How wind created mile high mounds on Mars

New York: Wind carved massive mounds of more than a mile high on Mars over billions of years, say researchers, suggesting that their location can help pin down when water on the Red Planet dried up during a global climate change event.

Wind could never do this on Earth because water acts so much faster, and tectonics act so much faster.First spotted during NASA's Viking programme in the 1970s, the mounds are at the bottom of craters. Recent analysis by the Mars rover Curiosity of Mount Sharp has revealed that the thickest ones are made of sedimentary rock, with bottoms made of sediments carried by water that used to flow into the crater and tops made of sediments deposited by wind.

However, how the mounds formed inside craters that were once full of sediments was an open question.To test whether wind could create a mound, the researchers built a miniature crater, filled it with damp sand and placed it in a wind tunnel. They tracked the elevation and the distribution of sand in the crater until all of it had blown away. Eventually all that was left of the sediment was a mound -- which, in time, also eroded away.