The Mariana Trench

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In 1875 in the Western Pacific, the crew of HMS Challenger discovered the Mariana Trench which turned out to be deeper than Everest is high by some two kilometres. Now trenches like Mariana Form when one tectonic plate slips under another and heads downwards towards the Earth's mental and there are around 50 of them globally. Now some people used to think that it was too dark and deep for life to exist there. Others imagined monsters lurking at the bottom of the ocean. The truth has proved to be more intriguing than either of those. With me to discuss the Mariana Trench are three people who were all veterans of this kind of environment. Alan Jamison, director of the Deep Sea Research Centre at the University of Western Australia. John Copley, professor of ocean exploration and science communication at the University of Southampton and Heather Stewart, director of Kelpie Geoscience and associate professor at the University of Western Australia. Heather, I'd like to come to you first. Can you just describe the Mariana Trench to us? How big is it? Where is it? And if we could see it, what would it look like? Yeah, fantastic. The Mariana Trench is what's called a subduction trench and what it looks like is this long curved, deep within the Western Pacific and that's formed as you introduced through a process of plate tectonics. So we have denser oceanic lithosphere, so the Pacific plate that plate encompasses the entire Pacific Ocean and that is being thrust and pulled underneath the adjoining continental plates. So this process of plate tectonics by which these oceanic plates are getting taken down into the mantle and recycled, that downward flexure causes these ultra deep parts of our world, most famously the Mariana Trench and the other trenches that surround the Pacific, the so-called Pacific Ring of Fire. And that's how these ultra deep places are formed and the maximum depth of the Mariana Trench is 10,925 meters. And that's about 98 times the height of St. Paul's Cathedral, which is just, it's a really hard number to sort of visualize in your head when you start to think about these sort of deep water environments. And how long is it exactly? It's about 2,550 kilometres long and it sort of arcs around the Mariana Isles in the Western Pacific there. Now, you're all experienced divers in these terrains. Heather, what's it like to go down a trench? It's absolutely incredible. I mean, all three of us around the table here have been submersibles, but from my personal point of view, there's the moment when you're sitting on the sea surface and you get the clear to dive call. And that color change, as you start to fall through the water column and the change from the sort of clear waters on the sea surface through the brightest shades of blue down to absolute pitch blackness. But then, of course, all of that, you're sitting in silence. And that is so humbling as well as very, very exciting. Because, of course, after a few hours, you start to come to the sea floor in these sort of deep, subduction trenches. And I've been lucky enough to dive to the bottom of the Tonga Trench. But that moment when you turn on this lights of the submersible and you start to see the sea floor coming up underneath you, it is absolutely fantastic. And as a geologist, knowing that you're the first person to set eyes on this seascape, if you will, but also starting to look and your brain is already starting to process what you're seeing out of the viewports and trying to put that into some sort of geological context. You know, are we landing on sort of soft sediment sea floor or are we coming down on rocks? What type of rocks are there? Are there any structure in those rocks? Are we seeing faults? You know, what life is encrusting and are being associated with that habitat down there? So you're constantly taking this information in and trying to form a sort of hypothesis and that you're testing during the submersible dive itself. But I mean, it's absolutely, you know, the very first dive I did, the pilot sort of joked that, you know, he had to turn up the oxygen because I was getting very excited. So I was using up more oxygen and the environment inside the sub. But it's truly, you know, the being there and sort of seeing it yourself is something that can't be replicated through other means. Fascinating. And Alan, I believe that you have gone amongst our guests the furthest down the Mariana trench. Can you tell us about that experience? Yeah, it was a good few years ago now, but it was a mistake. It was a mistake. I was really supposed to tell you. How can you go down the Mariana? Yeah. Yeah. A trench by mistake. Yeah, we'll come up one morning. It wasn't planned. We went there to do, I think it was four or five dives on the deepest place on earth. It was like, like the first one was the third time it's ever been done. And no one thought we'd ever do it. We'd probably get one in maybe two before the sub breaks. So we run at a time or there's well or whatever. And for some reason, we just did one every two days for a week. And we got all we ticked all the boxes because some of the dives have to do with the classification of the sub. Some of them because of the owner wants to do it at the time. Other ones were to do with the manufacturer. And we did four. And nobody expected us to do that. And so, interestingly, the guy called Dom Lorsch, he was the guy who did the first dive ever in 1960. He was with us. And he came in one day and said, there's another one. It's time for another one. You want to do it. And it's like, yeah, sure. And he said, well, where do you want to dive? And I said, well, I don't really want to dive challenge a deep because it's just done it four times. And there's actually nothing much there. That's the deepest bit for the man who's bought a challenge. Yeah, we've done it 22 times now. So I was right. There isn't much there. But I said, I want to go next door. There's a place next door called Serenade, which is like 10,700. And there was reasons to believe it would be slightly more interesting. So, yeah. And before and not next morning, we were down at 10,700 and something meters. And we found these big sulfur mounds and all sorts of interesting stuff. It was brilliant. So it wasn't planned. It wasn't really supposed to happen. What are the challenges for the submersibles themselves? I mean, because they must be operating under immense pressure. And yet, they've got to sustain an environment in which humans can live. Or exist for four or five hours or whatever. Yeah, there's two parts to it. So we've gone down to environments which are pressure-wise. There are about one ton per square centimeter or if not a bit more. So the engineering for that is actually relatively easy because it's linear. So you just make things thicker. We use titanium inside the sphere. And we use all sorts of materials that can get us back to the surface. And so on. But the other problem we have is not just the pressure adept. There's actually a distance from the surface. So communication with the surface is very difficult. For all sorts of safety reasons, we have protocols in place where we have to contact the surface every 15 minutes. Every half of it where it has to be a voice one. So we have an underwater telephone where we can talk to the surface. That's the biggest problem. It's trying to punch an acoustic signal through seven miles of water and then trying to listen for