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W.F. Bottke (SwRI)
Over the last several decades, it has been assumed that collisions and gravitational forces are the primary mechanisms governing the evolution of asteroids and meteoroids. While models employing these processes can explain some aspects of the main belt and near-Earth asteroid (NEA) populations, they also make numerous predictions that are inconsistent with observations (e.g., meteorite cosmic-ray exposure ages that are an order of magnitude longer than model predictions, the puzzling size and spectral diversity of NEAs, the peculiar orbital distributions of many asteroid families, the relatively shallow power-law slope of the NEA size-frequency distribution when compared to that expected for ``fresh" ejecta, the surprising number of km-sized asteroids with very fast or very slow rotation rates). To resolve these discrepancies, several researches have invoked the Yarkovsky effect, a thermal radiation force that causes objects to undergo slow but steady semimajor axis drift and spin up/down as a function of their spin, orbit, and material properties. Numerical results suggest that this previous known but generally neglected mechanism can be used to: (i) deliver asteroids (and meteoroids) with diameter D < 20 km from their parent bodies in the main belt to chaotic resonance zones capable of transporting this material to Earth-crossing orbits, (ii) disperse asteroid families, with drifting bodies jumping or becoming trapped in mean-motion and secular resonances within the main belt, and (iii) modify the rotation rates of asteroids a few km in diameter or smaller. Accordingly, I believe that Yarkovsky thermal forces should now be considered as important as collisions and gravitational perturbations to our overall understanding of asteroid evolution.
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Bulletin of the American Astronomical Society, 34, #3
© 2002. The American Astronomical Society.