Small levels of oxygen have developed 3.8 billion years ago, around 0.7 to 0.8 billion years earlier than thought. The researchers added that the new study may also prove that life formed earlier than thought.
The researchers, led by Robert Frei from the Department of Geoscience and Natural Resource Management at the University of Copenhagen, presented this claim after analysing the Earth’s oldest Banded Iron Formations (BIFs), which are marine chemical sediments used as geochemical archives from Western Greenland.
Accordingly, BIFs retain data about the composition and presence of oxygen/reduction mechanisms in the seawater and on the interaction of the Earth’s surface with the atmosphere.
They used concentrations of the elements chromium (Cr) and uranium (U) present in the BIFs as well as its isotope compositions, or the variations of the same elements with different atomic weight. The team adds that these elements were used because these weather quickly when the continental landmasses are exposed to reactive oxygen species (ROS) like oxygen. These are deposited with chemical sediments after being transported to the ocean by rivers after weathering, which will serve as indicators of the ROS weathering.
Most experts believe that oxygenation of the Earth’s atmosphere occurred in two ways. The first is named as the Great Oxidation Event, which happened about 2.5 to 2.4 billion years ago. The other one happened around 750 to 540 million years ago, during the Late Neoproterozoic Era. Scientists believe that animals emerged in this era, during the Cambrian explosion that occurred 540 to 520 million years ago.
Frei adds that the study also shows that the evolution of the earliest primitive life form began 3.8 billion years ago. Many believe that the Earth was uninhabitable at this period due to the lack of oxygen but because oxygen is now verified to have developed earlier, then this means that life also began earlier than thought. The team notes that the new study can help researchers understand further the evolution of life and biodiversity on Earth.