Gas And Dust Production From A Comet With A Small Active Area: Application To The Rosetta Target Comet 67p/churyumov-gerasimenko
Abstract
Comet 67P/Churyumov-Gerasimenko, the Rosetta mission target comet, has a mean radius of 2 km; and it is evident that most of its activity (i.e., gas and dust production into the coma) originates from an area that is only 4% of its entire surface. There is apparently a strong seasonal effect whereby this area is predominantly illuminated by sun light by perihelion and thereafter. The dusty-gas coma structure for a comet with a dominant active area deviates strongly from the typical models where gas and dust are produced more uniformly from the surface. Here we investigate the dusty-gas environment around a nucleus where the activity is limited to 4% of the surface. We show the overall structure of the coma, the distribution of gas, and the velocities and distribution of dust for a nominal dust particle size distribution for a relevant range of heliocentric distances. With such a limited active area, larger dust particles can be accelerated to higher velocities because of the concentrated gas flux right near the surface, but the limited active area also allows for some particles to fall back to the surface when as the gas flow expands by much greater than the typical inverse square variation. The physics of the dynamical conditions vary greatly from having moderately collisional (fluid) conditions above the active area near perihelion to being a transitional flow and nearly free flow when at heliocentric distances 3 AU throughout most of the coma. [We acknowledge support from NASA Planetary Atmospheres grant NNX09AB59G.]
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #42
- Pub Date:
- October 2010
- Bibcode:
- 2010DPS....42.2805C