DIX Planetary Science Seminar

Asteroids, comets, and their fragments may have served as delivery vehicles for organic matter to the early Earth. Amino acids, the building blocks of proteins in living systems, are among the most important organic compounds detected in meteorites. The abundances and distributions of amino acids vary both within and between meteorites, ranging from several ppm to approximately 300 ppm. Isotopic measurements of meteoritic amino acids show enrichment in heavy isotopes relative to terrestrial counterparts, supporting an extraterrestrial origin. Molecular distributions and carbon and hydrogen isotope ratios further suggest that some amino acids in Murchison and other CM2 meteorites were likely modified during aqueous alteration on their parent bodies. However, the extent to which aqueous alteration influences the molecular and isotopic evolution of amino acids remains an open question. At IMPMC (MNHN, Sorbonne University & CNRS, Paris), I investigated the evolution of meteoritic amino acids under aqueous alteration, both in the presence and absence of Fe-rich minerals by doing laboratory simulations. These studies revealed that aqueous alteration influences the distribution and hydrogen isotopic signatures of amino acids, whereas carbon isotopic data suggests inheritance from earlier precursor molecules. In addition, the D/H exchange site of amino acids have been identified, and we found that hydrogen from methyl group should have better retained their pre-accretional D/H values despite hydrothermal alteration on the parent body.