Failure modes and conditions of a cohesive, spherical body due to YORP spin-up

Abstract

This paper presents transition of the failure mode of a cohesive, spherical body due to YORP spin-up. On the assumption that the distribution of materials in the body is homogeneous, failed regions first appearing in the body at different spin rates are predicted by comparing the yield condition of an elastic stress in the body. It is found that as the spin rate increases, the locations of the failed regions move from the equatorial surface to the central region. To avoid such failure modes, the body should have higher cohesive strength. The results by this model are consistent with those by a plastic finite element model. Then, this model and a two-layered-cohesive model first proposed by Hirabayashi et al. are used to classify possible evolution and disruption of a spherical body. There are three possible pathways to disruption. First, because of a strong structure, failure of the central region is dominant and eventually leads to a breakup into multiple components. Second, a weak surface and a weak interior make the body oblate. Third, a strong internal core prevents the body from failing and only allows surface shedding. This implies that observed failure modes may highly depend on the internal structure of an asteroid, which could provide crucial information for giving constraints on the physical properties.