Diverse Assemblage of Presolar and Solar System Materials in Anhydrous Interplanetary Dust Particles: Coordinated NanoSIMS and TEM Analyses

A coordinated TEM and NanoSIMS isotopic imaging study of microtome sections of three anhydrous interplanetary dust particles (IDPs) revealed a diverse collection of primitive materials having disparate origins and histories. Presolar silicate grains that likely originated in asymptotic giant branch (AGB) stars were present in each IDP at abundances ranging from 140 (+320/-120) ppm to 2000 (+4600/-1700) ppm. A unique compound presolar grain was identified that consisted of a crystalline spinel core and amorphous silicate mantle having heterogeneous Fe content. This compound grain traces the changing conditions in the circumstellar region during condensation and is the first identified presolar spinel in an IDP. A presolar SiC grain, also rare in IDPs, was found to be enriched in 13C, 14N, and 28Si, consistent with mainstream SiC that originated in ∼ solar metallicity AGB stars. We determine presolar spinel and presolar SiC abundances of 760 (+1700/-630) ppm and 190 (+440/-160) ppm, respectively, in the individual IDPs.