Sand dunes often accumulate in the floors of craters.

Sand dunes often accumulate in the floors of craters. In this region of Lyot Crater, NASA’s Mars Reconnaissance Orbiter (MRO) shows a field of classic barchan dunes on Jan. 24, 2018. Just to the south of the group of barchan dunes is one large dune with a…
http://myfusimotors.com/2018/12/09/once-in-a-blune-dune/