Weird and wild southern polar dunes

A Piece of Mars: This 0.96×0.48 km (0.6×0.3 mi) scene shows a bit of a south polar dune field. The more recently-active dark sand is rippled, but there are bright splotches where something else has happened. Presumably it’s ground ice that sublimated away explosively, as happens at many high latitude locations on Mars, only here

Is it an old fossil barchan dune?

A Piece of Mars: There are many barchans on Mars, those lovely isolated crescent-shaped dunes. In a few places there are what looks like ancient preserved barchans, now lithified. The mound in the center of this 0.96×0.54 km (0.6×0.33 mi) scene shows what may be an example of a fossil barchan. If so, then this

Sand tails

A Piece of Mars: Up on the tallest volcanoes, the wind screams downhill at night. This 500x500m (0.31×0.31 mi) scene shows how dust is carried downhill, but only that which is trapped behind boulders and crater rims sticks around. The big hole may be a window into a lava tube. Formation of the window itself