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 subsurface depths of Jezero Crater—rather than the surface, which NASA’s Perseverance rover has been exploring for the past five years. The site of a huge, dried-up lake, Jezero also hosts ancient river deltas. These deltas were laid down by flowing water as early as 3.7 billion years ago, and are so vast that they can be seen from orbit. Now, however, Perseverance’s ground-penetrating radar has found evidence of an even older river-and-delta system at Jezero buried deep below the surface.

Published today in the journal The progress of science, the findings suggest that the red planet’s habitability window extends even further back in time than many scientists had imagined.

“It widens the window for fluvial deposition on Mars,” says Emily Cardarelli, a scientist at the University of California, Los Angeles, and the study’s lead author. “On Earth, these conditions produce minerals that can preserve 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 Perseverance’s exploration zone because it has a wealth of fluvial features that suggest the crater was once ripe for life — and for preserving the traces of life in rock. The new study relies on data from 78 traverses of the area from September 2023 to February 2024.

The rover used its radar capabilities to study layers of sediment buried more than 100 feet (35 meters) below ground—almost twice as deep as it had previously probed—where it recorded echoes of even older river-carved slopes and meandering, meandering channels. These underground features, the researchers say, formed as early as 4.2 billion years ago, hundreds of millions of years before the water-washed terrain that Perseverance has studied on the surface. That means there were several sustained periods of water flow in the crater’s history—several possibilities scattered across Jezero’s deep past, where it may have harbored life.

The result also reinforces that Mars is now a planet almost frozen in time, with land far more undisturbed than any on Earth. “The fact that we have this record at this age is remarkable,” says Cardarelli. On Earth, rocks of similar age lost any distinct signature of ancient rivers long ago. “They’ve been heated, they’ve been squeezed, and they’ve been changed by water,” she says. “They’ve had a tough time.

With this more intact geological record, astrobiologists hope that Mars may provide not only the first smoking gun evidence of extraterrestrial life, but also clearer data on how that life arose in the first place. This question, it turns out, may be just as important to understanding the origins of life on Earth as well: circumstances suggest that ancient asteroid impacts much like the one that carved Jezero Crater could also have exported any early Martian life to our own world.

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

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

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