Dunes in Nectaris Montes

This image from NASA's Mars Reconnaissance Orbiter (MRO) shows some of these on the slopes of Nectaris Montes within Coprates Chasma. Sand dunes in Valles Marineris can be impressive in size, with steep slopes that seem to climb and descend.

The brighter bedforms are inactive while the bigger dunes move over the landscape, burying and exhuming the surface.

https://photojournal.jpl.nasa.gov/catalog/PIA22455