them coming back. And we've kind of nailed it now. But some of the other problems we have is tracking. It's quite often well up until recently there hasn't been any products on the market that we can use to track where the sub is. So for the last five six seven years we've been doing it with no tracking at all. So we've got very rudimentary tracking but not like you would in shallow water. So there's a certain degree of challenges to do with just being very, very far away from the ship. As well as the pressure at the bottom. How does the sound travel back and forth between the ship and the submersible? We have a thing called an underwater modem. And it's an all-distributed military device that we push a button and say hello. And then you release the button and it scrambles into the acoustic signal goes up. And you can kind of tell it's weird. It scrambles into acoustic signal but you can tell who's talking. It's really bizarre. You can almost hear the accent and then it's here and then they can do it top back. And you have a lot of... We've got text message now as well which is quite nice. John, these depths are often called Hades Zones. What does that mean? What is a Hades Zones? It's from the Greek for Hades. So the idea is this is the greatest depths of the ocean. So there are these popular schemes for dividing the ocean up into different depth zones, giving them names. But environmentally, logically, most of them don't make sense. The Hades Zones is one that in a way does make sense if we just say, well, that's Ocean Trenches. Ocean Trenches tend to start at about 6,000 meters. But that said, there are some environments in the deep ocean that aren't Ocean Trenches, which are at more than 6,000 meters, which is where these zones kind of break down. But in a way you can think of it as a shorthand for being Ocean Trenches. Right, that's nice and simple. How was it discovered? The Marianne Trenches in particular. So you mentioned in your introduction HMS Challenger. So this is a global voyage of discovery in the early 1870s. And it has two main goals. One is scientific to map the ocean floor, understand its undulations, and the extent of life in the deep ocean, and also a strategic goal as well. And that's to scout the routes for submarine telegraph cables, which are such a huge technological revolution of that time. I mean, right up there with the invention of printing press and the impact they had on the world. Yeah, so we had telegraph cables across the Atlantic in the 1860s, presumably the Pacific was even more challenging. Exactly, and people wanted to wire up the British Empire. So one of the goals of HMS Challenger, the reason they got funded was the strategic goal. Anyway, 20th of March 1875, HMS Challenger has been, it's in the Pacific, and it has been pushed off course by baffling winds as they record in their log. And they decide to make a depth measurement where they've ended up. They lower a weighted line and they record a depth of 4,475 fathoms, which is 8,184 meters, I think. So that was the deepest place that they measured on their voyage. It's not actually the deepest point in the ocean, and it's not even the deepest place that's been measured at that time. So where they made that measurement, they were actually about 25 kilometers from what we now recognize as the deepest part of the Mariana trench, the Challenger deep. And about 2,700 meters short of that. And it wasn't then thought to be the deepest part of the world's oceans, because a year earlier, a ship called the USS Tuscarora, which was also scouting submarine telegraph cable routes in the Pacific for the United States, had measured 8,513 meters. For much further north in the Pacific, and what we now recognize as the Curel Camcacca trench. So HMS Challenger found this deep depression literally by accident near the Mariana Islands, and there were no other depth measurements in that area for another 24 years. So they found a deep spot. They didn't notice part of a trench. It wasn't called the Mariana trench at all at that time, and it wasn't even the deepest known point at that time. So if we jump forward a little bit, 1894, HMS Penguin measures, just over 9,100 meters in the southwest Pacific, and what we now recognize as the Curel Camcac trench, so that then becomes the deepest known place on Earth. But not for very long, 1899, a ship called USS Nero, began scouting submarine cable routes near the Philippines measures 9,636 meters. That becomes the deepest known place on Earth, what we now recognize as the Philippine trench. And that stayed as what people thought was the deepest place on Earth until 1951. And these were individual depth measurements, and people didn't realize they were part of these trenches and these features that Heather's described. That came also though at the end of the 19th century. So there was a map published of the depths of the world's oceans by a cartographer called Alexander Supan, and he showed that some of these places where there have been these big depth measurements were trench-like features. Not actually the Mariana one on his map, but he identified the illusion trench, and he also proposed that these things should be named after the geographic features that they're near to, so that people don't get confused. So that's why Mariana turns out to be Mariana because it's near the Mariana Islands. And the deep, and the deep, which is what it was called before on an earlier map in 1877, that becomes eventually the deepest known bit of the Mariana trench. Heather, what do we see when we get down to the bottom of the trench on the beds of the trenches in geological terms? Is this like a sort of conveyor belt of rock? Yes, indeed, and in that sort of really large scale, big geological processes frame, then we're looking at a conveyor belt of oceanic plate coming into the trench being bent and thrust down underneath that overriding plate. So that's where we get that conveyor belt. But in terms of when we're actually looking at the seascape, you know, it can vary quite a lot. So we have what are called hemipalagic and clay-rich sediments that drape that seascape that topography of rock. But once we're actually in the trench, we don't only have that oceanic plate, which are composed of volcanic rocks like basalts and things. We actually have the four arcs. So all these rocks and sediments are also getting scraped off onto the overriding plate as it's being subducted in. So we get this melons of sediments and rocks, but we can also see bits of exposed mantle in these trench environments as well. What does mantle look like? It's actually really cool and we've got some amazing footage of that. And it's these massive dark rocks, but they've got really big major faults and joints in them. So I mean, it's very characteristic and it's got a lovely sheen to them as well. So in terms of what you're looking at out of the viewports and what you're looking back on the video that's recorded, it's a very striking environment. But what's also really cool is that when the process of subduction is happening, it almost starts this catalyst of other things that are happening. So we see mud volcanoes and we see vent systems. You know, there's a shinkai vent system is on that four arc of the Mariana trench. And it's not like what we might think in terms of black smokers and you know, those amazing documentaries that we see where you've got that sort of pump of black material kind of coming out of the sea floor and those very dark, brown, big