L'étude des petits corps de système solaire (astéroïdes et comètes), qui se sont formés il y a 4.567 milliards d'années, nous renseigne sur les matériaux initialement présents dans la nébuleuse solaire et sur les processus opérants dans le système solaire primitif. Cette étude peut être notamment menée par l'analyse de cosmomatériaux dits primitifs, telles que des météorites (principalement les chondrites), des poussières interplanétaires (IDPs) ou encore des micrométéorites.Ce travail de thèse consiste en une multi-analyse d'une série de 58 micrométéorites antarctiques (AMMs) provenant de la collection CONCORDIA 2006 et 2016. Parmi elles, différents types texturaux reflétant les différents degrés de chauffage subi durant l'entrée atmosphérique sont représentés: 40 particules non fondues à grains fins (Fgs), 12 particules intermédiaires partiellement fondues (Fg-Scs), 1 particule partiellement fondue scoriacée (Sc) et 5 sphérules cosmiques complètement fondues (CSs). Les échantillons ont été étudiés par différentes méthodes analytiques: i) par spectroscopie Raman, permettant ici d'étudier la structure de la matière organique polyaromatique; ii) par spectroscopie IR, permettant ici d'étudier la matière organique essentiellement aliphatique ainsi que l'état d'hydratation et la minéralogie des échantillons; et 3) par spectrométrie de masse à ionisation secondaire (NanoSIMS), utilisée ici pour mesurer la composition isotopique du carbone et de l'azote de la matière organique contenue dans les AMMs. Dans le but de contraindre la diversité des corps parents échantillonnés par les cosmomatériaux, des chondrites carbonées de types 1 et 2 CM, CR et CI sont également étudiées.La combinaison des caractérisations Raman et IR a permi de mettre en évidence des différences entre les AMMs, en terme d'abondance, de structure et de composition chimique de la matière organique, de minéralogie et d'état d'hydratation. En particulier, 7 Fgs se distinguent des autres AMMs de part: i) une minéralogie hydratée avec phyllosilicates, ii) une richesse en matière organique polyaromatique et aliphatique, iii) une structure de la matière organique polyaromatique différente. Des expériences de chauffage, mises en place dans le présent travail, sur des grains de matrice de chondrites carbonées CM, CR, CI montrent que la traversée atmosphérique peut induire: la déshydratation des échantillons, une diminution de l'abondance en matière organique et une modification structurale de la matière organique polyaromatique. L'identification de 17 Fgs non hydratées montre que malgré une texture à grains fins, certaines Fgs peuvent avoir subi un chauffage significatif durant l'entrée atmosphérique. Les 7 Fgs identifiées apparaissent alors comme celles ayant été le moins modifiées par la traversée atmosphérique et sont donc les plus primitives de notre série. De plus, cette étude montre que l'état d'hydratation, la minéralogie et la matière organique sont des traceurs encore plus sensibles au chauffage subi lors de la traversée atmosphérique que la texture des micrométéorites.Des différences propres, ne s'expliquant pas par le chauffage atmosphérique, sont révélées entre les 7 Fgs hydratées et les chondrites carbonées CM, CR, CI étudiées. Ces différences sont: i) une signature spectrale spécifique des silicates en IR, ii) une richesse en matière organique aliphatique et iii) des caractérisques différentes de la matière organique aliphatique. De plus, l'analyse des compositions isotopiques du carbone et de l'azote montre une grande variabilité des rapports isotopiques parmi les AMMs contrairement aux observations dans les chondrites carbonées. Ces différences propres sont ici interprétées par l'échantillonnage de corps parents différents entre AMMs et chondrites carbonées. / The study of the Solar System's small bodies (asteroids and comets), formed 4.567 billions years ago, gives us an insight on the materials initially present in the solar nebula and on the mechanisms operating in the primitive Solar System. This study can be performed via the analysis of the so-called primitive cosmomaterials, as meteorites (mainly chondrites), interplanetary dust particles (IDPs) or even micrometeorites.This PhD thesis consists of a multi-analysis of a series of 58 Antarctic micrometeorites (AMMs) from the CONCORDIA 2006 and 2016 collections. This set of AMMs provides a large range of textural types reflecting different intensities of heating experienced during the entry in the atmosphere : 40 unmelted fine-grained particles (Fgs), 12 particles intermediate partially melted (Fg-Scs), 1 partially melted scoriaceous particle (Sc) and 5 completely melted cosmic spherules (CSs). To study