Activity and nucleus properties of 46 Pz.urule;Wirtanen

Astronomical observations of size and of related outgassing rates seem not to be compatible for the nucleus of comet 46 Pz.urule;Wirtanen, the target comet of the ROSETTA mission. This possible disagreement has caused speculations about peculiar properties of this comet nucleus. It is shown by model calculations which also takes into account vertical heat fluxes into the nucleus that there is a possibility to combine the results of astronomical observations within a model of a freely sublimating ice surface of this comet with an outgassing area of about half the dayside surface. The resulting half-size parameter (i.e. the radius of an equivalent sphere) can be shown to be of about R ≈ (725±230) m, and the nucleus is shown to have an active area of about half of the dayside surface, i.e. of about 25% of the total surface.