edifices and stuff. These vent systems in the Mariana, the shinkai vent system, for example, are made out of carbonate. So there are white pristine white chimneys that are preserved on the sea floor and the fluids that are erupting from these systems are being sampled and tested for the chemistry. So they're looking at what minerals are being dissolved by the water that is being taken down by this process of subduction and is percolating through the rock mass. And it's dissolving out all of these minerals and then it's reprecipitating them. And that's when Alan was talking about the sulfur mounds in the in the serenadeep, you know, the sort of bright yellows. I mean, the colors that you can see on the sea floor can take your breath away. Some of the other footage that we have from the Java trench, for example, I mean, Alan, we've got yellows and blues and all of these hemasynthetic bacteria that are living off the mineral content coming out of these vents and the cracks and fishers on the sea floor. And it just explained to us quickly what turbidity currents are. So turbidity currents there, you might like to think about them as underwater waterfalls where we've had something, whether it's through gravity. So it's just, you know, you've got a slope that is being loaded with sediment much like whenever you're driving through the highlands and you look, especially after heavy rainfall, you might see the the sides of the glen that you're driving through, you know, you can see the material is sort of slipping down slopes. So we can get the same comparable processes underwater in these trench systems as well. But then of course, we've got the more dramatic perhaps the more sort of well known events that are triggered by earthquakes or volcanic eruptions, for example. But basically these trigger movement of vast quantities of material down slope, huge speeds as well. And it is a really great mechanism for transporting not just sediment from higher slopes down into these trench basins, but also it's transporting food and nutrients for the communities that live down there. Well, let's go on to those communities and Alan, let me ask you what kinds of life are we seeing at these depths? Oh, there's all sorts. So there's kind of, you can kind of categorize all deep channels into two different categories. There's those that go down to about 8,000 and there's those that go beyond that. So when you look at things like fish, prawns, urchins, brilstar, sea stars, squid, octopus, you find all them deeper than 6,000 meters, but they rarely ever go beyond eight. So obviously there's a barrier there, which is quite difficult. If the species has adapted to high pressure and go beyond that, they go all the way and they don't seem to care about pressure at all. So they've got things like little tiny hoppers called amphipods. There are things called isopods and polykites, which are pill bugs and scale worms and there's normal looking jellyfish. There's anemones down there. But once this seems, once an animal seems to have evolved to break the 8,000 meter barrier, it almost adopts this complete resilience to pressure. And sometimes their depth range can be 5,000 meters, which is incredible. So at the very, very bottom, there's one animal which I think has become really important to us, because we're finding it at the bottom of every single deep trench we go to. You have to be deeper than about 8,000 and 9,000 meters to see it. And it's just an eminy. It's called a galathia entimum and they live in a little tube and they look like a little white flower. Really quite beautiful looking thing. But we can't find them anywhere else except at the very deepest points of the really deepest trenches. So there's that. Everything else tends to be quite small at the deepest points. But when you get to 8,000, there's quite a lot of large animals still kicking around, which is people find quite surprising. And they don't look weird. If anything came of goofy. And I believe you discovered a well named one called the snailfish. Oh, the snailfish is a known family. We discovered the Mariana snailfish. We just don't name them anymore because it's too difficult. But yeah, we find snailfish all the time. So we named the Mariana one because it was quite prestigious. So for quite a few years, it was the deepest fish in the world. Unfortunately, it's not anymore. There's one further north of Japan, which is slightly deeper. But they're all kind of the same. They all look goofy and weird and sort of flaccid-looking little things. But they are the deepest in the world. And weirdly, the family of fish of snailfish are not actually deep sea fish. They're shallow water fish. They've completely taken over. So there's 300 species. You find them up estuaries and stuff. So the snailfish, I know, are those of you that are deeper than actual proper, I like to consider proper deep sea fish. John, how do these animals and the enemies and so on, how do they withstand pressure at 10,000 meters below? How does it happen? Well, the challenge of pressure for animals in the deep sea is really often not what we perhaps imagine it is. So, to illustrate that, I was in the last expedition I was on in the Arctic. We took an ordinary uncooked chicken egg. And we sent it down to three and a half thousand meters on the outside of one of our deep-loving vehicles. That's about the average depth of the world's ocean. And it came back with a crack on it. And that's not because it's somehow stronger than after the merciful. So you know, we then cracked open in the galley to show that it was an ordinary egg. That's because, think about that chicken egg, what's it made of? It's made of solid matter for its shell and it's filled with liquid. And those are pretty much incompressible forms of matter. You know, if you imagine dropping a stone into the Mariana trench, it sinks down to the ocean. It doesn't at some point suddenly implode because there's no gas-filled space inside it for it to get squashed down into by the pressure. Similarly, with liquids, if you get a syringe of water, stick your thumb over the end and try and push down that plunger. You won't budge it compared to a syringe of air, the same kind of thing. So for deep sea animals whose bodies are made of solid matter in their tissues, liquid body fluids. In a sense, they're not mechanically with standing pressure, a difference in pressure between their insides and their outsides, in the same way that our deep-loving vehicles do. Our vehicles have to maintain a gas-filled space inside them and normal atmospheric pressure either to keep us alive as occupants or to keep electronics dry if it's an ungrued vehicle. But it's not like that for deep sea life. There is a challenge, but it's about what happens with molecules in cells, but it's not about mechanically with standing pressure. Can you just go into that a bit about the molecules in the cells because they act in a rather different way than the molecules in our cells do? So some of the problems with pressure, for example, involve protein molecules folding up into the right three-dimensional shape that they need to be to work as enzymes. And you know, we need the enzymes and they're carrying out all the living processes in cells. And that's a big problem because high-pressure traps water molecules on the unfolded protein as it's been kind of put together inside the cell and prevent it from folding up into the right shape to do its job. So that's one challenge of pressure. And