A Warmer and Wetter Early Mars
When
Where
Dr. Ramses Ramirez
Research Scientist
Earth-Life Science Institute
A Warmer and Wetter Early Mars
The debate over the early Martian climate is among the most exciting in planetary science. Although the geologic evidence (e.g., valley networks and modified craters) generally supports a warmer and wetter early Mars, climate models have had difficulty simulating such a scenario under the faint young sun, which has led to a number of competing hypotheses. Climate models with just CO2 and H2O have been unable to generate warm conditions. Others have supplemented this greenhouse gas warming with that from H2O or CO2 clouds, although the required warming is possible only under the most unlikely circumstances. Various secondary greenhouse gases, including CH4, SO2 and NH3 are photochemically unstable and are also unlikely solutions. Thus, the limited success of all these ideas has motivated suggestions that the surface geology may have formed under a very cold and icy climate instead, possibly interrupted by occasional transient warming episodes. However, none of these cold early Mars scenarios satisfy the geologic evidence nor produce the necessary fluvial erosion. Nevertheless, we had shown that warm global mean surface temperatures were possible with an early atmosphere rich in CO2 and H2. We further develop our ideas using a more advanced energy balance climate model and demonstrate that the observations can only be explained if a relatively large northern ocean had once existed on early Mars. Fluvial erosion is ineffective at smaller ocean sizes. The length of the warm period may also be shorter than previously predicted. I review the recent work and show that a brief - but warm and semi-arid climate - may be the best explanation for early Mars.
Host: Dr. Timothy Swindle