Dunefield in West Arabia Terra Unnamed Crater (extra-detail mgnf - RAW Frame; credits: NASA/JPL/Univ. of Arizona)

Barchan dunes are commonly found on Earth, and are generally crescent-shaped with a steep slip face bordered by horns oriented in the downwind direction (see here).
Barchan dunes form by unidirectional winds and are good indicators of the dominant wind direction. In this case, the strongest winds blew approximately North to South.

These dunes are most likely composed of basaltic sand that has collected on the bottom of the crater. Superimposed on their surface are smaller secondary dunes which are commonly seen on terrestrial dunes of this size.
Many smaller and brighter bed forms — most likely small dunes or granule ripples — also cover the substrate between the larger dark dunes.
The dark dunes overlie the small bright bed forms indicating that the darker dunes formed more recently.