Dark oxygen could rewrite Earth’s history
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Apply in minutes at mercury.com. So I guess if I was trying to tell a story, I would try and focus on the most interesting point. So we've been heading out to the North Pacific, approximately 1,200 miles away from land. We've been sailing for four and a half days, just straight out into the ocean. We haven't seen a ship in days. We are completely alone. We're in the middle of nowhere. You know, we're studying the seafloor and how the environment exists in its natural state.

So the first day that I am ever deploying my equipment, I am completely new to this. I'm putting it together with instructions from our supervisor and colleagues. Really excited about getting it onto the seafloor and also super nervous because deep sea research is super expensive. It doesn't always work. So we've got to get everything perfect.

If you've never seen deep-sea research equipment, picture the Mars rover. So the Mars rover can move by itself because it's on wheels, but it's probably the closest analogue there. So you're standing there on the side of the ship. You know, you're lifting something that's over a tonne on a boat that sometimes can swing quite a bit. It's a bit nerve-wracking to watch it. And you've got the most intricate system of cables and little pieces that have to stay connected.

So it's really scary. And then you just let it go. And it just disappears beyond the surface. And then it becomes a dot on a screen flying through the water column for nearly 5,000 kilometers. We use something called a respirometer lander, which can be pushed into the seafloor and incubate a section of the seafloor. And you can monitor the rates and changes in that mini example of the ecosystem over time.

And so it takes a little while to settle to the sea floor. And then eventually it does its thing. And then three days later, we pop back to where we dropped it off. We ask it to come back. Hopefully it says yes. And then it begins its ascent to the surface. And then the nerves come back all over again, right? Because you're like...

Oh right, over the last two days I am praying that it did what I told it to do, that it collected water samples, that it shut and that it's bringing the animals and the sediment to the surface.

But you have no idea. And there's this moment when you're standing at the edge of the ship and the crane is lifting the lander from the water. And we're all kind of like leaning over the boat as much as we can to get a look at the bottom of the lander to see whether it's been successful. Because everything that is now in that lander, your samples, the last thing you want is to lose it at the surface right before you get your sample.

You know, we're studying sites that people have never seen before in their life. So we're the first people to put eyes on these sites, which is just, it's really, really cool. So it's very slowly and very carefully placed back on the deck. You deal with the time-sensitive samples first. And then lastly, you pull any data off of the sensors that were on the machine. And for us, that was oxygen concentration.

So maybe eight to 12 hours after the recovery of the lander, we head into the lab. We connect it to the system. It's like super like really heavy duty old school laptops that are really funny to operate because, you know, you and I have MacBooks and iPhones and we're like looking at Windows XP like, OK, how does this work?

And again, this is my first deployment, so I'm kind of sitting there. It's all very, like, chunky, the process of getting through it, because I'm reading the manuals and, like, triple-checking everything I do. And then this graph pops out in Excel, and it's going up. And I'm kind of looking at it thinking, "Oxygen is not supposed to go up in the deep sea." If you give a closed environment full of animals that are breathing a set amount of oxygen,

it should go down. I mean, we're talking about going against the history of what we know in terms of oxygen in the sea floor. So I go back through the code and I'm like, no, it all looks right to me. Let's do it again. So there are three different oxygen sensors on the lander. I'm like, okay, this one's just not worked. So we do the second one. And it's the same. It's still going up. And even after the third sensor had given out oxygen, we were still like,

No, they're broken and we need to send them back to the manufacturer. And then it starts to click in our minds, right? Okay, it's not the sensors. So we start thinking about how much oxygen is in that little bit of water that we add. Could it be that? No, it's not that. There might be a bubble in the chamber. No, it's not that. So then we start to think about, is it possible that there's oxygen in the plastic? And it's not that either.

So I'm feeling very nervous because the whole time, you know, I'm a young student, I'm an early career researcher with not a lot of experience, and I'm just thinking to myself, I've done something wrong. I've done something wrong. Somebody's going to have a look at the machinery at some point and realize, I don't know, I put the sensor on upside down, so the data's upside down. That couldn't actually happen, by the way. That's just a joke. LAUGHTER

It was only once we came back, again, out to site with our fixed census. And by fixed, I mean exactly the same, because there was nothing wrong with them. We had them triple quadruple checked. This is when we start to think, okay, are we going to have to accept that perhaps this is actually happening?

I'm Noam Hassenfeld, and this week on Unexplainable, a mysterious finding at the bottom of the ocean that could rewrite everything from the way our climate works to the origin of life itself. Scientists are calling this finding dark oxygen because they found it where there's no sunlight, where photosynthesis is impossible.

So they've started asking a pretty big new question. Are we seeing oxygen production at the seafloor? And if we are, what does that mean for life as we know it? ♪

So I realize we haven't actually said who you are yet. Can you just say your name and the best way to introduce you on the show? Hi, my name is Alicia, and you can call me Alicia.

