It's Avalanche Season On Mars : Big Pic
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March 16, 2010 -- Gliding high above Mars, taking photographs of ice-covered cliff faces from orbit, NASA's Mars Reconnaissance Orbiter (MRO) captured this stunning image of an avalanche rolling down an escarpment in the northern polar region (see the full image).
Mars is often considered to be a "dead" world with very little in the way of geological activity and weathering processes, but as this photograph proves, Mars is anything but dead. And what's more, the HiRISE camera onboard the MRO had the amazing fortune to capture this dynamic event as it happened.
Mars avalanches consist of dust, rock and ices, looking very much like their terrestrial counterparts (just with less snow and ski huts). However, they tend to be triggered when the Martian atmosphere heats up as the northern hemisphere enters springtime.
This seasonal heating is thought to cause the sublimation (i.e. the transition between ice and vapor, with no intermediate liquid phase) of carbon dioxide ice, venting into the atmosphere, dislodging loose rock from steep cliffs.
What makes this photograph even more exciting is that this isn't the first time a Martian avalanche has been caught on camera. In 2008, the same satellite beamed back images of multiple avalanches along another polar region escarpment. That was one Mars year ago (one Mars year lasts 687 Earth days), so it would appear that the onset of spring has triggered some more avalanche activity.
-- Ian O'Neill, Discovery News.
Image credit: NASA/JPL/University of Arizona.
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