Far beneath the surface of the Pacific Ocean, in one of Earth’s least explored regions, scientists have found a surprising new source of oxygen — one that forms in complete darkness. The finding, described as “dark oxygen,” emerged from research conducted in the Clarion-Clipperton Zone (CCZ), an abyssal plain filled with mineral-rich rocks that now appear to be producing oxygen without any light.
A Discovery Buried in Battery Rocks
Stretching across 4.5 million square kilometers between Hawaii and Mexico, the CCZ is best known for its abundance of polymetallic nodules — potato-sized rocks filled with nickel, manganese, cobalt, zinc, and copper. These nodules are essential for the transition to green energy, especially for manufacturing batteries. Mining companies have even called them a “battery in a rock.”
But researchers have now found that these nodules are more than just mineral stockpiles. In a recent study published in Nature Geoscience, scientists confirmed that the nodules also generate oxygen 4,000 meters below sea level — far beyond the reach of sunlight. This process has been dubbed “dark oxygen,” and it could change how scientists think about the early history of life on Earth.
Oxygen Without Light: Challenging Our Assumptions
The discovery traces back to deep-sea ecologist Andrew Sweetman of the Scottish Association for Marine Science. Over a decade ago, he began examining how oxygen levels varied with ocean depth. In 2013, sensors unexpectedly recorded elevated oxygen levels in the CCZ — data he initially assumed was due to faulty equipment. But continued studies confirmed the oxygen was real and localized.
Sweetman began exploring whether the nodules’ electrochemical properties were responsible. Inspired by their nickname, “battery in a rock,” he wondered if they could be natural geobatteries, producing small electric currents capable of splitting seawater molecules into hydrogen and oxygen.
A 2023 study showed that bacteria and archaea could create dark oxygen. To eliminate this possibility, Sweetman and his team recreated CCZ conditions in a laboratory and treated the nodules with mercury chloride to eliminate microbial life. Even then, oxygen continued forming.
The research revealed that the nodule surfaces carry a charge of about 0.95 volts — enough to drive seawater electrolysis and release oxygen.
Rewriting the Timeline for Life — And Expanding Its Possibilities
This phenomenon suggests that aerobic life — organisms that rely on oxygen — may have developed on Earth before photosynthesis ever evolved. Sweetman noted that “there had to be oxygen and our understanding has been that Earth’s oxygen supply began with photosynthetic organisms. But we now know that there is oxygen produced in the deep sea, where there is no light.”
That insight has broad implications. Similar oxygen-creating processes might occur on other ocean-bearing worlds in the solar system, such as Enceladus or Europa. If geobatteries are forming oxygen deep under their icy crusts, it raises the possibility of extraterrestrial ecosystems forming in total darkness.
Science and Mining at a Critical Crossroads
While the scientific implications are vast, they are arriving at a politically sensitive moment. The CCZ is also the focus of deep-sea mining efforts, with companies eager to extract the nodules for battery production. The Metals Company, whose CEO coined the “battery in a rock” phrase, is one of many pushing forward with commercial plans.
At the same time, at least 25 countries are urging the International Seabed Authority (ISA) to pause or halt mining activity. They argue that without understanding the full ecological role of these nodules, commercial extraction could cause irreversible harm.
Lisa Levin of the Scripps Institution of Oceanography emphasized the risks in a comment to the Deep Sea Conservation Coalition, saying: “There are still new processes to discover that challenge what we know about life in our ocean. The production of oxygen at the seafloor by polymetallic nodules is a new ecosystem function that needs to be considered when assessing the impact of deep-sea mining.”
With global oceans already facing threats from acidification, deoxygenation, and pollution, scientists warn that disturbing such ecosystems may have unpredictable and far-reaching consequences.
Source: The Daily Galaxy / Digpu NewsTex