Sand dunes on Mars are subject to variety of wind regimes and impacting conditions that have produced a diverse catalog of dune shapes and sizes. Simple wind regimes, where atmospheric flow is directed in one direction, typically lead to the formation of crescentic dunes called barchans. These simple dunes are common in craters across the Southern Highlands. For example, see this observation where a fleet of barchans are migrating to the left (west).

This region also hosts remarkably complex dunes like this field in the Hellespontus Montes mountain range (see clip1.png). Dunes here migrate both east and west, coalescing and eventually converging at a central area where star dunes are found. Diurnal and seasonal shifting winds are responsible for the dune’s formation and activity.

Ultimately, it is the outsized influence of the giant Hellas Planitia basin, which is directly to the east, that controls most of the regional atmospheric flow. (See also: Multidirectional Dune Dynamics Under Seasonal Winds on Mars).

Written by: Matthew Chojnacki  (5 April 2010)