Scientists have successfully extracted and analyzed ancient air trapped inside a rock for over 815 million years, providing a direct glimpse into Earth’s distant atmospheric past. This groundbreaking study, led by geochemist Dr. Nigel Blamey and an international research team, developed a method to measure gases sealed inside microscopic bubbles within halite — a mineral form of rock salt. The research, published in Geology, not only pushes the boundaries of atmospheric science but also challenges long-standing assumptions about the composition of air during one of Earth’s most pivotal eras.
Extracting an Atmosphere From Deep Time
In 2016, researchers collected halite samples from a drill core in Australia, suspecting the presence of minuscule gas inclusions. These tiny pockets, preserved since the Neoproterozoic era, were long considered too small for reliable analysis. Using a carefully designed process, the team placed the halite in a vacuum chamber and gently crushed it to release its trapped gases. The liberated air was then fed into quadrupole mass spectrometers, enabling precise measurements of its composition.
“There was a lot of debate as to what the oxygen content was 800 million or more years ago,” Blamey said in a statement. “We’ve come up with a direct method of analyzing the content of those trapped fossil gasses in the atmosphere and found that the oxygen level was approximately half of what it is today.” The direct measurement approach eliminates the heavy reliance on indirect modeling, which has historically produced widely varying estimates. The implications are substantial, as oxygen availability is a key factor in understanding the evolution of early life.
Oxygen Levels and the Dawn of Animal Life
The team’s analysis revealed oxygen levels between 10.3 and 13.4 percent of the atmosphere during that time — significantly higher than the 2 percent once assumed for the late Precambrian. For comparison, modern Earth’s atmosphere contains 20.9 percent oxygen. These findings suggest that the planet’s atmosphere could have supported more complex life forms far earlier than previously believed.
“With this study, the oxygen in the air that allowed the earliest animals to breathe has been measured directly for the first time,” said Professor John Parnell of the University of Aberdeen’s School of Geosciences. “We measured the oxygen at 10.3 to 13.4 per cent of the atmosphere, which would have been enough for animals to flourish. In comparison, the oxygen content of modern Earth’s atmosphere is 20.9 percent. What is especially significant in this study is that we actually discovered a real atmosphere sample, where previous estimates have been made using indirect modelling methods. We had a good idea about how to get at the ancient air, and it’s very pleasing that our hunch has paid off.”
Scientific Debate and Alternative Interpretations
While the results are compelling, not all experts agree with the interpretation. A separate team, performing a re-analysis of the data, suggested that oxygen levels might have been closer to 6.6 percent. Although lower, this still far exceeds many traditional models for the era. The discrepancy highlights the complexity of studying such ancient systems, where chemical interactions over hundreds of millions of years can subtly alter the trapped gas signature. Critics also point out that dissolved gases within the halite could influence the readings, necessitating further refinements to the method.
The researchers have acknowledged these challenges and have already implemented stricter protocols to ensure the integrity of future samples. They believe that continued improvements in extraction and analysis techniques will not only resolve current debates but also open a new window into Earth’s atmospheric history stretching back well beyond what Antarctic ice cores can reveal.
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