A new study published in Nature from NASA's Exobiology and Evoluationary Biology program investigators and their colleagues looks at fossilized raindrops and what they indicate about conditions on the early Earth.
In ancient Earth history, the sun burned as much as 30 percent dimmer than it does now. Theoretically that should have encased the planet in ice, but there is geologic evidence for rivers and ocean sediments between 2 billion and 4 billion years ago.
Scientists have speculated that temperatures warm enough to maintain liquid water were the result of a much thicker atmosphere, high concentrations of greenhouse gases or a combination of the two.
Using evidence from fossilized raindrop impressions from 2.7 billion years ago, the team has deduced atmospheric pressure at the time, demonstrating that an abundance of greenhouse gases most likely caused the warm temperatures.
Source: University of Washington
Last Updated: 29 May 2012