Preservation of polar ice on near-Earth asteroids originating in the outer main belt: A model study with dynamical trajectories

Abstract

Many asteroids in the main asteroid belt may be ice-rich, particularly in the outer Main Belt (OMB). We model temperature and sublimation-driven ice loss for asteroids originating from the OMB, based on ensembles of trajectories from N-body integrations, as they become near-Earth asteroids (NEAs) or evolve onto orbits typical of Jupiter Family Comets (JFCs). We find that the majority of ice loss occurs long before an asteroid reaches a NEA- or JFC-like orbit. The least ice loss occurs at the polar regions of bodies with small axis tilt. The polar regions of these bodies remain so cold that ice does not retreat beyond the influence of the seasonal thermal wave (often less than 5 m) by the time the objects have reached NEA- or JFC-like orbits.