At the bottom of a crater on Mars, these dunes are covered in sheets of dry ice. As sand blows across the top of the ice, the sheets break up and blow apart, creating these streaks and lozenges.
Writes HiRISE's Candy Hansen:
In the winter time at high northern latitudes the terrain is covered by carbon dioxide ice (dry ice). In the spring as this seasonal ice evaporates many unusual features unique to Mars are visible.
On the floor of this crater where there are no dunes, the ice forms an uninterrupted layer. On the dunes however, dark streaks form as surface material from below the ice is mobilized and deposited on top of the ice. In some cases this mobile material probably slides down the steep face of the dune, while in other cases it may be literally blown out in a process of gas release similar to removing a cork from a champagne bottle.
Here is the original image of the crater full of dunes taken by the HiRISE camera on the Mars Reconnaissance Orbiter.
Learn more at the HiRISE Lab site.
Images via NASA/JPL/University of Arizona