Quasi-3-D model to describe topographic effects on non-spherical comet nucleus evolution

A new quasi three-dimensional code is presented and used to explore the thermal evolution of non-spherical-shape cometary nuclei. Calculations are done for spherical nuclei with different obliquities, spherical nuclei with crater-like depressions and spheroid-shape nuclei. The results obtained for both the gas and dust fluxes agree with previous simulations. Local dust crust formation can occur when the comet is located far from the Sun (around 3.5 AU), creating active and inactive areas on the surface. For a given set of parameters, the H₂O production rate is comparable to the one observed for comets. A pre-post-perihelion asymmetry exists for H₂O, CO₂ and CO production rates. It is shown that crater-like depressions can be erased within the lifetime of a comet and that spheroid-shape nuclei have a higher production rate than equal area spherical nuclei.