Astronomy 1010 Exam #2 Chapter 8 Questions and Answers Fully Solved Graded A+
The four planets closest to the Sun have similar compositions (rock/metal), and all have solid surfaces.
They are therefore grouped together as terrestrial ("Earth-like") planets. Even though they formed from
the same process of accretion in the Solar Nebula, you'll see here that their surfaces are significantly
different from one another.
Why are these planets so different? To answer this, we must start with an understanding of the
processes that cause planetary surfaces to change: volcanism, tectonics, erosion, and impacts. -
AnswersVolcanism/Tectonics: Rising mantle material
Erosion: Wind/Ice
Impacts: Meteorites
The level of each of the surface-shaping processes that occur on a planet throughout its history will
determine how its surface appears. The terrestrial planets were formed in basically the same
environment, so we can assume that the average frequency of impacts for all of the terrestrial planets
has been about the same.
In a hypothetical scenario where impacts are the only process that ever shape planetary surfaces, how
would the surfaces of the terrestrial planets compare?
(Tip: Note that "craters per area" refers to the number of craters in the same-sized region on each
planet—for example, craters per square meter.)
Choose one:
A. The larger planets would have more craters per area than the smaller planets.
B. All of the planets would have roughly the same number of craters per area.
C. The smaller planets would have more craters per area than the larger planets.
D. The planets closer to the Sun would have signi - AnswersB. All of the planets would have roughly the
same number of craters per area.
How would you explain the difference in cratering between these two pictures?
Image 1: Rough cratering
Image 2: Smooth surface, light cratering
, Choose one:
A. The surface on the left has experienced more recent volcanism or erosion than the surface to the
right.
B. The surface on the right has experienced more recent volcanism or erosion than the surface to the
left.
C. The surface on the right had fewer impacts by random coincidence. - AnswersB. The surface on the
right has experienced more recent volcanism or erosion than the surface to the left.
This image shows the relative sizes of the terrestrial planets and their order from the Sun (closest
toward the left, farthest toward the right). Assume that, based on crater counts, the geological age of
the planetary surfaces from oldest to youngest is Mercury, Mars, Venus, Earth.
Based on the information above, which of the following properties of a planet is most important in
determining its level of recent geological activity?
Choose one:
A. amount of water on the surface
B. rotation rate
C. albedo (percentage of sunlight that is reflected from the surface)
D. size
E. distance from the Sun - AnswersD. size
Observations show that, in general, larger planets and moons have had geological activity more recently
than smaller bodies have. All of the planets show past signs of volcanism, tectonics, and/or erosion, but
only the larger ones are still geologically active today. Why is this? One reason has to do with the
planet's interior. Most of the heat inside of Earth is left over from the accretion process during Earth's
formation. What would you expect to have happened as the Earth (or any other planet) cooled after its
formation?
Choose one:
A. The hard crust thickened, closing off volcanic vents, and the mantle began to solidify, slowing the
motion that causes volcanism and tectonics.
B. The hard crust became thinner, cracking more easily, and the mantle moved more freely, increasing
the motion that causes volcanism and tectonics.
The four planets closest to the Sun have similar compositions (rock/metal), and all have solid surfaces.
They are therefore grouped together as terrestrial ("Earth-like") planets. Even though they formed from
the same process of accretion in the Solar Nebula, you'll see here that their surfaces are significantly
different from one another.
Why are these planets so different? To answer this, we must start with an understanding of the
processes that cause planetary surfaces to change: volcanism, tectonics, erosion, and impacts. -
AnswersVolcanism/Tectonics: Rising mantle material
Erosion: Wind/Ice
Impacts: Meteorites
The level of each of the surface-shaping processes that occur on a planet throughout its history will
determine how its surface appears. The terrestrial planets were formed in basically the same
environment, so we can assume that the average frequency of impacts for all of the terrestrial planets
has been about the same.
In a hypothetical scenario where impacts are the only process that ever shape planetary surfaces, how
would the surfaces of the terrestrial planets compare?
(Tip: Note that "craters per area" refers to the number of craters in the same-sized region on each
planet—for example, craters per square meter.)
Choose one:
A. The larger planets would have more craters per area than the smaller planets.
B. All of the planets would have roughly the same number of craters per area.
C. The smaller planets would have more craters per area than the larger planets.
D. The planets closer to the Sun would have signi - AnswersB. All of the planets would have roughly the
same number of craters per area.
How would you explain the difference in cratering between these two pictures?
Image 1: Rough cratering
Image 2: Smooth surface, light cratering
, Choose one:
A. The surface on the left has experienced more recent volcanism or erosion than the surface to the
right.
B. The surface on the right has experienced more recent volcanism or erosion than the surface to the
left.
C. The surface on the right had fewer impacts by random coincidence. - AnswersB. The surface on the
right has experienced more recent volcanism or erosion than the surface to the left.
This image shows the relative sizes of the terrestrial planets and their order from the Sun (closest
toward the left, farthest toward the right). Assume that, based on crater counts, the geological age of
the planetary surfaces from oldest to youngest is Mercury, Mars, Venus, Earth.
Based on the information above, which of the following properties of a planet is most important in
determining its level of recent geological activity?
Choose one:
A. amount of water on the surface
B. rotation rate
C. albedo (percentage of sunlight that is reflected from the surface)
D. size
E. distance from the Sun - AnswersD. size
Observations show that, in general, larger planets and moons have had geological activity more recently
than smaller bodies have. All of the planets show past signs of volcanism, tectonics, and/or erosion, but
only the larger ones are still geologically active today. Why is this? One reason has to do with the
planet's interior. Most of the heat inside of Earth is left over from the accretion process during Earth's
formation. What would you expect to have happened as the Earth (or any other planet) cooled after its
formation?
Choose one:
A. The hard crust thickened, closing off volcanic vents, and the mantle began to solidify, slowing the
motion that causes volcanism and tectonics.
B. The hard crust became thinner, cracking more easily, and the mantle moved more freely, increasing
the motion that causes volcanism and tectonics.
