Photo: Martian "Lake Michigan" Filled Crater, Minerals Hint



Layers of clay and sulfate create a bright "bathtub ring" around Columbus crater, seen in a closeup on the crater's rim taken by the Mars Reconnaissance Orbiter.

These hydrated minerals, known to form only in the presence of water, suggest that the crater once held a body of water the size of Lake Michigan, a November 2009 study says.

Picture courtesy NASA/JPL/University of Arizona


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