Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008dps....40.5502r&link_type=abstract
American Astronomical Society, DPS meeting #40, #55.02; Bulletin of the American Astronomical Society, Vol. 40, p.498
Astronomy and Astrophysics
Astronomy
1
Scientific paper
Many small asteroids appear to be gravitational aggregates of cohesive components held together in groups by mutual gravity. Recently, numerical simulations of spin-up by the thermal YORP effect have been shown to give rise to binary asteroid configurations that closely match the observed properties of small binaries, such as near-Earth asteroid 1999 KW4 (Walsh et al. 2008, Nature 454, 188-191). During that study it was determined that the rotational stress response of a gravitational aggregate is sensitive to the details of its internal configuration, such as component size distribution. It is likely that a small amount of cohesion between components may also dramatically alter the stress response. To investigate this aspect, we have developed several models of cohesion in gravitational aggregates. Our most recent model features spring-like restoring forces between neighboring components that saturate and ultimately vanish under sufficient strain. We will present early spin-test results of this model, in which reconfiguration in response to imposed rotational stress is characterized, for starting conditions chosen from a large parameter space of asteroid shape, spin, and strength values. We find that configurations featuring uniform cohesion throughout the body fail (split) first in the middle of the body, as expected. Overall results will be compared with analytical theory and the properties of observed asteroids. The study will give insight into plausible strength scenarios for small bodies in the solar system. Planned future refinements include adding networks of flaws and cracks to represent a more realistic internal configuration. This work is supported by the National Aeronautics and Space Administration under Grant No. NNX08AM39G issued through the Office of Space Science, the National Science Foundation under Grant No. AST0708110, the French Programme National de Planétologie, the Poincaré Fellowship program, and Rotary International, District 1730.
Michel Pascal
Richardson Derek C.
Schwartz Stephen R.
Walsh Kevin J.
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