PNNL

Abstract

Presolar grains are small samples of stardust which can be found at low abundances in some of the most unaltered types of extraterrestrial materials. These grains condensed in the environments of massive stars before the formation of the solar system and survived incorporation into solar system materials without completely losing their isotopic, elemental and mineralogical makeup. Laboratory analyses of these presolar grains give insights into stellar nucleosynthesis and provide clues about the physical and chemical conditions during their formation as well as about interstellar exposure history and parent body processes. Since most presolar grains are less than 1 micrometer in diameter and represent only a few ppm of their host materials (e.g., meteorites or interplanetary dust particles), locating and studying these particles can be analytically challenging. Recently, we began using scanning Auger spectroscopy for the in situ elemental characterization of presolar grains and found that this technique, especially when paired with spatially matched NanoSIMS isotopic studies, can provide important insights that would be difficult to obtain with other analytical approaches. Here we discuss details of applying Auger spectroscopy to sub-micrometer sized geological samples and address practical issues such as sample preparation, measurement settings, data processing, and elemental quantification.