A model for the changing pore structure and dust grain size distribution in a porous comet nucleus

We present a simple model for the flow of dust in a porous icy nucleus of a comet. The model consists of an initial size distribution of pores which are assumed to reside on "filters" separated by some characteristic distance,L. The dust grains, which have a prescribed initial size distribution, pass through these filters at a given (drag) velocity and block some of the pores. Calculating the probability for pore blocking and particle trapping, we follow the evolution of the pore size distribution and the particle size distribution in both space (as a particular wave of dust passes through successive filters) and time (as successive waves of dust pass through the same filter).