Dynamical erosion of the asteroid belt and implications for large impacts in the inner Solar System

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.12.008 Byline: David A. Minton, Renu Malhotra Keywords: Asteroids; Asteroids, Dynamics; Cratering Abstract: The cumulative effects of weak resonant and secular perturbations by the major planets produce chaotic behavior of asteroids on long timescales. Dynamical chaos is the dominant loss mechanism for asteroids with diameters Da[sup.3]10km in the current asteroid belt. In a numerical analysis of the long-term evolution of test particles in the main asteroid belt region, we find that the dynamical loss history of test particles from this region is well described with a logarithmic decay law. In our simulations the loss rate function that is established at t[approximately equal to]1Myr persists with little deviation to at least t=4Gyr. Our study indicates that the asteroid belt region has experienced a significant amount of depletion due to this dynamical erosion -- having lost as much as [approximately equal to]50% of the large asteroids -- since 1 Myr after the establishment of the current dynamical structure of the asteroid belt. Because the dynamical depletion of asteroids from the main belt is approximately logarithmic, an equal amount of depletion occurred in the time interval 10-200 Myr as in 0.2-4 Gyr, roughly [approximately equal to]30% of the current number of large asteroids in the main belt over each interval. We find that asteroids escaping from the main belt due to dynamical chaos have an Earth-impact probability of [approximately equal to]0.3%. Our model suggests that the rate of impacts from large asteroids has declined by a factor of 3 over the last 3 Gyr, and that the present-day impact flux of D10km objects on the terrestrial planets is roughly an order of magnitude less than estimates currently in use in crater chronologies and impact hazard risk assessments. Author Affiliation: Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, United States Article History: Received 15 September 2009; Revised 2 December 2009; Accepted 3 December 2009