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This story was supported by a grant from the Pulitzer Center and co-published with the Post and Courier.
On July 22, 2024, a team of researchers released a shocking discovery: deep-sea rock concentrations appeared to be producing oxygen in the blackness of the ocean’s abyss.
The two of us were in the middle of filming a documentary about these potato-sized undersea oddities—known as polymetallic nodules—and suddenly they were making global headlines. The researchers dubbed their finding “dark oxygen.”
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But what grabbed us as journalists was how—within days of publication—the research ignited debate among dozens of diplomats then convening in Kingston, Jamaica, to decide the fate of those rocks.
Many researchers hope their work reaches policymakers, but it’s rare to see such an immediate effect.
Shortly after Nature Geoscience published the “dark oxygen” study, delegates from Costa Rica and Panama began citing it as a reason not to rush negotiations. According to a United Nations treaty that has been ratified or acceded to by 170 countries and regions (but not the U.S.), companies preparing to mine can’t extract nodules from international waters without agreement among those signatories on how that should be done. “Dark oxygen” became a rally call for prudence before opening up the high seas to deep-sea mining.
“Dark oxygen” steered a film we were already making into an entirely new direction. We had been following a separate group of researchers who had found the world’s oldest deep-sea test site, more than 50 years after mining. As one of us (Fieseler) first reported for the Post and Courier last year, they made a remarkable observation among the field of nodules there.
That discovery, however, had a much different fate.
What unfolded for us was a tale about the power of research in extreme environments. What grabs the public’s attention? What drives policy? Is it all just timing and luck?
The “dark oxygen” study has come under fire over the past year. Researchers at the University of Aberdeen in Scotland and at two companies—The Metals Company and Adepth—have separately posted scientific rebuttals in preprint papers. Nature Geoscience, the journal that published the research, has so far defended it, as have its authors.
A spokesperson for Nature Geoscience told one of us (Fieseler) via email that “concerns have been raised with us about this paper and we have been looking into them carefully following an established process, which is not yet complete.”
Meanwhile the decision to mine international waters is still being decided. This month delegates returned to the negotiating table in Jamaica. We traveled there this week to watch. But unlike last year, when many signs pointed toward a speedy decision and “inevitable” deep-sea mining operations, the pace has slowed. Acceleration has given way to rising precaution.
TRANSCRIPT
Clare Fieseler (reading from her 2024 Post and Courier article “Pulled from the Deep”): “About 10 million years ago … the ocean swarmed with beasts…. As [these creatures] passed, debris rained down to the bottom, including errant shark teeth, which joined [with] pieces of volcanic rock scattered below. Scientists believe that these scraps started to grow in size as they slowly attracted trace metals found within the ocean’s chemical soup, forming thin coatings dense in critical minerals like manganese, nickel and cobalt. For millions of years and in complete darkness, those rocks steadily grew in oceans around the world.”
Fieseler: My name’s Clare Fieseler. I’m a reporter and a scientist, and I’m here talking to a microbiologist who, along with his collaborators, has found something remarkable at the bottom of the sea.
Jeff Marlow: Each nodule can often fit in your hand.
Another.
And then as you get closer and closer and closer, you’d start to see different textures. Get even closer, and you’d start to see the life on top of them. They’re not just these barren bricks; they can also kind of be substrates for animals. There are worms that crawl on and in the nodules. There are little corals that can stick up. You know, they’re often centimeters tall, so they seem sort of negligible from our perspective. But these are the huge sequoias of the [laughs] abyssal plain.
This is what we saw—just, like, millions [laughs] of this size and shape just covering the seafloor.
They’re all over the place. They could not be more abundant. It’s really just about looking closer, looking at it with a different perspective that reveals something amazing.
Fieseler: You seem a little hesitant to say, like, a phrase similar to: “We found that nodules may be producing oxygen.” [Laughs]
Marlow: Mm, um.
Fieseler: Is there a reason?
Marlow: Is there a reason [laughs]? [CLIP: Carolyn Beeler speaking on PRX’s The World: “The discovery is that metals on the ocean floor can create oxygen without photosynthesis. They’re calling the oxygen created this way ‘dark oxygen.’”]
Fieseler: There’s a reason why Jeff Marlow is being cautious with me. His collaborators—Andrew Sweetman, Franz Geiger and the rest of their 16-person team—published a study in Nature Geoscience that could rewrite not just what we know about these nodules or about the ocean; it could rewrite what we know about how life began on planet Earth.
