Scientists have found a strange phenomenon called “dark oxygen” 4,000 meters below the surface of the Pacific Ocean in the Clarion-Clipperton Zone (CCZ). This oxygen is created without sunlight, challenging the idea that photosynthesis is the only way oxygen is produced on Earth.

The oxygen comes from polymetallic nodules—mineral-rich formations on the seafloor that contain metals like nickel and cobalt. These nodules seem to act like “geobatteries,” generating a natural voltage of around 0.95 volts that splits seawater into hydrogen and oxygen.

This discovery could change our understanding of how aerobic life on Earth began and raises concerns about the environmental effects of deep-sea mining in these delicate ocean regions.