1.4-Billion-Year-Old Air Reveals High CO2 and Unexpected Oxygen

Researchers measured gases from halite crystals dated about 1.4 billion years ago and report roughly ten times modern carbon dioxide and about 3.7% of modern oxygen.

Researchers extracted gases trapped in halite (rock salt) crystals that formed when a lake in what is now Ontario evaporated about 1.4 billion years ago. The crystals contain tiny fluid and air inclusions that act as direct samples of the ancient atmosphere. Using a method developed by lead author Justin Park, the team separated and measured gases that exist in both the liquid and gas phases. The measurements were reported in a study published in PNAS. Key findings: - The samples come from halite crystals dated to about 1.4 billion years ago from an evaporated lake in present-day Ontario. - The team used a technique developed by Justin Park to extract and measure gases from fluid inclusions that contain both brine and trapped air. - Reported carbon dioxide levels are about ten times higher than those of today. - Reported oxygen was about 3.7% of present-day atmospheric levels. - The authors report these values are consistent with a milder Mesoproterozoic climate and could reflect a transient oxygenation event within the period sometimes called the "boring billion." Summary: The measurements provide direct atmospheric data from the Mesoproterozoic and inform understanding of climate and oxygen availability long before complex animals appeared. Undetermined at this time.