Effets du rayonnement cosmique galactique sur les petits corps glacés du système solaire externe : indices pour la formation de la matière organique des micrométéorites antarctiques ultracarbonées

Abstract : Extraterrestrial materials, such as meteorites and interplanetary dust particles, provide constraints on the formation and evolution of organic matter in the young solar system. Micrometeorites represent the dominant source of extraterrestrial matter at the Earth's surface, some of them originating from large heliocentric distances. Micrometeorites recovered from Antarctica snows provide a unique source of pristine interplanetary dust particles, which underwent a minimal weathering at atmospheric entry. A few percent are characterized by very large carbon content with at least 50% in volume, much higher than the value found in meteorites. This organic matter exhibits extreme deuterium excesses and is unusually nitrogen-rich. Several formation scenarios have been proposed for the formation of the N-rich organic matter observed in UCAMMs, suggesting that these particles come from a parent body orbiting beyond the nitrogen snow line, in the outer Solar System where they are exposed to ions from the galactic cosmic rays. We experimentally evaluate the scenario involving high energy irradiation of icy bodies subsurface orbiting at large heliocentric distances by irradiating N2-CH4 ices with swift heavy ions provided by the GANIL facility. Chemical evolution was monitored by Fourier transform infrared spectroscopy with two experimental set-up : CASIMIR and IGLIAS. Ex situ mass spectroscopy measurement where also conducted. Results concerning the origin of the organic matter found in ultracarbonaceous micrometeorites and the origin of its deuterium enrichment will be presented and discussed.
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Basile Augé. Effets du rayonnement cosmique galactique sur les petits corps glacés du système solaire externe : indices pour la formation de la matière organique des micrométéorites antarctiques ultracarbonées. Astrophysique [astro-ph]. Université de Caen Normandie, 2017. Français. ⟨tel-01660412⟩

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