Study reveals how Earth's atmosphere became oxygen-rich over billions of years

An international team of scientists has mapped out the transformation of Earth’s atmosphere from oxygen-poor to oxygen-rich—a process that took nearly two billion years and was crucial for the development of complex life.

According to a statement released Thursday by the University of Western Australia (UWA), the researchers analyzed high-resolution oxygen isotope records preserved in ancient sulphate minerals. This approach helped them reconstruct how atmospheric oxygen gradually increased and interacted with the oceans over time.

The study, published in Nature and led by China’s Chengdu University of Technology in collaboration with UWA, identified three major phases of oxygen rise. These occurred during the Paleoproterozoic (2,500–1,600 million years ago), Neoproterozoic (1,000–538.8 million years ago), and Paleozoic (538.8–252 million years ago) eras. Stable, modern-like oxygen levels were achieved around 410 million years ago.

“The rise of oxygen in Earth’s atmosphere is fundamental to the emergence of oxygen-breathing complex life, planetary habitability, and the creation of vital natural resources,” said Matthew Dodd from UWA's School of Earth Sciences.

The study also revealed that after the Neoproterozoic oxygen increase, Earth’s mostly oxygen-poor oceans experienced periodic pulses of oxidation. These pulses triggered synchronized shifts in carbon, sulphur, and oxygen isotopes across hundreds of millions of years, indicating repeated cycles of atmospheric oxygen influencing ocean chemistry.

Dodd noted that the findings provide a key environmental framework for understanding the origin and evolution of life, as well as the development of important mineral and petroleum resources.

SR