Isotope studies on interplanetary dust particles (IDPs). Noble gases

Only a few laboratories have reported noble gas data for a single particle of interplanetary dust particles (IDPs) because of difficulties in analyzing extremely small particle sizes, ∼10μm and ∼10 ng, for which a noble gas detection system with low analytical blank level and high sensitivity is required. Noble gas studies performed on IDPs until now have been aimed at identifying their extraterrestrial origin and at estimating heating temperature experienced during their entry into the terrestrial atmosphere. Isotopics compositions of light noble gases He, Ne and Ar indicate solar-type noble gas component, and strongly support their extraterrestrial origin. Step-heating experiments show variable release patterns for He and Ne depending on the thermal history of particles, which may help in identifying the origins, asteroidal or cometary, of individual particles. Noble gases of extraterrestrial origin observed in deep-sea sediments are also described. (author)