Stardust material in the paired enstatite chondrites: SAH 97096 and SAH 97159

Abstract

Stardust grains, more commonly referred to as presolar grains, are solid condensates of stars that are studied in terrestrial laboratories with a variety of analytical techniques. Here we report on submicrometer silicate, oxide and carbonaceous stardust grains identified in the paired enstatite chondrites SAH 97096 and SAH 97159. A majority of the grains with O isotopic anomalies exhibit 17O excesses and probably originated in the dusty envelopes of low-mass AGB or RG stars. One grain is highly 17Orich and has a normal Si isotopic composition; based on its O and Si isotopic composition, an origin in a nova is most likely. However, another scenario that may explain this grain's O isotopic composition is a binary star system consisting of an evolved or mainstream star accreting material from its nova companion. Elemental characterization of the O-anomalous grains shows the presence of eleven magnesian silicate grains with or without Fe and three Fe-oxide grains; none of the grains contain Ca or Al. Carbon-anomalous grains have 12C/ 13C ratios from 19-78; most are probably SiC. The abundances of the O- and C-anomalous grains are 98±34 and 51±13 ppm, respectively, which is much higher than previously observed in other enstatite chondrites, and close to that of some carbonaceous chondrites. © Copyright owned by the author(s).