For decades, school textbooks have explained that oxygen on Earth is mainly produced through photosynthesis, a process that depends on sunlight. Plants, algae, and some bacteria use light to turn water and carbon dioxide into oxygen. But a new study of the deep sea has made us wonder if oxygen can also be made without sunlight. Scientists exploring the Pacific Ocean seafloor have reported the presence of what they describe as “dark oxygen” in an environment where sunlight does not reach. The discovery was made during research on polymetallic nodules found thousands of metres below the ocean surface. According to the research team, the findings could reshape scientific discussions about oxygen cycles in extreme environments and even influence the search for life beyond Earth.
What is ‘dark oxygen ’ discovered in the Pacific Ocean
The term “dark oxygen” is being used by researchers to describe oxygen detected in deep ocean regions where sunlight is completely absent. Traditionally, oxygen production has been closely linked to photosynthesis, which requires light energy. In the deep sea, especially at depths of around 4,000 metres, sunlight does not penetrate.According to the study published in the journal Nature Geoscience, researchers detected measurable levels of oxygen near polymetallic nodules on the Pacific Ocean floor. These nodules are mineral-rich deposits that have metals like nickel, manganese, and cobalt in them. The scientists observed that oxygen concentrations in certain sealed deep-sea experiments increased over time, even in the absence of light.
How was the oxygen detected on the Pacific seafloor
The research was carried out during deep-sea exploration missions in the Clarion Clipperton Zone of the Pacific Ocean. Scientists deployed specialised instruments to measure oxygen levels directly above the seabed.According to the authors of the study in Nature Geoscience, they used benthic chambers to isolate sections of the seafloor and monitor chemical changes. In these controlled conditions, oxygen levels unexpectedly rose instead of falling. Microbes and chemical reactions usually use up the oxygen in deep sediments. The rise indicated that some process was making oxygen in total darkness.The team took the same measurements several times to make sure the results were correct and that the equipment wasn’t to blame. We also did lab simulations to see if polymetallic nodules could make oxygen through electrochemical reactions.
What are polymetallic nodules and why are they important
Polymetallic nodules are rock-like structures that form on the ocean floor over millions of years. They have metals that are useful for batteries and electronics. They are also being looked into for possible deep-sea mining because they are valuable.According to the National Oceanic and Atmospheric Administration, these nodules are commonly found in the abyssal plains of the Pacific Ocean. A recent study by scientists suggests that the nodules may work like batteries. The minerals in them might help electrochemical reactions that break down seawater molecules into hydrogen and oxygen, even when there is no sunlight.This proposed mechanism is still being looked into, but it could be one reason why the experiments showed an increase in oxygen levels.
Why does this discovery matter for science
Scientists may need to change how they think about global oxygen cycles if they find oxygen in dark, deep-sea environments. If oxygen can be made without photosynthesis, it could mean that other extreme environments could have similar processes.Nature Geoscience says that the research team thinks the results could also have an impact on astrobiology. Scientists looking for life on other planets or moons often look for oxygen as a possible sign of life. Researchers may need to rethink how they think about oxygen in planetary atmospheres if it can form through chemical reactions that don’t involve living things in the dark.The discovery also adds to the discussion about mining in the deep sea. If polymetallic nodules help make chemical oxygen, then messing with them could hurt fragile ecosystems in the deep ocean. Environmental scientists have previously cautioned regarding the insufficient understanding of deep-sea ecological systems.
