South African raindrops tell about our climate 2.7 billion years ago

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Recently, researchers at the University of Washington have used fossilised raindrop impressions to discover an intriguing tale about the earth's atmosphere. "The story of these ancient raindrops begins on a wet day 2.7 billion years ago, somewhere in the vicinity of modern day South Africa," Edgar says.

As raindrops fell, they created impressions on the ground, some of which were eventually fossilised. Researchers have discovered a way to make these raindrops tell a story about the composition of the ancient atmosphere. "As a drop of water falls, it moves through the atmosphere. The atmosphere impacts the speed at which the water falls [...] the thicker the atmosphere, the smaller the splash." By measuring the size of raindrop fossils and comparing them to the size of modern raindrop splashes, Edgar says, researchers were able to clear up some of the mystery around the earth's ancient climate, billions of years ago.

They found, for example, that "the sun put out 30 percent less light than it does now. While the earth should have been frozen, it was not. Rivers and oceans ran freely." These ancient raindrops may point to the reason the earth did not freeze. The ancient raindrops likely fell through a thick atmosphere full of greenhouse gases. These abundant greenhouse gases warmed the planet, making it a very different place than it is today.

Read the full article on www.decodedscience.com.