Natural geobatteries are the possible explanation of the ocean’s dark oxygen production.

…natural mineral deposits known as polymetallic nodules located at the bottom of the ocean appear capable of generating oxygen without any source of light. These nodules are found as far as 20,000 feet below the ocean surface and range in size from particles to nodules as large as a human hand…

…The first indications that something strange was occuring within polymetallic nodules arrived over 10 years ago in a northeastern region of the Pacific Ocean. While on a sampling expedition in the area’s mountainous submarine ridge known as the Clarion-Clipperton Zone, Andrew Sweetman of the Scottish Association for Marine Science (SAMS) noticed odd readings on his equipment.

“When we first got this data, we thought the sensors were faulty because every study ever done in the deep sea has only seen oxygen being consumed rather than produced,” Sweetman says in an accompanying statement. “We would come home and recalibrate the sensors, but, over the course of 10 years, these strange oxygen readings kept showing up.” After double checking the findings using a different sensor array, Sweetman and his team knew they were “onto something groundbreaking and unthought-of.”

In 2023, Sweetman contacted Northwestern University electrochemistry expert Franz Geiger about the strange evidence and sent him multiple pounds of polymetallic nodules. Electrolysis, the process of splitting a target into its separate elements, needs only 1.5 volts to initiate in seawater—and after attaching sensors to a single nodule, Sweetman and Geiger detected voltages as high as 0.95 volts. This power increased even more when they placed the formations close together, much like stacking batteries.

“It appears that we discovered a natural ‘geobattery,’” Geiger says in a statement. “These geobatteries are the basis for a possible explanation of the ocean’s dark oxygen production.”

The existence and possible source of this dark oxygen may eventually rewrite the narrative of how life originated on Earth…

Of course the first thing that popped into my mind was what this would say about potential aerobic life on ocean worlds like the Jovian and Saturn moons.