Host phases and origin of noble gases in meteorites

A large fraction of the noble gases in carbonaceous chondrites are concentrated in a small amount of meteoritic matter (approx. <=2%). It consists of carbon (in different forms) and chromite which are the major host phases for three different varieties of noble gas components. The planetary component constituting the bulk amount of noble gases is taken to be of solar-system origin. The Ne-E, s-Kr and s-Xe components which occur in extremely small amounts are apparently presolar. They appear to be products of nucleosynthesis from other stars, trapped in interstellar grains which were never vaporized and homogenized since their import into the solar system. The CCFX component forming an appreciable fraction of the noble gases is of uncertain origin. (orig.)