A new scientific article highlights an extraordinary phenomenon of “dark oxygen” in the ocean’s pitch-black depths where oxygen is being produced without light.
Scientists have long held the notion that the atmospheric oxygen all life depends on comes predominantly from the ocean through photosynthesis. However, researchers uncovered metallic rock nodules more than 13,000 feet below the ocean surface that generate electrical currents to split seawater into hydrogen and oxygen, or seawater electrolysis.
Understanding Dark Oxygen
Professor Andrew Sweetman from the Scottish Association for Marine Science and his team investigated the Clarion-Clipperton Zone, an area of the Pacific Ocean between Hawaii and Mexico and target for deep-sea mining.
Across multiple sites, they deployed oxygen chambers over rock nodules more than 4,000 meters deep but contrary to expectations, the oxygen levels in the chambers increased. He initially dismissed the observation of dark oxygen due to the prevailing belief that only photosynthesis could produce oxygen.
“I basically told my students, just put the sensors back in the box. We’ll ship them back to the manufacturer and get them tested because they’re just giving us gibberish,” said Professor Sweetman. “And every single time the manufacturer came back: ‘They’re working. They’re calibrated.’”
Published in Nature Geoscience, the research reveals that these nodules are effectively “batteries in a rock” and contain enough critical metals to power 280 million electric vehicles.
“We don’t yet fully understand how the nodules produce this voltage,” said Professor Sweetman. “It’s possible that the energy comes from the potential difference between metal ions within the nodule layers, causing an internal redistribution of electrons.”
Seawater Electrolysis Raises the Stakes on Deep-Sea Mining
The vast abyssal plains on the ocean floor are dotted with polymetallic nodules containing trillions of dollars’ worth of metals, such as cobalt, nickel, and manganese, that are crucial for lithium-ion batteries and electric vehicles. The discovery of dark oxygen is raising the stakes in international negotiations over whether to mine the seafloor for battery materials and how to protect sensitive marine life in the process.
At the end of the International Seabed Authority’s annual meetings, a mining company announced its plans to submit the first-ever application to exploit minerals from the deep sea. In contrast, Hawaii banned deep-sea mining in its state waters this July.
These findings emphasize the potential risks associated with deep-sea mining operations that could disrupt the newly discovered oxygen production process and impact marine ecosystems. It also amplifies the need for an international moratorium on mining and a race to get rules in place before any mining begins.
Unraveling the Origin of Life
Many unanswered questions remain about how dark oxygen is produced and what role it plays in the deep-sea ecosystem. The discovery of dark oxygen adds complexity to the deep-sea ecosystem and highlights an unknown hydrogen production pathway. It also challenges existing theories about the origin of life on Earth and its potential existence on other planets.
“Previously, we believed that Earth’s oxygen supply originated with photosynthetic organisms. Now, we’ve found that oxygen is produced in the deep sea without any light,” said Professor Sweetman. “This discovery prompts us to reconsider where aerobic life might have begun.”
