In a first for Martian water science, NASA’s Perseverance rover has discovered geological evidence of a large, fast-moving river in Mars’ ancient past. The high-energy river once emptied into Jezero crater, which the rover has been exploring since early 2021, and is a totally different water system than anything seen previously on the red planet.
“It’s the first time we’re seeing environments like this on Mars,” says Katie Stack Morgan, Perseverance’s deputy project scientist at the Jet Propulsion Laboratory. “We’re thinking about rivers on a different scale than we have before.”
These days, evidence for Mars’ wet history is plentiful. Back in 2004, the Opportunity rover landed near what was once the shore of a salty sea. The Curiosity rover is currently exploring an ancient lakebed in Gale crater, complete with wave-made ripples, and has seen evidence of small, shallow streams too. Meanwhile, China’s recently defunct (probably) Zhurong rover found evidence of liquid water in Mars’ more recent history.
What Perseverance is seeing now is new: a fast, high-energy river used to tear through the area, carrying large debris and building huge stacks of sedimentary rock that, though wind eroded, still stand out today.
One such outcrop, named Pinestand, is anomalously large, at 20 meters high, and has scientists wondering if there might be some other explanation. But on Earth, such a formation is most commonly caused by rivers.
NASA’s Perseverance Mars rover captured this mosaic of a hill nicknamed “Pinestand.” Credit: NASA/JPL-Caltech/ASU/MSSS.Just under half a kilometer from Pinestand lies another telltale formation, which the team has named Skrinkle Haven. Skrinkle Haven consists of a series of curved bands of rock, and likely represents either sandbars that formed within the river, or the former banks of the river that shifted over time.
Wind erosion has cut the top off of the Skrinkle Haven formations, which may have once been much taller. But despite the passage of time, these exposed features remain helpful to scientists trying to understand the region’s geologic history.
In fact, Skrinkle Haven’s features are prominent enough that the geologic unit they are part of had actually been seen years ago from orbit. Perseverance is finally getting a close-up look.
The fan-shaped river delta that Perseverance is now exploring, even from orbit, looks like it must have been formed by water, but it hasn’t been clear until now whether it was a series of small streams or a large rushing river. Evidence now points to the latter.
Artist’s impression of Jezero crater as it may have looked in the ancient past, with ancient rivers flowing into it. Credit: NASA/JPL-CalTech.The entire region features coarse sediment grains and cobbles which, according to JPL Postdoctoral researcher Libby Ives, “indicate a high-energy river that’s truckin’ and carrying a lot of debris. The more powerful the flow of water, the more easily it’s able to move larger pieces of material,” she said. “It’s been a delight to look at rocks on another planet and see processes that are so familiar.”
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Featured Image: NASA’s Perseverance Mars rover captured this scene at a location nicknamed “Skrinkle Haven” using its Mastcam-Z camera between Feb. 28 and March 9, 2023. Credit: NASA/JPL-Caltech/ASU/MSSS.
