Last updated on April 25, 2014 at 1:22 EDT
Terraced Craters in Aitken Crater
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Terraced Craters in Aitken Crater

December 5, 2012
This crater has an unusual floor for its size. An impact crater of this size typically has a simple bowl shape, yet this example displays terraces and hummocks. The terraces give us insight into the impact material. A bolide that impacts a solid surface covered by loose material, for example mare covered by regolith, will use less of its energy to break up the loose material than solid material. The "excess" energy goes into excavating more material thus making for a larger diameter. Thus we see terrace at the boundary between the regolith and underlying more coherent material. The fact that the crater has no bright rays indicates that it is old - its rays have weathered into the background. LROC WAC context image of Kepler Crater showing the location of the boulder on the ejecta blanket [NASA/GFSC/Arizona State University].