  On 24 September 2023, the NASA OSIRIS-REx mission dropped a capsule to Earth
containing approximately 120 g of pristine carbonaceous regolith from Bennu. We
describe the delivery and initial allocation of this asteroid sample and
introduce its bulk physical, chemical, and mineralogical properties from early
analyses. The regolith is very dark overall, with higher-reflectance inclusions
and particles interspersed. Particle sizes range from sub-micron dust to a
stone about 3.5 cm long. Millimeter-scale and larger stones typically have
hummocky or angular morphologies. A subset of the stones appears mottled by
brighter material that occurs as veins and crusts. Hummocky stones have the
lowest densities and mottled stones have the highest. Remote sensing of the
surface of Bennu detected hydrated phyllosilicates, magnetite, organic
compounds, carbonates, and scarce anhydrous silicates, all of which the sample
confirms. We also find sulfides, presolar grains, and, less expectedly, Na-rich
phosphates, as well as other trace phases. The sample composition and
mineralogy indicate substantial aqueous alteration and resemble those of Ryugu
and the most chemically primitive, low-petrologic-type carbonaceous chondrites.
Nevertheless, we find distinct hydrogen, nitrogen, and oxygen isotopic
compositions, and some of the material we analyzed is enriched in fluid-mobile
elements. Our findings underscore the value of sample return, especially for
low-density material that may not readily survive atmospheric entry, and lay
the groundwork for more comprehensive analyses.
