French, American and Canadian scientists have discovered fossil evidence of a cyclical climate on the planet Mars.
New proof that life on Mars was possible in the distant past. The Curiosity rover has discovered the fossil record of a cyclic climate, alternating dry and wet seasons, an environment similar to that of Earth and therefore conducive to the appearance of living organisms, according to a study, dating from this Wednesday August 9 .
The red planet, whose current climate is extremely arid, would therefore have possessed, billions of years ago, abundant rivers and lakes, which have now evaporated. But unlike Earth, the surface of Mars is not renewed by plate tectonics, and traces of these ancient terrains have been well preserved.
“we quickly understood that we were working in lake and river depots”
NASA’s Curiosity rover has been exploring one of these terrains since 2012, the huge Gale crater and its 6 km high mountain made of sedimentary layers. “We quickly understood that we were working in deposits of lakes and rivers but we did not know what type of climate to link them to”, tells AFP William Rapin, CNRS researcher.
“Mars could for example have been a frozen planet, where a volcanic eruption suddenly warmed the climate and triggered the formation of liquid water”, adds this planetologist from the Institute for Research in Astrophysics and Planetology (University of Toulouse III – Paul Sabatier/CNES), who carried out the research with the Lyon geology laboratory and American and Canadian colleagues.
DRIED MUD CRACKS
As it slowly climbed the mountain slope, Curiosity came across salt deposits forming hexagonal patterns, in soil dated to 3.8 to 3.6 billion years old. Analysis of the rock by the robot’s American MastCam and Franco-American ChemCam instruments showed that they were cracks of dried mud.
“When a lake dries up, the mud cracks, and when it rehydrates, the crackle heals,” explains William Rapin. If this process is repeated on a regular basis, the cracks arrange themselves in such a way as to form hexagons, similar to patterns observed in ancient land basins which dry up seasonally. Modeling of terrestrial mud subjected to dry and wet cycles has further demonstrated “mathematically” this specific hexagonal formation.
It is therefore “the first tangible proof that Mars had a cyclic climate”, according to the researcher. As on Earth, dry and wet seasons followed each other at regular intervals, more than three billion years ago. And over a long enough period (several million years) for life to develop.