Oxygen in early Earth’s atmosphere may have come from rocks, finds study

However, scientific studies have suggested that these microbes had a life ancestor before the Great Oxidation Event. This indicates that there was some oxygen present prior to the noted event. 

To find out, the team conducted lab experiments to investigate the formation of oxygen in those years. 

The experiment involved crushing quartz rocks and later exposing the broken pieces to water. This caused a chemical reaction to occur between the water and the freshly broken rocks. 

As a result, molecular oxygen and other reactive oxygen species such as hydrogen peroxide were formed. This formation would have supplied small amounts of oxygen and triggered the evolution of early Earthly life.

Back in Earth's early years, events such as earthquakes, erosion, or glacier movement could have resulted in the crushing of rocks, resulting in this chain reaction. Scientists highlight that a similar process could also be occurring on the outer worlds, like Mars. 

The study is led by geochemists from the Chinese Academy of Sciences along with the University of Hong Kong, Tianjin University, and the University of California. The results have been reported in the Proceedings of the National Academy of Sciences.

Study Abstract:

Terrestrial reactive oxygen species (ROS) may have played a central role in the formation of oxic environments and evolution of early life. The abiotic origin of ROS on the Archean Earth has been heavily studied, and ROS are conventionally thought to have originated from H2O/CO2 dissociation. Here, we report experiments that lead to a mineral-based source of oxygen, rather than water alone. The mechanism involves ROS generation at abraded mineral–water interfaces in various geodynamic processes (e.g., water currents and earthquakes) which are active where free electrons are created via open-shell electrons and point defects, high pressure, water/ice interactions, and combinations of these processes. The experiments reported here show that quartz or silicate minerals may produce reactive oxygen-containing sites (≡SiO•, ≡SiOO•) that initially emerge in cleaving Si–O bonds in silicates and generate ROS during contact with water. Experimental isotope-labeling experiments show that the hydroxylation of the peroxy radical (≡SiOO•) is the predominant pathway for H2O2 generation. This heterogeneous ROS production chemistry allows the transfer of oxygen atoms between water and rocks and alters their isotopic compositions. This process may be pervasive in the natural environment, and mineral-based production of H2O2 and accompanying O2 could occur on Earth and potentially on other terrestrial planets, providing initial oxidants and free oxygen, and be a component in the evolution of life and planetary habitability.