Theory explains how Mars could have once been warm and wet

The mystery of how the surface of Mars, long dead and dry, could have flowed with water billions of years ago may have been solved by research that included a University of Washington astronomer. There is evidence that Mars had water at its surface 3.8 billion years ago or before, but scientists are divided on how that might have happened, especially since the sun was about 30 percent fainter back then, thus less able to melt water ice on Mars.

Earlier efforts with computer models to simulate a warm, wet Mars using only carbon dioxide and water have not been successful. Now, researchers at Pennsylvania State University and the University of Washington have published a paper in the journal Nature Geoscience arguing that the presence of a third ingredient alters that outcome, strengthening the greenhouse effect—where heat energy from sunlight is trapped in the atmosphere—enough to warm the surface and allow liquid water.

“We found that sprinkling a small amount of molecular hydrogen into a thick atmosphere composed primarily of carbon dioxide does the trick,” says co-author Tyler Robinson, a UW postdoctoral researcher. “While carbon dioxide is a strong greenhouse gas, it can’t solve the early Mars problem on its own. But carbon dioxide and hydrogen make a great team. A warm and wet Mars brings to mind a climate like modern Earth,” Robinson says. “Maybe, also like Earth, a warm and wet early Mars could have had life.”