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The Moon today The Moon today
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What the Moon is made of What the Moon is made of
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The Moon’s orbit The Moon’s orbit
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The fission theory The fission theory
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The capture hypothesis The capture hypothesis
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The coaccretion hypothesis The coaccretion hypothesis
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The giant impact hypothesis The giant impact hypothesis
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Encounter with Theia Encounter with Theia
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Earth, Moon, and tidal forces Earth, Moon, and tidal forces
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Late heavy bombardment Late heavy bombardment
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Cite
Abstract
This chapter considers how the very existence of the Moon, the only large satellite in the inner solar system, is a puzzle. The Moon is sufficiently large that one would think of it as a planet if it traveled around the Sun rather than Earth. Much of what the public now knows about the Moon comes from space missions, beginning in the 1960s and early 1970s. Six American Apollo missions each landed two astronauts on the surface. Three of the Soviet Union's unmanned Luna spacecraft touched down on the surface and then returned to Earth. After a long gap, lunar exploration resumed in the 1990s, when NASA's Clementine and Lunar Prospector spacecraft went into orbit. Recently, the pace of exploration has increased again, with the European Space Agency, Japan, China, and India, as well as NASA, all sending missions to the Moon.
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