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Even if Sweetman and his associates had actually determined oxygen concentrations properly in their research study, the system they provided for how oxygen was produced by the metal swellings, likewise called polymetallic blemishes, does not make good sense, stated Angel Cuesta Ciscara teacher of electrochemistry and physical chemistry at the University of Aberdeen in Scotland and co-author of the viewpoint post.

“That explanation of how it’s formed is simply impossible, because it violates the laws of thermodynamics,” Cuesta Ciscar informed Live Science. “Thermodynamics tells you what’s possible and what’s not possible if the laws of the universe are what we think they are. Until now, there’s nobody in four centuries of science that has been able to show that the laws of thermodynamics [do not apply].”

“Experimental artifact”Sweetman and his associates drew their initial conclusions from experiments they performed in the Clarion-Clipperton Zone (CCZ), a massive abyssal plain 13,000 to 20,000 feet (4,000 to 6,000 meters) deep in the North Pacific Ocean in between Mexico and Hawaii. The CCZ is cluttered with polymetallic blemishes, which are accretions of cobalt, nickel, manganese and other metals that are vital to produce batteries and electronic devices, making the location a target for deep-sea mining expedition business

The scientists got financing for the research study from The Metals Company, a Canadian deep-sea mining company, and UK Seabed Resources, a subsidiary of the British arm of Lockheed Martin that concentrates on deep-sea mining. The outcomes, released at what the authors of the viewpoint post called “a critical juncture in the development of international regulations for deep-sea mining,” suggested that mining polymetallic blemishes might have even worse influence on the community than formerly comprehended.

The Clarion-Clipperton Zone in the North Pacific Ocean is cluttered with metal swellings called polymetallic blemishes. (Image credit: U.S. Geological Survey )The research study explained constant emissions of oxygen from the seabed that Sweetman and his associates credited to polymetallic blemishes. Particularly, the scientists proposed that the distinction in electrical prospective in between metal ions within the blemishes might result in a redistribution of electrons, activating a charge that might divide seawater into hydrogen and oxygen.

The outcome at first appeared substantial, however when Tengberg and his coworkers looked better, “it became clear that it could not have been true,” he stated. Sweetman utilized unique chambers to determine oxygen concentrations at the seafloor that should be flushed with bottom water before keeping track of starts to prevent contamination with gas bubbles from greater up in the water column. This indicates that oxygen readings inside the chambers need to be comparable at the start of each experiment, however they are “all over the place,” Tengberg stated.

“You have to start your chamber incubations with bottom water composition equal — identical — to the ambient bottom water outside the chambers,” Hall stated, including that Sweetman’s beginning oxygen measurements were regularly greater than bottom oxygen concentrations typically acquired in the CCZ. “That is a clear sign that they did not do good chamber incubations and that their oxygen fluxes … cannot be trusted.”

Generally, experiments in the deep sea utilizing chamber incubations likewise determine other gases to get a clear image of the environment and its chemistry, however Sweetman and his associates did not offer this information, Tengberg stated. Especially, no previous research study has actually discovered oxygen production from polymetallic blemishes at the seafloor, Tengberg and his associates composed in the viewpoint post.

Polymetallic blemishes are abundant in cobalt, nickel and manganese, which are utilized to make batteries and electronic devices. (Image credit: Alex Welsh/Bloomberg through Getty Images)The 2024 research study did not present information from “negative control experiments,” which in this case would have been incubations without polymetallic blemishes to verify a lack of oxygen production when blemishes aren’t present, the critics composed. According to the viewpoint post and a 2024 preprint paper on the server Earth ArXiv that has actually not been peer-reviewed, this information exists– and it reveals oxygen production even in the lack of blemishes.

“This strongly suggests that the oxygen production is an experimental artifact,” Hall stated. The boost might have arised from oxygen bubbles that got caught and slowly liquified inside the chambers after they reached the seafloor and sat there unventilated, he included.

Seawater electrolysisElectrochemists on the opinion-article group offered extra arguments for why polymetallic blemishes are not likely to be a source of oxygen at the deep seafloor.

For one, seawater electrolysis needs a substantial quantity of energy and can not continue spontaneously, they argued. And Sweetman and his associates did not determine a source of energy huge enough to create an electrical charge and split seawater, they stated.

“The explanation that Sweetman and his collaborators are proposing is equivalent to suggesting that there is energy being created out of nothing, or, if you want, that things go uphill spontaneously, instead of going downhill,” Cuesta Ciscar stated. “We know that the energy in the universe is constant, and it’s not being created out of nothing.”

The research study likewise offered no hydrogen concentration measurements to support the concept of seawater electrolysis. For each oxygen particle produced by water electrolysis, 2 hydrogen particles likewise form, so the existence of hydrogen is an indicator of the response.

“There’s just, I would expect, an honest error that has not been recognized,” Cuesta Ciscar stated.

In action to the arguments in the viewpoint short article, Sweetman stated he and his group can not respond meaningfully till the evaluation of their extra proof concludes at Nature Geoscience (NG). “If the rebuttal at NG is rejected we will of course submit a response to the Frontiers piece,” he stated.

The scientists are now getting ready for a spring exploration to the CCZ, where they will release 2 extremely specialized landers to recognize precisely how dark oxygen might be produced. The job is moneyed by the Nippon Foundation, a personal company in Japan that promotes humanitarian work, diplomacy and commercial maritime advancement.

The look for dark oxygen continues, however numerous specialists question it will cause anything considerable, Hall stated. “We don’t believe in this,” he stated. “I hope that Nature Geoscience retracts the paper.”

Downes, P., Cuesta, A., Denny, A., Tengberg, A., Hall, P. O. J., Trellevik, L., Svellingen, W., Jaspars, M., Webber, A. P., De Freitas, F. S., Bento, J. P., Marsh, L., & & Clarke, M. (2025 ). Remarkable claims need remarkable proof: assessing nodule-associated dark oxygen production. Frontiers in Marine Science 12 https://doi.org/10.3389/fmars.2025.1721853

Sascha is a U.K.-based personnel author at Live Science. She holds a bachelor’s degree in biology from the University of Southampton in England and a master’s degree in science interaction from Imperial College London. Her work has actually appeared in The Guardian and the health site Zoe. Composing, she takes pleasure in playing tennis, bread-making and searching pre-owned stores for covert gems.

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