Deep-Sea Mystery: Scientists Investigate if Metallic Nodules Produce “Dark Oxygen”

A Groundbreaking Discovery Challenges Our Understanding of Oxygen Production

In a revelation that could rewrite biology textbooks, scientists are investigating whether metallic nodules on the ocean floor generate oxygen without sunlight—a phenomenon dubbed “dark oxygen.”

Last year, a team of marine researchers made waves when they reported unexpected oxygen production in the pitch-black depths of the ocean, far beyond the reach of sunlight-dependent photosynthesis. Now, they’re launching an ambitious three-year mission to confirm their findings and uncover the mechanisms behind this mysterious process.

The Original Discovery: Oxygen Where It Shouldn’t Exist

Marine scientist Andrew Sweetman and his team at the Scottish Association for Marine Science (SAMS) initially stumbled upon the phenomenon while studying deep-sea ecosystems. In areas rich with metallic nodules—potato-sized mineral deposits containing manganese, nickel, and cobalt—they detected rising oxygen levels, despite the complete absence of sunlight and photosynthetic organisms.

This discovery directly challenges the long-held scientific principle that oxygen production requires photosynthesis from plants, algae, or cyanobacteria. Instead, Sweetman’s team proposed that these metallic formations might act as “geobatteries,” using electrochemical reactions to split water molecules into hydrogen and oxygen.

Skepticism and Industry Pushback

The findings, published in Nature Geoscience, immediately sparked both excitement and controversy. While some scientists hailed the discovery as revolutionary, others—including deep-sea mining companies—questioned its validity.

The Metals Company (TMC), which had partially funded Sweetman’s earlier research, publicly dismissed the results. CEO Gerard Barron stated, “Extraordinary claims require extraordinary evidence—we’re still waiting.” Other critics raised concerns about methodology, though none of these critiques have yet been peer-reviewed.

Nature Geoscience confirmed it is reviewing concerns but has not retracted or amended the original paper. Sweetman, meanwhile, is preparing a formal rebuttal while pushing forward with new research.