A prime tourist attraction will be the Red Planet’s two giant polar ice caps, which feature two kinds of ice and differ in composition from those on the Earth. One type of ice cap is made of frozen water. These are a permanent fixture on the landscape and remain roughly the same for much of the Martian year. The other variety consists of dry ice, or frozen carbon dioxide, and they expand or contract depending on the season. In the summer, the dry ice vaporizes and disappears, leaving only the ice caps composed of water. As a result, the appearance of the polar ice caps will vary during the
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