STONE-6 experiment: testing the survival of microfossils in martian ana- logues rocks during entry into the Earth’s atmosphere

logues rocks during entry into the Earth’s atmosphere F. Foucher, F. Westall , J.-M. Bény , F. Brandstätter , and R. Demets , 1 Centre de Biophysique Moléculaire, UPR CNRS 4301, Orléans, France ([email protected]), 2 Institut des Sciences de la Terre d’Orléans, UMR CNRS 6113, Orléans, France, 3 Naturhistorisches Museum, Burgring 7, 1010 Wien, Austria, 4 European Space & Technology Centre (ESTEC), Keplerlaan 1, Postbus 299, 2200 AG Noordwijk, The Netherlands The oldest traces of life on Earth occur in cherts (silicified volcanic silts and sands) that were deposited in coastal environments ∼3.5 billion years ago [1, 2, 3, 4, 5, 6]. These microfossils are the remains of relatively evolved organisms, implying that life had to have appeared much earlier [6]. However, studies related to the origin of life are hampered by the fact that suitable rocks dating from the first billion years are lacking on Earth, since older materials are too heavily metamorphosed or have been destroyed by plate tectonics. Investigations are now focussed on the search for older microfossils on other planets and, in particular, on Mars. Mars does not appear to have undergone plate tectonic activity as on Earth and, if life appeared on that planet, its fossilised traces could be found embedded in rocks from the Noachian period (4.5 to ∼3.5 billion years ago), i.e. the period that is missing on Earth. One means of studying Noachian martian rocks would be to analyse sedimentary meteorites from Mars. This solution has the advantage of being cheaper than the explorations of martian rocks by rovers and allowing high resolution analyses in laboratory. However, the 49 meteorites of presumed martian origin found to date are all composed of basaltic volcanic minerals [7]. The aim of this study was thus to determine if martian sedimentary rocks, and the hypothetical microfossils they could contain, can survive the Earth’s atmospheric entry.