Cometary dust and origin of matter in the protoplanetary disk
The objective of this thesis is the analysis of extraterrestrial dust collected in Antarctica: chondritic Antarctic micrometeorites (AMMs) and ultracarbonaceous micrometeorites (UCAMMs). Models predict that 80% of the dust that falls to Earth is of cometary origin. AMMs share many characteristics wi...
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| Other Authors: | , , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
HAL CCSD
2021
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| Subjects: | |
| Online Access: | https://theses.hal.science/tel-03588921 https://theses.hal.science/tel-03588921/document https://theses.hal.science/tel-03588921/file/101608_GUERIN_2021_archivage.pdf |
| Summary: | The objective of this thesis is the analysis of extraterrestrial dust collected in Antarctica: chondritic Antarctic micrometeorites (AMMs) and ultracarbonaceous micrometeorites (UCAMMs). Models predict that 80% of the dust that falls to Earth is of cometary origin. AMMs share many characteristics with the cometary dust reported by the Stardust space mission, and the characteristics of UCAMMs suggest formation at very low temperatures, far from the early sun. Micrometeorites therefore offer an opportunity to understand the mechanisms of cometary dust formation. UCAMMs are mostly composed of an organic matrix containing small mineralogical assemblages. The large amount of organic matter (OM) present in UCAMMs allows its analysis without using the classical extraction methods used to extract insoluble organic matter (IOM) from meteorites. Analyses of the AMMs by Raman and infrared microspectroscopy indicate a polyaromatic OM with a high degree of disorder, with characteristics close to those of the cometary grains reported by the Stardust mission. The variability of the OM spectral parameters is however more important for hydrated chondritic AMMs than for those without phyllosilicates. The mid- and far-infrared spectra show that the non-hydrated AMMs contain pyroxene and olivine silicates and that the aqueous phases of the hydrated AMMs are mainly phyllosilicates. Infrared and Raman analyses of the UCAMMs show a relatively large amount of nitrogen in the organic matter, and the occasional presence of nitrile groups. Spatially resolved X-ray transmission microscopy (STXM-XANES) analyses of the OM show the presence of 3 organic phases of distinct compositions within the UCAMM OM. The nitrogen present in the UCAMMs is carried by only one of these three phases, which has N/C atomic ratios up to 0.2. The inorganic phases contained in the UCAMMs were analysed by transmission electron microscopy. They exist as isolated phases, or as small mineral assemblages in the organic matrix, or as aggregates of different minerals, ... |
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