Surface thermophysical properties determination of OSIRIS-REx target asteroid (101955) Bennu

In this work, we investigate the thermophysical properties of OSIRIS-REx target asteroid (101955) Bennu (hereafter Bennu), where thermal inertia plays an important role in understanding the nature of the asteroid’s surface, and will definitely provide substantial information for the sampling return mission. Using a thermophysical model incorporating, the recently updated 3D radar-derived shape model and mid-infrared observations of Spitzer-PUI, Spitzer-IRAC, Herschel/PACS and ESO VLT/VISIR, we derive the surface thermophysical properties of Bennu. The asteroid has an effective diameter of 510+6 −40 m, a geometry albedo of 0.047+0.0083 −0.0011, a roughness fraction of 0.04 +0.26 −0.04 and thermal inertia of 240 +440 −60 Jm −2 s−0.5 K−1 for a best-fitting solution at 1σ level. The best-estimate thermal inertia indicates that finegrained regolith may cover a large area of Bennu’s surface, with a grain size that may range from 1.3 to 31 mm, and our outcome further supports that Bennu would be a suitable target for the OSIRIS-REx mission to return samples from the asteroid to Earth.