so a lot of deep sea animals have these small molecules that we call chaperones that help to pull the water molecules off the unfolded proteins so they fold up into the right shape. Sometimes the animals have a different kind of protein structure. Their protein is made of a different sequence of these little like bead-like amino acids, which again helps them form the right structure under pressure. And it's also the cell membranes, the things that enclose the cells. Now that's normally a very fluid bilayer of lipid molecules, fat-like molecules. And a high pressure that can become very rigid and that can stop messages getting in and out of the cell and so on. So again, a lot of deep sea animals have different composition of lipid molecules in their membranes to overcome that. So a fundamentally different evolutionary path from say humans? Well adaptations to their environment just tweaks, if you like, as to nature coming up with a solution to these challenges. Heather, back to what we were talking about. You mentioned the landfalls and earthquakes and volcanoes. How stable is that? And does that impact on the animals living at the bottom or in the trench? Sometimes a stability, I mean it is a very dynamic environment, you know, being part of the ring of fire, the Pacific ring of fire, of course, you know, we've got volcanic eruptions, we've got volcanic squings on, we've got the earthquakes and everything. It is quite what we might call a sort of slippy boundary at the Mariana. So we don't, we see a lot of earthquakes. I mean it is an active subducting margin, but it's not a stuck. There are other margins that are sort of become stuck and then we've got a huge build up of geological forces that are trying to sort of unstick that margin. And that's where we get these huge earthquakes that cause such devastation in places. So in terms of the Mariana. So those earthquakes did trigger tsunamis and things like that. And the cancer trigger tsunamis for example, yeah. So as I was saying earlier in terms of keeping the movement of nutrients and sediments from the shallower for arc down into the trench basin. So that's a constant evolving and occurring process. So there it is constantly changing. And we've got some amazing footage from up and round corner, a little bit of the Japan trench, where you can see rock failures and the block failures. So sort of going back to the basics of sort of geotechnical elements. We can see that happening not just in this rock mass, but also with this semi consolidated. So the sediments that are a bit stuck together and are starting to behave more like a coherent rock than a soft squishy substrate. And we can see those failure planes and mechanisms happening as we traverse in the submersibles and the remotely operated vehicles that we're using. Alan, what happens when you go down there? What do you see? Is it a pristine environment? No, sometimes there are places that look very pristine. But I mean, I've probably done about, probably over 30 dives and I don't necessarily recall any dive that haven't seen something man made. Probably everyone, maybe there's one or two that haven't some of them are really bad. So I remember doing our 10,000 meter dive on the Philippine trench, which was the spot where the Galithia expedition in the 50s had found a rock that, which was a Galithian, Galithia Entomon by the way, the one I was mentioning earlier. So we don't want that spot, we filmed them alive. And that's great. But we also saw a bit something like 19 plastic bags on the same dive. Just floating around, you could read that logos off them. There was an eco-friendly plastic bag came past me like, really is that how eco-friendly is that? And then there are other dives, which I should have more serious to come back to, Mario and I trench diving the challenge of deep, the whole western side of the challenge of deep, which is where Don and got called Picard, dove in 1960s. And now a no-go zone because that whole area is just covered in discarded fiber optic cable. And so someone in the last 10, 20 years, maybe it's got something to do with listening to the naval based on glam or maybe it's in guys and military, I don't know, but people are doing a lot of experiments at the deepest point. And now we have hours and hours of footage of fiber optic cable either just discarded or actually taught and tight across a new, if you're in a self-propelled vehicle like a sub, you don't want to be anywhere near fiber optic cable. Very, very dangerous. And it's everywhere now, but it's only on challenge of deep, it's not anywhere else in the Mariana and it's not seen anywhere else in any other trench. So there are things like that where that's kind of almost deliberate. Someone's been doing something there. But one of the weirdest ones I think was last year where we were down, it was 5,000 meters somewhere, just on the equator, four days north of Samoa. And we were driving along and doing the usual thing, I was telling the pilot to go and have a look at this, going to have a look at that. And we saw this red thing, I thought, that's worse, we were wondering what that is. And it's going to have a look and pulled up alongside it. And it was just a packet of Chinese cigarettes just lying there, thousands of miles away from anywhere, as if they just dropped them out the pocket. And it's bizarre, it's really quite bizarre. It can really throw you as well when you're sort of going like, because you're so focused on trying to record as much scientific data and information in the commentary that as you're going along in the sea floor. And then I was like, I have to go and see something. And I think, you know, and Nova canton trough as well, I had a dive at six and a half thousand meters and I said to the pilot, I was like, oh, God, there's something over that, like that's going to be, and it was a cardboard box. It's just, you know, you're like, oh, oh, sugar, I've just like deviated from the plan because I thought that was going to be something, you know, geologically or ecologically monumental. And it's like, oh, okay. The poor French literature is probably bad. That was terrible. It had gates and magazines and plates and cook cans and beer bottles. But I mean, it's sitting in hurricane alley. So I think when these hurricane, it's not necessarily a story of human folly. I think when you have tsunamis and hurricanes, a lot of material just goes off shore. And if you happen to be next to a trench, it's going to end up there. And it's quite, quite depressing to see it. Although the point you make about fiber optic cables on challenger D seems to me to be quite interesting. The coolest thing about Marianne in terms of man made notiness is there's an SR 71 Blackbird. You know, the old aircraft from the 1960s, the big black really cool looking thing. And one on emcraft, they didn't want the Chinese to get it. So they took it out a gwam out to the Marianne and threw it off the back. You can see pictures of it online. So somewhere in the Marianne there's a blackbird, which would be the coolest dive ever. I'm going to differ, you know. We haven't released a cord that's probably where it is. I bet the Chinese have found it by now. Yeah, just not telling anyone. John, I want to come back to the animal stand there. How do they feed? What are they feeding on apart from human junk? Most of the time they're feeding on what rains down into the trench. And trenches are interesting because they act a little bit like a funnel in that there's