Problem Set 4 Solutions

# Problem Set 4 Solutions - Chapter 8 Review and Discussion 4...

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Chapter 8 Review and Discussion 4. Employ the concept of escape speed to explain why the Moon and Mercury have no significant atmospheres. Both the Moon and Mercury have low masses and low escape velocities. Yet both objects are in the inner solar system and experience high daytime temperatures. All gases, at these temperatures, will exceed the escape velocity. Neither object, then, has been able to hold an atmosphere. 6. Why is the surface of Mercury often compared with that of the Moon? List two similarities and two differences between the surfaces of Mercury and the Moon. Both Mercury and the Moon are heavily cratered. The crater walls on Mercury are generally not as high as on the Moon, however, and material ejected by striking meteorites landed closer to the impact site, just as you would expect on a world whose gravity is stronger than that of the Moon. Also, Mercury lacks extensive lava flow regions akin to the lunar maria. 9. What is a scarp? How are scarps thought to have formed? Why do scientists believe that the scarps formed after most meteoritic bombardment ended? A scarp is a cliff formed when Mercury’s surface wrinkled due to cooling. Scarps are found crossing craters, indicating they are younger than the craters. 13. In contrast with Earth, the Moon and Mercury undergo extremes in temperature. Why? The extreme temperature variations of Mercury are due, in part, to its lack of an atmosphere. An atmosphere helps to insulate the surface of a planet from cooling at night. Mercury’s very long day (slow rotational period) also plays a role. The Sun is up for a long period, allowing the rock to heat up. With an equally long night, there is ample time to cool down to a low temperature. Earth, in contrast to Mercury, rotates rapidly and has less time to heat up to high temperatures or cool down to low temperatures. 15. Describe the theory of the Moon’s origin favored by many astronomers. The favored theory for the formation of the Moon is that a large body, maybe Mars-sized, struck the Earth a glancing blow. Material thrown off could have then coalesced into forming the Moon. This theory explains two major features of the Moon. If the Earth was young but already differentiated enough to have an iron core and rocky mantle, the Moon would have formed primarily out of mantle material. This is consistent with the Moon being composed of rock very similar to the Earth’s mantle and explains why the Moon appears to have no iron core. 1

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Problems 2. The Moon’s mass is 1/80 that of Earth, and the lunar radius is 1/4 Earth’s radius. Based on these figures, calculate the total weight on the Moon of a 100-kg astronaut with a 50-kg spacesuit and backpack, relative to his weight on Earth. Newton's law of gravity states that the gravitational force is proportional to the product of the masses and
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Problem Set 4 Solutions - Chapter 8 Review and Discussion 4...

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