Etude en laboratoire de grains extraterrestres et de leurs analogues de synthèse

L étude en laboratoire de matériaux extraterrestres provenant d objets ayant peu ou pas évolué depuis leur formation il y a environ 4.6 milliards d années, peut améliorer notre connaissance sur les débuts de notre système planétaire. Par ailleurs, la simulation en laboratoire de certains processus que ces matériaux sont susceptibles de subir au cours de leur histoire apporte également de précieuses informations pour l interprétation des données issues des observations astronomiques ainsi que pour la compréhension de l évolution des solides du Milieu Interstellaire jusqu à leur incorporation dans des objets planétaires, objets incluant aussi toutes sortes de débris tels que les astéroÏdes, les comètes et toutes sortes de poussières accessibles à la collecte et/ou à l observation.Au cours de cette thèse, l analyse des matériaux organiques ainsi que des matériaux silicatés, jusqu alors peu étudiés conjointement, dans les poussières stratosphériques d origine cosmique, révèle une corrélation entre la minéralogie des grains et la longueur des chaînes carbonées. Ce lien ne semble pas le fruit de processus à la surface des corps parents des grains mais semble plutôt tracer des processus pré-accrétionnels. La conservation de composants peu altérés sur les corps parents dans les matériaux extraterrestres est encore une fois confirmée par la découverte, au cours de cette thèse, d inclusions dans la météorite carbonée Paris dont les spectres infrarouges sont très similaires à ceux des composés carbonés observés dans le Milieu Interstellaire. L étude de grains cométaires issus de la mission spatiale Stardust a montré, contrairement à l idée que les comètes soient composées uniquement de matériaux primitifs puisque conservés dans un réservoir froid, que celles-ci contiennent aussi un certain nombre de matériaux formés à haute température, confirmant alors de précédentes analyses d échantillons de Stardust et impliquant des échanges de matériaux à grande échelle radiale dans le jeune Système solaire.La deuxième partie de ce travail, consacrée à l étude d analogues de matière extraterrestre, porte sur le rôle qu ont pu jouer les matériaux à partir desquels les planètes telluriques se sont formées dans l apport de l eau sur la Terre dans le cadre du scénario dit de wet accretion . Les expériences effectuées au cours de cette thèse visant à simuler les interactions entre silicates et vapeur d eau ont montré que ces matériaux permettent de stocker d importantes quantités d eau à leur surface par adsorption des molécules de la phase gazeuse.Laboratory analyses performed on extraterrestrial materials originating from primitive bodies of our Solar System, that are bodies known to have suffered low alteration since their formation 4.6 billion years ago, can improve our knowledge on processes that have occurred in the early phase of our planetary system. Furthermore, laboratory simulations of some processes that these materials are likely to suffer during their life cycle also bring precious indications for interpreting observational data as well as for understanding the evolution of solids from the Interstellar Medium to their incorporation into planetary bodies, these latter including asteroids, comets and all kinds of dust that may be observed and/or collected back to Earth.During this thesis, the analysis of silicate as well as organic materials, which have not been much studied jointly so far, in stratospheric particles of cosmic origin, reveals a correlation between the mineralogy of the grains and the lengths of the chains of their carbonaceous component. This link does not seem to be due to parent body processing but rather to trace pre-accretionnal processes. The preservation of pristine components in extraterrestrial materials slightly altered on their parent bodies is again confirmed by the discovery in this work, of inclusions in the Paris carbonaceous chondrite whose infrared spectra are similar to the interstellar carbonaceous species. The study of cometary grains from the Stardust space mission showed, unlike the common idea that comets should be composed only of primitive materials since they reside in a cold reservoir, that comets do also contain a number of materials formed at high temperature, thus confirming results from previous studies of Stardust samples and implying large-scale radial mixing of materials in the young Solar system disk.The second part of my work, dedicated to experiments on primitive extraterrestrial amorphous silicates analogs, is aimed to study the role that materials from which Earth has accreted could have played in its water budget in the frame of the wet accretion scenario. The experiments performed along this thesis simulating interactions between silicates and water vapor, showed that silicates allow the storage of large quantities of water by adsorption onto their surface of molecules directly from the gas phase.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Microstructural Study of Micron-Sized Craters Simulating Stardust Impacts in Aluminum 1100 Targets

Various microscopic techniques were used to characterize experimental micro- craters in aluminium foils to prepare for the comprehensive analysis of the cometary and interstellar particle impacts in aluminium foils to be returned by the Stardust mission. First, SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) were used to study the morphology of the impact craters and the bulk composition of the residues left by soda-lime glass impactors. A more detailed structural and compositional study of impactor remnants was then performed using TEM (Transmission Electron Microscopy), EDS, and electron diffraction methods. The TEM samples were prepared by Focused Ion Beam (FIB) methods. This technique proved to be especially valuable in studying impact crater residues and impact crater morphology. Finally, we also showed that InfraRed microscopy (IR) can be a quick and reliable tool for such investigations. The combination of all of these tools enables a complete microscopic characterization of the craters

