Perseverance Confirms Jezero Crater Was Once a Lake

Mars today is a dry, inhospitable desert. But billions of years ago, it could have looked a lot like Earth, with liquid water flowing over its surface. Now, new analysis of data from the Perseverance rover confirms that the Jezero Crater, where the rover is currently exploring, was once a large lake and was even subject to flash floods. The presence of water supports the possibility that life could once have blossomed on Mars.

The analysis is based on images of the rocks on the western side of the Jezero Crater, which appears to be a river delta. Here, layers of sediment have been laid down in a fan shape which looks a lot like river deltas on Earth where a river flows into a lake. An international team of researchers found that the sedimentary layers confirm the presence of an ancient lake that was calm throughout its early life but later flooded dramatically.

“If you look at these images, you’re basically staring at this epic desert landscape. It’s the most forlorn place you could ever visit,” said Benjamin Weiss, professor of planetary sciences in MIT’s Department of Earth, Atmospheric and Planetary Sciences and a member of the analysis team. “There’s not a drop of water anywhere, and yet, here we have evidence of a very different past. Something very profound happened in the planet’s history.”

The researchers were able to tell that there was significant flooding due to the presence of large boulders up to 1 meter across which were embedded into the younger layers of the delta. These large boulders must have come from outside the crater, having been carried a distance of 40 miles or more by huge floods. The fact they sit on top of many older layers shows that the floods must have happened late in the lake’s history.

“You need energetic flood conditions to carry rocks that big and heavy,” said Weiss. “It’s a special thing that may be indicative of a fundamental change in the local hydrology or perhaps the regional climate on Mars.”

Researchers have long believed that Jezero was once a lake, hence the choice of this location for Perseverance to explore, but this couldn’t be totally confirmed until the rover visited the site and gathered data. Now, they can be sure that there was once abundant water there and that it was present for long enough for life to have potentially emerged.

“We now have the opportunity to look for fossils,” said team member Tanja Bosak, professor of geobiology at MIT. “It will take some time to get to the rocks that we really hope to sample for signs of life. So, it’s a marathon, with a lot of potential.”

The findings are published in the journal Science.

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