new observations confirm Jezero crater is an ancient lake

Artist’s impression of Lake Jezero – © NASA / JPL-Caltech

Analysis of the photos taken by the Perseverance rover in the Martian crater Jezero revealed signs of flash floods, confirming that the place was once a lake.

Signs of flash floods

If there Mars current is extremely arid, this was not always the case: evidence of a far bluer past for the red planet, characterized by the presence of oceans, rivers and lakes there are billions of years, keep piling up. Orbital images that suggested that the crater The lake, 49 kilometers wide, was once a vast body of water, so it was only natural that the location was chosen as the landing site for the mission Perseverance, whose main objective is to find traces of ancient life.

Once deployed, the rover of the NASA started taking pictures of its surroundings, including a series of steep escarpments about 2.2 kilometers away and a small hillock dubbed Kodiak at the South West. Thanks to his instruments Mastcam-Z and Remote Micro-Imager (RMI), the machine was able to obtain images of the layers of rocks and sediments of these formations.

Satellite image of Jezero Crater, highlighting the locations of the Perseverance rover and several geological features of interest – © NASA / JPL-Caltech / University of Arizona / USGS

Their recent analysis confirmed that the sediment layers on the eastern face of Kodiak, as well as the lower sections of the northwestern escarpments, were similar to those of a terrestrial river delta. “ Never before has such a well-preserved stratigraphy been observed on Mars “, valued Nicolas Mangold, lead author of the study, published in the journal Science. « This is the key observation that allows us to confirm once and for all the presence of a lake and a river delta in Jezero.. »



Additional clues were found at the upper sections of the escarpments. The presence of stones and larger blocks (some up to 1.5 m wide) scattered indicating in particular that they had been carried by flood water (whose speed would have reached 30 km / h) from outside the crater . Overall, the evidence suggests that the lake that once filled the crater The lake was quite dynamic, with water levels fluctuating with periods of flash floods and calm.

Sedimentary outcrops in the “Delta Escarpment”, the upper layers of which indicate flash floods in the distant past – © NASA / JPL-Caltech / LANL / CNES / CNRS / ASU / MSSS

The search for traces of ancient life continues

The team says this new study will serve as a basis for future missions, including determining where Perseverance will have to travel to take samples, which will then be sent to Earth for analysis by more sophisticated instruments.

« The fine-grained material at the bottom of the delta probably holds our best chance of finding evidence of organics and biosignatures, while the boulders will allow us to sample old pieces of crustal rock. », Concludes According to Sanjeev Gupta, co-author of the study.

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