Scientists thought that early Earth’s atmosphere 2.7 billion years ago was thicker to compensate for weaker sunlight. However, a study published on May 9 in the journal Nature Geoscience reveals that the air during this time only exerted half the pressure of today’s atmosphere.

According to researchers from the University of Washington and the University of Western Australia, this thin atmosphere could have influenced wind strength and other climate patterns at a time when only single-celled microbes populated the Earth. The atmospheric oxygen was still nonexistent and sunlight was one-fifth weaker than today. Nevertheless, they assert that further analysis is needed to verify the exact consequences of this atmospheric condition.

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


One of the lava flows analysed in the study, from the shore of Australia’s Beasley River. Gas bubbles that formed as the lava cooled, 2.7 billion years ago, have since filled with calcite and other minerals. The bubbles now look like white spots. Researchers compared bubble sizes from the top and bottom of the lava flows to measure the ancient air pressure. Credit: Sanjoy Som/University of Washington

The research team headed to Western Australia and exposed 2.7 billion-year-old basalt lava. The trapped air bubbles inside the lava revealed a lighter atmosphere.

Moreover, the finding suggests that microbes were absorbing nitrogen gas from the Earth’s atmosphere three billion years ago. The study’s co-author, Roger Buick, a professor of Earth and space sciences at the University of Washington, asserted in 2015 that nitrogen levels were different in a younger Earth.

“The levels of nitrogen gas have varied through Earth’s history, at least in Earth’s early history, in ways that people just haven’t even thought of before,” adds David Catling, one of the study’s co-author, who is also a professor of Earth and space sciences at the University of Washington. “People will need to rewrite the textbooks.”

The research team is currently planning to seek other rocks that can support their findings. Additionally, further studies can also give details into how Earth’s atmospheric pressure changed over time.