Martian Sand DunesWhat are these strange shapes on Mars? Defrosting sand dunes.
As spring now dawns on the Northern Hemisphere of Mars, dunes of sand
near the pole, as pictured
above, are beginning to thaw. The carbon
dioxide and water
ice
actually sublime
in the thin atmosphere directly to gas. Thinner regions of ice
typically defrost
first revealing sand whose darkness soaks in sunlight and accelerates
the thaw. The process might even involve sandy
jets exploding through
the thinning ice. By summer, spots
will expand to encompass the entire dunes. The Martian
North Pole is ringed
by many similar fields of barchan sand
dunes, whose strange, smooth arcs are shaped by persistent Martian
winds. |
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