Images indicate that Jezero crater on Mars was once a tranquil lake

Jezero crater on Mars, now a dry and windy depression, was a tranquil lake 3.7 billion years ago, indicates the first scientific analysis of images taken by NASA’s Perseverance robotic vehicle.

Analysis of the images, published today in the scientific journal Science, shows that there are signs in the crater of flash floods from the small river that fed the lake and that transported large rocks downstream of the lake bed.

The floods, according to the analyzed evidence, were strong enough to transport large rocks for tens of kilometers that were later deposited on the lake bed, where they still remain today.

The conclusion is based on images of rocks that outcrop the interior of the crater, on the western side. Satellite images have already shown this outcrop, which seen from above resembles river deltas on Earth, where layers of sediment are deposited in a fan shape.

The new “Perseverance” images, taken from inside the crater, confirm that this outcrop was in fact a river delta. Based on the sedimentary layers of the outcrop, scientists suggest that the river flowed into a calm lake for much of its existence, until a dramatic change in climate triggered episodic flooding at or near the end of the lake’s existence.

“If you look at these images, you’re basically looking at this epic desert landscape. It’s the most abandoned place you can ever visit,” said Benjamin Weiss, research team member and professor of planetary science in the Department of Science at Earth, Atmospheric and Planetary at MIT (Massachusetts Institute of Technology, private university in Cambridge, USA).

“There isn’t 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,” added the scientist, quoted in a statement releasing the analysis of the images.

Scientists hope to uncover more clues about Mars’ climate evolution as Perseverance explores the crater. Now that they’ve confirmed that the crater was once a lacustrine environment, they believe the sediments may contain traces of aquatic life. The robotic vehicle will collect sediment, which can be sent to Earth and thus studied.

“We now have the opportunity to look for fossils,” said researcher Tanja Bosak, associate professor of geobiology at MIT, who is part of the team that analyzed the images.

Perseverance landed in Jezero Crater on February 18, just over a mile (1.6 kilometers) from the western “delta”. For the first three months the vehicle was stationary while NASA engineers performed remote checks of the many instruments installed on board. During this period two cameras captured images of the surroundings.

After sending the images to Earth, scientists observed distinct sediment beds and concluded that the sediment must have been deposited by water flowing into a lake, rather than by wind or other geological processes.

Other images led scientists to conclude that the fan-shaped formation was in fact that of an ancient river delta.

“Without going anywhere, the Rover managed to solve one of the big unknowns, which was that this crater was once a lake,” said Benjamin Weiss.

Scientists explain that since the huge rocks, which will have been washed away by large floods, are in the upper layers of the delta, it is because they are more recently deposited material, since they settle in upper layers of older and much finer sediments. This indicates that much of its existence the ancient lake was fed by a peacefully flowing river.