Molecular Isotopic Characterization of the Alh 85013.50 Meteorite: Defining the Extraterrestrial Organic Compounds

Introduction: The Antarctic Meteorite Program has returned over 16,000 meteorites from the ice sheets of the Antarctic. This more than doubles the number of preexisting meteorite collection and adds important and rare specimens to the assemblage. The CM carbonaceous chondrites are of particular interest because of their high organic component. The Antarctic carbonaceous chondrites provide a large, previously uninvestigated suite of meteorites. Of the 161 CM chondrites listed in the ‘Catalogue of Meteorites’ 138 of them have been recovered from the Antarctic ice sheets [1], [2]. However, these meteorites have typically been exposed to Earth’s conditions for long periods of time. The extent of terrestrial organic contamination and weathering that has taken place on these carbonaceous chondrites is unknown. In the past, stable isotope analysis was used to identify bulk organics that were extraterrestrial in origin[3]. Although useful, this method could not exclude the possibility of terrestrial contamination contributing to the isotopic measurement. Compound specific isotope analysis of organic meteorite material has provided the opportunity to discern the terrestrial contamination from extraterrestrial organic compounds on the molecular level. In this work we examine both the water and solvent soluble organic compounds found in ALH 85013.50 meteorite using both compound-specific δD and δC analysis in order to determine the presence of extraterrestrial organic compounds and delineate those from the terrestrial compounds. Our goal is to validate the use of Antarctic carbonaceous chondrites as sources for organic information about parent bodies and provide insight into abiotic organic synthetic pathways.