This view from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter shows two classes of aeolian bedforms within Proctor Crater. The relatively bright, small ridges are ripples. From their study on Earth, and close-up examination by the MER rovers (roving elsewhere on Mars), we know that ripples are composed of fine sand (less than 200 microns in diameter) or fine sand coated with coarser sand and granules. The larger, darker bedforms are dunes composed of sand, most likely of fine size.
Image Number: NASA-PIA11833
Credit: NASA/JPL-Caltech/University of Arizona
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