In order to obtain mineralogical information and to determine if life ever existed on Mars, future space missions have the task to perform especially designed analyses either in situ or on samples collected on the Martian ground, and then brought back to Earth. The aim is to determine the mineralogical and chemical composition of these samples to enhance our understanding of the Martian geology and possible past or present biology. In this framework, laboratory research on biotic and abiotic minerals of exobiological interest can allow us to characterize possible discriminating factors useful for distinguishing a biological from a mineral origin. We have investigated the physical properties of calcium carbonate (CaCO3), which can be present on Mars. The polymorphs of CaCO3, aragonite and calcite, are interesting because on Earth these compounds are produced by abiotic processes as well as by biological activity. We performed infrared transmission spectroscopy aimed at examining the behaviour of thermal processed biotic and abiotic participate samples composed of calcium carbonate (mineral, fresh biotic and recent fossil aragonite and calcite), in order to discriminate their origin. Here we present the results of our spectroscopic and thermal studies focused also on carbonates linked to primitive terrestrial living organisms (fresh and fossil stromatolites) as well as morphological studies, by a Scanning Electron Microscope, of biotic and abiotic structures. The goal is to understand whether and how the different biomineralization can influence the structure and composition of the samples.
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