In a groundbreaking study, researchers uncovered ancient gases and fluids trapped within 1.4 billion-year-old rock salt crystals in northern Ontario, Canada. Their analysis reveals that oxygen and carbon dioxide concentrations during the Mesoproterozoic Era (1.8 billion to 800 million years ago) were suppressed to just 3.7% of current levels, while carbon dioxide was found to be ten times pre-industrial levels. These findings indicate a period of climatic stability, suggesting atmospheric oxygen levels temporarily exceeded the needs of early animals long before their emergence.
Examples of primary halite, mixed halite, and secondary halite rock inclusion aggregates. Image credit: Park et al., doi: 10.1073/pnas.2513030122.
Scientists have long recognized that liquid inclusions within rock salt crystals preserve samples of Earth’s primordial atmosphere.
However, accurately measuring these inclusions has presented significant challenges. These inclusions encompass both air bubbles and saline water, with gases like oxygen and carbon dioxide interacting differently in liquids compared to air.
“It’s astonishing to crack open a sample of air that is over a billion years older than the dinosaurs,” said Justin Park, a graduate student at Rensselaer Polytechnic Institute.
“Our carbon dioxide measurements are unprecedented,” stated Morgan Schaller, a professor at Rensselaer Polytechnic Institute.
“For the first time, we can trace this era of Earth’s history with remarkable precision. These are authentic samples of ancient air.”
Measurements indicate that Mesoproterozoic atmospheric oxygen levels sat at 3.7%, mirroring today’s levels. This high oxygen concentration was sufficient to support the existence of complex multicellular life, which would not arise for hundreds of millions of years.
Conversely, carbon dioxide was found to be ten times more abundant than present levels, effectively counterbalancing the “weak young sun” and fostering the climate conditions seen today.
One pivotal question arises: if oxygen levels were adequate for animal life, why did evolution take so long?
“This sample represents a snapshot in geological time,” Park explained.
“It may reflect a brief oxygenation event during this lengthy period, humorously dubbed the ‘billion boring years.'”
“This era in Earth’s history was marked by low oxygen levels, geological stability, and minimal evolutionary change.”
“Despite its moniker, direct observational data from this time is crucial for understanding the emergence of complex life and the evolution of our atmosphere.”
Prior indirect estimates suggested low carbon dioxide levels for this epoch, contradicting evidence of a lack of significant glaciation during the Mesoproterozoic.
The team’s direct measurements of elevated carbon dioxide, alongside temperature estimates from the salt, imply that Mesoproterozoic climate conditions were milder and more akin to today’s climate than previously assumed.
“Algae began to flourish during this period, continuing to play a vital role in global oxygen production today,” Professor Schaller remarked.
“The relatively elevated oxygen levels may directly result from the increasing prevalence and complexity of algae.”
“The insights we gained could represent an exciting moment in what is otherwise regarded as a billion years of monotony.”
The team’s research paper has been published today in the Proceedings of the National Academy of Sciences.
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Justin G. Park et al.. 2025. Bringing the Boring Billion to Life: Direct constraints from 1.4 Ga fluid inclusions reveal a favorable climate and oxygen-rich atmosphere. PNAS 122 (52): e2513030122; doi: 10.1073/pnas.2513030122
Source: www.sci.news
