Earth's Early Atmosphere Was Briefly a Methane Haze

A new research paper describes a period when Earth's atmosphere was filled with a thick, methane-rich haze much like that on Saturn's moon Titan, seen here in an illustration. Ron Miller/Stocktrek Images/Getty Images

If you don't think Earth is great, you're wrong. It keeps us alive, after all! It may rain diamonds on Jupiter and Saturn might have fabulous bling, but if a temperate climate, liquid water, and an atmosphere loaded with sweet, sweet oxygen are what you're looking for, Earth is the place to be.

But it wasn't always like this. Until around 2.4 billion years ago, this planet was a total hellhole, replete with wild temperature fluctuations fueled by an atmosphere of roiling, toxic gases. How our planet became such a Shangri La after such unpromising beginnings is a question that has nettled Earth scientists for decades. A new study published in the Proceedings of the National Academy of Sciences suggests the big change happened over the course of only about a million years — lightning fast, by geologic time standards — and involved a whole lot of methane, a key ingredient in modern cow belches and swamp gas.


The methane was actually the clincher in the Great Oxidation Event — also known as the Great Oxygenation Event — which introduced oxygen to our atmosphere and made multicellular life on Earth possible. This is not the first study to use atmospheric models and chemical records to show that ancient bacteria, Earth's only inhabitants at the time, produced enough methane to periodically blanket the planet in a soupy methane haze. A recent study of atmospheric nitrogen in the journal Nature, for instance, suggests the GOE took longer, but the oxygen researchers say they were able to calculate how suddenly these smoggy periods began and how long they lasted.

"High methane levels meant that more hydrogen, the main gas preventing the buildup of oxygen, could escape into outer space, paving the way for global oxygenation," said coauthor Aubrey Zerkle, a biogeochemist at the University of St. Andrews, in a press release. "Our new dataset constitutes the highest resolution record of Archean atmospheric chemistry ever produced, and paints a dramatic picture of Earth surface conditions before the oxygenation of our planet."

After about a million years of methane haze, enough hydrogen had been pushed into space that the oxygen concentration of Earth's atmosphere increased by more than 10,000 times, and multicellular life on our planet had one of the essential components to succeed. Just what makes oxygen so valuable? Watch this BrainStuff video to learn more: