Properties of 19P/Borrelly

Properties as temperatures, sublimation, and outgassing rates, are determined for different surface parameters to model the surface of the nucleus of comet 19P/Borrelly. The derived outgassing properties indicate that only about 6% of the day-side surface of this cometary nucleus can be expected to contribute to the astronomically observed gas production rate. This is in agreement with DS-1 imaging and thermal measurement results. The small value of the day-side active areas indicates a Halley-type surface of only locally restricted active areas or zones, while most of the surface is passive but hot with maximum temperatures above 300 K. Thus, it is expected that the comet surface is mainly covered by a hot upper surface layer of refractory materials. The temperature of the local active areas with free sublimation is expected in the range of about 200 K.