Non-Random Spatial Distribution of Impacts in the Stardust Cometary Collector

In January 2004, the Stardust spacecraft flew through the coma of comet P81/Wild2 at a relative speed of 6.1 km/sec. Cometary dust was collected at in a 0.1 sq m collector consisting of aerogel tiles and aluminum foils. Two years later, the samples successfully returned to earth and were recovered. We report the discovery that impacts in the Stardust cometary collector are not distributed randomly in the collecting media, but appear to be clustered on scales smaller than approx.10 cm. We also report the discovery of at least two populations of oblique tracks. We evaluated several hypotheses that could explain the observations. No hypothesis was consistent with all the observations, but the preponderance of evidence points toward at least one impact on the central Whipple shield of the spacecraft as the origin of both clustering and low-angle oblique tracks. High-angle oblique tracks unambiguously originate from a noncometary impact on the spacecraft bus just forward of the collector. Here we summarize the observations, and review the evidence for and against three scenarios that we have considered for explaining the impact clustering found on the Stardust aerogel and foil collectors

Multiscale correlated analysis of the Aguas Zarcas CM chondrite

In this paper, we report the results of a campaign of measurements on four fragments of the CM Aguas Zarcas (AZ) meteorite, combining X‐ray computed tomography analysis and Fourier‐transform infrared (FT‐IR) spectroscopy. We estimated a petrologic type for our sampled CM lithology using the two independent techniques, and obtained a type CM2.5, in agreement with previous estimations. By comparing the Si‐O 10‐µm signature of the AZ average FT‐IR spectra with other well‐studied CMs, we place AZ in the context of aqueous alteration of CM parent bodies. Morphological characterization reveals that AZ has heterogeneous distribution of pores and a global porosity of 4.5 ± 0.5 vol%. We show that chondrules have a porosity of 6.3 ± 1 vol%. This larger porosity could be inherited due to various processes such as temperature variation during the chondrule formation and shocks or dissolution during aqueous alteration. Finally, we observed a correlation between 3D distributions of organic matter and mineral at micrometric scales, revealing a link between the abundance of organic matter and the presence of hydrated minerals. This supports the idea that aqueous alteration in AZ’s parent body played a major role in the evolution of the organic matter

Organics Captured from Comet Wild 2 by the Stardust Spacecraft

Organics found in Comet Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some are similar, but not identical, to those in interplanetary dust particles (IDPs) and carbonaceous meteorites. A new class of aromatic-poor organic material is also present. The organics are rich in O and N compared to meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than meteorites and IDPs. D and 15N suggest that some organics have an interstellar/protostellar heritage. While the variable extent of modification of these materials by impact capture is not yet fully constrained, a remarkably diverse suite of organic compounds is present and identifiable within the returned samples

SEQUENCAGE DE L'ADN PAR ELECTROPHORESE (ETUDE DES EFFETS THERMIQUES SUR LA MIGRATION)

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

The secret to a perfect tan on TNOs: alcohol, water and Sun radiation

International audienceThe comparison between laboratory experiments and astronomical observations is fundamental to spread light on the properties of frozen surfaces in space. Cosmic rays, solar ions and UV photons induce changes in both the structure and chemical composition of these surfaces, that can be characterized by means of infrared spectroscopy. The irradiation also determines variations in the visible spectra. We carried out various ion irradiation experiments of astrophysical relevant species in order to support the interpretation of spectral observation of small Solar System bodies that exhibit frozen volatiles on their surfaces. Among them centaurs, Kuiper-belt objects (KBOs) and trans-neptunian objects (TNOs). Our aim is to simulate the space weathering of small bodies frozen surfaces and in particular to interpret the red color observed on water and methanol rich surfaces, as in the case of (486958) 2014 MU69

Techniques and instruments to analyze, characterize and study returned samples

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Near-infrared Methanol Bands Probe Energetic Processing of Icy Outer Solar System Objects

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Polyaromatic Units Set the Albedo of Dark Extraterrestrial Materials

International audiencePrimitive extraterrestrial materials are generally dark, a characteristic often associated with the presence of polyaromatic organic material and/or sulfides. We show in this study that the reflectance level measured at 0.55 μm of IDPs and some meteorites is correlated to the degree of graphitization of the polyaromatic organic matter. The reflectance level of the primitive surfaces therefore allows us to obtain information on the polyaromatic organic material present on the surface of solar system small bodies observed by remote sensing or visited by space missions. We discuss our results in view of the sample return missions Hayabusa2 and OSIRIS-REx