Isotopic composition of light elements in ultracarbonaceous micrometeorites by secondary ion mass spectrometry at high mass resolution, contribution to the knowledge of cometary surfaces

• Main Author: Bardin, Noémie
• Other Authors: Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris Saclay (COmUE), Jean Duprat
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2015
• Subjects: Ultra-Carbonaceous Micrométéorites; Organic Matter; Cometary Surfaces; Isotopic and Elemental Composition; Secondary Ion Mass Spectrometry; High Mass Resolution; Instrumental Mass Fractionation; Secondary Polyatomic Ions; Micrométéorites ultra-carbonées; Matière organique; Surfaces cométaires; Composition isotopique et élémentaire; Spectrométrie de masse à émission ionique secondaire; Haute résolution en masse; Fractionnement en masse instrumental; Ions secondaires polyatomiques; [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]; Antarctic; The Antarctic; Antarc*
• Online Access: https://theses.hal.science/tel-01256780; https://theses.hal.science/tel-01256780/document; https://theses.hal.science/tel-01256780/file/VD2_BARDIN_NOEMIE_17122015.pdf

This thesis covers the isotopic analysis of carbon-rich interplanetary dust (ultracarbonaceous micrometeorites), in order to better understand the isotopic fractionation process of light elements (hydrogen and nitrogen) observed in the organic phases of primitive extraterrestrial matter. It is possible, within a collection of micrometeorites coming from the central regions of the Antarctic continent, to identify ultra-carbonaceous micrometeorites (UCAMMs – for Ultra-Carbonaceous Antarctic MicroMeteorites) which contain about ten times more carbon than the primitive meteorites. These particles are extremely rare and open the possibility to study in laboratory cometary particles of large sizes (100-200 microns). This thesis focuses on the isotopic analyses of UCAMMs, in order to understand the isotopic fractionation processes of light elements (hydrogen and nitrogen) observed in the organic matter of the primitive solar system. Mineralogical, chemical and structural analyses on two fragments of ultra-carbonaceous micrometeorites were performed in the framework of collaborations using techniques of scanning electron microscopy, electron microprobe, infrared microspectroscopy (SOLEIL synchrotron). The main work of this thesis concerns the isotopic analysis of two UCAMMs by Secondary Ion Mass Spectrometry (SIMS) using the NanoSIMS ion microprobe. The instrumental developments performed in collaboration between the CSNSM and the Curie Institute teams allow to resolve molecular interferences with a mass resolving power higher than 20 000 retaining a sensibility compatible with the measurements considered here. So, it has been possible to measure for the first time the hydrogen isotopic composition with the polyatomic ions 12C2D- and 12C2H- and to compare its spatial distribution with that of the nitrogen (12C15N-/12C14N-) obtained on the same surface with the same magnetic field. A protocol for producing a series of standard samples was developed from polymers isotopically enriched in deuterium in order to determine ...