After almost 6 years of exploration of the Gale Crater, NASA’s Curiosity robot has passed the milestone of 2,000 sols or days on the surface of Mars. Such longevity has allowed Curiosity to highlight that the essential conditions for the emergence of life were met in the past on Mars.
Since August 2012, the Curiosity rover has been exploring the surface of Mars and has traveled more than 18 km in the crater Gale. It has just crossed a ridge rich in iron oxide during its ascent of Mount Sharp, a mountain that rises 5 km above the bottom of the crater. Throughout its journey, Curiosity has characterized numerous sedimentary deposits, often invisible from orbit and which are witnesses of past fluvial, lake or wind erosion.
These observations made it possible to establish that Mars was in the past a habitable planet. Climbing the slopes of Mount Sharp, Curiosity is now studying the history of this habitability, probably more than 3 billion years old.
The ChemCam instruments, a suite of remote sensing instruments installed on Curiosity rover, is used almost daily. Thanks to its laser, It measures the composition of the rocks of Mars without touching them from 2 m to 7 m from the rover. It detects many chemical elements that tell us the genesis of these rocks and their transformation over time. It is at the origin of several important discoveries on the geology of Mars and its biological potential: discovery of rocks comparable to terrestrial primitive continents; detection of mineral veins testifying to a prolonged aqueous subterranean activity; cataloging sediment sources; monitoring the abundance of water and carbon dioxide in the atmosphere.
To date, Curiosity has activated more than 550,000 times the ChemCam laser on Mars. 17,000 measurement points have been obtained, which is an unprecedented composition library on Mars to date.
The SAM instrument on the hand, is used to characterize the molecular composition of soils and rocks, collected using the articulated arm of the robot, as well as from the atmosphere. The largest instrument of Curiosity is therefore much less often used than ChemCam with “only” a few tens of measurements of the atmospheric composition, and a dozen solid samples characterized. But by its characteristics, SAM is the only instrument to have demonstrated the presence of perchlorates (strong oxidizers) and nitrates in the analyzed sedimentary rocks. In addition, it was the first to detect the presence of organic matter on Mars, 40 years after the first attempt made by the Viking probes, in clay samples taken from the floor of the crater. Finally, the SAM measurements also made it possible to detect the presence of methane in the atmosphere.
In 2020, the US rover Mars 2020 and that of Europe Exomars 2020 should come to support the research carried out by Curiosity with on board more advanced equipment: the SuperCam instrument, heir to ChemCam, and the MOMA instrument, heir to SAM, which will allow scientist to further their analysis of Martian environments throughout the history of the planet and their potential for the eventual emergence of life.