Dunes on Ice

Dark dunes caught in a crater in the southern midlatitudes appear to be slowly climbimg out of the crater. Winds push the sand to the NW (upper left), burying features on the crater wall that may be gullies. Gullies tend to be the youngest features in their environments, but this image may show an exception to the rule: the dark dunes override the gully-like features, so these features must have formed before the dark dunes encroached on them.