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D. Loizeau, N. Mangold (IDES-Orsay), F. Poulet, J.-P. Bibring, A. Gendrin, C. Gomez, Y. Langevin, B. Gondet (IAS-Orsay), V. Ansan, P. Masson (IDES-Orsay), G. Neukum (FU-Berlin), OMEGA Team, HRSC Team
The hyperspectral imager OMEGA aboard Mars Express found hydrated minerals in the region of Mawrth Vallis, Mars, by the detection of the 1.9 μm hydration absorption band, caused by the H2O molecule inside the mineral structure. For these hydrated minerals, the combination bands due to the Fe-OH bond at 2.3 μm and the Al-OH bond at 2.2 μm reveal the presence of clay minerals: ferric smectites and montmorillonites (Poulet et al., this conference). HRSC images indicate that the clays correspond to bright outcrops on the plateaus each side of Mawrth Vallis. These plateaus are part of highly cratered Noachian terrain (> 3.7 Gy). On these bright clay rich outcrops, MOC images show light-toned layered deposits, as seen by Malin and Edgett (Science, 2000). The intense wind erosion of these outcrops implies that clays are not only surfacial, but that the bright sedimentary rock itself is made of clays. The observation of such a large amount of clays in this region implies extensive alteration of igneous rocks by water, and the subsequent deposition of clays.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.