these samples, I used different analytical methods : i) Raman spectroscopy, to study the structure of the polyaromatic organic matter; ii) infrared (IR) spectroscopy, to analyze the aliphatic organic matter as well as the hydration state and the mineralogy of these samples; and iii) nanoscale secondary ion mass spectroscopy (NanoSIMS) to measure the isotopic composition of carbon and nitrogen of the organic matter contained in the AMMs. In order to constrain the diversity of parent bodies sampled by cosmomaterials, I also studied type 1 and 2 CM, CR and CI carbonaceous chondrites.The combination of Raman and IR techniques reveals differences among AMMs in terms of abundance, structure and chemical composition of the organic matter, mineralogy and hydration state. In particular, 7 Fgs distinguishing themselves from others AMMs as they show : i) a hydrated mineralogy with phyllosilicates, ii) an abundance in polyaromatic and aliphatic organic matter and iii) structural differences in the polyaromatic organic matter. Heating laboratory experiments, on CM, CR and CI carbonaceous chondrite matrices show that the atmospheric entry can induce : a dehydration of the samples, a drop in the abundance of organic material and a structural modification of polyaromatic organic matter. The identification of 17 non-hydrated Fgs reveals that, in spite of their fined-grained texture, some Fgsmay have experienced significant heating during their entry in the atmosphere. The 7 identified Fgs then appears as the ones that were the least affected by the atmospheric entry and thus the most primitive of our series. Moreover, this study shows that the hydration state, the mineralogy and the organic matter are more sensitive tracers to heating experienced during the atmospheric entry than the texture of micrometeorites.Intrinsic differences, which cannot be explained by the atmospheric entry, are also revealed between the 7 hydrated Fgs and CM, CR and CI chondrites. These differences are : i) a specific spectral signature of silicates in IR, ii) an abundance in organic and aliphatic material and iii) different characteristics of the aliphatic organic matter. Moreover, the analysis of the isotopic composition of carbon and nitrogen shows large variabilities among AMMs, in opposition with observations among carbonaceous chondrites. These intrinsic differences are explained here as AMMs and carbonaceous chondrites sampling distinct parent bodies.

Les météorites et particules de poussière interplanétaire apportent des contraintes sur la formation et l’évolution de la matière dans le système solaire. Les micrométéorites, dont certaines proviennent des régions externes du système solaire, représentent la source dominante de matière extraterrestre arrivant sur Terre. Les micrométéorites collectées dans les neiges antarctiques sont dans un excellent état de conservation du fait de conditions géographiques et météorologiques favorables à leur préservation. La collection CONCORDIA/CSNSM de micrométéorites contient en particulier des micrométéorites peu altérées thermiquement lors de leur entrée atmosphérique. Certaines sont caractérisées par une très haute teneur en matière organique, dépassant 50% en volume, très largement au dessus des valeurs habituelles trouvées dans les météorites. Cette matière organique présente de plus la spécificité d’être fortement enrichie en deutérium et contient jusqu’à cinq fois plus d’azote celle extraite des météorites.Les différents scénarios proposés pour expliquer la formation de cette matière et satisfaisant à l’ensemble des caractéristiques de ces micrométéorites impliquent des corps parents orbitant au-delà de Neptune, dans la ceinture de Kuiper ou dans le nuage de Oort. La température y est suffisamment basse pour condenser à leur surface les molécules volatiles comme l’azote et le méthane tandis qu’ils sont exposés à l’action radiochimique du rayonnement cosmique galactique. Afin de contraindre ces scénarios, des expériences ont été conduites en exposant différentes glaces N2-CH4 aux faisceaux d’ions du GANIL simulant ce rayonnement. L’évolution chimique des glaces au cours de l’irradiation et pendant le recuit des échantillons a été suivie par spectroscopie infrarouge au moyen de deux dispositifs disponibles au CIMAP : la chambre d’analyse CASIMIR et le nouvel appareil IGLIAS. Des analyses complémentaires ex situ ont été menées par spectrométrie de masse. Les résultats apportant des éléments de réponse à l’origine de la matière organique des micrométéorites ultracarbonées ainsi que sur l’origine de leur enrichissement isotopique seront présentés et discutés. / 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.

