37th DPS Meeting, 4-9 September 2005
Session 11 Comets
Oral, Monday, September 5, 2005, 4:20-6:00pm, Law LG19

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[11.06] Thermal evolution model of the Rosetta target 67P/Churyumov-Gerasimenko

M.C. De Sanctis, M.T. Capria (IASF-INAF), A. Coradini (IFSI-INAF)

Rosetta will arrive to comet 67P/Churyumov-Gerasimenko in 2014. At the moment, little is known about this comet, but the successful design of the ROSETTA mission requires some preliminary knowledge of the comet physical parameters. These quantities cannot be determined only through ground-based observations, so predictive models of the thermal evolution and differentiation of a cometary nucleus are necessary. We have developed a comet nucleus thermal evolution model that helps in the estimations of the above cited quantities. The results have been computed with a numerical code solving simultaneously the heat conduction and gas diffusion equations through an idealized spherical comet nucleus (De Sanctis et al., 1999, 2000, Capria et al., 2000 a,b). We applied this model to a comet nucleus with the characteristics of Churyumov-Gerasimenko. Our results indicate that the peculiar dynamical history of this comet has a strong effect on the comet evolution. The models foresee the formation of a dust mantle during the orbital stage at large perihelion distance, with strong reduction of the overall activity and sinking of the sublimation fronts. When the perihelion distance reduction occurred at the last close encounter (1959) the comet was probably ``reactivated". In our models we see a slight increase of the activity passage after passage: the nucleus is progressively ablated and this leads to the reduction of the depth of the sublimation fronts and a slow increase of the activity. The perihelion asymmetry in the gas activity reported by some observers is reproduced by our models without any seasonal effects, but with only the effect of the heat storage in the cometary nucleus. The computed gas fluxes are in general agreement with those estimated from the observations.

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Bulletin of the American Astronomical Society, 37 #3
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