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How do the north and south polar caps of Mars differ during summer?
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Mars
An especially serene view of Mars (Tharsis side), a composite of images taken by the Mars Global Surveyor spacecraft in April 1999. The northern polar cap and encircling dark dune field of Vastitas Borealis are visible at the top of the globe. White water-ice clouds surround the most prominent volcanic peaks, including Olympus Mons near the western limb, Alba Patera to its northeast, and the line of Tharsis volcanoes to the southeast. East of the Tharsis rise can be seen the enormous near-equatorial gash that marks the canyon system Valles Marineris.
During the Martian summer, the north and south polar caps exhibit distinct behaviors regarding their composition and persistence:
- North Polar Cap: The seasonal cap, which is composed of frozen carbon dioxide, disappears completely during the summer. This process leaves behind a small, residual cap consisting of water ice.1
- South Polar Cap: Unlike the north, the south polar cap retains a small residual cap throughout the summer that is composed of both carbon dioxide ice and water ice.1
These seasonal changes are part of a cycle where polar caps grow during the fall as temperatures drop and recede during the spring. The underlying polar regions themselves consist of thick, layered sediments rich in water ice that remain exposed during the summer months after the seasonal carbon dioxide frost has sublimated.12