Oct. 6, 2021
Research Highlight

Clues to Oxygen on Earth before the Great Oxidation Event

A new study seeks to settle a debate about the amount of molecular oxygen in Earth’s early atmosphere. Researchers supported by the NASA Astrobiology Program have been studying an event in Earth’s history known as the ‘Great Oxidation Event,’ when a rise in atmospheric oxygen altered the environment and the biosphere of our planet some 2.4 billion years ago.

The team used computer models to estimate how much oxygen was present before the Great Oxidation Event. The model incorporates what is known about the molybdenum (Mo) in Earth’s geological record. The presence of Mo in the rock record can be used as a proxy to estimate the amount of oxygen that was present in the environment when the rocks were formed.

Evaporation, convection, rainfall and winds can even out heat imbalances in the atmosphere. Here, cumulus clouds carry solar energy away from Earth’s surface over South America.
Cumulus clouds over South America. The composition of Earth's atmosphere has changed throughout time, and these changes have had a profound effect on the evolution of life. In a new study, astrobiologists have provided details about oxygen levels in Earth's ancient atmosphere.Image credit: NASA, Astronaut Photo-graph ISS006-E-19436.

The model revealed a range of possible oxygen levels on Earth before 2.4 billion years ago. The results indicate that oxygen was present in the atmosphere before the Great Oxidation Event, but at very low levels.

The Earth’s transition from an oxygen-poor to an oxygen-rich atmosphere had profound consequences for the evolution of life, and many scientists believe that complex life such as human beings could not have evolved without a sustainable oxygen atmosphere.

The study, “Reconciling evidence of oxidative weathering and atmospheric anoxia on Archean Earth,” was published in the journal Science Advances.

A full article about this research from Arizona State University is available here.