New Research Suggests Deep-Sea Oxygen Production Could Redefine Theories on Life’s Origin

A study published in the journal Nature observed the production of oxygen in the depths of the Pacific Ocean, in a region between Mexico and Hawaii. Researchers from the Scottish Association of Marine Sciences (SAMS), responsible for the discovery, named the process dark oxygen and believe that the research may suggest a new alternative for the origin of life on Earth. According to Professor Rafael André Lourenço, from the Oceanographic Institute (IO) at USP, the discovery is commonly referred to in Brazil as “black oxygen”, however, the most appropriate term, based on the translation of the study, would be “dark oxygen”, a name that suggests the production of oxygen unrelated to sunlight and known photosynthetic processes.

According to the professor, SAMS researchers were initially monitoring the Pacific Ocean at a depth of 4,000 meters to study the consumption of oxygen by benthic organisms, which live and feed on the seabed. Lourenço explains that the scientists expected that, as oxygen was being consumed, the concentration of this substance on the seabed would be lower. However, they observed that the presence of the gas in the marine sediment was, in fact, increasing.

“This increase in oxygen production at the bottom of the sea made no sense at all, since they were in a very deep region, where sunlight was not able to reach, therefore, there could be no photosynthesis. The discovery occurred somewhat by chance and perhaps this was the origin of the name dark oxygen, it is a way of producing oxygen in a completely dark region with no chance of photosynthesis occurring”, he explains.

Polymetallic nodules

According to the expert, scientists decided to collect sediments from the seabed and found the presence of polymetallic nodules, which are small particles of metals such as nickel, copper and zinc connected by mineral deposits. These nodules have different oxidation-reduction potentials, meaning they transfer electrons between them and, together with the electric current that passes through the water, produce the electrolysis of water, that is, the breakdown of its molecule into hydrogen (H₂) and oxygen (O²) gases.

“This process can be easily reproduced in laboratories using batteries. A battery is nothing more than a few metals with a type of connection, and when the circuit is closed using water, for example, electrons begin to flow between the metals that make up the battery, which generates the electrolysis of the water. So it is basically as if these polymetallic nodules on the seabed were functioning as a battery,” explains Lourenço.

Life on Earth

According to the professor, the discovery of dark oxygen raises the possibility that polymetallic nodules may have been responsible for the production of oxygen long before the emergence of organisms capable of photosynthesis, such as cyanobacteria. The most widely accepted theories currently suggest that these microorganisms, which emerged approximately 3 billion years ago, are primarily responsible for the mass production of oxygen on Earth and the modification of the atmospheric structure as we know it today.

According to Rafael Lourenço, there are indications that liquid water already existed on the planet around 4 billion years ago, that is, 1 billion years before the emergence of the first cyanobacteria. “It is possible that these minerals were already on the planet since its solidification and producing oxygen in the water long before the first photosynthetic organisms. So I believe that this discovery may not change the idea of ​​the origin of life on the planet, but rather suggest that another component may have contributed to the formation of oxygen in the atmosphere,” he concludes.