Earth's ancient atmosphere was much thinner than what is found today at Mount Everest, a new research has suggested.
Many believe that the Earth's atmosphere billions of years ago compensated for the weak sunlight by having a thicker atmosphere. However, researchers from the University of Washington (UW) who studied trapped bubbles inside old rocks found evidence that the Earth's atmosphere was actually thinner before.
They also investigated the presence of gases and how the interplay of climate and biology affected the young Earth.
UW Earth and space sciences professor and co-author Roger Buick said that trapped bubbles in cooling lava were used to determine the lava elevation from million years ago. Buick's team used a paleobarometer to measure the weight of ancient air.
For the study to push through, the team had to look for a site with ancient lava formed at sea level. Co-author Tim Blake from the University of Western Australia pointed them to the Beasley River where 2.7 billion-year-old basalt lava sits exposed.
As lava cools from top to bottom, trapped bubbles in the bottom become noticeably smaller than the top bubbles. The difference in size is due to the varying degrees of air pressure exerted on the lava as it cools. The research team bore through superimposing lava flows to measure the size of bubbles.
Initial on-site estimates showed that early atmosphere was lightweight - a finding supported by more detailed x-ray scans from different lava flows. The bubbles showed that early atmospheric pressure was less than 50 percent of what the Earth has today.
"We're still coming to grips with the magnitude of this," said Buick. "It's going to take us a while to digest all the possible consequences."
The findings of their study complemented Buick's earlier finding that Earth's microbes were taking in most of the atmosphere's nitrogen.
Researchers believe that this lighter atmosphere have several climate implications. The team already uncovered some evidence that suggests presence of liquid water. This means that the ancient atmosphere had many greenhouse gases like carbon dioxide and methane, and only small amounts of nitrogen.
"We are 95 percent sure that the pressure was between 0 and 0.5 atmospheres," said Blue Marble Space CEO and lead author Sanjoy Som. The finding represents information about the pressure at Mount Everest's elevation of 5,500 meters (3.4 miles).
The layers of the stromatolite which the team studied also showed evidence of single-celled microbes that have thrived despite the early Earth's thin atmosphere.
This suggests that the Earth's environment had the ability to sustain life on its surface even if the sun was dimmer and the tides were bigger. Life can thrive even in ancient atmospheric conditions, said Som, who is also an astrobiology researcher at NASA's Ames Research Center.
A past study of ancient rocks revealed that photosynthesis occurred earlier than previously thought. How this correlates with the present study is not yet known.
The team is now looking at studying other rocks to back up their finding and investigate further how atmospheric pressure changed over time. Their study will hopefully contribute to understanding other planets with thin atmospheres similar to the young Earth.
The study was published in Nature Geoscience on May 9.
