Dark oxygen made by deep sea ‘batteries’

The scientists worked out that the metal nodules are able to make oxygen precisely because they act like batteries.

“If you put a battery into seawater, it starts fizzing,” explained Prof Sweetman. “That’s because the electric current is actually splitting seawater into oxygen and hydrogen [which are the bubbles]. We think that’s happening with these nodules in their natural state.”

“It’s like a battery in a torch,” he added. “You put one battery in, it doesn’t light up. You put two in and you’ve got enough voltage to light up the torch. So when the nodules are sitting at the seafloor in contact with one another, they’re working in unison – like multiple batteries.”

The researchers put this theory to the test in the lab, collecting and studying the potato-sized metal nodules. Their experiments measured the voltages on the surface of each metallic lump – essentially the strength of the electric current. They found it to be almost equal to the voltage in a typical AA-sized battery.

This means, they say, that the nodules sitting on the seabed could generate electric currents large enough to split, or electrolyse, molecules of seawater.

The researchers think the same process – battery-powered oxygen production that requires no light and no biological process – could be happening on other moons and planets, creating oxygen-rich environments where life could thrive.