Author: Cara Giaimo / Source: Atlas Obscura

It’s not a great idea to sunbathe on Mars. But if you really wanted to, and you lived a few billion years ago, we now know where you might have gone. In a recent study in the Journal of Geophysical Research, planetary geomorphologist Mackenzie Day and astrobiologist David Catling announced their discovery of about 800 “ghost dunes”—the imprints of ancient sand piles—clustered in two different locations on Mars.
Examining these former dunes can tell us more about the red planet’s historic climate, and might contain more surprises as well.As Liza Lester explains at the American Geophysical Union’s GeoSpace blog, when the dunes formed, Mars was a little more exciting, with flowing water and active volcanoes. About two billion years ago, streams or lava flows began covering the dunes with sediment, which hardened around them like a mold. Then wind blew the sand away from the inside, leaving an empty shell behind—a “ghost dune.”

On Earth, you can find ghost dunes in the Snake River Plain, in Idaho. (They date…
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