A 'see-sawing' atmosphere over 2.5 billion years ago preceded the oxygenation of our planet and the development of complex life on Earth, a new study has shown.
Research, led by experts at Newcastle University, UK, and published today in the journal Nature Geoscience, reveals that the Earth's early atmosphere periodically flipped from a hydrocarbon-free state into a hydrocarbon-rich state similar to that of Saturn's moon, Titan.
This switch between "organic haze" and a "haze-free" environment was the result of intense microbial activity and would have had a profound effect on the climate of the Earth system.
Similar to the way scientists believe our climate behaves today, the team say their findings provide us with an insight into the Earth's surface environment prior to oxygenation of the planet.
Study lead Dr Aubrey Zerkle, based in the School of Civil Engineering and Geosciences at Newcastle University, explains: "Models have previously suggested that the Earth's early atmosphere could have been warmed by a layer of organic haze.
"Our geochemical analyses of marine sediments from this time period provide the first evidence for such an atmosphere.
"However, instead of evidence for a continuously 'hazy' period we found the signal flipped on and off, in response to microbial activity.
"This provides us with insight into Earth's surface environment prior to oxygenation of the planet and confirms the importance of methane gas in regulating the early atmosphere."
Dr Zerkle, working along with Dr James Farquhar at the University of Maryland, USA, and Dr Simon Poulton at Newcastle University, UK, analysed the geochemistry of marine sediments deposited between 2.65 and 2.5 billion years ago in what is now South Africa.
They found evidence of local production of oxygen by microbes in the oceans, but carbon and sulphur isotopes indicate that little of that oxygen entered the atmosphere.
|Contact: Dr. Aubrey Zerkle|