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Sunday, May 5, 2002 Why the Poles are Different Different poles. Credit: NASA (CNN) - The north and south poles on Mars look extremely different from each other, and scientists now think they know why: Circulation patterns in the red planet's thin atmosphere tends to keep all the water in the north, leaving the south pole high and dry. Mars exploration by unmanned spacecraft has shown the northern hemisphere has a large polar cap made up mostly of frozen water while the southern hemisphere has a much smaller cap made up almost entirely of frozen carbon dioxide, or dry ice. A new computer model suggests the apparently permanent difference results partly from the much higher elevation in the south -- which is an average of three miles higher than the north. "It seems quite plausible to me," Hinson said. "I think it's an important step in understanding how climate change on Mars might be occurring." @ 14:49 EST