Thermal Evolution Models of the 9P/Tempel 1 Comet Nucleus for Interpreting the Deep Impact Results

Thermal evolution models of comet 9P/Tempel 1 have been developed to understand how thermal evolution models of comet nuclei can help to interpret the results of Deep Impact and vice versa, how the Deep Impact results can constrain the comet nuclei models. We found a general agreement between the models' outcomes and the mission results, without need of an ad hoc choice of initial parameters. We found that a 'standard' model of a porous, low-density nucleus made of initially amorphous water ice, volatile ices, and dust can reproduce the general activity pattern of 9P/Tempel 1, if the dynamical characteristics of this comet are taken into account. The general aspect of the nucleus is well reproduced by the presence of a dust mantle on the nucleus that, even if very thin, quenches water production. The models foresee the natural formation of a dust mantle on the comet's surface, and the water flux source is mainly a subsurface diffuse source, in agreement with the observations. However, no simple correlation is found between production rates of different volatile gases and their relative abundances in the nucleus. From our models' results we can affirm that the coma abundances of volatile species do not match their abundances in the nucleus.