The Hidden Mechanism of Earth’s Oxygen Production: Revealing the Emergence of Oxygen for Sustaining Life.
For billions of years, Earth was a suffocating planet dominated by volcanic gases and oxygen-deprived oceans. However, a radical change altered its destiny: the air began to fill with oxygen, allowing complex life to emerge. How exactly did this process happen? A team of Australian scientists believes they have found the answer.
According to a study published in Nature Communications by the University of Western Australia, the element that sparked the change was phosphorus, an essential nutrient for photosynthesis. When large amounts of phosphorus reached the primitive oceans, they fueled the massive growth of photosynthetic microbes, triggering the event that forever changed Earth’s atmosphere.
### A Planet Without Air and a Chemical Opportunity
Over 2.4 billion years ago, Earth’s sky would have been reddish, and its surface a toxic environment dominated by methane and dissolved iron. In that scenario, life was microbial, and oxygen barely existed. Dr. Matthew Dodd, the study’s lead author and geobiologist at the University of Western Australia’s School of Earth and Ocean, explains that the change was not sudden but a result of a biogeochemical cycle that fed back on itself.
“The phosphorus was the catalyst. When it increased in the oceans, photosynthetic microbes multiplied, buried more carbon, and released oxygen into the air. It was the moment when Earth took its first deep breath,” Dodd stated.
The scientists were able to demonstrate this link by analyzing data and simulating ocean chemistry in climate models. They observed that during the Great Oxidation Event (GOE), both marine phosphorus and atmospheric oxygen fluctuated simultaneously, showing a direct relationship.
### How the Oceans Released Oxygen into the Sky
To investigate this further, scientists studied phosphorus burial, an indicator of nutrient concentration in seawater. They also measured carbon isotopes reflecting biological productivity and organic carbon burial in sediments. The results were conclusive: every pulse of phosphorus corresponded to an increase in atmospheric oxygen. Numerical models – over a thousand simulations – reproduced these oscillations, confirming that phosphorus variations controlled the rate at which the atmosphere became oxygenated.
In other words, the oceans acted as the planet’s first “lung.” By burying organic carbon on the seafloor, the oxygen that would have been consumed remained free to accumulate in the air. This chemical balance allowed atmospheric oxygen to go from insignificant traces to levels sufficient to sustain complex life.
### The Great Oxidation Event: The Invisible Revolution
The Great Oxidation Event, occurring between 2.43 and 2.06 billion years ago, was a turning point in Earth’s history. It represented the and marked the beginning of a new geological era. Before the GOE, Earth was an anoxic world; afterward, it transformed into a dynamic ecosystem where eukaryotic cells, precursors of plants and animals, could evolve.
Dr. Dodd and his team describe this process as a “planetary metabolic shift,” driven by biology and modulated by ocean chemistry. They emphasize that while there were already microbes capable of releasing oxygen through photosynthesis, the true trigger was the sudden increase in phosphorus, allowing their activity to surpass Earth’s capacity to consume that oxygen. Only then did the atmosphere begin to transform.
Earth’s lung is not the Amazon, it’s the ocean! More than 50% of oxygen is produced in the ocean, through photosynthesis by millions of microscopic algae (phytoplankton).
### A Model that Transcends Earth
Beyond its geological significance, the discovery has astrobiological implications. The presence of oxygen is considered one of the main indicators of life on exoplanets. However, not all oxygenated atmospheres are proof of biology.
Dodd warns that “oxygen can also be generated by non-biological processes.” Therefore, understanding how nutrients and oceans interact with the atmosphere allows us to distinguish living worlds from sterile ones. “Our work provides a verifiable biological pathway for the creation and maintenance of oxygen. This knowledge will be essential for interpreting future detections of atmospheres on exoplanets,” the researcher explained.
Phosphorus thus becomes an indirect marker of habitability: its abundance or scarcity could determine whether a planet has the conditions for, eventually, complex life.