Would you mind giving any more official detail? Yeah. How about just your full name and what you do as a scientist? Okay. My name is Alicia Smith and I am a deep sea ecologist. I am currently finishing up my PhD in which I have been looking into baseline characterization of deep sea environments. And how did you first get interested in the ocean?

So I come from a very multicultural family. I was very fortunate to spend a period of my childhood on the island of Mauritius in the Indian Ocean.

And literally from the second that I put my head under the water and had a look at a coral reef, I thought, oh my God, this is amazing. How can I do this for the rest of my life? And luckily I was only, God, 11 or 12 at the time. And then somebody told me, you can be a marine biologist. And since then, I just haven't let go of that thought. Every day I wake up and think I could be a marine biologist.

And here we are nearly at the end of doctoral studies and now in my first job as a science coordinator.

So what was this study about? What were you actually researching? So the purpose of our project was to characterize a baseline in seafloor conditions for a deep-sea mining project. So there are lots of things called polymetallic nodules on the seafloor that we were studying. They are potato-sized rocks that are scattered all over the seafloor.

They exist across the globe, but they have to be at abyssal depths, so between three and six kilometers. And they contain commercially imported minerals. So the purpose of our study was to go out and see how that seafloor functions normally and to look at perhaps how resilient it might be following an activity such as deep sea mining.

And do these nodules have something to do with the oxygen at the bottom of the ocean? Yeah. So my brilliant supervisor, Andrew Sweetman, he watched a documentary on deep sea mining. And in the documentary, the narrator uses the term battery in a rock. And in his head, it just clicked. You know, what if the nodules are acting as natural batteries? And how would that actually work?

So the theory is that the battery is carrying out electrolysis.

which is the splitting of water into hydrogen and oxygen. Electrolysis is something that we've been well aware of for a very long time as a chemical process, but we weren't aware of it as a natural occurrence in the deep sea. So we think that the oxygen production is occurring from the electrolysis of seawater. So within the nodule, you've got millions of layers where...

these minerals have precipitated out over and over again, and they have different charges. So our theory is that as seawater passes over the nodules, the difference in abundances of minerals across the nodule create a difference in charge, which produces the energy for seawater electrolysis.

And is this something you can actually test? Yes. So our colleagues in Northwestern Uni, this was Franz Geiger, he took a nodule, he placed it in some artificial seawater, and then he attached an anode and a cathode to form a circuit, and then measured the voltage differences across the nodules. And he observed oxygen being produced. And you can actually see it bubbling, which is insane. ♪

What Alicia's collaborator at Northwestern did isn't exactly what's happening at the bottom of the ocean. He added some electricity to simulate various things happening on the ocean floor. But without the polymetallic nodule, nothing happened. With the nodule, bubbles. Oxygen. Which could have some pretty huge implications. First of all, dark oxygen — oxygen produced without sunlight —

it might rewrite the story scientists tell about the origin of life on Earth. A lot of scientists think that life started in these deep-sea hydrothermal vents, but that life probably would have needed a source of oxygen. And this was way before any plants were around to do photosynthesis. So dark oxygen might have played a key role in the very first life on Earth. And it gets even wilder. If oxygen can be produced without sunlight,

Just think about what that means for the search for life outside our planet. There are all kinds of places we've discovered that might support life but don't have access to sunlight. Like Jupiter's moon Europa, which scientists think has this massive ocean covered by a thick layer of ice.

life might just be hiding away down there, living on oxygen created by unseen deep-sea moon rocks. But for all this life-changing potential, if these nodules at the seafloor really are producing oxygen, it's getting Alicia kind of worried. It makes me wary of our next moves because I feel like the ocean is showing us again

Irreversible damage. After the break. Support for the show comes from Greenlight. If you're a parent, you know how important it is to set your kids up for success. But there are some important practical things kids just don't learn in school. Like how to manage money responsibly.

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You can sign up for Greenlight today and get your first month free when you go to greenlight.com slash unexplainable. That's greenlight.com slash unexplainable to try Greenlight for free. greenlight.com slash unexplainable. Support for Unexplainable comes from Constant Contact. If you're a small business owner, you know you need to get your name out there. But deciding how to actually do it can be a little overwhelming. It might even feel like you need a marketing degree to figure it out.

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Alicia and her team didn't go out in the North Pacific to look for dark oxygen. Like she said earlier, oxygen was one of the last bits of data they checked when they pulled the sensors off their equipment. The reason they were out there in the first place was to study those polymetallic nodules all over the seafloor. Because those nodules don't just make oxygen. They're extremely attractive to mining companies.

