HR: 0800h
AN: P11A-0101    [Abstracts]
TI: Modeling the Coma Dynamics of a Comet with an Icy Grain Halo
AU: * Combi, M R
EM: mcombi@umich.edu
AF: University of Michigan, Space Research Building 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Tenishev, V M
EM: vtenishe@umich.edu
AF: University of Michigan, Space Research Building 2455 Hayward Street, Ann Arbor, MI 48109 United States
AB: Extended sources of gas have been invoked to explain the observed spatial distributions of cometary species such as H₂CO, CO, and CN and C_2 jets. However, these have generally been situations of either trace species (as in CN and C_2) or a fraction of a minor species (as in native vs. extended CO), which would not otherwise have a major dynamical effect on the basic expansion of a dusty water-dominated coma. The role of the icy grains has also been explored for explaining the scattered solar continuum distribution of particles as well as solid ice spectral features observed at moderately large heliocentric distances in Comet C/1995 O1 (Hale-Bopp). Comet C/1996 B2 (Hyakutake) represented an extreme case where several large outbursts of icy particles produced a large excesses of gas (and dust) away from and in addition to the contribution from nucleus alone lasting for several days as the grains and fragments sublimated. The remarkable outburst of 19-20 March 1996 increased the previous quiescent gas production initially by a factor of 3. Sublimation of large amounts of gas from slowly moving grains at a range of distances from the nucleus should have a major dynamical effect on the expansion of the dusty-gas coma from the canonical picture. In order to study this problem we present results from a dusty-gas kinetic Direct Simulation Monte Carlo (DSMC) model for the coma that includes direct production from the nucleus as well as substantial production from an extended source of slowly moving sublimating grains. The DSMC model includes the dynamical coupling of the gas, refractory dust, and sublimating icy particles. Results for the effects of various outburst strengths and size distributions of icy outburst particles on the energy balance and dynamics of the coma will be shown. This work has been supported by grant NAG5-13239 from the NASA Planetary Atmospheres Program.
DE: 6000 PLANETARY SCIENCES: COMETS AND SMALL BODIES
DE: 6005 Atmospheres (1060)
DE: 6008 Composition (1060)
DE: 6017 Erosion and weathering
DE: 6020 Ices
SC: Planetary Sciences [P]
MN: Fall Meeting 2005