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D. D. Durda, W. F. Bottke (Southwest Research Institute), E. Asphaug (Univ. of California, Santa Cruz), D. C. Richardson (Univ. of Maryland)
The exciting discoveries of what is now a growing suite of asteroid satellites have renewed interest in the diversity of collisional mechanisms that may lead to the formation of small-body satellites and binary pairs. Understanding how asteroid satellites form is important because they hold important clues to the collisional environment of the asteroid population, and models of their formation may provide constraints on internal structures of asteroids beyond those possible from observations of satellite orbital properties alone. Since collisions are the dominant evolutionary process affecting asteroids, it is plausible that these satellites are by-products of cratering and/or catastrophic disruption events. Basic analytic arguments and preliminary numerical investigations have identified several collisional processes as plausible formation mechanisms; these include: (1) mutual capture following catastrophic disruption, (2) rotational fission due to glancing impact and spin-up, and (3) reaccretion in orbit of ejecta from large, non-catastrophic impacts. We will present initial results, focused on scenario (1), from a planned systematic investigation directed toward mapping out the parameter space of these three collisional mechanisms. Our work takes advantage of state-of-the-art numerical tools that have not been applied in previous asteroid satellite work. These include: (1) smooth-particle hydrodynamics (SPH) codes, which accurately model the pressures, temperatures, and energies of asteroid-asteroid impacts, and (2) efficient N-body codes which can track the trajectories of tens-of-thousands of individual collision fragments in an expedient manner. Simulations using SPH codes are used to model the various impact phases between colliding asteroids. Once the relevant portions of the impact phase are complete (crater formation/ejecta flow fields established with no further fragmentation/damage), the outcomes of the SPH models are handed off as the initial conditions for N-body simulations, which follow the trajectories of the ejecta fragments for an extended time to search for the formation of bound satellite systems.
This work is supported by a grant from the National Science Foundation.