The Contribution of Grains to the Water Production of Comets

Details The Contribution of Grains to the Water Production of Comets The Contribution of Grains to the Water Production of Comets

Dec 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999baas...31q1589p&link_type=abstract

American Astronomical Society, DPS Meeting #31, late abstracts, #59.29; Bulletin of the American Astronomical Society, Vol. 31,

Astronomy and Astrophysics

Astronomy

Scientific paper

Analysis of narrow band photometry of 85 comets near perihelion by A'Hearn et al. (Icarus 118:223-270, 1995) can be interpreted to give the average H2O production rate of a comet as a function of heliocentric distance. The observed rate agrees with the calculated one out to a heliocentric distance of 2-3 AU; beyond that, the observed production rates are much higher. Even corrections that take into account the effect of the coma, the emissivity, the latitude, the active fraction of the surface, or heat conduction to and from the interior, have not been able to reproduce the observations. The contribution of sublimation from the interior, given the high porosity of comet nuclei, is not expected to resolve the discrepancy. We suggest that the additional gas production is the result of sublimation from ice grains ejected by the gas flow from the nucleus. We model this by computing the temperature of an ice grain of a given size in the radiation field of the Sun. The real and imaginary indices of refraction used are appropriate for a mixture of water ice and some additional, generic, dark material (dirt). The ratio of dirt to ice can be varied but is typically taken to be 0.5 by mass. We compute the absorption and scattering properties of the grains from Mie theory and find their steady state temperature and sublimation rate as a function of heliocentric distance. A fit to the observations of A'Hearn et al. is found, which depends on the sizes of the grains and their abundance as a function of heliocentric distance. For example, assuming a grain production rate independent of heliocentric distance, a grain size of 7 microns reproduces the observations quite well.

Affiliated with

Also associated with

No associations

Rating

The Contribution of Grains to the Water Production of Comets does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The Contribution of Grains to the Water Production of Comets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Contribution of Grains to the Water Production of Comets will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1725045