ExoMars rover to search for signs of ancient life in vast Martian clay deposit
A new study led by Inés Torres Auré of the University of Lyon in France, which was published in Icarus, suggests that the clay deposits in the region where the ExoMars Rosalind Franklin rover will search for signs of life extend far beyond previous estimates. One of the hypotheses also suggests that a vast ocean once covered the landing site. The ExoMars rover is slated to land in the Oxia Planum region, which features extensive clay deposits formed by an ancient water system, according to the study, ‘Clay Continuity between Oxia Planum and Mawrth Vallis.’
After landing, the rover will closely analyze the region to find out whether these clay sediments bear any traces of past life within them. The ExoMars mission will also try to decipher the type of water environment that sustained Martian life, if it ever existed at all. Data from hyperspectral imagers—specifically the OMEGA instrument on ESA’s Mars Express and CRISM on NASA’s Mars Reconnaissance Orbiter—led to the detection of these clay minerals on the Martian surface along the margins of the Chryse Planitia basin. Most of these minerals belong to the Fe/Mg-rich phyllosilicate family and are abundant at Oxia Planum.
Because Oxia Planum lies in an open basin, there is a possibility that a vast body of water several kilometers deep shaped the clay deposits about four billion years ago. Another scenario is that these vast plains were flooded by waters from ancient underground reservoirs. However, the exact history will remain uncertain until the ExoMars rover touches down and investigates the ground to verify the most plausible scenario. According to the study, the specific clay signatures found at Oxia Planum also appear at Mawrth Vallis. Interestingly, this latter region is almost 300 kilometers away from Oxia Planum and was previously considered as a potential landing site for the rover.
Breaking down how the Rosalind Franklin mission will channel its search for life, ExoMars project scientist Jorge Vago stated, “Because the area is so large, we are not talking about a localised occurrence, but rather a regional or global process that would have required immense amounts of water. We are targeting the oldest deposits in the sequence, which makes the potential implications for the geology and early climate of Mars very relevant for the Rosalind Franklin mission in its search for life.” These clay deposits will play an integral role in the quest to find biosignatures on Mars. As scientists build a better understanding of these minerals, reconstructing the Martian climate will become easier, directly aiding the evaluation of the planet's early habitability.
According to Auré, the revelation that Oxia Planum’s clays pre-date those of Mawrth Vallis presents researchers with a brand-new timeline. Auré is confident that the ExoMars rover will uncover a significantly extensive process responsible for shaping these ancient clays across the Red Planet's surface. Using the aforementioned OMEGA and CRISM instruments, scientists reconstructed the rock layering between Mawrth Vallis and Oxia Planum. While both units host similar kinds of clays, the team also detected a paleosurface—a remnant of an ancient, heavily cratered, exposed surface that was later buried by younger deposits. This paleosurface marks a pause in sediment deposition, followed by changes in water chemistry and mineral composition at both sites.
“We have identified a pause in deposition, which is quite puzzling because it implies a period of minimal surface activity (except for meteorite bombardment), followed by a shift in water chemistry and mineralogy in both Oxia Planum and Mawrth Vallis," said Auré. Now, the wait begins for the Rosalind Franklin rover to utilize its cameras, ground-penetrating radar, and advanced spectrometers to examine the Martian surface and seek out whether life truly took hold on the now-barren planet.
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