Scientists Launch Deep-Sea Mission to Validate Controversial Dark Oxygen Discovery

At a press conference in London this week, Professor Andrew Sweetman of the Scottish Association for Marine Science introduced the landers named Alisa and Kaia, after his daughters, which are engineered to withstand pressures 1200 times greater than those at the surface. The expedition, funded by a 2 million pound grant from The Nippon Foundation over three years, marks the most detailed examination yet of a process that defies the long held scientific consensus that oxygen requires sunlight and photosynthesis to form.

The Original Discovery

The mission follows Sweetman's 2024 findings, published in Nature Geoscience, which suggested that potato sized polymetallic nodules on the ocean floor generate oxygen through a form of natural electrolysis, splitting seawater into hydrogen and oxygen without sunlight. The discovery immediately drew criticism from deep sea mining companies and some scientists who argued that air bubbles trapped in measurement devices may have skewed the results.

We have utilised these instruments for the last two decades, and we have never encountered bubbles during our deployments, Sweetman told reporters, noting that tests were conducted to eliminate that possibility. He added that 90 percent of the 65 experiments conducted in the Clarion Clipperton Zone showed oxygen production, not consumption.

Industry Pushback

The Metals Company, a Canadian deep sea mining firm that originally funded part of Sweetman's research, has published a paper challenging the findings, suggesting the detected oxygen likely originated from the surface. In terms of commercial interest, there is certainly a motive to suppress this line of research, Sweetman responded.

What's at Stake

The Clarion Clipperton Zone, stretching between Hawaii and Mexico, contains an estimated 21 billion tonnes of polymetallic nodules rich in manganese, nickel, copper, and cobalt. These metals are crucial for electric vehicle batteries and green technology. Mining companies are preparing to extract these nodules, but if dark oxygen indeed sustains deep sea ecosystems, removal could have profound consequences for marine life, including microbes, sea cucumbers, and predatory anemones.

The Science Behind Dark Oxygen

The hypothesis is that high voltage potentials, up to 0.95 volts on nodule surfaces, may contribute to dark oxygen production through seawater electrolysis. As millions of years of metallic layers built up in the nodules, similar to a voltaic pile, the differing electric potential could theoretically produce enough energy to split water into oxygen and hydrogen.

The New Expedition

The new landers will measure oxygen flux, electrical activity around nodules, and pH levels while collecting sediment cores and water samples. Each nodule can host millions of microbes, and the team plans to identify organisms using DNA and RNA sequencing.

The first expedition is scheduled to depart for the Clarion Clipperton Zone in May, with preliminary results expected by June. Sweetman said they will be able to confirm dark oxygen production within 24 to 48 hours after the landers come up, though the world will probably not know the results until the ship returns in June.

Independent Verification

Matthias Haeckel, a biogeochemist at Germany's GEOMAR Helmholtz Centre for Ocean Research, told reporters his own studies showed no indications of oxygen production from nodules, but confirmed Sweetman will join his expedition later this year to compare methodologies.

Implications Beyond Earth

UNESCO's Intergovernmental Oceanographic Commission has endorsed the project as a United Nations Ocean Decade activity, and NASA has expressed interest in findings that could inform the search for extraterrestrial life. If oxygen can form without sunlight driven photosynthesis, then perhaps life could exist on cold, dark planets. According to Sweetman, the team is already in conversation with experts at NASA who believe dark oxygen could reshape our understanding of how life might be sustained on other planets without direct sunlight.

The production of oxygen at the seafloor by polymetallic nodules represents a new ecosystem function that needs to be considered when assessing the impact of deep sea mining. The May expedition will provide crucial data to either confirm or refute one of the most controversial marine science discoveries of recent years.