Parts of the deep Pacific Ocean are covered in metallic lumps known as polymetallic nodules. A study published last year suggested they produce oxygen without sunlight. NOAA Office of Ocean Exploration and Research, 2019 Southeastern U.S. Deep-sea ExplorationResearchers who discovered dark oxygen on the ocean floor are planning a new project to learn even more about their mysteriousand controversialfinding.Last year, the scientists made headlines when they published a paper about an unexpected revelation: They found evidence that naturally occurring battery rocks on the floor of the Pacific Ocean, some 13,000 feet below the surface, were producing oxygen. These potato-sized lumps of metal, known more formally as polymetallic nodules, were generating oxygen electrochemically and without light, they wroteby splitting water molecules into their hydrogen and oxygen components. Thats unusual, as oxygen is typically produced by plants through photosynthesis.The discovery of this dark oxygen was a big deal, prompting scientists to reconsider their long-held beliefs about how complex life might have evolved on Earth. The findings raised the possibility that aerobic life had begun by feeding off oxygen produced by metals, instead of oxygen produced by photosynthesizing cyanobacteria, as was previously thought.But the research was also controversial. After the paper was published in July in the journal Nature Geoscience, some scientists and deep-sea mining companies began to criticize the studyincluding The Metals Company, which funded some of the research. The firm plans to mine the polymetallic nodules for valuable rare earth metals like cobalt, nickel, copper and manganese, which are used in solar panels, smartphones, wind turbines and batteries.The companys leaders say they have submitted a rebuttal to the Nature Geoscience paper, but its still undergoing the peer-review process, per CNNs Katie Hunt. The rebuttal has been posted to the preprint server EarthArXiv.After decades of research using the same methods, no credible scientist has ever reported evidence of dark oxygen, Gerard Barron, The Metals Companys chief executive officer and chairman, said in a statement shared with New Scientists Madeleine Cuff. Extraordinary claims require extraordinary evidence. Were still waiting.Other scientists are also trying to replicate the teams findings. Scientific research is a process, and it may be some time before a conclusive answer is reached, Amy Gartman, a geochemist at the U.S. Geological Surveys Pacific Coastal and Marine Science Center, tells CNN.Against this backdrop, the team behind the initial dark oxygen discovery is planning to launch a new, three-year project in hopes of reproducing their original findings and investigating the underlying mechanisms at play in the deep ocean.Our discovery of dark oxygen was a paradigm shift in our understanding of the deep sea and potentially life on Earth, but it threw up more questions than answers, says Andrew Sweetman, lead author of the Nature Geoscience paper and the leader of the new three-year project, in a statement. This new research will enable us to probe some of these scientific questions.More specifically, the team hopes to explore whether microbial reactions also play a part in the production of deep-sea oxygen. They also want to learn more about how hydrogen is released during the process, as well as whether that hydrogen might be a source of energy for microbial life on the ocean floor.With funding from the Nippon Foundation in Japan, the team will deploy custom-built equipment that can descend 36,000 feet below sea level to collect samples of water. The first research expedition is scheduled to depart from San Diego in January 2026, per New Scientist.Learning more about dark oxygen could have major implications for several scientific fields, including space exploration. If oxygen can form without sunlight-driven photosynthesis in plants, then perhaps life could exist on cold, dark planets.If we show that oxygen production is possible in the absence of photosynthesis, it changes the way we look at the possibility of life on other planets, too, says Sweetman, an ecologist with the Scottish Association for Marine Science, in the statement. Indeed, we are 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.In the meantime, the scientists hope that deep-sea mining companies will consider postponing their projects until researchers can learn more about the potential production of dark oxygen and its effects on the worlds oceans.More broadly, the burgeoning deep-sea mining industry is facing pushback from scientists, policy experts, governments and corporations. Opponents argue that mining operations could harm marine life, damage underwater ecosystems, contribute to underwater pollution (including noise and light pollution) and reduce the seafloors ability to sequster carbon.Before we do anything, we need toas best as possibleunderstand the [deep sea] ecosystem, Sweetman told reporters last week, perBBC News Victoria Gill. I think the right decision is to hold off before we decide if this is the right thing to do as a global society.Get the latest stories in your inbox every weekday.Filed Under: Chemistry, Conservation, Evolution, Microbes, Bacteria, Viruses, Minerals, Mining, New Research, Oceans, Pacific Ocean, Scientists, Water