A team of scientists has unveiled new deep-sea landers to test a controversial claim that metallic rocks on the ocean floor generate oxygen without sunlight.
If confirmed, the discovery of so-called “dark oxygen” would challenge long-standing beliefs about how oxygen first appeared on Earth and how early life evolved.
The claim, however, has drawn scepticism from parts of the scientific community and from the deep-sea mining industry, which plans to extract valuable metals from the seabed.
British marine ecologist Andrew Sweetman, who led the original 2024 research, announced plans for a new expedition to gather clearer evidence.
At a press briefing, Sweetman introduced two newly designed landers capable of diving to depths of up to 11 kilometres. The instruments will operate under pressures more than 1,200 times greater than those at sea level.
Scientists plan deep-sea expedition to probe ‘dark oxygen’ https://t.co/L6jgRboO0B
— CTV News (@CTVNews) January 20, 2026Unlike earlier missions, the new landers include sensors built to measure seafloor respiration with greater precision. Sweetman said the technology resembles equipment used in space exploration.
Researchers will deploy the landers in the Clarion-Clipperton Zone, a vast stretch of the Pacific Ocean between Hawaii and Mexico. The area contains polymetallic nodules rich in metals used in electric vehicle batteries and advanced electronics.
Sweetman’s team believes these nodules release enough electrical charge to split seawater into hydrogen and oxygen through electrolysis. If correct, the process would represent a previously unknown natural source of oxygen.
Startling findings in 2024 suggested that metallic nodules on the sea floor produce oxygen and might support life. Now researchers are planning an expedition to learn more and refute criticism from mining companies https://t.co/aVHQ6Jo3fV
— New Scientist (@newscientist) January 20, 2026Critics have argued that the oxygen detected in earlier experiments came from trapped air bubbles inside measuring tools. Sweetman rejected that explanation, saying his team has used the same instruments for two decades without such issues.
The debate unfolds as governments and corporations push to finalise rules for deep-sea mining, an industry scientists warn could cause irreversible environmental damage. Sweetman acknowledged concerns about mining but said his research does not aim to halt commercial activity. Instead, he wants to collect data that could reduce ecological harm if extraction proceeds.
Biogeochemist Matthias Haeckel of GEOMAR Helmholtz Centre for Ocean Research said his own studies show no evidence of oxygen production from nodules. Still, he confirmed plans to compare methods with Sweetman later this year.
The new expedition, funded by the Nippon Foundation, will take place in May. Sweetman said preliminary results should emerge within 48 hours of the landers’ recovery. Final conclusions, however, may take months, as further testing will continue after the research vessel returns in June.
