When NASA’s Curiosity rover arrived at the “sulfate-bearing unit” last fall, scientists thought they’d seen the last evidence that lakes once covered this region of Mars. That’s because the rock layers here formed in drier settings than regions explored earlier in the mission. The area’s sulfates – salty minerals – are thought to have been left behind when water was drying to a trickle.
So Curiosity’s team was surprised to discover the mission’s clearest evidence yet of ancient water ripples that formed within lakes. Billions of years ago, waves on the surface of a shallow lake stirred up sediment at the lake bottom, over time creating rippled textures left in rock.
“This is the best evidence of water and waves that we’ve seen in the entire mission,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California. “We climbed through thousands of feet of lake deposits and never saw evidence like this – and now we found it in a place we expected to be dry.”
Layers of History
Since 2014, the rover has been ascending the foothills of Mount Sharp, a 3-mile-tall (5-kilometer-tall) mountain that was once laced with lakes and streams that would have provided a rich environment for microbial life, if any ever formed on the Red Planet.
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