Scientists uncover the 2.3-billion-year-old secret that helped keep Earth habitable
Scientists may have solved a 2.3-billion-year-old mystery about how Earth maintained enough oxygen to support life. Ancient rocks reveal that phosphorus recycling in the oceans created a self-sustaining cycle that helped keep oxygen levels high, even as the planet underwent dramatic environmental changes. The discovery challenges assumptions about Earth's early atmosphere and raises new questions about why complex…
Key points
- Researchers studied 2.3-billion-year-old rocks from South Africa to explain how Earth kept oxygen after the Great Oxidation Event.
- They found a feedback loop in which sulfate-driven microbes released phosphorus, boosting carbon burial and oxygen buildup.
- The findings suggest early oxygen levels fluctuated and may inform modern ocean oxygen loss and the search for life beyond Earth.
Scientists have identified a 2.3-billion-year-old recycling system in Earth's oceans that may explain how the planet maintained enough oxygen to remain habitable. The research, published in Nature Communications, involved University of California, Riverside geologist Andrey Bekker and colleagues who studied rocks from South Africa.
The team focused on the period after the Great Oxidation Event, when oxygen became a lasting part of the atmosphere. They found that changes in ocean chemistry created a natural cycle in which biological activity supported continued oxygen accumulation.
How the ancient cycle worked
As oxygen spread into the oceans, it altered seawater chemistry and raised sulfate concentrations. Certain microbes used this sulfate to break down organic material more efficiently, releasing phosphorus back into the water.
More phosphorus increased biological productivity, allowing more organic carbon to be buried in seafloor sediments rather than decomposed. Because decomposition consumes oxygen, burying carbon helped favor further oxygen buildup in the atmosphere.
Living things cannot grow or function properly without phosphorus. Once more of it became available in the oceans, it allowed more organic carbon to be buried. A side effect of that process is that more oxygen continued to be released into the atmosphere.
— Andrey Bekker
What the findings suggest
The results indicate that Earth's oxygen history may have been more turbulent than previously recognized, with levels rising and falling dramatically after the Great Oxidation Event. This could change how scientists interpret the delayed appearance of complex life.
The research also has implications for modern oceans, where climate change is contributing to oxygen loss that could disrupt phosphorus recycling. It may additionally help in the search for life on ocean-bearing worlds beyond Earth.
