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Refining Asteroid Collisional Timescales

Student Sam Van Kooten and Professor Larry Molnar

Tuesday, November 19, at 3:45 p.m. in SB110.

To shed light on the formation of the solar system, we can analyze the history of the asteroid belt, but this requires a good understanding of the asteroid life cycle. Of the three main parts of the cycle, our understanding of the collisional process is most in need of quantitative verification. To help address this, we have computed asteroid collisional disruption timescales (i.e. the average time before an asteroid is destroyed by collision) with more rigor than published calculations. We treated each of four zones in the asteroid belt separately. Within each zone, we computed intrinsic collision probabilities as a function of collisional speed. We also computed size-frequency distributions accounting for varying albedos, using a sample of albedos from the WISE satellite for each zone. We found significant variation in probabilities and albedos among the zones. These zone-specific analyses allowed us to generate distinct timescales for each zone. Our final result, plotted against asteroid size, shows a scale factor difference between zones and a common shape significantly different from previous computations.

This allows a number of future applications. Our reassessment of how often collisions occur might change the balance of which of several processes dominate the life cycle of asteroids. Second, models of the strength of asteroids, used in our calculations, can be verified with observations in the Koronis Zone, a relatively empty region of the asteroid belt where sets of rubble from large past collisions can be individually counted to tell how often large collisions have happened. This allows for a direct comparison with our prediction of how often such collisions should happen. Finally, our collisional rates can be used to produce new zone-by-zone models of the historical evolution of asteroids, which can be checked by our size-frequency distributions.





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