The mass, morphology, and internal structures of three particles from the HAYABUSA sample return mission, analyzed with Synchrotron radiation X-ray tomographic microscopy.

Abstract

The Hayabusa sample return mission, launched in 2003 by the Japan Aerospace Exploration Agency (JAXA), was the first ever space mission to sample material from an asteroid: the S-type, near-Earth asteroid (25143) Itokawa. More than 1500 particles, varying in size from <1 μm to 180 μm, were recovered from the uppermost regolith layer of the asteroid. The main aim of this study is to determine a precise mass for three of these particles. The mass will then be used in a forthcoming study where the concentration of solar wind derived, trapped, and cosmogenic noble gases of the individual particles will be measured. Due to the small particle size (75-145 μm), a normal weighing procedure on a micro- balance would result in large errors (up to 100%) in the mass and thus also in the noble gas concentrations, as well as the cosmic-ray-exposure (CRE) ages derived from cosmogenic noble gases. A precise mass, combined with the detection limit of the noble gas spectrometer used, allows the determination of the minimum cosmic-ray-exposure age that could still be resolved. The mass is measured by determining the volume of the constituent mineral phases (with known densities), using synchrotron radiation X-ray tomographic microscopy (SRXTM). This also allows non-destructive studies of the morphology and internal structure of the particles. While Hayabusa particles have been studied with SRXTM before, none of the particles from this study have so far been analyzed.