Isotopic analysis of large presolar SiC grains from the Murchison meteorite

Abstract

Carbon, N, O and Si isotopic compositions of five large presolar SiC grains have been analyzed. All five grains are mainstream grains. ²⁹Si/²⁸Si and ³⁰Si/28Si ratios of the grains are 7 to 14%, and 8 to 12% higher than the solar ratios, respectively. Their Si isotopic ratios show that those grains are more enriched in ²⁹Si and ³⁰Si than smaller SiC grains. Although more analysis is needed, large SiC grains might have originated from high-metallicity AGB stars.