Breathable, oxygen-rich air is a valuable commodity in the universe, as the movie Spaceballs so poignantly chronicles. But reconstructing the rise of the delightfully oxygenated air we all know and love is "a famously difficult challenge" for scientists, according to a 2014 Nature paper. After all, it's not as if researchers can pop back in time to measure Earth's prehistoric atmospheres, so instead, scientists have previously been forced to rely on indirect evidence of past oxygen levels.
Now, research led by Nigel Blamey, a professor of Earth sciences at Brock University, has finally countered this longstanding stumbling block. Along with an international team of scientists, Blamey has pioneered a novel way to unlock genuine air samples dating back at least 800 million years, to the Neoproterozoic geological epoch.
In their newly published paper "Paradigm shift in determining Neoproterozoic atmospheric oxygen," which appears in the August issue of Geology, Blamey and his colleagues show that ancient air trapped in microscopic bubbles within halite—the fancy word for rock salt—can be freed and analyzed with specialized equipment.
"There was a lot of debate as to what the oxygen content was 800 million or more years ago," said Blamey 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."
To get a nice healthy wiff of that nearly billion-year-old atmosphere, the team placed halite crystals from southwest Australia in a vacuum chamber and crushed them, releasing the actual air that circulated during this bygone era in our planet's history.
"It's a direct measurement of the atmosphere of that time, not an interpretation," emphasized study co-author Uwe Brand.
These atmospheric time capsules are then pulled into a highly sensitive instrument called a quadrupole mass spectrometer, where their oxygen levels are determined. Blamey's team measured 31 of these fossil gas samples from the Neoproterozoic, and discovered that their average oxygen content was 10.9 percent, five times higher than previous estimates concerning Earth's paleoatmosphere 800 million years ago.
The result challenges prevailing models about the oxygenation of the planet, suggesting that oxygen made up a tenth of the atmosphere about 100 to 200 million years earlier than expected (oxygen gas currently makes up about 21 percent of the Earth's air).
That, in turn, has implications for the evolution of life on Earth, which is intricately tied to oxygenation. "Our finding answers one big question: Did life come first or atmospheric oxygen?" said Brand.
"It is the latter."
So breathe in that sweet oxygenated air, because it has been slowly percolating to that sweet 21 percent level for billions of years. Now, finally, scientists have found a way to snatch real atmospheric snapshots of this essential, life-giving process.