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As you read this story, you will learn the following:
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Scattered across the abyssal plain known as the Clarion-Clipperton Zone (CCZ), polymetallic nodules represent potato-sized prizes for mining companies seeking materials for humanity’s green energy transition.
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A study analyzing these modules showed that these blocks of rock are capable of producing “dark oxygen” 4,000 meters below sea level where light cannot reach.
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While the discovery could upend our understanding of how life on Earth originated, the research also complicates negotiations around deep-sea mining regulations because it shows how little we know about ocean depths.
Nestled between Hawaii and the west coast of Mexico is the Pacific Clarion-Clipperton Zone (CCZ), a 4.5 million square kilometer abyssal plain bordered by the Clarion and Clipperton fault zones. Although the sea is a vibrant ecosystem teeming with marine life, the CCZ is best known for its large collection of potato-sized rocks called polymetallic nodules.
These rocks may number in the trillions and contain rich deposits of nickel, manganese, copper, zinc, and cobalt. These special metals are so critical to the batteries needed for future green energy that some mining companies refer to the nodules as “batteries in the rock.”
However, a study reports that these nodules may be more than just a collection of valuable materials for electric cars, they also produce oxygen 4,000 meters below the surface where sunlight cannot reach.
This unexpected source, called “dark oxygen,” redefines the role these nodules play in CZZ. These rocks could rewrite not only the script of how life began on this planet, but also the potential of other worlds within our solar system, such as Enceladus or Europa. The results of the study are published in the journal natural geosciences.
“For aerobic life to begin on Earth,” said Andrew Sweetman, a deep-sea ecologist at the Scottish Marine Science Association and the study’s lead author. said in a press statement“, “There must be oxygen, and our understanding is that the earth’s oxygen supply begins with photosynthetic organisms. But we now know that oxygen is produced in the deep ocean where there is no light. So I think we need to revisit the question: Where did aerobic life begin?
The journey to discovery began more than a decade ago, when Sweetman began analyzing how oxygen levels decrease further into the ocean depths. So people were surprised in 2013 when sensors returned increased oxygen levels in the CCZ. At the time, Sweetman thought the data was the result of a malfunctioning sensor, but future research suggests that this abyssal plain was somehow producing oxygen. Sweetman noted the nodules’ “battery in the rock” slogan and wondered whether the minerals found in these nodules acted in part as a kind of “battery for the Earth” by separating hydrogen and oxygen through electrolysis of seawater.
A 2023 study showed that various bacteria and archaea can produce “dark oxygen,” so Sweetman and his team recreated the conditions of the CCZ in the lab and killed all the microorganisms with mercury chloride—and surprisingly, oxygen levels continued to rise. according to scientific americanSweetman found that these nodules had a voltage of about 0.95 volts on their surface, likely charging as they grew, with different sediments growing irregularly throughout. This natural charge was enough to split seawater.
The discovery adds to the heated debate over what to do with these nodules. Mining companies like Metallica see these nodules as the answer to our energy problems, and the company’s CEO coined the phrase “battery in the rock.” However, 25 countries want the governing body – the International Seabed Authority (ISA) Council – to impose a moratorium, or at least a precautionary one, to allow more research to be done to see how mining the nodules will affect the ocean. This is particularly important given that the world’s oceans already face a range of climate challenges, including acidification, deoxygenation and pollution.
In response to this finding, Lisa Levin of the Scripps Institution of Oceanography (who was not involved in the study) highlighted in comments to the Deep Sea Conservation Alliance why such a moratorium is so important to protect these deep-sea nodules:
This is a great example of what it means to be bounded by the deep ocean, a relatively unexplored part of our planet. There are still new processes waiting to be discovered that challenge our understanding of ocean life. The production of oxygen on the seafloor by polymetallic nodules is a novel ecosystem function that needs to be considered when assessing the impacts of deep-sea mining. These findings underscore the importance of further independent deep-sea scientific research in the global ocean to inform deep-sea policy.
The ISA is still negotiating with key players over deep sea mining regulations.
So while the future of the world’s oceans is approaching a critical moment when it comes to conservation or development, science is proving once again that disrupting these ecosystems could have consequences we can’t even imagine.
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