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Spotlight | L w 8 ive from the Labs cnrs I international magazine Contact information: LATMOS , Paris and Guyancourt. Michel Cabane > michel.cabane@latmos.ipsl.fr IRAP, Toulouse. Sylvestre Maurice > sylvestre.maurice@irap.omp.eu Pierre-Yves Meslin > pierre-yves.meslin@irap.omp.eu CheMin once more, which in particular analyzed a drilled sample. It turned out that the rocks were made up of a mixture of mud and clay intertwined with mineral veins containing sulfates and other compounds. Such minerals usually form in the presence of relatively fresh water, while calcium sulfates indicate water with a neutral or mildly alkaline pH. Moreover, the minerals observed showed a low degree of oxidation, and could have been oxidized by microorganisms as a source of energy, just as they are by chemolithotrophic bacteria on Earth. Researchers are convinced that the data collected by Curiosity confirms that the conditions for the emergence of life were once present on Mars. Admittedly, evidence for this has been piling up over the past decade: ancient riverbeds, the presence of carbonates and clays, possible intermittent brine flows in ravines, and so on. The Opportunity mission, launched in 2003 but still operational today, even discovered rocks formed in an aqueous environment—although highly acidic and providing little energy. As Maurice explains, “this is the first time that all the ingredients needed for the emergence of a prebiotic chemistry— one that allows the emergence of life— have been observed in a single location on Mars.” And that’s not all. Remote sensing carried out by the Mars Express spacecraft had previously shown that clays are present on Mars, particularly in 3.7 to 4 billion-year-old terrains. This led to the idea that the best place to look for possible habitable conditions was in the oldest terrains. However, the clays analyzed by Curiosity are obviously more recent. “This shows that the lacustrine conditions discovered by Curiosity lasted longer than we thought,” Meslin explains. “And that the planet’s window of habitability exceeds our expectations.” Heading for Mount Sharp Yet none of this means that life did actually exist on Mars. “We have clear evidence of habitability,” Maurice insists. “But we must now check whether we can discover complex carbon chemistry.” With this in mind, the scientists are pinning their hopes on the layers of sulfates and clays detected by various orbiting spacecraft on the summit of Mount Sharp, which Curiosity will be ascending in the next few months. Maurice is excited at the prospect. “This will be the climax of the mission. Discovering highly-complex molecules, or better still, an elementary form of life, would be the icing on the cake.” Meanwhile, after a forced break in April 2013 due to a planetary conjunction between Earth, Mars, and the Sun that prevented communication with the rover, Curiosity entered a new phase of its mission in early May. Specifically, during the first nine months, the scientists guided the rover according to what they saw as being “most interesting.” Hence a highly detailed study of a few outstanding sites, while Curiosity covered a mere 500 meters from the moment it landed until its visit to Yellowknife Bay, nine kilometers away from Mount Sharp. “Curiosity is now traveling between 50 and 100 meters per day, which enables us to perform so-called ‘contextual’ science that can document the chemical and geological diversity of the terrain we find ourselves in,” Meslin explains. “For instance, we recently studied volcanic rocks of a type that had never been seen on Mars before,” he adds. One thing is certain: with the nominal mission scheduled to last two to four years, the specialists are in for quite a few more surprises. 01. Institut de recherche en astrophysique et planétologie (CNRS / Université Paul-Sabatier). 02. Laboratoire atmosphères, milieux, observations spatiales (CNRS / UVSQ / UPMC). 03. Laboratoire interuniversitaire des systèmes atmosphériques (CNRS / Upec / Université Paris-Diderot). 06 These images show the similarity between sulfate-rich veins observed on Mars (Yellowknife Bay area) by NASA’s Curiosity rover, and sulfate-rich veins seen on Earth (Egyptian desert). 06 07 © NASA/JPL-Cal tech/MSSS © NASA/JPL-Caltech/LANL/CNES/IRAP/LPGNantes/ CNRS; Ear th imag e: LGLyon 07 Curiosity used its Mast Camera (Mastcam) to record this view of a rock outcrop informally named “Shaler,” located in Glenelg (inside Gale Crater).


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