Confirmed: Oxygen can be produced without photosynthesis
For centuries, it was believed that oxygen on Earth was produced exclusively by living organisms through photosynthesis, a process dependent on sunlight. New research shows this is not the only pathway.
At depths of around 4,000 metres (13,000 feet) in the Pacific Ocean, far beyond the reach of sunlight - researchers observed oxygen being produced in complete darkness.
The discovery was made by a team led by the Scottish Association for Marine Science while studying the Clarion–Clipperton Zone, a vast abyssal plain between Hawaii and Mexico. Sensors placed on the seafloor recorded rising oxygen concentrations, contradicting expectations based on known biological processes.
Further investigation identified the source as polymetallic nodules, rock concretions rich in manganese, nickel, cobalt, and other metals. The researchers found that these nodules can generate electrical potentials when clustered together on the seabed.
Under certain conditions, this electrical charge appears sufficient to drive seawater electrolysis, a chemical reaction that splits water molecules (H₂O) into hydrogen and oxygen, without the involvement of light or living organisms.
The findings have important implications.
They suggest that oxygen production can occur through geological and electrochemical processes, which may influence how scientists think about the early evolution of oxygen-using life on Earth. They also raise concerns about deep-sea mining on ecosystems we don’t understand
Study:
Evidence of dark oxygen production at the abyssal seafloor
Nature Geoscience, 2024