Dark sand dunes on the surface of Mars are puzzling Nasa scientists, who have sent their Curiosity Mars rover to explore them. They hope to find out how Martian winds affect the distribution of sand on the Red Planet and shape these dunes in what is the first study of this kind outside Earth.

From February to April 2017, the Rover went on to investigate four different sites near a linear dune. The idea was to compare this data with previous information collected by the rover in late 2015 and 2016 – whose investigations had then focused on crescent-shaped dunes.

The linear dunes explored this year lie uphill and about 1.6 kilometres south from the crescent dunes but both study locations are part of a Martian dark-sand swath known as the Bagnold Dunes. They are in the vicinity of Mount Sharp, a layered mountain on Mars that the Curiosity Rover is climbing.

Using the Curiosity rover, scientists hope to answer a number of questions regarding the mysterious dunes. The most pressing is how wind is producing different-shaped dunes despite them being close to each other.

"At these linear dunes, the wind regime is more complicated than at the crescent dunes we studied earlier," said Mathieu Lapotre of Caltech, in Pasadena (California) who took part in planning for the dune campaign. "There seems to be more contribution from the wind coming down the slope of the mountain here compared with the crescent dunes farther north."

Other interrogations will also be addressed, including whether Martian winds sort grains of sand in ways that affect the distribution of mineral compositions – as this could change the way they then study Martian sandstones.

Martian dunes
This 360-degree mosaic from the Mast Camera (Mastcam) on NASA's Curiosity Mars rover looks out over a portion of the Bagnold Dunes which stretch for several miles. NASA/JPL-Caltech/MSSS

Beyond their analyses of the dunes, the Curiosity team is conducting a wider study of Mount Sharp. They have already discovered in the plains that surrounded the mountain evidence for ancient Martian lakes with the conditions to harbour life – but whether this life one day existed is still unknown.