Interstellar Dust in Collected Interplanetary Dust Particles

During the past decade interplanetary dust particles (IDPS) have been collected in the earth's stratosphere. Isotopic studies of these particles have demonstrated that many of them are greatly enriched in deuterium and at least some of them carry this enrichment in smaller subcomponents. Deuterium enrichments of a similar magnitude are seen in simple molecules in interstellar clouds. Deuterium enrichment in IDPs can be taken as evidence for the presence of interstellar material. It is not clear at this time whether the carriers of the isotopic anomalies represent true, unaltered interstellar dust grains, or whether they represent an altered component with a molecular 'memory' of original interstellar grains. The spectra of different components in the collected dust provide suggestive matches to similar components evident in the astronomical spectra of dust in comets, dense molecular clouds, and emission nebulae. The known extraterrestrial nature of the particles, the possible presence of interstellar material in them, and their spectral similarity to many astronomical objects all argue that the collected IDPs provide useful analogs for the modelling of interstellar dust.