Climate Change on Venus and the Role of Geological Sources of Volatiles

Southwest Research Institute, San Antonio TX

Investigators

Abstract

AST 0098483 Bullock Drs. Mark Bullock and David Grinspoon, at the Southwest Research Institute, are developing an evolutionary climate model for Venus that calculates surface temperature evolution as a result of outgassing of volatiles by volcanoes, heterogeneous reactions of atmospheric gases with surface minerals, and the exospheric escape of hydrogen. This model should serve as a guide for geophysicists to examine the role that large changes in surface temperature may have played in the tectonic and volcanic history of the planet. The Venus evolutionary climate model will be improved substantially by incorporating a detailed microphysical model of the clouds, parameterizing solar absorption in the clouds to account for changes in the near-UV absorber, and by investigating the effects of comet and asteroid impacts as both sources of volatiles and dust to the atmosphere. The model will also take advantage of improved estimates of the time-dependence of volcanic activity, now becoming available from a more detailed global analysis of Magellan spacecraft data. The present climate of Venus is controlled by an efficient carbon dioxide-water greenhouse effect and by the radiative properties of its global cloud cover. Both the greenhouse effect and sulfuric acid clouds are sensitive to perturbations in the abundance of atmospheric water vapor and sulfur gases. Outgassing of carbon dioxide, water vapor, and sulfur dioxide by volcanic activity has most likely played a major role in establishing the planetary albedo, through cloud formation, and high surface temperatures through the greenhouse effect. Planetary-scale processes involving the transport and sequestering of volatiles affect these abundances over time, driving changes in climate. ***