These scientists aren’t the only people interested in polymetallic nodules. There’s an entire industry that wants to suck up the nodules from the bottom of the sea for profit. In fact, the team’s research was funded by the Metals Company, one of the leading firms pushing for deep-sea mining.
Marlow: Through all this data and all of our troubleshooting we were able to conclude that the nodules—or something inside and around them—was producing oxygen.
Federica Calabrese: Yeah, exactly like that, so I …
Fieseler: I see it there.
Calabrese: Yeah, especially here, you can …
Marlow: That is kind of the way science works, it is confusing, it’s messy. Through experiments and thoughtful analyses, you get at what the story really is, and I think we’re really just at the start of that.
Fieseler: To make sense of all this, I called up an old friend, Andrew Thaler, a deep-sea ecologist who used to run the deep-sea mining industry’s only trade publication. He’s been tracking this stuff for years.
Andrew Thaler: The reason we wanna go mine the deep sea, the reason we need these metals and the reason we need these minerals is because we wanna get off fossil fuels, and in order to get off fossil fuels, we have to rapidly electrify the world’s power grid.
Energy production through renewable resources means energy storage, and energy storage means batteries, and polymetallic nodules are—you’ll see this all the time when you see any of the mining company CEOs give a talk: they’ll hold up a polymetallic nodule, and they’ll say …
[CLIP: Gerard Barron, CEO of the Metals Company, appearing on 60 Minutes: “That is a electric vehicle battery in a rock.”]
[CLIP: Barron speaking on 121 Mining Investment TV: “This is like a battery in a rock.”]
Thaler: “This is a Tesla battery.” And they’re not wrong. .
Fieseler: The most profitable nodules are located in the Pacific between Hawaii and Mexico, in an area called the Clarion-Clipperton Zone, or CCZ. For over 50 years mining companies have been testing equipment and conducting environmental studies to try and figure out how mining could impact the abyss—because nobody knows for certain how many years it might take the seafloor to recover. So I went to Woods Hole, Massachusetts, to talk to Jason Chaytor. He’s a federal scientist who studies the seafloor.
Jason Chaytor: The impetus for working on nodules had nothing to do with nodules at all.
So here is, actually, the Data Library.
We were just looking for an area to study how the seabed responds to change over time. Oh, it’s here somewhere [laughs].
Actually, for this project, I, I looked for some maps and navigation data and just couldn’t find it and then realized that the original navigation records were on typed-out, you know, sheets of paper.
I came across a museum finding aid from the Mariners’ Museum in Newport News, Virginia, that made reference to the ships that Deepsea Ventures had used in the 1970s—late ’60s, 1970s—in reference to the Blake Plateau.
Fieseler: The coordinates had been lost to history because Deepsea Ventures went out of business just 20 years in. Other companies tried; none pulled it off. Mining the ocean floor never made economic sense.
After five years of searching for the coordinates, planning an expedition, Chaytor and his team returned to the Blake Plateau off the coast of South Carolina in 2022 to rediscover a lost deep-sea mining test site—the oldest in the world, in fact—and see how the seafloor had changed.
[CLIP: Scientist audio: “So as we said before this was a previous—a testing site for deep-sea mining, and this occurred about in the late ’60s, early ’70s.”]
Chaytor: You know, my first impression of, of that field—it’s remarkable.
They, they’re just crops—you know, like a crop field of, of nodules scattered everywhere.
Some of the first views of, of the disturbance that we found definitely look like just long train tracks through these nodule fields—you know, areas of piled-up nodules separated by open sediment with, with no nodules—and they just kind of kept going off into the distance.
So we ended up with more than 550,000 photographs. What we’re doing is merging ’em together to try and make a seamless picture of the seafloor.
You know, at this point it’s now 54 years. Some of those tracks look like nothing has happened to them, like they would look like they just recently were made.
They are coated with ferromanganese crust. In, in most cases what’s inside them …
Fieseler: You know what that is?
Thaler: That looks like a dredge track in an abyssal plain.
Fieseler: You are the first person to be seeing these.
Thaler: So that’s no recovery.
Fieseler: Yeah.
Thaler: I mean, it’s not, it’s not really new data. Like, we know that recovery doesn’t happen over decadal time scales. Like, I’m sure this is what everyone would expect to see.
Fieseler: Yeah.
