Deuterium enrichments in chondritic macromolecular material-Implications for the origin and evolution of organics, water and asteroids

Here we report the elemental and isotopic compositions of the insoluble organic material (TOM) isolated from several previously unanalyzed meteorites, as well as the reanalyses of H isotopic compositions of some previously measured samples (Alexander et al., 2007). The IOM in ordinary chondrites (OCs) has very large D enrichments that increase with increasing metamorphism and decreasing H/C, the most extreme delta D value measured being almost 12,000 parts per thousand. We propose that such large isotopic fractionations could be produced in the OC parent bodies through the loss of isotopically very light 112 generated when Fe was oxidized by water at low temperatures (<200 degrees C). We suggest that similar isotopic fractionations were not generated in the IOM of CV and CO chondrites with similar metamorphic grades and IOM H/C ratios because proportionately less water was consumed during metamorphism, and the remaining water buffered the H isotopic composition of the TOM even a H was being lost from it.