Many scientists believe that Earth had a thicker atmosphere in its early years than it does now. However, a new study conducted by University of Washington (UW) researchers used ancient gas bubbles trapped in 2.7 billion-year-old lava rocks to reveal that the air at the time possessed - at most - half the pressure of today's atmosphere. The findings could help reveal the secrets of life on early Earth and other planets.
The idea that primordial Earth had a thicker atmosphere stems from the belief that it would need to compensate for weaker sunlight. The new findings could reveal the gases that were present in this early atmosphere, as well as the way that biology and climate worked in ancient times.
"For the longest time, people have been thinking the atmospheric pressure might have been higher back then, because the sun was fainter," said Sanjoy Som of UW and lead author of the study. "Our result is the opposite of what we were expecting."
Scientists have used bubbles trapped in cooling lava to determine the elevation of lava from millions of years ago, but Som and his team used the technique to determine the weight of air during ancient times. In order to do so, they needed to find a site where the lava formed at sea level.
The team examined a site in Western Australia that possessed 2.7 billion-year-old basalt lava containing low areas that make their way into glassy shards, which indicates that the molten lava reached seawater. After determining the area suitable for their research, they drilled into the lava and examined the ancient gas bubbles.
The results reveal that at the time, Earth possessed a lightweight atmosphere that was less than half the pressure of today's. We already know that primordial Earth's atmosphere contained no oxygen, but the new findings suggest even stranger conditions than previously thought - conditions that would have drastically effected various climate patterns.
"We're still coming to grips with the magnitude of this," said Roger Buick, UW professor of Earth and space sciences and co-author of the study. "It's going to take us a while to digest all the possible consequences."
The team's next step is to look for other rock formations with ancient gas bubbles that can further support the findings and reveal that variations in atmospheric pressure at other points in Earth's ancient history.
The findings were published in the May 9 issue of the journal Nature Geoscience.
