Word: aphelion
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Dates: during 1970-1979
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...possibility of monsoons is not as farfetched as it seems. Mars has an eccentric orbit that causes large variations in the planet's distance from the sun. The Martian north pole is currently tilted toward the sun only when the planet is also at its greatest distance, or aphelion, from the sun. In contrast, the southern hemisphere is tilted toward the sun at the planet's closest approach, or perihelion. As a result, the southern polar cap gets warm enough to evaporate almost completely each summer, releasing most of its dry ice into the atmosphere. The northern polar...
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