关于这张图
Sand dunes of many shapes and sizes are common on Mars. In this example, the dunes are almost perfectly circular, which is unusual. They are still slightly asymmetrical, with steep slip faces on the south ends. This indicates that sand generally moves to the south, but the winds may be variable. This is part of a series of images to monitor how frost disappears in the late winter; this observation appears to be free of frost. A previous image shows when the surface was covered by frost. https://photojournal.jpl.nasa.gov/catalog/PIA25795
