THEMIS Image of the Day, January 3, 2019. Dark dunes fill part of the floor of this unnamed crater in Terra Sirenum. There are numerous gullies on the rim of the crater.
Winds are moving the sand towards the upper left of this image, filling the lower sections of many gullies.
Meanwhile, the gullies in the southern (bottom) part of the crater show signs of pasted-on terrain, which may be dust-covered snow or ice.