Ancient Earth’s atmosphere weighted less than half of today’s air, said researchers at University of Washington (UW). They analyzed bubbles of gas trapped in rocks from that time. A paper with detailed results was published Monday in Nature Geoscience.

The study took place in Western Australia, where researchers observed a 2.7-billion-year-old stromatolite. Layers of the rock showed evidence of single-celled photosynthetic life. A theory suggests that microbial life prospered, even under a thin an atmosphere.

The new research suggests that Earth’s atmosphere might have been half as thick as it is today. Image courtesy of Daily Genius

Previous theories have proposed that early Earth contained a thicker atmosphere, given conditions of mild sunlight. New findings also show which gasses were in the atmosphere and how they interfered with biology and climate.

“For the longest time, people have been thinking the atmospheric pressure might have been higher back then because the sun was fainter. Our result is the opposite of what we were expecting.” said lead author Sanjoy Som.

Researchers looked at bubbles trapped in cooling lava as a “paleobarometer”. This technique was designed decades ago by study’s co-author Roger Buick, a UW professor of Earth and space Sciences. He was able to determine the weight of air in our planet’s youth.

Recently, he used the same method to measure air pressure from early Earth. Researchers needed a place where lava had formed at sea level. They analyzed molten lava immersed into seawater, from the Beasley River in Australia.

New findings may be hard to digest, said study authors

Rigorous measures of bubbles trapped in rocks demonstrated a “surprisingly” lightweight atmosphere. The results were also confirmed by an X-ray analysis made at several lava flows. “The atmospheric pressure at that time was less than half of today’s.” said researchers.

2.7 billion ago, Earth was plagued with single-celled microbes. Sunlight was one-fifth weaker, while the atmosphere contained no oxygen, said UW in a press release issued Monday.

A lighter atmosphere than expected could have impacted wind strength and other climate patterns. Even the boiling point of liquids could have been altered. Professor Buick said researchers are still trying to address the magnitude of new discoveries.

He added it could take some time for the scientific community to “digest all the possible consequences”. Researchers also suggested that early atmosphere must have contained more heat-trapping greenhouse gasses, including methane and carbon dioxide.

Co-author David Catling said people will need to rewrite textbooks. Levels of nitrogen gas have changed over centuries in ways that scientists have never imagined, he added. New findings will be confirmed by studying other suitable rocks. 

Source:University of Washington Press Release