Depouillement et interpretation des donnees spatiales d’imagerie hyperspectrale de mars (OMEGA/MEx) : Evolution volcanique de la surface de Mars

Abstract : Geologic studies of martian volcanic regions have demonstrated the diversity and complexity of the martian volcanism through various morphologies, witnesses of the volcanic and magmatic evolution of this planet. A better understanding of this volcanism nevertheless requires a better knowledge of the mineralogical composition of these regions. This composition highly depends on the internal conditions of the planet and its evolution. In my PhD thesis, I focused on the internal and volcanic evolutions of Mars from a study of the mineralogy obtained with the visible near-infrared imaging spectrometer OMEGA / Mars Express.The OMEGA dataset has allowed the mapping of key anhydrous mineral of the martian surface at a global scale with a kilometer spatial resolution. These minerals are major mafic minerals (pyroxene and olivine), and ferric phases, including nanophase ferric oxides. Their spatial distributions confirm the basaltic composition of the southern hemisphere and the low albedo regions of the northern plains, as well as the nanophase nature of ferric oxides present in the martian dust. These global maps represent complete and final products and are available for the community.In addition to this global analysis, the global distribution of olivine on the surface of Mars was the subject of a more detailed local study highlighting several aspects of the martian volcanism and magmatism. Hesperian olivine enriched lavas that have filled dozens of craters and depressions in the southern hemisphere were identified. Olivine was also identified in the northern plains associated with material excavated by craters (<20 km) and with extended outcrops, suggesting that the northern plains were also partly filled with these lavas. These observations can be explained by a planetary event of olivine enriched fissural volcanism during the early Hesperian. They also indicate that the upper layer of sediment present in the northern plains is very fine (<100m) and of volcanic origin. This olivine enrichment of hesperian lavas, unlike olivine-depleted noachian terrains, questions the variation of internal conditions of the planet between these two periods, and/or significant alteration of the noachian terrains. Olivine associated with large crater ejectas (> 20 km) in the northern plains, and buttes in the southern hemisphere suggests that the buried noachian/primitive crust was olivine enriched in some locations. Finally, olivine found in buttes on terraces of Argyre and Hellas basins, interpreted as mantle ejectas, indicates that the martian mantle have experienced an overturn after its crystallization.The last chapter of my work was to identify the source regions of Martian meteorites by looking for some similarity in their spectral signatures in the near infrared with those of the martian surface. A major outcome of this study is that the basaltic shergottites Shergotty and Los Angeles have spectral signatures similar to those of the hesperian volcanic massifs such as Syrtis Major, Hesperia Planum and Thaumasia Planum. Such an analogy is consistent with an old age for these meteorites.
Keywords : Mineralogy
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Anouck Ody. Depouillement et interpretation des donnees spatiales d’imagerie hyperspectrale de mars (OMEGA/MEx) : Evolution volcanique de la surface de Mars. Autre [cond-mat.other]. Université Paris Sud - Paris XI, 2012. Français. ⟨NNT : 2012PA112295⟩. ⟨tel-00835283⟩

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