NASA’s Curiosity rover recently spotted some of the most compelling evidence yet of ancient water on Mars, in the form of rippled rocks shaped by waves.
The ripples formed billions of years ago, when liquid water still covered the Martian surface. Across Mars, from the Curiosity rover near Gale Crater to Perseverance in Jezero Crater, probes are exploring these ancient waterbeds for intel on Mars’ geological history and its potential for astrobiology. Might there be fossilized microbes among all the red rocks and dust?
Curiosity began its mission in 2012 in the low elevations Gale Crater but is now on Mount Sharp, a 3-mile-high mountain once covered with lakes and streams. If life ever existed on Mars, from what we know of its presence on Earth, these ancient water pathways are a good place to look.
The rover spotted the rock textures—small ripples, looking a bit like dried-up tire treads—in a layer of rock on Mount Sharp called the Marker Band, according to a NASA release.
“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, in the release. “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.”
The Marker Band and its environs formed in drier climates than the areas Curiosity has already been through. In other words, the NASA team figured the water on Mars may have already vanished by the time the rock currently being studied was formed. There are ice sheets and ice caps on Mars’ poles, and meteorite impacts on the planet have kicked up subterranean ice, but liquid water hasn’t been on the planet for billions of years, at least as far as we know. Mars is cold and has a thin atmosphere, so water freezes at its surface, and the planet’s ancient water is thought to have mostly been lost to space (at least 87% of it, according to NASA).
The Marker Band is so hard that Curiosity has failed to take a sample of it even after several drilling attempts, but if the rover isn’t able to get a sample from softer rock, it still has exciting ventures ahead.
The Martian valley of Gediz Vallis holds an assortment of rocky debris scientists believe was swept there by ancient landslides. That makes the valley a repository of rocks from high on Mount Sharp, regions Curiosity wouldn’t be able to access. By probing those boulders, scientists will get insights about otherwise inaccessible stories from Mars’ past.
Though the recently found water ripples are some of the clearest evidence of ancient water on Mars, they’re hardly the first. Click through for other images that show how water has shaped the Martian landscape.