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Communication Dans Un Congrès Année : 2018

Photodesorption and photochemistry of ices in Titan lower atmosphere

Résumé

Complex photochemical processes are initiated in the thermosphere of Titan at about 1000 km by the dissociation and the ionization of N2 and CH4 by the VUV solar photons. This leads to the formation of a number of hydrocarbons and nitrile species, which might condense in the troposphere and the lower stratosphere of Titan (<150 km) [1]. The most energetic solar photons are absorbed at higher altitude but longer wavelength photons (λ > 300 nm) can reach these lower atmospheric layers [2]. These photons are not energetic enough to cause photochemical transformations of molecules in the gas-phase. However, molecules in the solid-phase could undergo photochemical transformation. Additionally, aerosols with longer wavelength absorption could transfer that energy to other molecules resulting in indirect photo-induced transformations as demonstrated experimentally by our recent works [3, 4, 5]. We will present here an experimental study simulating the reactivity of ices in the atmosphere of Titan and will discuss the photoreactivity occurring in the lower atmospheric layers of Titan despite the absorption of the most energetic photons. Acknowledgments This work is supported by NASA Solar System Workings grant " Photochemistry in Titan's Lower Atmosphere". The research work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration. NC acknowledges the European Research Council for their financial support (ERC Starting Grant PRIMCHEM, grant agreement n°636829). References [1] Barth, E. L., Modeling survey of ices in Titan's stratosphere, (2017), Planetary and Space Science 137, 20-31. [2] Tomasko, M. G., et al., Rain, winds and haze during the Huygens probe's descent to Titan's surface, (2005), Nature 438, 765-778. [3] Gudipati, M. S., et al., Photochemical activity of Titan's low-altitude condensed haze, (2013), Nature Communications, 4: p1648. [4] Couturier-Tamburelli, I., et al., UV-Vis Light-induced Aging of Titan's Haze and Ice, (2018), ApJ, 825:117. [5] Fleury B., et al., Photoreactivity of condensed acetylene on Titan aerosols analogues, (2018), under review.
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insu-04444316 , version 1 (07-02-2024)

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B. Fleury, M. S. Gudipati, I. Couturier-Tamburelli, Nathalie Carrasco. Photodesorption and photochemistry of ices in Titan lower atmosphere. American Geophysical Union, Fall Meeting 2018, Dec 2018, Washington, United States. pp.abstract #P21F-3411. ⟨insu-04444316⟩
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