Surprise geology! Where researchers thought they were sampling sedimentary rocks, these are magmatic rocks they found, forcing them to review their scenarios.
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Almost a year and a half after its landing on March on February 18, 2021, in the Jezero crater, the Rover Perseverance of NASA has already traveled more than 12 kilometers on the surface of the red planet, taken more than 300,000 images and launched a number of analyzes. Some results have already been revealed, such as the first Martian sounds or the confirmation that Jezero had formerly welcomed a large lake like Lake Geneva, but we expected more. Particularly on the geology of the region, supposed to have been conducive to a possible appearance of life, in the distant time when Mars was not the arid and cold star that it became. This expectation ended on August 25 with the simultaneous publication, in Science and Science Advances magazines, of four studies concerning the Martian subsoil.
“This is the first package of geological publications, summarizes Sylvestre Maurice, astrophysicist at the Institute of Research in Astrophysics and Planetology, whose team provided the Supercam instrument of Perseverance, and co -author of two of these studies . The instruments all together make their verdict. “And this verdict is above all that of a surprise. “Reading the results surprised us, continues the French researcher: Mars has imagination, in the sense that terrestrial paradigms do not necessarily work on this other planet.”
At the back of the crater which was once (there are 3.4 to 3.7 billion years) covered by a lake, the planetologists expected to see sedimentary rocks. It is missed: Perseverance detected magmatic rocks containing olivine, mineral that, on earth, we find in abundance in the mantle. On our planet, we would assume that these rocks formed in depth have rose to the surface taking advantage of the tectonics of the plates. Easy. Boredom, underlines Sylvestre Maurice, “is that there is no tectonics of plates on Mars”.
Geologists must therefore imagine other scenarios, on endless durations, with important phases of erosion stripping the surface layers and revealing the buried rocks. “It betrays a long and complicated story, explains Sylvestre Maurice, it is the expression of a different geology from what is happening on our planet. And it feels good to get out of this box that is the earth, for Show us that there are other possibilities. “
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