Characterization of icy surfaces on Mars using hyper spectral data : a radiative transfer inversion

• Main Author: Andrieu, François
• Other Authors: Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Université Paris Saclay (COmUE), Frédéric Schmidt
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2015
• Subjects: Mars; Radiative Transfer; Remote sensing; CO₂ Ice; Water Ice; Massive inversion; Transfert Radiatif; Télédétection; Glace de CO₂; Glace d'eau; Inversion massive; [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]; polar night
• Online Access: https://theses.hal.science/tel-01328824; https://theses.hal.science/tel-01328824/document; https://theses.hal.science/tel-01328824/file/72780_ANDRIEU_2015_diffusion.pdf

Mars has a complex climate, characterized by carbon dioxide and water cycles, and dust transport at all scales. These cycles are mainly controlled by the seasonal condensation of CO₂ and water ice deposits at high latitudes during the polar night and their sublimation during the local spring. There are a lot of interactions between the CO₂ , water and dust cycles on Mars and they influence each other. An active seasonal process illustrates particularly well these links: the cryoventing, cold CO₂ gas jets triggered by seasonal sublimation of CO₂ deposits, which can put dust from the regolith in suspension into the atmosphere durably, and whose activity seems to be modulated by the exchange of water at the surface.The purpose of this thesis is to allow the use of the available hyperspectral imaging data to their full potential, to bring new constraints on seasonal exchanges between surface and atmosphere and the interactions between the different cycles (CO₂ , water , dust), focusing on cold gas jets. To achieve this, a semi-analytical radiative transfer model in compact ices and an effective inversion method were developed and validated.The radiative transfer model describes the interaction of light with a surface quantitatively, using the following parameters: thickness of the layer, volume proportions and grain-sizes of impurities, surface roughness. It is based on several key assumptions: geometrical optics, piecewise-continuous media quasi-spherical inclusions. The two-stream approximation is used for the radiative transfer inside the layer, but the surface specular reflectance is estimated taking into account the variability of the facets orientations from the surface roughness. This model was validated both numerically and on laboratory data.The inversion method consists in exploring synthetic databases generated by the radiative transfer model and determining the most likely sets of parameters to reproduce a given measure. The inversion is based on the Bayesian formalism: the manipulated variables are ...