Modelling of the processes of dunes formation on the surface of comet 67P/Churyumov–Gerasimenko

Abstract

ABSTRACTThe paper discusses selected mechanisms that can significantly contribute to the formation of dune structures on the surface of comets. In these considerations, mechanisms related to the dynamics of dust on the surface of the nucleus were taken into account. In the first step, the maximum dimensions of particles that can be entrained into the cometary atmosphere as a result of local sublimation of water ice have been determined. Then, three processes related to the movement of dust on the surface of the comet nucleus were considered, such as dust migration, a landslide that can turn into a local avalanche, and fluidization of unstable dust. The thermodynamic process responsible for initiating these mechanisms is ice sublimation. These mechanisms cause the dust to move by liquefaction of the given layer. Due to the complex and regular structure of a cometary nucleus, moving dust can suddenly stop flowing. For individual mechanisms responsible for the formation of dune structures, the maximum angular width for a given particle, particle mobility coefficient, and static fluidization pressure were determined. It should be noted that in those parts of the comet nucleus that are illuminated by the Sun, these mechanisms can occur almost simultaneously, leading to the formation of dune structures by piling up particles.