Oxygen may have first accumulated in Earth's atmosphere 3 bln years ago

A study by a team of researchers has shown that oxygen production by photosynthetic cyanobacteria may have initiated as early as 3 billion years ago.

A general consensus asserts that appreciable oxygen first accumulated in Earth's atmosphere around 2.3 billion years ago during the so-called Great Oxidation Event (GOE).

However, the study has given a nontraditional way of thinking about the earliest accumulation of oxygen in the atmosphere, arguably the most important biological event in Earth history.

It was found that oxygen production by photosynthetic cyanobacteria may have initiated as early as 3 billion years ago, with oxygen concentrations in the atmosphere potentially rising and falling episodically over many hundreds of millions of years, reflecting the balance between its varying photosynthetic production and its consumption through reaction with reduced compounds such as hydrogen gas.

"There is a growing body of data that points to oxygen production and accumulation in the ocean and atmosphere long before the GOE," lead author Timothy W. Lyons, a professor of biogeochemistry in the Department of Earth Sciences at the University of California, Riverside, said.

Lyons and his coauthors note that once oxygen finally established a strong foothold in the atmosphere starting about 2.3 billion years ago it likely rose to high concentrations, potentially even levels like those seen today.

Then, for reasons not well understood, the bottom fell out, oxygen plummeted to a tiny fraction of today's level, and the ocean remained mostly oxygen free for more than a billion years.

The study was published in the journal Nature.