A study of water production and temperatures of rotating irregularly shaped cometary nuclei

Calculations of water production rates and temperatures for rotating irregu larly shaped bodies with and without topography are presented. These calcul ations are compared with the case of a spherical nucleus. For any combinati on of orbital parameters, rotation axis orientation, spin period, and physi cal properties of the nucleus (geometric albedo, emissivity, and thermodyna mical properties) the heat diffusion equation in the surface normal directi on is solved with the energy balance at the surface, which includes shadowi ng effects, as a boundary condition. This is done for all the cells in whic h the object is divided and for a complete orbital revolution around the Su n. Some of the main results obtained are: 1) Bodies with topographic featur es produce more water vapor than equal area spheres along most of their orb its; 2) Asymmetries in the behavior at pre and postperihelion are less pron ounced than in the case of the sphere at large heliocentric distances; 3) J et-like structures in the inner coma can result from topographic features; 4) Diurnal oscillations can be detectable away from perihelion, even for sl ightly irregular bodies.