NASA's Curiosity rover has confirmed what scientists have been anticipating: there has been a very old and huge salt lake on Mars. So liquid water. So of life?
She has long been the planet of little green men. Then the red planet, modern observations showing a sphere of rocks and ocher-colored sand. But the most recent explorations, thanks in particular to NASA's Curiosity rover, show that Mars was a blue planet. Translate: with liquid water on the surface.
Last Monday, the US space agency announced that the small autonomous robot, which has worked relentlessly for seven years, has discovered new evidence of the existence of a large and very old salt lake.
Located in the trough of Gale crater, this lake stretched 154 kilometers in diameter here 3.5 billion years.
Since 2012, Curiosity has been sending incredible images and leading scientific data across the space. Look at the picture above: we believe it, right?
If NASA's rover soon found traces of water in the Martian soil, it now updates mineral-enriched rocks in the soil of the Gale crater through drilling and analysis by its young embedded laboratory (photo below) .
In other words, there was at least one oasis on Mars here more than 3 billion years ago. This is confirmed by NASA in an article published in Nature Geoscience .
How was this lake formed? A huge meteor first hit the ground of Mars. As often happens in this kind of event, a crater is formed, but with a central relief related to the side effects of the impact itself (illustration below ).
By capillarity, the water present in the Martian subsoil is raised towards the bottom of the crater, filling little by little the volume released by the meteor (illustration below) .
Gradually, the water and wind (there is a tenuous atmosphere on Mars) brought sediment that accumulated at the bottom of the crater Gale. These strata were then exposed by erosion (illustration below) .
They are a great testament to Mars' past, which the Curiosity rover explores and drills relentlessly. "Gale Crater preserves this unique record of Mars changes , " says William Rapin, a member of the rover team.
Even more incredible, the analysis of these rocks shows that the lake has gone through different episodes of abundance and drought, kinds of climatic variations. The drought finally prevailed.
NASA scientists even make a parallel with the Altiplano (plain altitude) which stretches 1,500 km in South America, large expanse very dry nestled at 3000 m altitude on which one finds ancient large salt lakes that have been alternately in water and dry, with temporary vegetation. And many minerals in their basement. Like on Mars.
Curiosity will continue to explore and drill this crater Gale. With a specific mission: find traces of life on Mars. It will be joined in 2020 and in 2021 by two other rovers from NASA and the European Space Agency (ESA), who will have the same goal.
Because, as William Rapin, one of the California Institute of Technology (Caltech) bosses, puts it, the key question that arises today is: "When and how long was Mars? able to accommodate microbial life on its surface? "
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Mars: when the red planet was a blue planetOuest-France.frENLARGE