this stuff that we has a poetic name Marine Snow. But basically it is poo of all the animals that live in the ocean and it is dead bodies of all things living in the ocean. And this marine snow sinks down. It does get concentrated in the trenches through this sort of funnel effect. And so the bottom of your trench, I mean it's combination of both the toilet and the mortuary. But that's what things will make a meelof. And they'll make a meelof of anything that they can. So I'd be enough, some of the animals that live in the bottom of the trenches are able to digest things like wood, which a lot of animals in the ocean don't bother with. It's quite hard to kind of crack the molecules in wood to make a meelof it. But if that sinks and nothing has eaten it on the way down, and that's what you get at the bottom of the trench then there's a strong driver for any organism that can make a meelof it. Now there are some places in trenches though that are really exciting where there are chemical-fueled islands of life that break all the rules. So they're what we call cold seaps there as Heather mentioned where you got these plates. Subducting you get the sediment being scraped and squeezed on the subducting plate. And that squeezes whatever's in that sediment out of it. And so if that's had rotting organic matter in it over many, many millennia, that's broken down into methane. Methane gets pushed out of the seabird. You get these what we call cold seap communities. And that's where life is incredibly abundant. Now they haven't been seen yet in terms of animal colonies in cold seaps in the Mariana's, but they have been seen in the Curel-Kamchakka and the Illusion Trenches more than 9,000 meters deep, which are the deepest known islands of this chemically powered life which we have on Earth, which are hugely exciting. From a scientific perspective, the Mariana must be an achievement to go down there. But is it the most interesting scientifically or is it just the feather in your cap of having been deeper than anywhere else? It's a bit of worth. It's not certainly not the most interesting. I think it's most prestigious and it's sometimes when you have something with a prestigious name to it, it does kind of cloud de-reputation that's gone. So from a purely scientific point, I think we've spent a lot of time going to other trenches. We've done Mariana with six times, but for various different reasons and different boats and different nationalities, whatever. There's been reasons for doing it, but it's no one trench represents all other trenches. And so it's the deepest one, therefore it's an overlap. It's not the same as the rest of them because it's deeper than them. The biggest problem in Mariana we've got is that one of the only big trenches in the world that does not lie along a coastline. So all that organic matter that comes into the surface that rains down its food is the only one that doesn't have it. There is some or somehow attached to or associated with a continental plan mass. It's also quite low to the question of the equator. And so there's not a lot of food in the surface that anyway. So it is what we call all the good traffic, which means it's in an area of the ocean that doesn't have a lot of energy. And it doesn't have any seasonality. And so there's lots of reasons why Mariana doesn't represent anything other than the fact it's super deep. So if the question you're trying to ask is what happens at mega deep depth? I guess it's your one. If it's the question is what happens in trenches or what happens across a massive depth range? There are many other places you need to go to as well. The analogy I always use is like if you're trying to understand high altitude biology or high altitude flore and fauna. How much would Mount Everest tell you about every other mountain in the world? Not very much, you've told your lawyer about altitude but I won't tell you anything about a mountain-gort and Kilimanjaro. So do I get John in that case? It's the implication of what Alan's saying that the environment in Mariana is actually very static and constant compared to others. It depends on what time scale we're talking here. Now everywhere in the deep ocean is changing as a result of impacts of human activity. So climate change affects all of the ocean including the deepest depths in the ocean and it affects it in several different ways. I mean we are getting warming of waters and that is getting deeper and so on but fundamentally for deep ocean what's changing is the flow of oxygen that reaches the deepest parts of the ocean. So all the animals that we've been talking about, the animals they need oxygen. The oxygen dissolved in seawater. Where does oxygen come from? Well it dissolves from the atmosphere into the ocean in the polar regions. The surface where dense, deep currents form and sink and then they spill out across the ocean basins. So life at some point like the bottom of the area of the trench, the oxygen that those animals are consuming began its journey into the deep actually in the Antarctic and it takes several hundred years for it to kind of flow and get there. And that flow is getting weaker as a result of climate change. Yes although does that mean that climate change is going to affect them in 300 years time? It does, yes indeed. And that change is already on its way from changes that we've made in the atmosphere. So we already know that overall globally the deep ocean will end up with about 10% less oxygen than it had in pre-industrial times. Now it's very patchy in different bits will be affected more than some others but overall globally it's on track for 10% less than it had already. It's going to change the distributions of species around the world, some can tolerate that, some can't. Their distributions are going to shift. And that's a change that's already baked in. That's already happened. It's on its way to the deep ocean. It just hasn't reached the deepest places yet. Hello it strikes me that when you're looking at something like the trenches it involves a lot of different skills. It involves geologists, it involves engineers, it involves biologists, all sorts of people. How do they work together? Do they understand what the other is doing? Very much so I think I think I can speak on all of us. I think the most rewarding expeditions have been the cross multi-disciplinary ones. And each discipline thinks a little bit differently. The engineers, the geologists, the physical oceanographers, the biology chemists. And I think that fusion and that sort of spark between the different disciplines and making hearing about their research questions and their concerns or their technological challenges or what aspects they're trying to overcome. And then you can sort of, well actually we do it this way. Or you can learn from each other. But I've worked over 20 years now with all these different disciplines and learned so much. And I think in order to undertake successful research, you need to be able to work together with everyone in these environments. And it's certainly I've learned a lot in terms of, you know, I'm a geologist not an engineer in terms of the challenges in terms of how you build vehicles to put down to these sort of depths and things, you know, working with Alan, for example, as an engineer. It's fascinating and it's allowed me to think better and more strategically and more creatively about how to sort of address geological questions. You know, like how can we get physical samples and cores