In the next five to ten years, companies across the globe want to start extracting these polymetallic nodules from the seafloor because they contain minerals that we need to manufacture batteries for energy storage to cut our carbon emissions. Terrestrial mines and reserves of these minerals is dwindling and the deep sea reservoir of nodules represent a new source of

And it's really driving home the point that

When we are looking for alternative solutions on our planet to save us from the mess that we've made, it's really important that we don't cause further damage by extracting something that we think is a solution and in the process removing fundamental functions of the deep sea that perhaps we weren't aware of before. Yeah, what would happen if we removed...

nodules and say the oxygenation levels in the ocean just significantly went down? I mean, we don't know. That's the point of research, right? We don't know. That's kind of why I'm excited about this cusp, because in 10 years time, that's probably going to be a study that someone models and then we'll know. And the ocean is responsible for producing around half of the oxygen that exists on planet Earth. And that could partly come from

seawater electrolysis from the nodules, right? But we don't know. So until we close the gap there, we could be causing irreversible damage with the best intentions. Are we unknowingly removing a source of oxygenation in the ocean that was actually far more important than

on a global scale for regulating oxygen levels in the ocean and by extension, our climate. So yeah, I think that's probably the most important message for today is just we need more research. You know, you're talking about human impact. The research that you participated in, this was funded by this mining company, the metals company. How do they feel about your findings? Um...

I mean, not overly positive. Yeah, I think they understand that the science is very exciting and the nuances of the situation is that they are funding this research to discover things about the ocean, but we have discovered something that really drives home that we still don't know enough, even after, you know, the Project Lifetime project.

And that we need to keep going and not carry out any potentially harmful activities, which I understand from a business point of view is probably not

Great. But oxygen production in the deep sea is not the nail in the coffin for deep sea mining. It's just one thing on a long list of reasons to maybe think about this a bit more. Yeah. When I reached out to the metals company, they told me they didn't agree with your study and that they're planning to publish a rebuttal. I don't know. Does it feel like they're just unhappy with your conclusions? Yeah.

I guess you could say that. I don't know, because there's not much else you can conclude from the data. So I'm not really sure what else we were supposed to say. But yeah, I think the frustration is probably stemming from the fact that it's obviously being picked up by deep sea conservation, anti-mining groups.

They saw the paper come out and thought, exactly, this is what we've been saying, no deep sea mining. So I can understand the frustration from that perspective, but equally, we didn't really ask for that. We kind of just did our study, as asked, found something weird, discovered what was causing the weird thing, and then published it, because that is the scientific process. So I guess...

We weren't surprised to see the response. And yeah, I look forward to engaging in more constructive, you know, back and forth with them in the future. You know, if they are identifying points that require further research, then great. I know where to focus my efforts. Yeah, I mean, all of this is just a wild story. Like, you're potentially overturning some of the basic assumptions of how our planet works, right?

And you're doing this near the beginning of your career. And, you know, you said you weren't sure if this was you or the data. I mean, how does all of this feel? It feels like a privilege to me. I feel like it sounds really corny, but it's been a bit of an honor to be part of this process. I mean, how wonderful will this story be to tell people in 50 years time that, hey, do you remember like reading in your textbook about... I'm just kidding. Yeah.

No, it honestly feels like I've said it a few times to people. It was just right place, right time for me. And I feel so lucky to have been part of something so exciting because...

Everyone is looking at their own thing. They're in their own pigeonhole. And I just happened to be part of this pigeonhole that discovered something so crazy that it just went against everything we knew. So yeah, I would say take all of the chaos along with the good.

I would do it all again if I had to choose. I mean, you're joking. I'm so grand textbook thing. This could end up in textbooks, right? Like this could end up in middle school textbooks. Maybe. I don't know. I don't. Are we still learning about the C in school? I think.

I think it's important to find out where oxygen comes from. Yeah, that's true. Maybe like a little like asterisk in the photosynthesis chapter in your like biology. By the way, there's also oxygen in the seafloor. That's all we can hope for, right? A little asterisk for our careers. Yeah, that would be great.

This episode was produced by me, Noam Hassenfeld. We had editing from Jorge Just and Meredith Hodnot, who runs the show. Mixing and sound design from Christian Ayala. Music from me and fact checking from Melissa Hirsch. Manding Nguyen is trying to get to the heart of it all. And Bird Pinkerton heard a low rumble. Tortoises came crawling out of the floor, out of the walls, out of the pillars spanning the hall. They stared at her and they waited.

Special thanks to Danielle DeYonga for her help this week. And if you have thoughts about the show, send us an email. We're at unexplainable at Vox.com. And you can also leave us a review or a rating wherever you listen. It really helps us find new listeners. You can also support this show and all of Vox's journalism by joining our membership program today. You can go to Vox.com slash members to sign up. And if you signed up because of us, send us a note. We'd love to hear from you.

Unexplainable is part of the Vox Media Podcast Network, and we'll be back next week. And we're back with Canva Presents Secret Sounds Work Edition. Caller, guess this sound. So close. That's actually publishing a website with Canva Docs. Next caller.

Definitely a mouse click. Nice try. It was sorting a hundred sticky notes with a Canva whiteboard. We also would have accepted resizing a Canva video into 10 different sizes. What? No way. Yes way. One click can go a long way. Love your work at Canva.com. Support for this show comes from Amazon Business.

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