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Chimie des atmosphères planétaires : de la Terre à Titan , de Titan à la Terre primitive

Nathalie Carrasco 1
1 IMPEC - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : The Earth and Titan, largest satellite of Saturn are often compared by their atmospheric similarities: both have a dense atmosphere mainly made of nitrogen, with a pressure of the order of magnitude of a bar at the surface. However their composition significantly differs because of the second mostly abundant constituent: oxygen on Earth and methane on Titan. Terrestrial atmosphere is therefore oxidizing whereas Titanian atmosphere is reducing. This major difference leads to radically different chemistry patterns for organic species: oxidation lyses organic skeletons whereas photochemistry in reducing conditions leads to an efficient growth of the carbon chains. A reducing atmospheric chemistry therefore produces complex structures and a wide-range of possible chemical functions, providing abiotic organic materials of interest for astrobiology. Titan's atmosphere is therefore considered as a presently observable prebiotic model for Early Earth. During my career I studied both oxidizing and reducing atmospheric mechanism and I am now specifically interested in the contribution of ionic species to the reductive chemical growth. Those efficient ionic processes are actually involved in the production of the solid organic haze surrounding Titan. I plan to study their influence in the prebiotic atmospheric chemistry, which might have occurred on the Early Earth.
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Nathalie Carrasco. Chimie des atmosphères planétaires : de la Terre à Titan , de Titan à la Terre primitive. Planétologie et astrophysique de la terre [astro-ph.EP]. Université de Versailles-Saint Quentin en Yvelines, 2012. ⟨tel-00667618⟩

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