Stratocumulus clouds above the northwestern Pacific Ocean Credit: NASA.

According to a new paper called Atmospheric oxygenation three billion years ago published in the journal Nature, oxygen may have filled Earth’s atmosphere hundreds of millions of years earlier than previously thought.

Life and Oxygen

This implies that life potentially evolved earlier than previously thought. Since plants use carbon dioxide, water, and sunlight to create energy – oxygen is created as a by-product in that process, 6 H2O + 6 CO2 + sunlight → C6H12O6 (dextrose) + 6 O2.

So if life evolved even earlier, this by itself implies that life appeared relatively fast when the conditions were right for it to exist, suggesting that more worlds in the universe could harbor life.

Earth is 4,5 billion years old and it has been widely assumed that oxygen levels remained low during the first 2 billion years. It was also assumed that the first time oxygen appeared in the atmosphere was about 2,3 billion years ago in what is called the Great Oxidation Event – which is thought to originate from cyanobacteria.

Rocks Got The Answer

This new discovery comes just soon after the discovery made by another team of researchers. That team also dated oxygen further back in time, based on ancient rock examination. They noted that oxygen may have transiently existed much earlier, about 2,6 to 2,7 billion years ago.

And this new study pushes the appearance back even further, to about 3 billion years ago. The team of researchers examined metal samples from South Africa, which can serve as markers of atmospheric reactions with oxygen. These metal samples relate to the age of its surroundings (such as samples of soil sediments) to serve as an age-determinative.

As one of the study authors Sean A. Crowe, who is a biogeochemist at the University of British Columbia writes, “The fact oxygen is there requires oxygenic photosynthesis, a very complex metabolic pathway, very early in Earth’s history,”. “That tells us it doesn’t take long for biology to evolve very complex metabolic capabilities.”.

The researchers argue that the atmospheric oxygen levels 3 billion years ago were about 100,000 times higher than what can be explained by natural chemical reactions, not involving life.

With this new method used by the researchers, future research will be able to confirm the results by using the same method but looking at other places around the world.

Atmospheric oxygenation three billion years ago