Astrobiologists have made a new discovery that could explain how the early Earth was warm enough for life more than 3 billion years ago, even though the Sun was 20 percent dimmer than today. The answer to the ‘faint young Sun’ paradox may come down to the atmospheric composition of the young planet. The study shows that reasonable amounts of carbon dioxide in the atmosphere, mixed with a dash of methane, could have helped warm the Earth so that water remained in liquid form at the surface.

Liquid water is thought to be essential for the origins of life as we know it, and determining when and how the conditions for liquid water developed on Earth can help astrobiologists understand how life first gained a foothold on our planet.

The research was supported in part by the Exobiology and Evolutionary Biology Program, and was published this month in the journal Astrobiology.