If Venus once had an ocean, where did it go?
Answer: a. It exists as abundant water vapor in the planet's atmosphere.
b. It was lost to space.
c. The water broke into hydrogen, which escaped to space, and oxygen, which became trapped in the planet's surface rocks.
d. It exists trapped in the crust but below the surface.
e. It is all frozen, in the form of large polar ice caps.
Mercury is a difficult planet to spot in Earth's sky because:
Answer: a. It is so small.
b. It is so faint.
c. It is always close to the sun.
d. all of the above
e. none of the above
What causes Mercury's 3:2 spin-orbit resonance?
Answer: a. The planet's nearness to the sun
b. The planet's very eccentric orbit
c. Tidal torques operating on the planet
d. all of the above
e. none of the above
What is thought to have caused the craters on Venus?
Answer: a. Most are volcanic in origin; some are due to meteoritic impacts.
b. As in the case of Mercury, all the craters are due to meteoritic impacts.
c. Because meteorites cannot survive passing through the atmosphere of Venus, all craters must be volcanic.
d. Venus has very few craters and their origin is not known.
Which of the following are greenhouse gases in the Earth's atmosphere?
Answer: a. carbon dioxide & oxygen
b. argon & water
c. water & oxygen
d. carbon dioxide & water
Which of the following characterizes a shield volcano?
Answer: a. It sits above a hot spot in the planet's mantle.
b. It is formed by moving tectonic plates.
c. It erupts only briefly before subsiding forever.
d. It cannot grow very large.
Why is one hemisphere of Mars believed to be older than the other?
Answer: a. One hemisphere is darker.
b. One hemisphere is more heavily cratered.
c. One hemisphere is lower.
d. One hemisphere leans more away from the Sun.
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