Thermal evolution model of 67P/Churyumov-Gerasimenko, the new Rosetta target

Abstract

Rosetta, the ESA mission dedicated to the detailed study of a comet nucleus before and after the onset of activity, will arrive at 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 the cometary nucleus are necessary. We have developed a comet nucleus thermal evolution model that helps in the estimation of the above 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 and we show the results obtained applying this model to a comet nucleus with the characteristics of Churyumov-Gerasimenko. Our models indicate that the peculiar dynamical history has a strong effect on the comet: during the orbital stage at large heliocentric distance the comet was covered by a dust crust that is removed when the comet arrives at the present orbit. The computed gas fluxes are in general agreement with those estimated from the observations.