Asteroids and comets are thought to be critical for understanding the origin and evolution of the Solar system and possibly the origin of life on Earth. Several countries and space agencies have launched missions to these small bodies. The most recent one is the OSIRIS-REX mission to Asteroid (101955) Bennu that provides an unprecedented opportunity to thoroughly map and investigate the geophysical state of a primitive asteroid. In this work we study the motion of particles near the surface of Bennu. An application of the results is to give assistance for the selection of the sample site.