Researchers from the University of Washington have shown how the early earth had a thicker atmosphere to compensate for weaker sunlight.
New research from the University of Washington uses bubbles trapped in 2.7 billion-year-old rocks to show that air at that time exerted at most half the pressure of today's atmosphere.
Lead researcher Sanjoy Som, who did the work as part of his UW doctorate in earth and space sciences, said the people have been thinking for long that the atmospheric pressure might have been higher back then because the sun was fainter.
"Our result is the opposite of what we were expecting," he added.
The idea of using bubbles trapped in cooling lava as a "paleobarometer" to determine the weight of air in our planet's youth occurred decades ago to co-author Roger Buick, a UW professor of earth and space sciences.
Others had used the technique to measure the elevation of lavas a few million years old. To flip the idea and measure air pressure farther back in time, researchers needed a site where truly ancient lava had undisputedly formed at sea level.
Research found that the earth was home only to single-celled microbes 2.7 billion years ago, sunlight was about one-fifth weaker and the atmosphere contained no oxygen. But this finding points to conditions being even more otherworldly than previously thought. A lighter atmosphere could affect wind strength and other climate patterns, and would even alter the boiling point of liquids.
The new study is an advance on the UW team's previous work on "fossilized raindrops" that first cast doubt on the idea of a far thicker ancient atmosphere. The result also reinforces Buick's 2015 finding that microbes were pulling nitrogen out of earth's atmosphere some three billion years ago.
Co-author David Catling, a UW professor of earth and space science, opined that the levels of nitrogen gas have varied through earth's history.
The study is published in the Journal of Nature Geoscience.