A startling discovery in the depths of the Pacific Ocean has turned our understanding of oxygen production on its head. Researchers have found metallic nodules scattered across the seafloor generating oxygen in complete darkness, without the help of any living organism. This phenomenon, dubbed “dark oxygen,” marks the first time scientists have observed oxygen production without the involvement of organisms, challenging our current understanding of life’s emergence on Earth.
Lead researcher Andrew Sweetman, a professor at the Scottish Association for Marine Science (SAMS), initially doubted the findings, stating, “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.” However, consistent results from the instruments confirmed the groundbreaking discovery. The research, published in the journal Nature Geoscience, suggests that the metallic nodules found in the Clarion-Clipperton Zone (CCZ), an abyssal plain in the north Pacific, produce oxygen through seawater electrolysis. This process involves seawater splitting into oxygen and hydrogen in the presence of an electric charge, likely generated by the difference in electric potential between metal ions within the nodules.
These polymetallic nodules, common on the ocean’s abyssal plains, are rich in oxides of iron and manganese, as well as valuable metals like cobalt, nickel, lithium, and rare earth elements such as cerium. The research team, initially focused on assessing the potential environmental impact of mining these nodules, discovered the unexpected oxygen production during their study. They employed special experimental chambers to measure oxygen concentrations at various locations in the CCZ.
Typically, oxygen levels decrease with depth due to limited light penetration, leading to fewer photosynthetic organisms and lower oxygen production. However, instead of the expected oxygen decline, the team observed steady emissions from the seabed. The discovery of dark oxygen at a depth of 13,000 feet (4,000 m), where no light can penetrate, challenges the established belief that Earth’s oxygen is primarily produced through photosynthesis. This discovery raises profound questions about the origins of life on Earth, which is estimated to have begun approximately 3.7 billion years ago.
Professor Sweetman emphasized the implications of this discovery for our understanding of life’s origins, stating, “For aerobic life to begin on the planet, there has 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. I think we therefore need to revisit questions like: where could aerobic life have begun?”
The findings also raise concerns about the potential impact of mining polymetallic nodules, which could be a vital source of oxygen for deep-sea ecosystems. Professor Sweetman stated, “Through this discovery, we have generated many unanswered questions and I think we have a lot to think about in terms of how we mine these modules, which are effectively batteries in a rock.” The discovery of dark oxygen has opened a new window into the complexities of Earth’s oxygen cycle and the potential for life to thrive in environments previously thought to be devoid of this essential element. Further research is needed to fully understand the implications of this discovery for both the origins of life and the future of deep-sea mining.
