Question 1

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.

Accepted Answer

Venus's atmosphere is characterized by a super-rotation, where the atmosphere rotates much faster than the planet itself. This results in a unique circulation pattern, with one dominant Hadley cell in each hemisphere extending from the equator to the poles, rather than the multiple cells found on Earth. This single cell in each hemisphere is responsible for the strong zonal winds and the transport of heat from the equator towards the poles.

Question 2

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

Accepted Answer

Venus has a very thick atmosphere composed mostly of carbon dioxide, with clouds of sulfuric acid, making it very efficient at circulating heat. This results in a relatively uniform temperature distribution across the planet, with little difference between the temperature at the equator and the poles.

Question 3

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.

Accepted Answer

Both the atmospheric pressure and surface temperature on Mars are too low, with surface temperatures too low to keep water from freezing or too high at the low atmospheric pressure, causing water to boil away. This means that any liquid water that may exist on Mars would quickly freeze or vaporize. Therefore, permanent liquid water cannot exist on Mars today.

Question 4

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

Accepted Answer

As of 2021, no soft landing of an unmanned spacecraft at the north pole of Mars has been conducted to determine the composition of the polar ice caps. However, the other three methods listed (measuring reflected sunlight, measuring temperature from orbit, and using infrared cameras to probe the spectrum) have been used to determine the composition of the ice caps.

Question 5

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.

Accepted Answer

The northern Martian polar cap is composed partially of water ice, which causes it to decrease in size during the summer but not completely disappear.

Question 6

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.

Accepted Answer

The initial and rapid recession of the edge of the white polar cap region toward the poles in springtime is primarily caused by the sublimation (transition from solid to gas) of CO2 ice, not by the melting of H2O ice or other processes.

Question 7

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.

Accepted Answer

The neutrons detected by Mars Odyssey can only penetrate the top meter or so of the Martian surface, making it difficult to detect evidence of large bodies of frozen water well below the surface.

Question 8

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

Accepted Answer

Dust devils are strong wind vortexes that can pick up and transport dust and small particles on the surface of Mars, but they do not produce methane. The other three processes have been suggested as possible sources of methane on Mars. Volcanic activity could release methane trapped in the subsurface, microbes could produce methane as a byproduct of their metabolism, and small meteorites exposed to ultraviolet radiation could generate methane through interactions with water and other compounds on the Martian surface.

Question 9

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.

Accepted Answer

Mars experiences snowfall primarily in the form of carbon dioxide ice, also known as dry ice, due to its thin atmosphere and cold temperatures.

Question 10

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.

Accepted Answer

The snow observed on the south pole of Mars was made up of carbon dioxide, not water, methane, or ammonia. Mars' atmosphere is made up primarily of carbon dioxide, which freezes at the planet's poles due to the extremely low temperatures.

Question 11

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.

Accepted Answer

On Mars, CO2, which is a major component of its atmosphere, condenses out as snow during winter, significantly reducing atmospheric pressure. This effect is much more pronounced than on Earth, where CO2 is only a minor component.

Question 12

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.

Accepted Answer

Oceans of liquid water once existed on the surface, but these evaporated and the water vapor was dissociated by ultraviolet radiation from the Sun.

Question 13

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.

Accepted Answer

The Sun's increasing luminosity over time likely contributed to the greenhouse effect on Venus, raising temperatures and causing water to evaporate.

Question 14

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.

Accepted Answer

Venus does not experience the movement of tectonic plates, which is a necessary process for the recycling of sulfur dioxide deep beneath the surface and the outgassing of it through volcanoes. Therefore, the sulfur dioxide minerals on Venus are not recycled and remain locked up in rocks and minerals.

Question 15

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.

Accepted Answer

Carbonate rocks are formed from the residue left over after carbon dioxide dissolved in water reacts with rocks. This process is known as chemical precipitation and can result in the formation of rocks such as limestone and dolomite.

Question 16

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.

Accepted Answer

Carbonate rocks are typically formed through the interaction of carbon dioxide (CO2) with water and minerals, processes that are known to occur on Earth and have also been observed on Mars, indicating the potential for carbonate rock formation on both planets.

Question 17

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.

Accepted Answer

The greenhouse effect relies on greenhouse gases in the atmosphere, such as carbon dioxide and methane, to trap and re-radiate infrared energy from the planet's surface. Mars has a very thin atmosphere with a low concentration of greenhouse gases, which means that the greenhouse effect is much less effective than on Earth. As a result, Mars has a much colder surface temperature than predicted by its distance from the sun and its lack of an atmosphere would suggest.

Question 18

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.

Accepted Answer

The runaway icehouse effect involves a planet cooling down, not warming up. The process described in option C, where the planet becomes warmer allowing more carbon dioxide to escape into space, is contrary to the cooling trend of an icehouse effect.

Question 19

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.

Accepted Answer

UV radiation penetrated the Martian atmosphere as UV-absorbing gases were depleted, providing enough energy for N₂ to escape.

Question 20

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.

Accepted Answer

The presence of carbonate rocks indicates that there was once a significant amount of liquid water on Mars, as these rocks form in water-rich environments. The other choices all support the belief that large amounts of liquid water once existed on Mars: evaporites suggest the presence of dried-up bodies of water, a deficiency of neutrons can be caused by the presence of hydrogen (which is a key component of water), and mudslides following meteoric impacts suggest the presence of wet, unstable soil.

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

The circulation pattern in Venus's atmosphere consists of:

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

Why can permanent liquid water not exist on Mars today?

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?

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

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

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

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?

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

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

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

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

Carbonate rocks result from:

Carbonate rocks might be expected to be found on:

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?

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?

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?

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

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