from these deep areas without using a big drill ship like the Japanese vehicle, Chikyu, you know, trying to think a little bit more out of the box. But I think also in terms of the big discoveries, I think if you look back at how those expeditions and how the people on board have worked together, that's helped contribute to some of these big discoveries that are making in the deep sea now as well. It struck me in this discussion how remarkable the research into biology has been. John, I've got a question for you. How do you study these animals when presumably if you bring them up to the surface, they're not going to survive, are they? They don't survive. No, they don't explode. Okay, because of the pressure thing that we talked about in reverse. Okay, there's nothing in them to expand as they come up if it's solid tissue and liquid body fluids. But we can learn a lot from the specimens that we do get, of course. We can look at the adaptations they've got. We can look at what molecules are in their cells and so on. These days, though, we're also able to preserve animals actually at the sea floor, which is really useful. So for example, you can collect a specimen and you can process it in a way that its tissues are preserved in something that allows you to see what genes are actually switched on at the moment that you encountered it. So that, otherwise, we can do that with specimens we bring up, but of course, they've gone through a lot of changes on the way up. But actually being able to preserve things in situ is giving us really big insights in what we call genomics and transcriptomics, seeing what genes are actually being switched on in that organism, in its environment to understand how it's adapted to the conditions down there. Historically, Alan, people have believed that this is an area of giant monsters and all sorts of mysterious creatures. Do you encounter that sort of attitude today, despite the fact that we now have a much better idea of what's down there and they're not giant monsters? Yeah, it's all the time. One of the most common questions you get is about questions about megalodon and stuff like that. And I think when you start looking into the energy in these systems, it could never ever support a large animal, especially not a lot of that kind of size, but even bigger than a shoe is quite difficult to maintain those kinds of tips. As you see, it's just all to do with education, I think, in the way in which deep seas portrayed in the media and things like that. I think we can probably do it a bit more responsibly and stop referring to monsters and creatures and stop making movies about it. But then, you know, little snailfish aren't going to make a Hollywood movie, right? So, you know, they don't even have any teeth. Well, they did make a Disney movie about a clownfish. So maybe the snailfish could come next. Who knows? I'm very interested in deep sea vents and deep sea mining. Is that something that you have to engage with that debate about whether the minerals should be exploited in this way? I mean, I work primarily on deep sea vents, which we don't get in subduction trenches in the same way, these black smoker systems and so on. Yes, deep sea, that is one of the environments that's being targeted for a form of deep sea mining. There are others as well. People get very excited these days about the manganese nodules. That's a totally different environment, totally different set of ecological kind of challenges involved there. For deep sea vents, the active ones, which have these incredible colonies of species living around them, we don't actually need to do any more research to say that mining active deep sea vents would risk extinction of species. And we've been very clear to that to the international regulators. And I hope when they do draw up some kind of code for this activity in the future, that will be the top line for this environment is that active deep sea vents must be protected. And one final question is the Mariana trench less interesting now because it's pretty well known what's down there. And it's not as active as the other trenches or will people still want to go down. Heather? I think as Alan hinted at you know, just because it is the deepest, of course, you know, there's still going to be a lot of interest activity down there. But I mean, for me, you know, the south sandwich trench, the Tonga trench, the Kermadek trench are much more interesting from a geological perspective in terms of the activity going on there where managing to document sort of volcanic pyroclastic density currents at, you know, in the rocks that have been deposited by those features at 8000 meters washed out, which has never been done before. So we're starting to look at new process. We're getting little glimpsies as to volcanic processes at depth in these environments now that hadn't been noticed before. So there's still a lot to be learned from these environments, but I think certainly sort of widening and working elsewhere and engaging with with with other researchers as well. There's also another way to look at it because the Mariana is massive right if the volume of the Mariana is about the same as the volume of Himalaya and the size of a submersible might let say is the size of a land Rover. So if you put a land Rover on Himalaya and said, like, how long is it going to take for you to document everything on this thing? It's going to take you a while. So you could theoretically spend your entire life just working on that thing. But again, within the book ends of it being this is what happens in the Mariana trench. You can't necessarily make bigger statements about this is what happens in every trench, but it's still valid. And the Mariana trench really is actually five different areas. There are some ducking sea munch, which partition it. So from an animal that challenged a duck, for example, could not get to the top of Mariana trench without having a decompressed by thousands and thousands of meters. So this technically is five bins. So yeah, there's all sorts of interesting things to do. Thanks to John Coppley, Heather Stewart and Ellen Jamison. And next week it's the Roman arena and the role of gladiator fights in imperial politics. Thank you for listening. And the In Our Time podcast gets some extra time now with a few minutes of bonus material from Misha and his guests. So tell me, what did we miss out, John? I personally am really fascinated in kind of like the inner space race that took people to the bottom Mariana trench for the first time. And the context for that. There were various private individuals who were designing these vehicles and engaged in this work and innovating and so on. And then the French Navy wanted to get involved and then they had a bit of a bust up. And eventually the US Navy got involved and bought up the technology at a time when they were re in during the Cold War. This is around about 1960 when they were really flexing their muscles publicly in terms of capability in the ocean. They sent a submarine underneath the North Pole for the first time. The surface wasn't a North Pole. They had the first circumnavigation submerged by a nuclear submarine and they wanted to be the people to get to the deepest point for the first time. So that whole story I think is a very interesting mirroring the space story. To some extent the Russia, the Soviet Union really weren't involved in sending people. They were sampling deep trenches in the late 1950s and looking at life down