Birth of the presolar Nebula: The sequence of condensation revealed in the Allende meteorite

This work applies the well-known supernova-trigger hypothesis for solar system formation to explain in detail many properties of the Allende meteorite. The Allende carbonaceous chondrite meteorite is an assemblage of millimetre- to centimetre-sized Ca-Al-rich inclusions (CAI's), fine-grained alkali-rich spinel aggregates, amoeboid olivine aggregates, olivine chondrules and sulfide chondrules set in an extremely fine-grained black matrix. Detailed isotopic, chemical and textural properties show that these components formed in the above order as independent cosmic grains. Some CAI's contain micron-sized metal nuggets in which the normally incompatible refractory (Mo,Re,W) and platinum group (Pt,Os,Ir,Ru) metals are alloyed together in approximately 'cosmic' proportions, suggesting that these nuggets also condensed as cosmic grains. (orig./WL)