(Paris) New evidence that life on Mars was possible in the distant past: The Curiosity rover has discovered fossil evidence of a cyclical climate that alternates between dry and wet seasons, an environment similar to Earth’s and therefore conducive to life. The manifestation of life is living beings, according to Wed’s study.
The Red Planet, whose current climate is extremely dry, had abundant rivers and lakes billions of years ago, which have now evaporated. But unlike Earth, Mars’ surface is not replenished by plate tectonics, and traces of this ancient terrain are well preserved.
NASA’s Curiosity rover has been exploring one such terrain since 2012, the massive Gale crater and its 6-kilometer-high mountain of sedimentary layers. says William Rabin, a researcher at CNRS and lead author of the study published in nature.
Mars, for example, could be a frozen planet where a volcanic eruption suddenly warmed the climate and led to the formation of liquid water, adds this planetary scientist from the Research Institute of Astrophysics and Planetology (University of Toulouse III – Paul Sabatier / CNES) who conducted The research is with the Lyon Laboratory of Geology and American and Canadian colleagues.
Climbing the mountain slope slowly, Curiosity came across salt deposits forming hexagonal patterns, in the soil dating from 3.8 to 3.6 billion years ago.
Analysis of the rocks by the American MastCam and the French-American ChemCam robot showed that they were cracks of dry clay.
“When the lake dries up, the mud cracks, and when it gets wet, ‘the crackle’ heals,” explains William Rabin. If this process is repeated on a regular basis, the cracks arrange themselves in such a way as to form hexagons, similar to the patterns observed in ancient earthen ponds that dried seasonally. Modeling of terrestrial clays subjected to dry and wet cycles has more “mathematically” demonstrated this specific hexagonal configuration.
It is idle to live
So it is “the first concrete evidence that Mars once had a periodic climate,” according to the researcher. As on Earth, the dry and wet seasons have followed each other at regular intervals, for more than three billion years. And over a long enough period – several million years – for life to evolve.
Such a climate is one of the conditions for the transition of organic matter from inert to life. “Curiosity has already detected simple organic molecules that can be formed by geological or biological processes,” the CNRS details in a press release.
For example, amino acids, which sometimes combine to form more complex molecules that make up organisms, such as RNA or DNA. However, such a process needs to form cycles that, as independent experiments in the laboratory have shown, continue to organize research.
“In a very dry world, these molecules never have a chance to form; in a very wet world, too,” adds the planetary scientist.
Therefore, the Red Planet has the necessary balance for the evolution of life forms. what kind? Scientists think of primitive single-celled microorganisms as archaea or bacteria, which are our most distant ancestors.
How they appeared on Earth remains a mystery, as plate tectonics has erased the trace of the oldest fossils. “What we are missing on Earth is the saga of the origins of life at the molecular level,” comments William Rabin.
Mars recorded its remains and it could allow us to understand on a small scale what happened on our infancy planet. If, of course, it turns out that life forms have already appeared on Mars, or are aborted, exploration missions such as Curiosity or Perseverance are trying to find them.
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