Increasingly, astronomical observations of planets are being used to reveal the active processes within planetary atmospheres and between atmospheres and planetary surfaces. The growing sophistication of photochemical models for atmospheric processes, and calculations of reactive interaction of atmospheres and surfaces, will benefit from additional constraints provided by theoretical models of volcanic gas compositions. On the one hand, new models for volcanic gases are already integral to studies of planetary bodies with active volcanism such as the Jovian satellite Io. On the other hand, theoretical models of volcanic gas compositions will help constrain models of the evolution of atmospheres and surfaces on planets with volcanic histories. The abundances and speciation of volcanic gases reflect the pressure at volcanic vents, temperatures, oxidation states, and compositions of parental magmas, all of which can be used to explore the interiors of volcanically-active planetary bodies.
A program of theoretical geochemical modeling will be led by Dr. Mikhail Zolotov that will lead to testable predictions about the composition and speciation of volcanic degassing and its effect on atmospheres and surfaces of planetary bodies. Bulk compositions of degassed volatiles will be bracketed from cosmochemical, terrestrial volcanological, and experimental data on the solubility of volatiles in magmas. To the greatest extent possible, this study will constrain magma temperature, vent pressures, and the oxidation state of planetary interiors. The work will greatly expand thermodynamic databases so that chemical equilibria in gas-solid systems can be used to model speciation of volcanic gases at the bulk compositions, vent pressures, temperatures and oxidation states of magma determined to be plausible for planetary bodies. The analysis will include speciation in the H-C-O-S-Cl-F-N system. Specific models will be developed for volcanic degassing on Mars, Venus and Mercury, and comparative studies will be performed.
Results of this project will assist other researches who analyze the impact of volcanic degassing on atmospheric and surface chemistry, climatic effects of volcanism, and physics of eruptions, as well as coupled atmosphere-lithosphere evolution on terrestrial planets. An interactive website will be developed for research and education to demonstrate the importance of volcanic degassing on atmospheric, geochemical, geological, and biologic processes on planetary bodies. The website will include a code to compute speciation of volcanic gases at given temperature, pressure, and bulk composition in an interactive mode. Portions of the research will be carried out by a graduate student whose results will be presented at national meetings. Results will also be incorporated into geochemistry, biogeochemistry and cosmochemistry courses for undergraduate and graduate students. A public lecture will be given about extraterrestrial volcanism and the role of volcanic degassing on planets, satellites, and large asteroids. ***