Thaler: It is, it is pretty dramatic, though.
Fieseler: Yeah, it’s one of these things where it’s like, “Oh, this image could change everything,” or it could change absolutely nothing ’cause people don’t understand it.
Thaler: I mean, like, most people, like, wouldn’t have any context for what this is to begin with.
Fieseler: We’re here at the largest gathering of ocean scientists in North America right now in New Orleans.
There are a couple different scientists here that are presenting on their own deep-sea mining research, and so I’m gonna be going in and talking to a couple people. And then we just wait ’til 4:00 P.M. to see what happens when Jason Chaytor presents his work at his poster session.
Thaler: So this is it.
Fieseler: Mm-hmm. These are all the tracks.
Thaler: Oh, wow, and you know what’s really interesting about the site is that there was a recent publication revealing the largest deepwater coral reef in the world on the Blake Plateau, and it’s about 20 kilometers [roughly 12.4 miles] from the site.
Fieseler: Yeah.
Thaler: It’s, like, right there.
Fieseler: Yeah.
Thaler: So the very first time anyone tried experimental deep-sea mining, they almost hit one of the biggest coral reef systems on the planet.
Fieseler: Yeah.
Chaytor: Whether it has major impact is not what we’re after. We aim for it to be useful.
Basically to inform people of, you know, it’s, it’s not a perfect analogue for the stuff that’s going on now, but it’s like, “Yeah, it does take a long time for something to recover—if, if it does recover at all, so.”
But it’s also the nature of science; it’s kind of this accumulation of information and knowledge.
Just because it comes out and I don’t get a whole bunch of phone calls—you know, it’s not why, you know, we do the work that we do, especially as a government scientist, because there is a reason for doing it. There’s a mission. There’s a purpose. There’s a goal.
Fieseler: After just two hours the poster session ended.
Fieseler (reading from her 2024 article): “Four security guards herded the scientists out and turned off the lights…. Chaytor was certain that scientists decades from now would see its value. That’s what mattered to him. [But] for non-scientists, this unique view about human destruction in unreachable places may fade into history’s footnotes once again.”
Fieseler: Chaytor remarkably discovered this old mining site in U.S. waters, but today the nodules that most miners want to get at are out there, in international waters, which are currently protected by the United Nations Convention on the Law of the Sea. It’s a treaty ratified by most of the world’s countries.
The law says the international seabed is special, like the moon, like Antarctica. It is legally designated “the common heritage of mankind.”
But there’s a catch: countries of the world can vote to open up the seabed to mining if they can agree on a code—a set of rules that would govern commercial activities out on the high seas. The organization in charge of these negotiations is the International Seabed Authority, or ISA, a United Nations–affiliated group. It is currently meeting in July 2025 in Kingston, Jamaica.
Thaler: The mining code that they’re negotiating is the mining code for all mineral resources of the seabed in areas beyond national jurisdiction. So that’s not just polymetallic nodules in the CCZ; that’s hydrothermal vents on the Mid-Atlantic Ridge …
Fieseler: It’s everything.
Thaler: That’s cobalt-rich seamounts on the Rio Grande Rise—it’s, it’s everything.
Fieseler: So here’s the thing: we’ve been at this for, like, 50 years, but right now we’re closer to mining the deep sea than we’ve ever been before.
[CLIP: Barron speaking at Nasdaq: “The future is metallic.”]
[CLIP: Barron speaking on MINING.com: “But I think the better news was the election of President Trump.]
[CLIP: Barron testifying to Congress: “Four days’ sailing from San Diego lies the Clarion-Clipperton Zone, where polymetallic nodules sit 2.5 miles [about four kilometers] deep on the seafloor.”]
[CLIP: Barron speaking on Disruptive Investing: “They form like this rock in my hand.”]
[CLIP: Barron speaking at the Saint Helena Forum: “They’re in a part of the ocean known as the abyssal plain, and it’s the ecosystem on our planet with the least life.”]
[CLIP: Representative Ed Case of Hawaii and Barron speak during a congressional hearing.]
Case: “And you’ve stated in the press that where you wanted to mine is a, quote, unquote, ‘marine desert.’ Do you stand by those statements?”
Barron: “Thank you for the question. Yes, I do.”
Thaler: The abyssal plain is the largest singular ecosystem on the planet. But that doesn’t mean it’s devoid of life. The abyssal plain may actually be one of the most biodiverse ecosystems on the planet. But the animals that are dependent on the abyssal plain are tiny.
