NASA’s Perseverance Mars rover discovers even older lost rivers at Jezero Crater

NASA’s Perseverance Mars rover discovers even older lost rivers at Jezero Crater

By Joseph Howlett edited by Lee Billings

The latest evidence that Mars was once a warmer, wetter world comes from a surprising place — the hidden underground depths of Jezero Crater — rather than its surface, which NASA’s Perseverance rover has explored for the past five years. The site of a vast dry lake, Jezero is also home to ancient river deltas. Created by running water 3.7 billion years ago, these deltas are so extensive that they can be seen from orbit. Today, however, Perseverance’s ground-penetrating radar has found signs of an even older river and delta system at Jezero, buried deep beneath the surface.

Published today in the magazine Scientific advances, The results suggest that the Red Planet’s habitability window extends even further back in time than many scientists had imagined.

“This extends the window for river deposition on Mars,” says Emily Cardarelli, a scientist at the University of California, Los Angeles and lead author of the study. “On Earth, these conditions produce minerals capable of preserving fossils.

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Jezero is the crash site of an asteroid that slammed into the surface of Mars nearly four billion years ago. NASA chose it as the Perseverance exploration area because it has a wealth of riverine features that suggest the crater was once ripe for life and to preserve the telltale traces of life in the stone. The new study is based on data from 78 crossings of the area from September 2023 to February 2024.

The rover used its radar capabilities to study layers of sediment buried more than 35 meters underground, nearly twice as deep as it had previously probed, where it recorded echoes of river-cut slopes and even older winding, winding channels. According to the researchers, these underground features formed 4.2 billion years ago, hundreds of millions of years before the water-washed terrain Perseverance studied on the surface. This means there have been several sustained periods of water flow in the crater’s history – multiple opportunities scattered throughout Jezero’s deep past in which it could have harbored life.

The result also reinforces the fact that Mars is now a planet almost frozen in time, with land far less disturbed than any other planet on Earth. “The fact that we have this record at this time is remarkable,” Cardarelli says. On Earth, rocks of similar age have long lost any clear signatures of ancient rivers. “They were heated, crushed and altered by water,” she said. “They went through a difficult time.

With this more intact geological record, astrobiologists hope that Mars can provide not only the first-ever compelling evidence of extraterrestrial life, but also clearer data on how that life arose in the first place. It turns out that this question might be just as important for understanding the origins of life on Earth: circumstantial evidence suggests that ancient asteroid impacts, similar to the one that hollowed out Jezero Crater, might also have exported any early Martian life to our own world.

The new buried river delta “is very clear evidence of a long duration of activity,” says Jack Mustard, a planetary scientist at Brown University who has studied Jezero Crater extensively. “And that’s very exciting to have.” Mustard says the distinct delta beneath the ground is not surprising because periods of sporadic flow are common in the formation of rivers and lakes. “If you were to ask someone how the Mississippi Delta formed,” he said, “you would see several episodes of overlapping deltas. »

Cardarelli says we haven’t heard the last of Jezero from Perseverance. “There’s a lot more to say about this particular area and other areas inside the crater,” she says. “We’re still digesting all of our data.”

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