Deuterium enrichments in interplanetary dust

Interplanetary dust particles (IDPs) collected in the Earthʹs stratosphere comprise a diverse assemblage of materials with both cometary and asteroidal origins. Laboratory studies of IDPs show that they are chemically, mineralogically and isotopically heterogeneous on submicrometer scales. Many IDPs appear to have escaped the significant hydrous and thermal alteration processes which have strongly modified even the most primitive meteorites from their original compositions. ments in deuterium are common among IDPs, with the largest anomalies occurring among the most fragile (cluster) particles. The D/H ratios of cluster IDPs vary by two orders of magnitude, reaching a maximum of .008, roughly 50 times the terrestrial value. Significant, but much smaller effects have been previously observed in primitive meteorites, and are attributed to the survival of molecular cloud material. The larger, and more highly variable deuterium excesses observed among IDPs suggest that they may contain well preserved presolar molecular cloud materials. The chemical characterization of the deuterium-rich phases is still at an early stage.