there, but they weren't looking at these kinds of demonstrations of capability in the same way. Hello, what did we miss? I think the evolution of the Pacific ocean as a whole is really interesting. So if we go back to 200, 300 million years, we had a supercontinent called Pangaea and it was surrounded by a super ocean called Panthalasa. And basically Pacific is the last remnant of that ancient ocean. And that's why it's so much older than the Indian and Atlantic. So they opened at 200 million years ago as this supercontinent Pangaea started to break apart. That's when the Atlantic and the Indian Ocean started to open. But what is really cool is that in the Northwest Pacific, actually just near the Mariana, is where they sampled the oldest oceanic crust in 1989. And it was drilled by a big international collaboration called Ocean Julling Program. And that was hundreds, it proved rocks that are Jurassic and age 170 million years old. And that is just fantastic. And I love the fact that the Pacific Ocean is this old ocean made of old geological rocks, oldest oceanic rocks that we have on our planet. And that's why the Pacific Ocean technically is contracting as it's getting consumed rather than the Atlantic and Indian that are still opening and widening at this time. So that's still the breakup of Pangaea? Yes, yeah. I love that. I love that the geological time scale is still sort of trundling on. And it's just this, this conveyor belt of sort of motion. So if we think about plate tectonics and the earth being made up of these sort of jigsaw pieces, all sort of moving relative to each other in summer, sliding past one another, that's a strike slip, sort of margin or ones being consumed by another. That's your conversion. That's your subduction areas and other ones are sort of where we get new crust being formed. So that conveyor belt of evolution to on the thing that surprises me is a biologist, though when I hear about this geological history is, is that nevertheless, even though the Pacific is the oldest bit of ocean crust we've got, it's still really to me very young, you know, compared to three of billion rocks on land in some places. Yeah, well, 4.6 billion year. So central of central Canada, even the northwest of Scotland, that's some of the oldest rocks in our planet is 4.3 million billion. But I think it shows how dynamic the ocean is. Yes, you know, that's the thing. It's much more dynamic than the land. But Alan, anything you feel we missed out on? I got a funny story about a party. Go on then. So, yeah, so by the chance of deep was not discovered in 1875, it was discovered in 1952, right, by the challenge of two, right. So I read this book once, it was called the Hydrographous Tale and it's by a guy called Steve Richie, who ended up rear admiral Steve Richie. He was the highest rank in Hydrography on the Royal Navy. And he had done the soundings for the DD landings. He ended up on challenger two and he sounded what is now challenged deep with 10th is. And I remember talking to my boss, I used to work in Aberdeen for many years. I said to my boss, like this guy says to guy, he discovered John's deep. My boss said, yeah, he lives just up the road. I was like, you kidding me. So I ended up at his 93rd birthday party. And he led to the town called Callister and he's finally been there for 200 years. And then we turned up thinking there's going to be this free-low man in this cottage. I really hope there's rum at that party. Oh, it was a bad, moral story. It was written some African poncho in his house. It's all like oil and canvas drawings of some harbour and born it was somewhere. It was brilliant. And fortunately, he died a couple years later. But it was great to just, you know, I've actually went to the birthday party of the guy who just got the ticket. So let me get this straight. That challenger deep was only really identified by him. It's murky because someone gets a deep sowning which says there's something big there. But then refining just exactly where the deepest point is takes a little time. So challenger deep as a feature of a map turns up in 1877. Okay. But it's not, you know, that's before there was a Mariana trench or whatever. And it's just, and that's one measurement. And they just draw a kind of a circle around it. By the way, did they have to, did the challenge, the original challenge yet? Did they have to have rope going down five kilometers or something? They did. I wrote it down actually. Hang on. Yeah. It was a phenomenal. I was it, they covered 70,000 nautical miles, but they had 144 miles of Italian hemp for the soundings that they were doing. And quite often they had a bucket on the end of that rope. So they could take like a little sample of the sediment that was down there. But I mean, imagine keeping track of all of that wire. And it wasn't actually the absolute cutting edge technology at the time. So Lord Kelvin, the absolute polymath genius, 1872, he'd invented a wire sounding machine using piano wire to measure the ep. So what they do is they lower a weighted line. And they kind of look at the rate at which the line is paying out. And when it slows down, they assume the bottom of it is now touching the seabed. And it's, you know, in really deep water. In really deep water, yeah, the ocean currents can take it into any of us. And that's why a lot of the early measurements are way off for things. Lord Kelvin's piano wire machine is much more reliable. Now he sent one to the HMS Challenger, but they couldn't get it to work properly. It was still a prototype. And so they just shelved it and they went and we tried and tested it. But they still had to visit 12 and a half miles of piano wire with them as well. And actually that's something that because of the popularity of upright pianos amongst the middle classes of the 19th century led to mass production of piano wire, which meant it was available in these huge lengths for ocean sounding. What do we use for ocean sounding today? Acoustics. But very, very accurate, right? Yeah. Yeah. Yeah. So I mean, yeah, we know that, you know, Challenger Deep, for example, is 10,925 meters. Plus or minus six. Yeah. Plus or minus six. Error margin. And it's, you know, that's, that's using sort of a sound to sort of goes from the ship down to the sea floor. Boundary is off the sea floor and comes back up. What was interesting? It was the meteor in 1926 used sound to measure water depth for scientific purposes. It had been used by the military pre 1926, but the first use for scientific purposes was actually in the South Atlantic in the South Sanwich trench. And it was an expedition and they measure. We went back and surveyed it in 2019. Yeah. And we were within one meter of what they recorded in 1926. Good. It was the Germans that had been out on RV meteor. And it was, you know, that way that it's just, you know, like that. It was almost a hundred years later. There is a stop gap in here. So it's meteor deep. In between the ropes and the acoustics, there was a thing called bombsounding which was brilliant. So you stand on the back of the boat. You do like a stick of dynamite. You throw off so it blows up on the surface. And there's a kid in the hole who pushes a stopwatch when the bang goes off. And then pushes the stopwatch when he hears the echo. And then you divide the lens of the stock on the dynamite. You may have a echo coming back. So you basically listen to the bang. So you know that speed goes around 1500 meters per second. So you divide the time