Des grains cométaires en laboratoire: premiers résultats de la mission Stardust.

Abstract : My thesis is dedicated to SXRM (Synchrotron X-Ray Microscopy) and µ-FTIR (micro Fourier Transformed InfraRed) analyses of comet Wild 2 samples brought back to Earth by the Stardust mission. SXRM experiments allowed the study of both the elemental composition of Wild 2 grains and their slowing down into the aerogel. A XANES study at the edge of iron shows that the information concerning the incident particle is preserved in the terminal particle found at the end of the track. Fluorescence mappings were used to determine the elemental composition of comet Wild 2, showing that, normalised to iron, Ca, Ti, Cr, Mn, Ni, Ge and Se are present in chondritic abundances. Enrichments in Cu, Zn and Ga are observed, indicating that at least a part of the refractory phase of Wild 2 formed during a late stage of nebular condensation from a gas phase depleted in most refractory elements. Sulphur seems depleted, which is surely a clue for an incomplete condensation process, stopped before all the sulphur is condensed. The µ-FTIR study coupled to Raman studies of grains extracted from the aerogel shows that organic matter in Wild 2 is dominated by aromatic rings linked together by aliphatic chains. The study of the 3.4 µm band shows that the aliphatic chains are longer (or less branched) than in IDPs and grains from the interstellar medium (ISM). Comparison with observations of the diffuse ISM reveals that organic matter in Wild 2 is clearly not interstellar and appears simpler than that contained in interstellar grains.
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Submitted on : Monday, September 15, 2008 - 7:32:48 PM
Last modification on : Friday, April 5, 2019 - 8:11:42 PM
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Faustine Grossemy. Des grains cométaires en laboratoire: premiers résultats de la mission Stardust.. Astrophysique [astro-ph]. Université Paris Sud - Paris XI, 2008. Français. ⟨tel-00321787⟩

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