The shape and surface environment of 2016 HO3

Abstract

Asteroid 2016 HO${}_3$ is a fast-rotating Near-Earth asteroid (NEA), and a potential target for future exploration. Studying the surface of this asteroid and whether it retains any regolith are primary science objectives, which can provide key clues to the formation and evolution of this small body. In order to support such future explorations, the stability condition for and distribution of regolith on a non-spherical fast-spinning small body are explored in this paper using derived models of 2016 HO${}_3$. First, a tri-axial ellipsoid shape model of 2016 HO${}_3$ is established based on light curve data. The possible shape configurations are presented. Then, the ambient environment accelerations are analyzed and compared. The stability conditions to retain regolith on the surface of the ellipsoid model is derived and evaluated numerically. The influence of shape, density, cohesion and the angle of friction on the distribution is discussed. Finally, the motion of failed regolith is investigated. The results show that 2016 HO${}_3$ is likely an elongated asteroid, which has a length to width ratio smaller than 0.48. A layer of millimeter-sized to centimeter-sized grains can exist on the surface of asteroid 2016 HO${}_3$, preferentially kept near the polar and the short axis regions. The required cohesion to bind such particles to the surface is less than 0.2 Pa. Meanwhile, any regolith disturbed from the surface will undergo periods of sliding and bouncing before escaping. This research can provide a reference for preliminary mission design for future missions to asteroid 2016 HO${}_3$.