The geophysical environment of Bennu

• The OSIRIS-REx mission to Asteroid Bennu will achieve an unparalleled investigation of a small, primitive rubble pile asteroid.
• The geophysics of these bodies is largely unknown and unconstrained, and will shed fundamental new insight into the geophysical evolution of primitive materials in the solar system.
• This paper sets the stage for the geophysical investigation of this body, laying out a range of possible hypotheses for its characteristic shape that ensures its future relevance once the actual measurements are made.

An analysis of the surface and interior state of Asteroid (101955) Bennu, the target asteroid of the OSIRIS-REx sample return mission, is given using models based on Earth-based observations of this body. These observations have enabled models of its shape, spin state, mass and surface properties to be developed. Based on these data the range of surface and interior states possible for this body are evaluated, assuming a uniform mass distribution. These products include the geopotential, surface slopes, near-surface dynamical environment, interior stress states and other quantities of interest. In addition, competing theories for its current shape are reviewed along with the relevant planned OSIRIS-REx measurements.