Mars rover snaps pictures of giant, dark sand dunes

The Mars rover Curiosity has moved in for a closer look at giant sand dunes on the Red Planet sending back fresh images of their dark, rippled surface along with a few partial selfies.

Pictures of the dunes, taken by the rover's black-and-white navigational cameras, were posted online by NASA late Thursday. They show a mix of sand, rocky terrain and large, grey hills in the distance; often with one of Curiosity's wheels or other components in the frame.

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The rover's latest effort marks the first time active sand dunes have been explored on another planet. It is hoped that theobservations will answer questions about how dunes and wind interact in a low-gravity, low-pressure environment.

"These dunes have a different texture from dunes on Earth," said Nathan Bridges of Johns Hopkins University who co-heads Curiosity's "dune campaign" in a statement.

"The ripples on them are much larger than ripples on top of dunes on Earth, and we don't know why."

The so-called Bagnold Dunes are on the northwestern flank of Mount Sharp, which Curiosity reached last year. One of the dunes is as large as a two-storey building and as broad as a football field, according to NASA. Observations from orbit indicate the dunes are moving about one metre per year.

Curiosity is monitoring the area's wind speed and direction, and will collect samples for analysis.

"We've planned investigations that will not only tell us about modern dune activity on Mars but will also help us interpret the composition of sandstone layers made from dunes that turned into rock long ago," said campaign co-head Bethany Ehlmann of the California Institute of Technology and NASA's Jet Propulsion Laboratory.

"We will use Curiosity to learn whether the wind is actually sorting the minerals in the dunes by how the wind transports particles of different grain size," Ehlmann said.

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Since landing in 2012,the rover has beenstudying how Mars's ancient environment changed from wet conditions favourable for microbial life to its current harsh and dry condition.

The rover suffered a short circuit during a drilling operation in February and was side-lined until mid-March. NASA says it has travelled about 315 meters in the past three weeks whiledrilling for samples around Mount Sharp.