2023-05-16 17:00:00
New images obtained by NASA’s Perseverance rover could show signs of what was once a mighty river on Mars, which would have run deeper and faster than scientists have had evidence in the past. The river was part of a network of waterways that emptied into Jezero Crater, the area the rover has been exploring since it landed more than two years ago.
Understanding these aquatic environments would help scientists in their efforts to find signs of ancient microbial life that might have been preserved in Martian rocks.
Perseverance is exploring the top of a fan-shaped clump of sedimentary rock that is 250 meters (820 feet) tall and shows curving layers that suggest a stream of water. One question scientists want to answer is whether that water flowed in relatively shallow streams — more like those in Gale Crater, based on evidence from NASA’s Curiosity rover — or in a more powerful river system.
Two new mosaics pieced together from hundreds of images captured by Perseverance’s Mastcam-Z instrument suggest the latter, revealing important clues: coarse sediment grains and pebbles.
“These materials indicate a high-energy river that would be transporting a large amount of debris. The more powerful the flow of water, the more easily it can move larger chunks of material,” said Libby Ives, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory (JPL) in Southern California. who is in charge of operating the Perseverance rover. An expert in the study of Earth’s rivers, Ives has spent the last six months analyzing images of the red planet’s surface. “It’s been a delight to look at rocks on another planet and see processes that are so well known,” said Ives.
following the curves
Years ago, scientists observed a series of curved bands in the rock layers inside Jezero crater that they called “the curvilinear unit.” They were able to see these layers from space, but now they can finally see them up close, thanks to Perseverance.
A spot within the curvaceous unit, dubbed “Skrinkle Haven,” is captured in one of Mastcam-Z’s new mosaics. Scientists are sure the curving layers here were formed by a powerful flow of water, but detailed Mastcam-Z shots have left them debating what kind of flow it would be: a river like the Mississippi, meandering through landscape, or a braided current like the Nebraska Platte, which forms small islands of sediment called shoals.
Perseverance, NASA’s Mars rover, captured this mosaic of a hill nicknamed the “Pinestand.” Scientists believe that the high sedimentary layers piled on top of each other at this site could have been formed by a deep, fast-flowing river.
Credit: NASA/JPL-Caltech/ASU/MSSS
When viewed from the ground, the curved layers appear arranged in rows that stretch across the landscape. They could be the remains of a river bank that changed over time, or the remains of sandbanks that formed in the river. The layers were probably much higher in the past. Scientists suspect that after these clumps of sediment became rock, they were eroded by the wind over billions of years and sculpted to their current size.
“The wind has acted like a scalpel that has cut through the top of these reservoirs,” said Michael Lamb, a Caltech researcher who is a river specialist and a contributor to the Perseverance science team. “On Earth we see deposits like this, but they are never as exposed as they are here on Mars. The Earth is covered in vegetation that hides these layers.
A second mosaic captured by Perseverance shows a separate location that is part of the curvilinear unit and is about a quarter mile (450 meters) from Skrinkle Haven. “Pinestand” is an isolated hill with sedimentary layers that curve skyward, some as high as 20 meters (66 feet). Scientists believe that these upper layers could also have been formed by a mighty river, though they are exploring other explanations as well.
“These layers are abnormally high for rivers on Earth,” said Ives. “But at the same time, the most common way to create these types of landforms would be a river.”
The team continues to study the Mastcam-Z images for additional clues. They are also looking below the surface, using the ground-penetrating radar instrument called the Radar Imager for the Subsurface Mars Experiment (RIMFAX) aboard Perseverance. What they learn from both instruments will contribute to an ever-expanding body of knowledge about Mars’ ancient aquatic past.
“The exciting thing here is that we have entered a new phase in the history of Jezero. And it’s the first time we’ve seen environments like this on Mars,” said Perseverance deputy project scientist Katie Stack Morgan of JPL. “We are thinking about rivers on a different scale than we had before.”
More about the mission
A key goal for the Perseverance Mars mission is astrobiology, which includes searching for signs of ancient microbial life. The rover will characterize the planet’s past geology and climate, pave the way for human exploration of the red planet, and be the first mission to collect and store Martian rocks and regoliths (loose rock and dust).
Subsequent NASA missions, in cooperation with ESA (European Space Agency), would send spacecraft to Mars to collect these sealed samples from the surface and bring them back to Earth for in-depth analysis.
The Mars 2020 Perseverance mission is part of NASA’s Moon to Mars exploration focus, which includes the Artemis missions to the Moon that will help prepare humanity for exploration of the red planet.
JPL, which is managed by Caltech for NASA in Pasadena, California, built and manages operations of the Perseverance rover.
For more information on Perseverance, visit the website: mars.nasa.gov/mars2020/
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