Mechanisms of dust emission from the surface of a cometary nucleus
Spohn, T.; Thiel, K.; Krankowsky, D.; Lammerzahl, P.; Benkhoff, J.; Grun, E.; Fechtig, H.; Klinger, J.; Hesselbarth, P.; Kochan, H.; Kohl, H.; Seboldt, W.
Germany
Abstract
Cometary nuclei consist of mixtures of ices and non-volatile particulates in mass proportions of similar magnitudes. Dust is carried by the gas drag of the sublimating ices. Gas drag from free expansion of the gases from the nucleus dominates the acceleration of dust particles after their release from the surface. Significant gas pressure can build up in the ice matrix by sublimation of ices of different volatility and by non-uniform heat absorption in the ice. A dust mantle of several mm thickness which builds up over the sublimating ice surface quenches the gas outflow and causes a pressure build up across the mantle. The pressure gradient can become unstable and microeruptions of gas and dust occur. These mechanisms are in agreement with findings from recent simulation experiments in which emission speeds of 1 to 2 m/s have been observed for particles of about 10-4 m in radius