Thermal evolution and activity of Comet 9P/Tempel 1 and simulation of a deep impact

Abstract

We use a quasi 3-D thermal evolution model for a spherical comet nucleus, which takes into account the diurnal and latitudinal variation of the solar flux, but neglects lateral heat conduction. We model the thermal evolution and activity of Comet 9P/Tempel 1, in anticipation of the Deep Impact mission encounter with the comet. We also investigate the possible outcome of a projectile impact, assuming that all the energy is absorbed as thermal energy. An interesting result of this investigation, is that the estimated amount of dust ejected due to the impact is equivalent to 2--2.6 days of activity, during "quiet" conditions, at perihelion. We show that production rates of volatiles that are released in the interior of the nucleus depend strongly on the porous structure, in particular on the surface to volume ratio of the pores. We develop a more accurate model for calculating this parameter, based on a distribution of pore sizes, rather than a single, average pore size.