HYDROMA · Origin and evolution of organic matter in carbonaceous chondrites: influence of hydrothermal processes

Carbonaceous chondrites (CC) are believed to be fragments of carbonaceous asteroids from the asteroidal belt. They contain up to 4wt% of organic compounds, showing a huge diversity and extremely variable H and N isotope compositions. These isotope compositions can relate to synthesis environments but the exact nature of the processes that influenced the formation of organic compounds in CC remains unresolved. Part of the issue comes from the occurrence of hydrothermal alteration on the chondrites that exhibit the largest content in organic matter. Hydrothermalism may have modified the chemical and isotopic signature of organic molecules, but the extent of these modifications is not yet constrained, leaving a lot of uncertainties on the interpretation of H and N isotope ratios. The HYDROMA project aims at determining the effects of hydrothermalism on the D/H and 15N/14N ratios of organic molecules in CC. This project will rely on an innovative experimental approach to quantify isotopic exchange of hydrogen and nitrogen between organic compounds and the hydrothermal fluid. HYDROMA will provide a self-consistent determination of the extent and kinetics of the modification of the isotopic signatures recorded in organic molecules. Hence, it will improve the understanding of H and N-isotope systematics of organic matter in CC. HYDROMA will permit using isotope composition of organic compounds to constrain the hydrothermal events (duration, temperature) on carbonaceous asteroids. This multidisciplinary research will shed new light on the origin and reprocessing of organic matter in the early solar system, and its delivery to rocky planets, including the Earth, thus disclosing the origin of prebiotic molecules on our planet.