Nasa's Curiosity Rover Captures Petrified Sand Dunes on Mars

This sandstone outcrop - part of a geological layer that Curiosity's science team calls the Stimson unit - has a structure called crossbedding on a large scale that the team has interpreted as deposits of sand dunes formed by wind.

Similar-looking petrified sand dunes are common in the US southwest.

"Geometry and orientation of the crossbedding give information about the directions of the winds that produced the dunes," the US space agency said in a statement.

The Stimson unit overlies a layer of mudstone that was deposited in a lake environment.

Curiosity has been examining successively higher and younger layers of Mount Sharp, starting with the mudstone at the mountain's base, for evidence about changes in the area's ancient environment.

Outcrops of the Stimson unit sandstone are still accessible to the rover and researchers plan to use the rover to collect and analyse a drilled sample of Stimson unit sandstone this month.

Curiosity has been working on Mars since early August 2012. It reached the base of Mount Sharp last year after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain.