37th DPS Meeting, 4-9 September 2005
Session 56 TNOs and Centaurs
Poster, Thursday, September 8, 2005, 6:00-7:15pm, Music Recital Room

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[56.09] Alteration of cometesimal composition through collisions: preliminary results

Z.M. Leinhardt, S.T. Stewart-Mukhopadhyay (Dept of Earth and Planetary Sciences, Harvard University)

We present preliminary results from newly coupled shock hydrocode (CTH) and N-body gravity (pkdgrav) simulations of collisions between cometesimals to investigate the evolution of composition and structure in bodies residing in the two comet source reservoirs: the Kuiper Belt and the Oort Cloud. Comets are the most pristine materials in our solar system and provide fundamental information about the initial conditions for planet formation. However, comets have not been perfectly preserved - impacts within the Kuiper Belt and between cometesimals before scattering to the Oort Cloud are likely to have significantly altered a fraction of the material from their initial state.

In this paper we present two sets of validation tests of our hybridized code. Impacts between small bodies in the Solar System can be divided into two regimes: those dominated by material strength and those dominated by self-gravity. For asteroids, the transition size to the gravity regime falls between a few hundred meters to 1 km in radius. Comets are both weaker and have lower gravity; hence, collisions between cometesimals may lie in the transition region between the strength and gravity regimes. To consider strength-dominated collision events, the model will be validated by simulating laboratory experiments in ice and ice mixtures.

In the gravity regime, we will model high speed impacts and compare the results to the catastrophic disruption threshold (QD\star) expected from scaling arguments and other numerical simulations. We use typical collision parameters for the two comet reservoirs (collisions between objects before scattering into the Oort Cloud and mutual collisions within the Kuiper Belt). These validation simulations are a precursor to a broader study of how impact parameters and initial internal structure affect the evolution of the chemical and physical properties of cometesimals.

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Bulletin of the American Astronomical Society, 37 #3
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