[pt] O espaço interplanetário contem partículas de poeira cósmica originárias do meio interestrelar ou que são produtos da erosão de Asteroides, Meteoróides e Cometas. As partículas que chegam à superfície da Terra são chamadas de micro-meteoritos. Os micrometeoritos participam dos processos de erosão da superfície terrestre e, por isso, são estudados para se ter uma melhor compreensão da evolução do nosso planeta e do Sistema Solar. Um novo programa de pesquisa iniciado em 2016 no Departamento de Física da PUC-Rio tem os objetivos de 1) desenvolver um meio experimental para simular os impactos de micrometeoritos com a superfície terrestre e 2) analisar, as mudanças físico-químicas causadas pelos impactos nos minerais terrestres. A fim de simular o impacto dos micrometeoritos, empre-gou-se a técnica de Ablação por Laser, o que permitiu fazer deposições a taxas controladas de energia em áreas determinadas das amostras. Para este trabalho foram escolhidas amostras dos silicatos mais abundantes encontrados na crosta terrestre, como jadeíta, quartzo e feldspato. A ablação dos silicatos foi efetuada em dois meios: amostra no ar ou amostra em H2O. A principal técnica analítica utilizada foi a espectroscopia Raman. Complementarmente foram utilizadas a micros-copia óptica e a perfilometria. Um total de cerca 500 espectros Raman foram obti-dos, e várias bandas para cada amostra nos dois meios, antes e depois da ablação, foram analisadas estatisticamente. A análise energética e morfológica dos impactos por laser mostrou que a técnica de ablação por laser é razoavelmente boa para simular os impactos dos micrometeoritos com a crosta terrestre. A análise dos espetros Raman mostrou que depois da ablação, tanto no ar como em H2O deionizada, os três silicatos apresentaram modificações na intensidade, na largura e na posição do centro de várias das suas bandas principais. Constatou-se que, quando há modificações, o comportamento é o mesmo para todos os silicatos: deslocamento dos centros das bandas para números de onda menores. Os resultados da análise por espectroscopia Raman são encorajantes para a utilização desta técnica na caracterização e interpretação das mudanças espectrais e estruturais na superfície terrestre depois do impacto de micrometeoritos. Este trabalho, no melhor do nosso conheci-mento, nunca foi feito. A perspectiva é dar continuidade a esta linha de pesquisa, aumentando o número de experimentos de ablação por laser e estendendo a análise das amostras irradiadas a outras técnicas de caracterização complementares a espetroscopia Raman (espetroscopia UV-Vis-NIR, FTIR, ....). Além disso, numa fase futura de estudo, serão estudadas amostras mais complexas, onde material orgânico será adicionado aos silicatos já estudados. / [en] The interplanetary space contains particles of cosmic dust that come from the interstellar medium, or that are the product of the erosion of Asteroids, Meteoroids and Comets. The particles that reach the Earth s surface are called micrometeorites. Micrometeorites participate in the erosion processes of the Earth s surface and, therefore, are studied in order to have a better understanding of the evolution of our planet and the Solar System. A new research program was initiated in 2016 in the Department of Physics of PUC-Rio with the objectives of 1) finding an experimental means to simulate the impacts of micrometeorites with the terrestrial surface, and 2) analyzing the physical-chemical changes caused by the impacts on terrestrial minerals. In order to simulate the impact of micrometeorites the Laser Ablation technique was employed, which allowed us to make energy depositions at controlled rates in certain areas of the samples. For this work, we chose samples of the most abundant silicates found in the earth s crust, such as jadeite, quartz and feldspar. The ablation of the silicates was carried out in two medium: the sample in air, and the sample in H2O. The main analytical technique used was Raman spectroscopy. In addition, optical microscopy and profilometry were used. About 500 Raman spectra were obtained, and several bands for each sample and in each medium, before and after ablation, were statistically analyzed. The energetic and morphological analysis of the laser impacts showed that the technique of laser ablation is reasonably good to simulate the impacts of micrometeorites with the terrestrial crust. The analysis of the Raman spectra showed that after the ablation, in air as well as in deionized H2O, all three silicates presented modifications in the intensity, width and position of the center of several of their main bands. It was found that, when there were modifications, the behavior was the same for all silicates: a shift of the center of de bands to smaller wavelengths. The results of the analysis by Raman spectroscopy are encouraging to use this technique in the characterization and interpretation of the spectral and structural changes in the terrestrial surface after the impact of micrometeorites. This work, to the best of our knowledge, has never been done before. Its perspective is to give continuity to this line of research, incrementing the amount of experiments by laser ablation and extending the analysis of the irradiated samples to other characterization techniques that complement Raman spectroscopy (UV-Vis-NIR spectroscopy, FTIR, …). Also, in future studies, more complex samples will be studied, where organic material will be added to the already studied silicates.