Isotopic Composition and Origin of Meteoritic Nanodiamonds studied by Atom-Probe Tomography and Complementary Techniques

Abstract

Presolar grains, which formed in the outflows of distant stars, are the only source of information from other star systems that is accessible to direct laboratory microanalysis [1]. Meteoritic nanodiamonds (NDs), separated from carbonaceous chondrite meteorites by acid dissolution [2], are the smallest suspected type of presolar grain, 3 nm in median diameter [3]. Bulk analyses of billions of NDs in aggregate, accompanied by disordered C and other acid residue, have been conducted by stepped heating. They reveal trace amounts of isotopically anomalous Xe-HL, which originates from corecollapse supernovae [4,5], but bulk measurements of the C isotopic ratios are within the limits of variation in our solar system [6, and references therein]. Isotopic analysis of individual NDs is necessary to solve the mystery of their origins and to connect our knowledge of NDs to our knowledge of the stars.