Updated collisional probabilities of minor body populations

Abstract

The consistent increase in the discovery rate of new asteroids and Trans Neptunian Objects (TNOs) in these last years has urged an update of the values of intrinsic probability of collision and impact velocity for some minor body populations. With the statistical method of Dell'Oro & Paolicchi ([CITE]), we have recomputed the values of impact probability and velocity for Hilda asteroids, for Trojans vs. Short Period Comets (SPC), and for TNOs. The algorithm of Dell'Oro and Paolicchi is particularly suited for the task since it can account for resonant behaviour (Dell'Oro et al. [CITE]) and for the clustering of the perihelion longitude of Main Belt asteroids and Hildas, caused by the presence of a forced component in the eccentricity. The Hilda population turns out to be well sampled in the orbital parameter space since no significant changes are found for the collision frequency among Hildas, and of Hildas with Main Belt asteroids, although a much larger sample of orbits has been used in our computations (232 objects) vs. the smaller group used in previous computation by Dahlgren ([CITE]) (40 objects). We also computed the impact rate of SPCs vs. Trojans that turned out to be an order of magnitude lower respect to the Trojans vs. Trojans impact rate. The relative velocity is instead about 30% higher. Using reasonable estimates of SPC and Trojan number densities, we find that approximately 1 every 100 collisions involving Trojans may be with an SPC. In the case of TNOs there is a consistent discrepancy between our values of the collision probability and impact speed, and those computed by Davis & Farinella ([CITE]). The consistent increase in the number of known TNOs (186 at present, only 16 at the time of the Davis and Farinella's work) has led to a better knowledge of their distribution in the phase space and, consequently, to more reliable estimates of the collisional probability and impact velocity.