🌊 What if oxygen doesn't need photosynthesis at all?
More than 4,000 meters down on the Pacific seafloor, in total darkness, fist-sized metallic rocks appear to be producing oxygen through electrochemistry alone. Researchers call it "dark oxygen," reported in Nature Geoscience in July 2024.
The discovery was pure accident. Andrew Sweetman's team was measuring oxygen consumption in sealed seabed chambers when levels kept rising instead of falling. They sent sensors back for recalibration four or five times over nearly a decade before accepting the data was real.
The proposed mechanism: polymetallic nodules (manganese, cobalt, copper oxides that form over millions of years) act like natural geo-batteries, generating enough voltage to split seawater. The effect persisted even after microbes were killed off.
Worth noting: this is fiercely debated. Critics argue the measured voltage falls short of what thermodynamics requires, and possible sensor artifacts haven't been ruled out. It's a live scientific argument, not settled fact.
But if real, it rewrites our oxygen budget for the deep ocean and suggests oxygen could accumulate on lightless ocean worlds like Europa without any biology. It also lands in a policy fight, since those same nodules are targets for deep-sea mining.
#science #deepsea #astrobiology
