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Hundreds of crescent-shaped pits on Mars may contain clues to the ancient life of the planet. These pits are a new type of dune on the surface of Mars and are now called ghost dunes.
The dunes are the most common features on the surface of Mars and they come in different shapes and sizes. The newly spotted ghost dunes are actually the negative space left by the long-disappeared sand dunes and are caused by the changing directions of the wind. When the wind blows and exposes the surface, it leaves a solid mold in the shape of the lost dune.
"No matter which of these pits is not enough to tell you that it's a dune, or an old dune field, but when you put them all together, they have so much In common with the dunes on Mars and Earth you have to use some kind of fantastic explanation to explain them other than as dunes, "said Mackenzie Day, a global geomorphologist at the University of Washington. in Seattle and author of the new study.
"One of the most interesting things about ghost dunes is that they tell us, for sure, that the wind on Mars was different in the past, when they formed. The fact that the wind was different (when the ghost dunes were formed) tells us that the environmental conditions on Mars are not static for long periods, they have changed over the last two billion years, something that we need to know to interpret the geology on Mars. "
Ghost dunes were discovered on Earth in eastern Idaho in 2016. Similar dunes were detected in satellite images of Hellas Basin and Noctis Labyrinthus on Mars. show that the minefield of Noctis Labyrinthus has more than 480 potential ghost dunes, while the smooth eastern surface of Hellas Planitia is covered with more than 300 crescent-shaped pits, which are strangely similar to the dunes of Barchan, the most common dune type on Mars and the deserts of the Earth The size and shape of the pits are compatible with active dune fields on Mars.
"They all go the same way, which is normal for the dunes as they migrate and form in the same wind regime "" So the shape and size tell us that these are features that come from an ancient dune system. "
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