In this nice, VIS image, taken by the NASA - Mars Odyssey Orbiter on September, 16th, 2015, and during its 61.026th orbit around the Red Planet, we can see almost one half of an Unnamed Impact Crater which contains a (truly) small Dunefield in the central part of its otherwise fully flat Floor.
This picture was collected during the Martian Northern Hemisphere's Spring, and the Dunes, as well as the Edges of the Crater, are still (partially) covered by Water-Ice Frost. However, as the season moves into the Northern Hemisphere's Summer, the Dunes - as well as the Edges of the Crater - will shed (---> get rid, be free of) the Frost, and then appear much darker (almost black, sometimes).
Just out of curiosity, this Unnamed Impact Crater is located in the Martian Region known as Vastitas Borealis.
Latitude (centered): 70,0743° North
Longitude (centered): 352,6330° East
This image (which is an Original Mars Odyssey Orbiter b/w and Map Projected frame published on the NASA - Planetary Photojournal with the ID n. PIA 20101) has been additionally processed, magnified to aid the visibility of the details, extra-contrast enhanced and sharpened, Gamma corrected and then colorized in Absolute Natural Colors (such as the colors that a normal human eye would actually perceive if someone were onboard the NASA - Mars Odyssey Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.