The belief that photosynthesis is the primary source of oxygen on the planet may be changing. Scientists have discovered, 4,000 meters deep in the Pacific Ocean, metallic minerals that produce oxygen in an environment devoid of light.
The discovery was made by chance by a team from the Scottish Association for Marine Science (SAMS) while measuring oxygen levels on the ocean floor to assess the impacts of deep-sea mining.
According to biogeochemist Andrew Sweetman, the lead author of the article published in *Nature Geoscience*, “When we first obtained these data, we thought the sensors were faulty, because all previous studies in the deep sea had only observed oxygen being consumed rather than produced.” The sensors were recalibrated, but the unusual readings persisted for ten years.
How Do Polymetallic Nodules Produce Dark Oxygen?
To understand the phenomenon, researchers abandoned the optode sensors and used another method, which confirmed the results. They collected rocks from the analyzed nodules and tested them in the laboratory.
The metals combined in the nodules, such as cobalt, nickel, copper, lithium, and manganese, are essential elements in batteries. This potential attracts mining companies and may be responsible for spontaneous reactions.
During testing, some nodules produced up to 0.95 V of voltage. This means that, when grouped together, they could function as batteries in series, reaching the 1.5 V needed to perform electrolysis on water and separate oxygen. “It seems we’ve discovered a ‘geobattery’,” said co-author Franz Geiger.
The Importance of Dark Oxygen for the Origin of Life on Earth
Distributed across the seafloor, these nodules form fields of mineral concentrations composed of layers of various materials accumulated around a core. The possibility that oxygen, called “dark” by Sweetman due to the lack of sunlight, is being synthesized naturally is surprising.
Interviewed by *ScienceAlert*, SAMS marine scientist Nicholas Owens, who was not involved in the research, highlighted that “the discovery of oxygen production through a non-photosynthetic process requires us to rethink how complex life on the planet may have originated.” According to the expert, this could be one of the most exciting discoveries in ocean science in recent times.
