Images taken by NASA’s Perseverance rover confirm that Mars’ Jezero crater was once a calm lake, constantly fed by a small river about 3.7 billion years ago.
The study shows the amount of water that flowed into the crater (which today is a dry, wind-eroded depression) and indicates where the rover could look for signs of life.
The first scientific analysis of the images also reveals evidence that the crater was flooded.
This flood was vigorous enough to sweep large pebbles tens of miles upstream and deposit them on the lake bed, where the massive rocks still stand.
The researchers based their findings on images of the rocks inside the crater on its western side.
The satellites had previously shown that this outcrop, when viewed from above, resembled the deltas of the Earth River, where fan-shaped layers of sediment are deposited while the river feeds into a lake.
Taken from inside the crater, new images confirm that this outcrop was indeed a river delta.
According to the study, the lake was quiet for much of its existence, until dramatic climate change triggered episodic floods at the end or toward the end of the lake’s history.
Benjamin Weiss, a professor of planetary science in the department of earth, atmospheric and planetary sciences at the Massachusetts Institute of Technology (MIT), was part of the analysis team.
He said: “If you look at these images, you are basically looking at this epic desert landscape. It is the most desperate place you can visit.
“There is not a drop of water anywhere and yet here we have evidence of a very different past.
“Something very profound happened in the history of the planet.”
Now that they have confirmed that the crater was once a lake environment, scientists believe its sediments could contain traces of ancient aquatic life.
Perseverance will look for locations to collect and preserve sediment, and these samples will eventually be returned to Earth, where scientists will be able to investigate them during Martian life.
Team member Tanja Bosak, an associate professor of geobiology at MIT, said: “We now have the opportunity to search for fossils.
“It will take some time to get to the rocks that we really hope to test for signs of life. Therefore, it is a marathon with a lot of potential ”.
Professor Weiss added: “The most amazing thing that has come out of these images is the potential opportunity to capture the moment when this crater moved from an Earth-like habitable environment to this desolate wasteland we see now.”