Several billion years ago, geological evidence indicates that Mars was warmer and wetter, with flowing rivers and lakes on its surface. This is hard to explain because the Sun was fainter then, and Mars's orbit is more distant than Earth's. The atmosphere of early Mars was probably thicker, but additional greenhouse gases besides carbon dioxide are needed to provide enough warming. Here we perform a survey of the warming effect of all plausible greenhouse gases on early Mars. We isolate a few species that are particularly effective at warming the planet, calculate how much they raise temperatures at different concentrations, and discuss whether they could have built up to high concentrations in Mars's early atmosphere. Our work provides an important reference for future calculations that incorporate chemistry and other effects.
To read the full article please see Journal of Geophysical Research: Planets