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M. A. Bullock (Southwest Research Institute), R. J. Phillips (Washington University), D. H. Grinspoon (Southwest Research Institute)
The construction of the Tharsis rise on Mars was most likely associated with massive magmatic activity during the mid-Noachian. Based on an elastic lithospheric thickness of 100 km, the volume of magma associated with the Tharsis load was on the order of 300 million cubic kilometers, emplaced over a period of a hundred to several hundred million years. Assuming a water abundance of 5 this corresponds to a global layer of water 100 m thick. A large fraction of the observed valley networks were likely emplaced after most of the Tharsis load was in place. Water and carbon dioxide delivery to the atmosphere during and after the construction of Tharsis would have had a significant impact on atmospheric temperatures, the greenhouse effect, and cloud formation. We have developed climate models for early Mars that explore the effects of large increases in atmospheric water and carbon dioxide during periods of enhanced magmatic activity. We will report on the possible climate effects of large-scale eruptions of surface water on Mars that may have been associated with the formation of Tharsis and subsequent development of the valley networks.
This work has been supported by NASA's Comparative Planetary Atmospheres and Planetary Geology and Geophysics Programs.