THE DUST ENVIRONMENT OF COMET 29P/SCHWASSMANN-WACHMANN 1 FROM DUST TAIL MODELING OF 2004 NEAR-PERIHELION OBSERVATIONS

Abstract

A Monte Carlo inverse dust tail modeling of ground-based images of comet 29P/Schwasssmann-Wachmann 1 has been performed. The images of the comet were acquired on several nights in 2004 July, a few days after the 2004 perihelion passage. The analysis takes into account the rotation properties of the comet, incorporating dust ejection from active areas on the nucleus surface. We demonstrate that these models provide a significant improvement over models with a fixed sunward hemispherical particle emission cone, owing to the observed coma asymmetry, giving an excellent fit to the observed intensity isophote fields. The rotation parameters, defined by the argument of the subsolar meridian at perihelion, Φ, and the obliquity, I, are found to be compatible with those derived by Sekanina from morphological studies (Φ = 279° and I = 100°). We found that if dust emission is assumed to be produced by a single active area driven by insolation, this must then be located on the southern hemisphere near –35° latitude. We have devised a method to impose Afρ(t) constraints the overdetermined system of equations leading to the solution of the dust mass loss rates and size distribution function. When those constraints are applied, the time-averaged particle size distribution function was found to be characterized by a power law of index in the range –3.7 to –3.3, and a dust loss mass rate approximately in the nominal range of 300-900 kg s–1, depending on the different model approaches, and for an albedo time the phase function of 0.1, confirming the fact that this comet is perhaps the most active source of interplanetary dust, providing some 3%-10% of the mass required to replenish the losses of the interplanetary dust cloud if it is in a steady state.