Dunes Frozen in Time

Sand dunes are found in many places on Mars. At most of these places the dunes are slowly moving, blown by the wind, just like on Earth. However, in this location in south Melas Chasma they appear to have turned to stone. The large dunes are slowly being eroded and disappearing, replaced by smaller structures of scalloped sand. https://photojournal.jpl.nasa.gov/catalog/PIA23668