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J. R. Green, C. L. Folsom (Caltech/Jet Propulsion Laboratory)
The production and release of dust/ice grains from a cometary surface are complex and poorly characterized phenomena. It has been shown1 that the flow of gas with entrained dust/ice grains from a comet surface may be oriented from 0-90o with respect to the outgassing surface, depending on nearby terrain features. As a consequence, it is possible for the stream flow from an active area to impinge on and impact cometary surface terrain features. We have developed an analytical model to investigate the effects of erosion on the cometary surface by the free stream flow of dust/ice grains and the production of new particles through the action of fatigue fracture. After an initial saltation, creep, and suspension of small loose particles, erosion of the surface occurs due to the fatigue chipping of embedded grains by the impact of the previously released particles. Fatigue cracks propagate along the grain boundaries leading to dislodging of grains and their incorporation into the stream flow away from the area. Major assumptions in this work are: "target sites" are randomly oriented; each particle collides only once; expulsion occurs due to fatigue cracks. We calculate the mass flow rate of particles eroded from an area as a function of the angle of the velocity vector of the incoming stream, concentration of incoming stream, the mechanical properties of the materials, and the incoming and outgoing grain sizes. Results show that the release of dust/ice grains eroded from the surface by fatigue fracture can be a substantial local phenomenon contributing to the dust/ice flux from the surface. The erosion of the terrain features will lead to alterations in their shape and level of activity. Implications for the evolution of terrain features will be discussed.
1. Crifo, J.F. and A.V. Rodionov, Icarus 129, 72-93, 1997
The author(s) of this abstract have provided an email address for comments about the abstract: jacklyn.r.green@jpl.nasa.gov