6 Polar Caps
The permanent polar caps of Mars constitute the largest known reservoirs of H2O on the planet. The permanent caps are distinguished from the seasonal snow covers that have been known for centuries. The seasonal snow consists of CO2 that condenses out of the atmosphere in the winter hemisphere . During summer, the seasonal snow cover gradually evaporates, and the permanent cap is exposed. The permanent polar caps are recognisable as topographic domes rising about 3 km above the surrounding terrain. They have an extent of around 1000 km in the north and 400-800 km in the south. They consist of layers of H2O, dust and CO2 that have been deposited through millions of years. Bright white areas indicate a currently active interaction with the Martian climate system. Dark areas reveal an extensive layering thought to preserve a record of climate changes on Mars. The caps may contain preserved samples of biological origin, and geological indications of meltwater may be a clue to subsurface environments where life might exist. The polar regions are thus particularly interesting in relation to the search for life on Mars.
KeywordsSublimation Rate Seasonal Snow Cover Basal Melting Mars Orbiter Laser Altimeter Thermal Emission Spectrometer
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