Dust in Comet 67P/Churyumov‐Gerasimenko

Abstract

Comet 67P/Churyumov-Gerasimenko has been designated the new target for the ESA Rosetta mission, launched successfully on 2004 March 2. We have analyzed an image set taken in 2003 March, in which the comet appeared to have a conspicuous dust antitail. We employed a Monte Carlo code, similar to that by Fulle (1989), by which we have computed the dust size distribution as a function of time, the dust mass-loss rate, the Afρ quantity, and the particle velocities. The dust environment is found to be very asymmetric around the perihelion passage, with much larger dust mass-loss rates at preperihelion times. We conclude that the comet emits large particles (in the millimeter to centimeter range), with a total dust mass-loss rate in excess of 130 kg s-1 at preperihelion times, when the instruments on board the Rosetta orbiter and lander will be operating. Although our conclusions regarding the temporal trends in both the dust mass loss and the Afρ quantity are qualitatively similar to those found by Fulle et al. (2004), we found smaller particle velocities and correspondingly larger values in the Afρ. These conclusions indicate a potential challenge for the lifetime of the Rosetta orbiter and lander on-board instruments as a result of a highly dusty environment from at least 150 days before perihelion (comet heliocentric distance of r = 2.1 AU) to about 20 days after perihelion passage. The mass-loss rate then decreases to the 10 kg s-1 level about 80 days after perihelion.