[CLIP: Scientists discuss a creature in the abyssal plain.]
Scientist 1: “So when we get close there’s a lot of these little, tiny hexactinellids, or glass sponges.”
Scientist 2: “Little spots. It’s quite beautiful.”
Thaler: In this moment, science really has the key role to play. We have never, in human history, started an extractive industry from the position of understanding the environment first. That’s never happened. The traditional arc of industrial development is: we find oil in Pennsylvania, we, we, we drill as much as we can, and only 10 or 20 or 50 years later do we realize how much harm it’s done. We’ve never had an opportunity where we get to go in first.
Marlow: On July 22, 2024, the paper came out, and the fact that this came out in the middle of the ISA meetings, into this kind of media and political firestorm, was a shock [laughs].
Fieseler: Dark oxygen broke through. Delegates at the ISA meeting were talking about the research from the floor in the middle of negotiations.
But almost right away the Metals Company, which had funded the research, began trying to discredit the scientists.
The Metals Company says dark oxygen is, quote, “bad science.” A spokesperson told me that the company’s rebuttal is still undergoing scientific peer review. And the company declined to comment further.
Marlow: I think a lot of the initial attention was like, “We did it! We found this intriguing thing—end of story.” But to me and my colleagues, this is the beginning of the story.
And that’s the next step that we have to figure out: Like, does it matter in the real world …?
Fieseler: Right.
Marlow: Or is it like, “They kind of do this weird thing, but it doesn’t really matter”?
Fieseler: Yeah.
Marlow: Yeah. The consequences of being wrong either way are huge.
Fieseler: I remember when my editor at The Post and Courier first asked me why an audience would care about this story. The rocks are boring, the science is not sexy, but the unknown—and how much we still don’t know about the sea—that’s what draws people in.
Marlow: The quest for life beyond Earth is really one, when you get down to it, of life extracting energy from its environment. And that’s the same thing we’re studying with the nodules. So to me it is the same thing [laughs]. Those sorts of unknown unknowns are so hard to come across in science because it’s often at the exploratory limit of our understanding, so that might happen in outer space.
Those kind of first forays into new, unknown habitats and environments are where the big discoveries could happen, where you reveal something you’d never seen before. To do that at a part of our planet that is so huge—these nodule-covered parts of the seafloor are enormous—the fact that that was lurking in our own seafloor for so long is really surprising to me.
Fieseler: That’s really what this story’s about—and why dark oxygen broke through. It’s not about the rocks or how they’re removed or what they do. It’s like: What else don’t we know about our planet—or the universe? And can we imagine a future where we exploit for profit a place where we don’t even know what we don’t know?
[CLIP: Scientists discuss creatures in the abyssal plain]
Scientist 3: “Ah, you can see, see his little chelae, hands, so his hands—his little claws”
Scientist 4: “Yep.”
Scientist 3: “There, you see him reaching down, and he’s probably cleaning his, cleaning his swimmerets …” Scientist 5: “Are those eggs, maybe?“
Scientist 6: “Are they what?”
Scientist 5: “The blue things, are they maybe eggs?”
Scientist 6: “It does look like eggs.”
Scientist 7: “What is that tube thing—maybe a tube worm?”
Scientist 8: “Tube worm, tube, yeah.”
Scientist 9: “Yeah, those look more like hydroids than anything else.”
Scientist 3: “Here’s this, this egg stuff, maybe, again or a bryozoan that’s behind him. All right, buddy, you’re in the way. You need to move; I got invertebrates to look at. Come on.”
Scientist 9: “Oh, he doesn’t seem to want to.”
Scientist 3: “Lots of tentacles in all directions.”
Scientist 9: “He does not look like we’ve seen, seen ’em.”
Scientist 3: “Yeah, he looks similar to the helmet jelly, where he’s got that bell with the red internals …”
Scientist 9: “Yeah.”
Scientist 3: “And then these tentacles that go up and down, but I don’t know which kind he is. He’s very neat.” Scientist 9: “Yeah, the pink looks like it was probably a reflection from our lights, but it looks like where he could maybe illuminate?”
Scientist 3: “Yeah, possible. It could also be food from—that he’s eaten. He’s pretty neat. I like him.”
This story was supported by a grant from the Pulitzer Center and co-published with the Post and Courier.
