Refractory Phases in Primitive Meteorites Devoid of [TSUP]26[/TSUP]A[CLC]l[/CLC] and [TSUP]41[/TSUP]C[CLC]a[/CLC]:Representative Samples of First Solar System Solids?

Abstract

A large number of Ca-Al-rich refractory inclusions in primitive meteorites incorporated the short-lived nuclide ^26Al at the time of their formation with an initial ^26Al/^27Al ratio of 5x10^-5. However, there exist inclusions and refractory phases like corundum and hibonite in these meteorites that have no evidence of ^26Al. A suite of refractory inclusions from these meteorites also have well-defined initial ^26Al/^27Al ratios that are lower by factors of 5-1000 compared to the canonical value of 5x10^-5. Refractory phases free of ^26Al are also devoid of the short-lived nuclide, ^41Ca. Heterogeneous distribution of the short-lived nuclides in the early solar system and possible formation of refractory inclusions from large clumps of interstellar matter devoid of ^26Al are among the suggestions made to explain these observations. In this Letter, we suggest that the refractory phases devoid of ^26Al and ^41Ca represent some of the first solar system solids that formed in the inner region of the solar nebula prior to the injection of these freshly synthesized nuclides from a stellar source into this region.