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Significant compositional and structural heterogeneity at nm to mm scales is an important characteristic of primitive extraterrestrial materials. Here, we report the analysis of high‐resolution Fourier transform IR hyperspectral imaging analytical measurements at the micron scale on a fragment of the Paris carbonaceous chondrite, supported by Raman and SEM‐EDS measurements. The fragment is crushed in a diamond compression cell. The micro‐FTIR analyses are performed in transmission with two setups, an imaging microscope with a matrix detector using a thermal source and a system using a single point detector coupled with the synchrotron source at the SOLEIL synchrotron facility. We obtain the spatial distribution of chemical/mineralogical components. We confirm at a larger scale (10 μm) the presence of hydrated amorphous silicates observed at a smaller scale (1 μm). Based on the relative abundance of different minerals (hydrated amorphous silicate, olivine, diopside, and serpentine), we propose a sequence of aqueous alteration. Considering the spatial correlation of minerals with organic matter, we discuss the effects of aqueous alteration on the organic matter in bulk. In particular, we detect an increase in the CH2/CH3 ratio in the altered zone and present the possible scenarios that led to the observed chain length shortening/cracking of hydrocarbons. [ABSTRACT FROM AUTHOR]

Abstract: In January 2006, the NASA Stardust mission will return, trapped in aerogel, the first samples of cometary and contemporary interstellar dust. Their analyses will require high spatial resolution techniques. An example is Synchrotron X-ray analysis, which could be useful for in situ identification of the captured grains. In the case of aerogel, it is possible to optically scan the samples and locate the trapped grains, which can then be extracted in pieces of aerogel, called “keystones”, a few hundreds of microns large and self-supported on microforklifts that contain one incident grain and its penetration track. The non-destructive identification of the material distributed inside a keystone can be completed using Synchrotron X-ray microbeams either in the fluorescence or the absorption mode. In order to develop an analytical protocol, we analysed a keystone containing a dust grain originating from the chondritic swarm identified in the Orbital Debris Collection Experiment (ODCE) that was deployed for 18 months outside the Russian space station MIR. The results we present concern μ-fluorescence mappings and XANES at the Fe K-edge measurements. They indicate a very strong tendency of the incident particle to break up into many fragments during the slowing in the aerogel. Furthermore, a structural evolution of the grain is also possible, during the slowing down in the aerogel. These non-destructive techniques might be among the only ones to be used for analysing the interstellar grains trapped in the Stardust aerogel and for those cometary grains that might have lost most of their material along the penetration track. [Copyright &y& Elsevier]

Abstract: On 15 January 2006, the NASA Stardust Capsule Sample Return came back to Earth with its load of cometary and contemporary interstellar grains trapped in aerogel collectors. These cometary grains are the first samples of known parent body and their study in the laboratory will give new clues on the nature of the cometary materials. Using Synchrotron X-ray Microscopy (SXRM), some analogues of Stardust''s samples were analysed. The aim was to develop an analytical protocol and to study the effects of the slowing down of hypervelocity particles into aerogel on the physical and chemical properties of the collected grains. Our samples originate either from the NASA Orbital Debris Collection Experiment (ODCE) deployed outside the MIR station, or from light gas gun shots of Allende meteorite grains into aerogel at velocities of 6km/s. They consist of grains trapped in pieces of aerogel, a few hundreds of microns large. Using synchrotron X-ray microbeam, micro-fluorescence mappings and X-ray absorption near-edge structure (XANES) spectra were performed, bringing information on elemental analysis, repartition and speciation of Fe in our samples. In particular, the XANES studies obtained at the iron K-edge show that iron is present in different oxidation states in the samples, rather in a ferric form at the track entrance while rather in a ferrous form at the end of the track as well as in the final grain. The tests performed on the Allende meteorite dust grains for which the Fe2+/Fe3+ ratio is a priori known, tend to show that the final particle presents the same oxidation state as the initial incident one, a very encouraging clue for the validity of the future interpretation of Stardust samples analyses. [Copyright &y& Elsevier]