Implications of isotopic anomalies and presolar grains for the formation of the solar system

Isotopic anomalies are widespread in primitive chondritic meteorites and most of them can be tied to specific presolar materials from the Sun\u27s parent molecular cloud. The known types of presolar materials come from many stellar and interstellar sources and exhibit a wide range of thermal and chemical stability. Bulk compositions and the abundances and characteristics of presolar grains indicate that CI chondrites and CM2 matrices originated from unfractionated samples of the Sun\u27s parent molecular cloud. In the least metamorphosed members of other chondrite classes, correlations between the abundances and characteristics of presolar grains and the bulk compositional properties of the host meteorites indicate that the chondrite classes arose through different degrees of partial evaporation of the dust inherited from the Sun\u27s parent molecular cloud. Condensation from a gas of solar composition is effectively ruled out as the primary mechanism for the volatility-controlled fractionations among the chondrite classes