Activity of comets: Gas Transport in the Near-Surface Porous Layers of a Cometary Nucleus

Yuri V. Skorov (1, 2) , Rik van Lieshout (3) , Jürgen Blum (2) , Horst U. Keller (2)

1 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
2 Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig]
3 UvA - University of Amsterdam [Amsterdam] = Universiteit van Amsterdam

►Knudsen's formula widely used in cometary research is of limited accuracy for modeling the gas transport through short dust channel. As an alternative, Clausing's formula is suggested, accurately describing the kinetics of transport through a single cylindrical capillary. ► Accurate statistical calculations are performed for media formed either by ballistic deposition (RDB) of test particles or by random filling of a control volume (RSP). The medium permeability and the return flow of re-condensed molecules are estimated for the different model parameters. The permeability depends on the medium porosity in a nonlinear way. ► We preserve the overall structure of Clausing's formula and introduce the effective radius of the capillary is an unknown function of porosity. The explicit form of this functional dependence is derived from a nonlinear approximation based on statistical modeling results. ► The retrieved algebraic expression allows us to accurately calculate the permeability of layers whose thickness and porosity vary in the range of values expected for the near-surface regions of a cometary nucleus. The simplicity of this approach makes it practical to include the block that describes the transport of gas in the overall thermal model of a cometary nucleus.

Mots clés: Comets; Nucleus; Gas; Dust

Domaines: Planète et Univers [physics]

Yuri V. Skorov, Rik van Lieshout, Jürgen Blum, Horst U. Keller. Activity of comets: Gas Transport in the Near-Surface Porous Layers of a Cometary Nucleus. Icarus, 2011, 212 (2), pp.867. ⟨10.1016/j.icarus.2011.01.018⟩. ⟨hal-00734588⟩