Buried by ejecta

A Piece of Mars: To see this one well you’ll have to click on the image. At the lower right, a 240 m (787 ft) diameter crater formed when a bolide hit the surface, throwing out ejecta on the surrounding terrain. Zooming in, you can see that the ejecta has a distinctive rough surface. Farther from the crater there are smooth patches where ejecta didn’t fall. What I like about this is the many small bedforms (ripples), some of which are covered by ejecta and some of which aren’t. Closer to the crater, you don’t see so many of these bedforms because the ejecta is thick enough to have buried them. The crater itself is fairly “young” for a geologic feature on Mars, but enough time has passed to allow small bedforms to accumulate inside it (ripples like these don’t form overnight). (HiRISE ESP_052794_1545, NASA/JPL/Univ. of Arizona)

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