PhD Defense


"Investigation of near-infrared properties of opaline silica and kaolinite for interpreting their geological origin on Mars"

5th november at 2 p.m. - Amphitheatre LPG - Laboratoire de Planétologie et Géodynamique - Building 4 of the Sciences Faculty, University of Nantes

Abstract : Alteration minerals are key objects to understand the geological history of the planetary bodies’ surfaces. In this work, we studied the near-infrared spectroscopic properties of opaline silica and kaolinite in order to constrain the surface paleoclimatic conditions at the surface of Mars during the past. A preliminary geomorphologic study of opal-bearing deposits on Mars shows four types of deposits: aeolian deposits, hydrothermal deposits, alluvial fan/fan delta and bedrock. Spectroscopic criteria, distinguishing continental weathering and hydrothermal opals, show that aeolian deposits are relicts of hydrothermal deposits.. Other deposits are of weathering origin, except hydrothermal deposits that have a spectral signature consistent with low-temperature hydrothermal activity. Near-infrared properties of kaolinite are proxies of its crystalline degree. Poorly-ordered kaolinites are exclusively of continental weathering origin while well-ordered kaolinites can form by either hydrothermalism or continental weathering.