Research finds oxygen was present in Earth's atmosphere much earlier than assumed

A new geological study based on data from Western Greenland has indicated that small levels of atmospheric oxygen were developed 3.8 billion years ago, some 0.7-0.8 billion years earlier than thought.

Today, most researchers agree that the oxygenation of Earth's atmosphere happened in two major steps: the first during the so-called Great Oxidation Event about 2.5-2.4 billion years ago and the second during the Late Neoproterozoic Era around 750 to 540 million years ago.

The latter is thought to have been the cause for the emergence of animals during the so-called Cambrian explosion around 540 to 520 million years ago.

Researchers led by Professor Robert Frei released a study indicating evidence for the presence of small concentrations of oxygen on Earth already 3.8 billion years ago.

The researchers analysed Earth's oldest Banded Iron Formations (BIFs) from Western Greenland. BIFs are marine chemical sediments originally comprised of alternating layers of silica and Fe-hydroxides and are widely used as geochemical archives.

The reason for this is that they retain information on the composition and presence of oxygenation/reduction processes in ambient seawater and on the interaction of the atmosphere with Earth's surface.

The fact that the analyses of the BIF layers from Western Greenland show elements that require presence of oxygen in the atmosphere opens up for the possibility of evolution of the earliest primitive photosynthetic life forms as early as 3.8 billion years ago.

The research is published in the Journal Scientific Reports.