Astronomy Chapter 9 Homework
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Rank the five terrestrial worlds in order of size from smallest to largest.
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Moon, Mercury, Mars, Venus, Earth
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What is differentiation in planetary geology?
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The process by which gravity separates materials according to density
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When we say that a liquid has a high viscosity, we mean that it
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flows slowly like honey.
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The lithosphere of a planet is the layer that consists of
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the rigid rocky material of the crust and uppermost portion of the mantle.
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The core, mantle, and crust of a planet are defined by differences in their
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composition.
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The terrestrial planet cores contain mostly metal because
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metals sank to the center during a time when the interiors were molten throughout.
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Which of the following best describes convection?
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It is the process in which warm material expands and rises while cool material contracts and falls.
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Which internal energy source produces heat by converting gravitational potential energy into thermal energy?
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both A and B
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The main process by which heat flows upward through the lithosphere is
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conduction.
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Which of the terrestrial worlds has the strongest magnetic field?
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Earth
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Which of the following most likely explains why Venus does not have a strong magnetic field?
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Its rotation is too slow.
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Which of the following has virtually no effect on the structure of a planet?
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its magnetic field
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T/F: The strength of a rock depends on its composition, its temperature, and the surrounding pressure.
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True
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T/F: Very high pressures, like those found deep within planetary interiors, can compress rocks so much that they stay solid even when temperatures are high enough to melt them under ordinary conditions.
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True
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T/F: Earth is the only planet in the solar system known to have plate tectonics.
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True
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What is the longest-lasting internal heat source responsible for geological activity?
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radioactive decay
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Which of a planet's fundamental properties has the greatest effect on its level of volcanic and tectonic activity?
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Size
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Which two properties are most important in determining the surface temperature of a planet?
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distance from the Sun and atmosphere
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About how large (on average) is an impact crater compared to the size of the impactor?
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10 times larger
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When we see a region of a planet that is not as heavily cratered as other regions, we conclude that
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the surface in the region is younger than the surface in more heavily cratered regions.
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Shallow-sloped shield volcanoes are made from lava that
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has a medium viscosity.
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Which of the following describes erosion?
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the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
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What is basalt?
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a type of rock that makes relatively low-viscosity lava
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How did the lunar maria form?
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Large impacts fractured the Moon's lithosphere, allowing lava to fill the impact basins.
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Why does the Moon have a layer of powdery \"soil\" on its surface?
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It's the result of gradual erosion by micrometeorites striking the Moon.
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Why do we think Mercury has so many tremendous cliffs?
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They were probably formed by tectonic stresses when the entire planet shrank as its core cooled.
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Valles Marineris is a
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large canyon on Mars.
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The polar caps on Mars are composed of
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mostly solid carbon dioxide and some water ice.
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Choose the correct explanation of whether the discovery should be considered reasonable or surprising.
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This would be exciting, but not surprising. Heat from Martian volcanoes may well be enough to melt water under the Mars' surface.
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How have we been able to construct detailed maps of surface features on Venus?
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by using radar from spacecraft that were sent to orbit Venus
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Spacecraft have landed on all the terrestrial worlds except
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Spacecraft have landed on all of the terrestrial worlds.
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Why are there fewer large craters on the seafloor than on the continents?
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The seafloor crust is younger than the continental crust.
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Why is continental crust lower in density than seafloor crust?
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Continental crust is made from remelted seafloor crust and therefore only the lower-density material rises to form it.
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How fast do plates move on Earth?
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a few centimeters per year
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Deep trenches in the ocean mark places where
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one plate slides under another, returning older crust to the mantle.
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T/F: In the inner solar system, the largest surface features are found on the largest planets.
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False
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Choose the correct description of the conveyor-like action of plate tectonics on Earth.
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Earth's lithosphere is broken up into plates that float on the underlying mantle. The tops of the mantle's convection cells drag the bottoms of the plates, making them move. This movement causes spreading in some places and subduction in others.
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What do we conclude if a planet has few impact craters of any size?
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Other geological processes have wiped out craters.
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How many of the five terrestrial worlds have surfaces being constantly reshaped by plate tectonics?
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One
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The cores of the terrestrial worlds are made mostly of metal because ______.
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metals sunk to the centers a long time ago when the interiors were molten throughout
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Which of the following is not generally true of all the terrestrial world lithospheres?
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The lithosphere is broken into a set of large plates that float on the softer rock below.
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Which internal heat source still generates heat within the terrestrial worlds today?
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Heat from radioactive decay.
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The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that ________.
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a large baked potato takes longer to cool than a small baked potato
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Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
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On human time scales, the mantle looks like solid rock, so not much would be seen.
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Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?
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Mars's interior has cooled so much that its molten core layer no longer undergoes convection.
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Which of the following most likely explains why Venus does not have a global magnetic field like Earth?
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Its rotation is too slow.
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You discover an impact crater that is 10 kilometers across. Which of the following can you conclude?
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It was created by the impact of an object about 1 kilometer across.
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Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
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The maria formed after the heavy bombardment ended.
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Which of the following is the underlying reason why Venus has so little wind erosion?
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its slow rotation
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Which of the following best describes the geological histories of the Moon and Mercury?
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Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
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Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
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The high surface temperature that has \"baked out\" all the liquid water from Venus's crust and mantle.
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All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?
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Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.
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What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?
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plate tectonics and widespread erosion
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Why are there fewer large impact craters on the Earth's seafloor than on the continents?
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Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts.
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Why is Earth's continental crust lower in density than seafloor crust?
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Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones.
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Which two factors are most important to the existence of plate tectonics on Earth?
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mantle convection and a thin lithosphere
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What's the fundamental reason that Mars has so little geological activity compared to Earth?
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its small size compared to Earth
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Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny?
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its size
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The choices describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
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Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
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The choices describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
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Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
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The choices describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
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Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
