On Earth this SO₂ is recycled deep beneath the surface to be outgassed by volcanoes and again become part of the atmosphere. On Venus this SO₂ is not recycled. Why this difference?

A)There are no active volcanoes on Venus.
B)Venus does not experience the movement of tectonic plates.
C)On Venus, the sulfur dioxide minerals are dissolved by acids in the atmosphere.
D)Because of the higher temperature on Venus, the SO₂ minerals formed there are different from those on Earth; they are essentially permanent and nonrecyclable.

Question 75

Carbonate rocks result from:

A)compression of frozen CO₂ (dry ice).
B)atmospheric carbon dioxide combining chemically with minerals in the soil or the planetary regolith.
C)cooling and solidification of magma in a CO₂-rich atmosphere.
D)carbon dioxide dissolved in water reacting with rocks, the residue being deposited in solid form.

Question 76

Carbonate rocks might be expected to be found on:

A)all rocky, planet-sized bodies: Mercury, Venus, Earth, Mars, and the Moon.
B)only Earth.
C)Earth and Mars.
D)the three largest terrestrial planets: Earth, Venus, and Mars.

Question 77

The greenhouse effect, which heats a planet's surface above the predicted equilibrium surface temperature for the planet without an atmosphere, is far less effective on Mars than on Earth. Why is this?

A)The Martian surface temperature is very low, and this reduces the effectiveness of the greenhouse effect.
B)There is less energy being conducted upward from the Martian interior to the surface of Mars because of the thickness of its crust compared to that of Earth.
C)The Martian atmosphere contains no gases that can absorb solar radiation.
D)The Martian atmosphere is very thin and traps less infrared radiation from the surface.

Question 78

Each of the following is a stage in the runaway icehouse effect believed to have operated on Mars in the past EXCEPT one. Which is NOT?

A)Rain and snow wash carbon dioxide out of the atmosphere.
B)The efficiency of the greenhouse effect changes.
C)The planet becomes warmer, allowing more carbon dioxide to escape into space.
D)The planet becomes cooler, allowing for more rain.

Question 79

The early Martian atmosphere probably contained as much nitrogen as Earth's atmosphere. But the present Martian atmosphere is less than 5% nitrogen gas. Where did the original nitrogen gas go?

A)It was locked up in the rocks and minerals of the Martian surface.
B)At the elevated temperatures of the early Martian atmosphere, nitrogen's average velocity was high enough to cause it to escape.
C)As UV-absorbing H₂O and CO₂ were depleted, UV radiation penetrated the Martian atmosphere. This was absorbed by N₂, which received enough energy to escape.
D)It is still present in nitric acid droplets and vapors in the Martian clouds.

Question 80

Each of the following supports the belief that large amounts of liquid water once existed on Mars EXCEPT one. Which is the exception?

A)Evaporites have been found on the surface.
B)There is a deficiency of neutrons (produced in collisions of cosmic rays with rocks below the surface) escaping from the surface.
C)Mud slides seem to follow some meteoric impacts.
D)Scientists have found few carbonate rocks on Mars.