Predicted Abundances of Carbon Compounds in Volcanic Gases on IO

• Published in: The Astrophysical journal Vol. 618; no. 2; pp. 1079 - 1085
• Main Authors: Schaefer, Laura, Fegley, Jr., Bruce
• Format: Journal Article
• Language: English
• Published: IOP Publishing 10-01-2005
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/426113

We use chemical equilibrium calculations to model the speciation of carbon in volcanic gases on Io. The calculations cover wide temperature (500-2000 K), pressure (10 super(-8) to 10 super(+2) bars), and composition ranges (bulk O/S atomic ratios 60 to 3), which overlap the nominal conditions at Pele (1760 K, 0.01 bars, O/S 6 1.5). Bulk C/S atomic ratios ranging from 10 super(-6) to 10 super(-1) in volcanic gases are used with a nominal value of 10 super(-3) based on upper limits from Voyager for carbon in the Loki plume on Io. Carbon monoxide and CO sub(2) are the two major carbon gases under all conditions studied. Carbonyl sulfide and CS sub(2) are orders of magnitude less abundant. Consideration of different loss processes (photolysis, condensation, kinetic reactions in the plume) indicates that photolysis is probably the major loss process for all gases. Both CO and CO sub(2) 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 ratio of 10 super(-3).