Dynamical Erosion of the Asteroid Belt and Implications for the Rate of Large Impacts on the Terrestrial Planets

Details Dynamical Erosion of the Asteroid Belt and Implications for the Rate of Large Impacts on the Terrestrial Planets Dynamical Erosion of the Asteroid Belt and Implications for the Rate of Large Impacts on the Terrestrial Planets

Sep 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.2702m&link_type=abstract

American Astronomical Society, DPS meeting #41, #27.02

Mathematics

Probability

Scientific paper

We have performed a series of numerical integrations of test particles in the main asteroid belt region (2-4.4 AU) under the gravitational perturbation of the giant planets and Mars neglecting all non-gravitational effects. We find that the dynamical loss history of test particles from this region is well described with a piecewise logarithmic decay law, that is ndot = Bit-1 , where n is the number of test particles, t is the elapsed time, and Bi is the slope of loss rate over the time interval [ti, ti+1]. In our simulations the loss rate function that is established at t = 1 My persists with little deviation to at least t = 4 Gy. Dynamical chaos is the dominant loss mechanism for asteroids with diameters D > 10 km in the current asteroid belt. Because the dynamical depletion of asteroids from the main belt is approximately logarithmic, an approximately equal amount of depletion occurred in the time interval 10-200 My as in 0.2-4 Gy, roughly 30% of the current number of large asteroids in the main belt over each interval. We find that the probability of impact onto the Earth by asteroids lost due to dynamical chaos over the last 3 Gy is 0.3%. If dynamical erosion of large asteroids is the dominant source of D > 10 km impactors in the terrestrial planet zone since the end of the Late Heavy Bombardment, then the rate of large impacts has declined by a factor of 3 over the last 3 Gy. We estimate that the present-day flux of D > 10 km asteroidal impactors on the terrestrial planets is about an order of magnitude less than current estimates used in crater chronologies.

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