36th DPS Meeting, 8-12 November 2004
Session 16 Jovian System
Poster I, Tuesday, November 9, 2004, 4:00-7:00pm, Exhibition Hall 1A

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[16.09] Chemistry of Carbon Gases in Volcanic Gases on Io

L. Schaefer, B. Fegley, Jr. (Planetary Chemistry Laboratory, Department of Earth and Planetary Sciences, Washington University)

We use chemical equilibrium calculations to model the chemistry of carbon in volcanic gases on Io (Schaefer and Fegley 2004, ApJ, in review). The calculations covered temperatures from 500 - 2000 K, pressures from 10-8 to 10+2 bars, and bulk O/S atomic ratios from ~ 0 to 3. These conditions overlap the nominal conditions at Pele, where T = 1760 K, P = 0.01 bar, and O/S ~ 1.5. Bulk C/S atomic ratios ranging from 10-4 to 10-1 are used in the equilibrium calculations, with a nominal value of 10-3 based upon upper limits for carbon on Io from Voyager observations of the Loki plume. Carbon monoxide and CO2 are the two major carbon gases under nearly all conditions studied. Carbonyl sulfide and CS2 are orders of magnitude less abundant. Consideration of different loss processes including photolysis, condensation, and kinetic reactions in the plume indicates that photolysis is probably the major loss process for all gases. Both CO and CO2 should be observable in volcanic plumes and in Io's atmosphere at abundances of several hundred parts per million by volume for a bulk C/S atomic ratio of 10-3. This work is supported by the NASA Planetary Atmospheres program.

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Bulletin of the American Astronomical Society, 36 #4
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