there was indeed a lake in the Jezero crater

Images obtained by the Perseverance rover confirm that a lake existed in the Jezero crater on Mars 3.6 billion years ago. Its height was 100 meters lower than the data obtained from orbit suggested.

The first results from the Perseverance rover confirm how promising the Jezero crater, where the Mars mission landed, was. The rover’s landing site was a good home to a lake once, 3.6 billion years ago. This lake was 35 kilometers in diameter and several tens of meters deep. The announcement, relayed by the CNRS, is the subject of a publication in the journal Science October 7, 2021.

« Observations of orbital spacecraft have shown that the Jezero crater of Mars contains a prominent body of fan-shaped sedimentary rock deposited at its western margin. “, Recall these scientists. The images of probes in orbit around Mars had suggested the geological complexity and history of this basin. The interest of the area is now confirmed by the SuperCam instrument of the rover: the Jezero crater contained a lake fed by a river, via a delta (a triangular-shaped mouth).

The lake was 100 meters lower

« Our rover images constrain the hydrological evolution of the Jezero crater and potentially the climate and ability of the young Mars ”, write the researchers. The quality of the images taken by Perseverance made it possible to interpret the geology of the place. They were however taken at a distance, more than 2 kilometers from the geological formations studied.

The rover observed, after its arrival on the red planet in February 2021, “ a set of inclined sedimentary strata, sandwiched between horizontal strata », Describes the CNRS in its press release. This geometry is similar to what we know of deltas on Earth and the team was able to use it to determine the shape of the lake, its altitude and the type of deposits.

Result: the height of the lake was 100 meters lower than suggested by the orbital data. Scientists were able to determine that it was a closed lake, the level of which fluctuated. An advantage of this enclosed lake structure is that the deposits that may have formed were undoubtedly well preserved. However, it is not excluded that we are therefore facing a less dynamic lake, with less hydrological activity, than an open lake.

The estimated level of the lake, 100 meters lower than expected. // Source: NASA / JPL-Caltech / MSSS / LPG

What if Perseverance climbs the delta?

Images of the rover also helped to see strata above the lake deposits. Their characteristics are different, with the presence of large pebbles and boulders. It could be a sign of flash floods, possibly significant climate change, at the end of the period Jezero crater housed the lake. For now, scientists do not know what context may have caused a change in the flow of the river.

« Our results provide information for Perseverance sampling strategies in the Jezero crater “, Anticipate the authors. The ideal would be to bring the rover up on the delta, to approach the boulders. The area could be relevant in order to take some of the samples of the mission, which will one day have to return to Earth.

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Source: Numerama by www.numerama.com.

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