X-Ray Computed Tomography of Samples Returned From Asteroid Bennu By NASA's OSIRIS-REx Mission

NASA’s OSIRIS-REx mission collected 121.6 g of material from the surface of asteroid Bennu and returned it to Earth in September 2023. This material is processed and stored in a pristine environment under gaseous nitrogen (GN2) by the Astromaterials Acquisition and Curation Office at NASA Johnson Space Center (JSC–Curation). One of the goals of JSC–Curation’s preliminary examination is to characterize the bulk sample using nondestructive methods, such as X-ray computed tomography (XCT), while maintaining the samples’ pristine nature. We built custom containers using curation-compliant materials (e.g., aluminum) that maintain an air-tight seal but are also sufficiently X-ray-transparent for collecting high-quality XCT data. Samples are sealed while in a GN2-purged glovebox, then transferred to the Astromaterials X-ray Fluorescence and Computed Tomography (X-FaCT) Lab at NASA JSC for XCT scanning using a Nikon XTH 320 scanner with a 180 kV transmission target source. So far, 28 stones have been scanned with reconstructed voxel sizes ranging from 5.00 to 13.00 µm/voxel edge. The XCT data have revealed a diversity of textures and minerals, including variable degrees and styles of brecciation and several lines of evidence for local fluid-rock interactions. Further investigations of these data, in coordination with other, more destructive analytical methods, will help unravel Bennu’s geological history. These XCT data have also been useful for calculating and modelling physical and thermal properties, aiding sample processors during sample chipping, and providing 3-D context of polished sections. Finally, XCT data are sometimes the only petrographic information for samples that were chosen for destructive analytical techniques.