More than a billion years before dinosaurs—and long before plants and animals—Earth looked very different.
In what is now northern Ontario, a shallow, salty lake once sat under a warm sun, slowly drying out like today’s Death Valley.
As the water evaporated, it left behind crystals of rock salt. Trapped inside those crystals were tiny pockets of liquid and air, sealed away as the salt was buried under layers of sediment.
For 1.4 billion years, those microscopic bubbles remained untouched, quietly preserving a direct sample of Earth’s ancient atmosphere. Now, scientists have finally opened them.
A research team led by graduate student Justin Park at Rensselaer Polytechnic Institute, working with Professor Morgan Schaller, has analyzed gases trapped inside these ancient salt crystals.
Their work extends the direct record of Earth’s atmosphere back by roughly 1.4 billion years—far earlier than any previous measurements based on real air samples.
The findings were published in the journal Proceedings of the National Academy of Sciences.
Studying ancient air has long been a scientific challenge. Researchers have known for decades that salt crystals can trap fluid inclusions containing air and briny water.
The problem is that gases behave differently when dissolved in water than when they are free in air. Untangling those effects and reconstructing the true atmospheric composition has been extremely difficult.
Park solved this problem by developing new methods and using custom-built lab equipment that allowed the team to carefully separate and analyze the gases.
For the first time, scientists were able to directly measure carbon dioxide and oxygen levels from the Mesoproterozoic era, a period sometimes called the “boring billion” because it appeared relatively stable and uneventful in Earth’s history.
The results were surprising. Oxygen levels were about 3.7 percent of today’s atmosphere—much higher than many scientists expected.
That amount of oxygen would have been sufficient to support complex multicellular life, even though animals would not appear for another 800 million years.
Carbon dioxide levels were also unexpectedly high, around ten times higher than today. This helps explain how Earth stayed warm despite the Sun being weaker back then. The higher carbon dioxide likely prevented global freezing and created a climate not unlike modern conditions.
So why didn’t animals evolve sooner if oxygen levels were already relatively high? The researchers caution that their sample represents only a snapshot in time. The elevated oxygen may reflect a brief increase rather than a long-lasting state. Still, it suggests that Earth’s atmosphere may have been more dynamic during this era than previously thought.
The timing is also intriguing. Red algae appeared around this period and are still major producers of oxygen today. Their growing abundance may have helped boost oxygen levels in the ancient atmosphere.
By cracking open these ancient salt crystals, scientists have gained a rare and direct glimpse into Earth’s deep past. These findings are helping rewrite our understanding of how Earth’s atmosphere evolved—and how the conditions for complex life slowly came together.
Source: KSR.
