Hundreds of crescent shaped pits on Mars were the sites of huge, ancient sand dunes – and could hold evidence of alien life, researchers say.
The curves of these ancient dune ‘ghost dunes’ record the direction of prevailing winds on the Red Planet, providing potential clues to Mars’s past climate.
Ghost dunes are the negative space left behind by long-vanished sand dunes. Lava or water-borne sediments partially buried the dunes and hardened, preserving the dunes’ contours.
Wind subsequently blew sand off the exposed tops and scoured it out from inside, leaving a solid mold in the shape of the lost dune.
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Ghost dunes were first discovered on Earth on the Snake River Plain in eastern Idaho in 2016.
The new study identified similar ghost dunes in satellite images of Hellas basin and Noctis Labyrinthus on Mars.
Dunes are a common feature on the wind-blown surface of the Red Planet, but the new study is the first report of preserved dune casts on Mars.
‘Any one of these pits is not enough to tell you that it’s a dune, or from an ancient dune field, but when you put them all together, they have so many commonalities with dunes on Mars and on Earth that you have to employ some kind of fantastic explanation to explain them as anything other than dunes,’ said Mackenzie Day, a planetary geomorphologist at the University of Washington in Seattle and an author of the new study
‘One of the cool things about the ghost dunes is that they tell us, for sure, that the wind on Mars was different in the ancient past, when they formed,’ she said.
Understanding the winds of the past can help researchers reconstruct how sediments could have traveled over the surface, how major features formed and if the ancient climate differed from modern atmospheric conditions, Day said.