Possible rewrites:- Martian river’s history may be revealed in Perseverance’s images- Perseverance rover’s photos could document a once-wild river on Mars- Record of ancient Martian river may be captured in Perseverance’s pictures

New images taken by NASA’s Perseverance rover may show signs of a once-powerful river on Mars, which was deeper and faster-moving than scientists have ever seen evidence for in the past. The river was part of a network of waterways that flowed into Jezero Crater, the area the rover has been exploring since landing more than two years ago. Understanding these watery environments could help scientists in their efforts to seek out signs of ancient microbial life that may have been preserved in Martian rock.

Perseverance is exploring the top of a fan-shaped pile of sedimentary rock that stands 820 feet (250 meters) tall and features curving layers suggestive of flowing water. Scientists want to answer whether that water flowed in relatively shallow streams or a more powerful river system. Two new mosaics stitched together from hundreds of images captured by Perseverance’s Mastcam-Z instrument reveal important clues: coarse sediment grains and cobbles.

“Those 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,” said Libby Ives, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory. Following the Curves, scientists noticed a series of curving bands of layered rock within Jezero Crater that they dubbed “the curvilinear unit.” They could see these layers from space but are finally able to see them up close, thanks to Perseverance.

One location within the curvilinear unit, nicknamed “Skrinkle Haven,” is captured in one of the new Mastcam-Z mosaics. Scientists are sure the curved layers here were formed by powerfully flowing water, but Mastcam-Z’s detailed shots have left them debating what kind: a river such as the Mississippi, which winds snakelike across the landscape, or a braided river like Nebraska’s Platte, which forms small islands of sediment called sandbars.

A second mosaic captured by Perseverance shows a separate location that is part of the curvilinear unit and about a quarter mile (450 meters) from Skrinkle Haven. “Pinestand” is an isolated hill bearing sedimentary layers that curve skyward, some as high as 66 feet (20 meters). Scientists think these tall layers may also have been formed by a powerful river, although they’re exploring other explanations, as well.

The team is continuing to study Mastcam-Z’s images for additional clues. They’re also peering below the surface, using the ground-penetrating radar instrument on Perseverance called RIMFAX (short for Radar Imager for Mars’ Subsurface Experiment). What they learn from both instruments will contribute to an ever-expanding body of knowledge about Mars’ ancient, watery past.