Effect of the greenhouse gases (CO2, H2O, SO2) on Martian paleoclimate

Abstract

There is general agreement that certain surface features on Mars are indicative of the presence of liquid water at various times in the geologic past. In particular, the valley networks are difficult to explain by a mechanism other than the flow of liquid water. It has been suggested in several studies that a thick CO 2 atmosphere on Mars early in its history could have provided a greenhouse warming that would have allowed the flow of water either on the surface or just below the surface. However, we have examined this effect with a detailed radiation model and have found that if reduced solar luminosity early in the history of the solar system is taken into account, even three bars of CO 2 will not provide sufficient greenhouse warming. The addition of water vapor and sulfur dioxide (both plausible gases that may have been emitted by Martian volcanoes) to the atmosphere also fail to warm the surface above 273K for reduced solar luminosity conditions. The increase in temperature may be large enough, however, for the formation of these features by brines.