it takes between the bang and the echo by 1500 meters per second. That gives you the depth. And so some of the, there's a guy called Bob Fisher and Coolingborg and these guys. They would sort of draw it based on these things. And just hand drawn when a Philippine trench. I think we were there and tell you what, it's not bad. It's not bad because given there just lob and dynamite off the back of the boat. There's a scientific paper with Bob Fisher stood on the back deck with a basically a case of TNT. Just like line off as a guard, just lob and end of the ocean. I hate to be writing the risk assessment for a trip. And then eventually when we get echo sounding, you know, after bombsounding, that was in part because of the Titanic. So there was a German inventor who after Titanic came up with a way, well, can we detect, you know, potential collision obstacles using sound looking ahead. And then people said, well, if we turn that vertically, we can use that to measure ocean depth. Got it. Ah, see for. Yeah. I'll do this. Just a little bit. Yeah. I was also very interested, by the way, in the, the fact that the fiber optic cables are only a challenge or deep. And I can just imagine the type of the endless covert activity that is going on in places with noise. It's not, it's not a little bit, it's everywhere. Yeah. It really is. And you don't want to get tangled up in it. It's with no idea if it's 1000 meters long or 10,000 meters long, but it's everywhere. We don't have just someone on the end of it. So whenever you're going along there, you've got to keep your eye out. And as soon as it's here, it's cut the dive, just move. We're obviously through a map of it and try to recommend an area to not take a tele, or an unteltered vehicle because it's pretty bad. Why do you want to get rid of the, um, get rid of the fiber optic cable? And so, presumably, you can reuse it if it's all these lots of different reasons. Some of it's obviously under some of it. Some of it's under water cable, which is. Yeah, it's about getting live communication back to the surface. So there's ways in which you can do that by having a surface boy that gets winched below the surface. So no one can see it. So you can, if you imagine you had a, a flotation device with a beacon on it 100 meters under the surface and it's connected all the way to the bottom. Now, you can listen to some rings coming out of a gwam, which is, let's be honest, this is what it's got something to do with that. Yeah. But you don't want someone being able to steal your listening device. So you have a little winch that then comes up for an hour, beams all your information about it, so then pulls it back down again. Right. And so there are those in the area we think. Uh, but to, to get that technology right and to get stuff down there, fiber optic is the way to go. And the vehicle John talked about the fiber optic RLV. We had that out and it was, it was, it was terrible. Uh, we were, happened to be there when it imploded. The whole thing imploded. It was just a very experimental, but it was just a complete disaster. But all that fiber optic is gone now. It's all lying in the bottom and see again. So it's, it's, it's, it's, it's, it's, it's, it's basically, it's really missing today. You know, we don't have anything apart from some mesh balls that go that depth. Technology is moving forward. And I think we need to move away from those sort of, yeah, there's two solutions to one was super fine fiber optic. Nothing was super heavy. Japanese went real big heavy stuff. And then the Americans went super thin and both turned out to be the wrong. And then someone's recently did a completely untethered one and that got lost as well. So it's not easy. So we're going somewhere in between feels like the right thing to do. If it was easy other people would, yeah, we wouldn't be doing it as a group. Yeah. Yeah. Yeah. I've come across quite a lot of fiber stuff in terms of drones as well now. Yes. That's the same stuff that was in the American, it was torpedo wire. That's what it just, it just falls out. So the faster you go, the better it works. If you stop and try to do anything, it breaks. Yeah. Yeah. Which of course, from a research perspective, we're wanting to stop to pick up the samples of the communities and the rocks. And things that are down there. Yeah. Is it something that occurred to me is when you were talking about the life down there. And I think it's one of the sort of funny thing is, is the snail fish eating the amphipods? But of course, amphipods eat soft things that are falling down and are decaying. So what do the snail fish do to stop the amphipods eating them from the inside out? They have an internal jaw. So there's two mouths. The big mouth at the front is sucking animal in. But if they just swallow it, the animal then just bore itself out of stomach. So it has our second jaw inside its head when it swallows it just brings the animal to make sure it's dead. Oh my God. But what is really from a non-biologist sort of, you know, and that's what I was talking about when you pick up things from lots of different disciplines. So that, you know, if you come across something unusual or noteworthy that isn't from your own discipline, you know that it's important. But when I'm looking back at some of the video and watching this snail fish, so you see them sort of suck up the amphipod. But then as it's the second internal jaw is working, they sort of collapse and they have a little food coma on the seafloor as this is working. So you just see them. Yeah, they're just sort of set sort of, you know, doing a beach. Well, what my family call a beach whale impression after you've had too big a meal. But they're just all sort of set on the seafloor going, oh, cranky, you know. But really, at least it means I'm not going to get consumed by my dinner from the inside out. You know, it's just sort of funny things like that that keep you going. But I mean, I think as we're sort of exploring more and more of these environments and stuff, you know, the discoveries that we're making as makes it all worthwhile, it makes the episode trip so we are away from family and friends. But also the other thing that I failed to ask you about, which I should have done, was about what the implications of the research are for human health. Because that was a fascinating aspect of it in terms of, I think it's to do with the enzymes and the protein folding. Right. Well, there are a lot of insights we can get from deep sea animals. I mean, I'm not so familiar with actual trench organisms, but it's something I keep an eye on. And, you know, deep sea life can inspire us in two different ways, actually for material science. So I was co-author in description of a species called the Scalyfoot Snail, and it's teaching us how to make better solar panels. Because it can create tiny crystals of a metal mineral that room temperature. And this is what people want to be able to do for solar panels. And now people have been able to recreate this process in the lab with kind of off the shelf ingredients. I also was involved in describing a species deep sea shrimp, which has got tiny little bristles on it, which have inspired a new nano material that's fantastic for heat and sound insulation. So there's those sorts of things. And then there's a lot on the biomedical side. And one of the chaperone molecules that you get in a lot of deep sea life in laboratory studies can help to rescue human proteins that get bent out of shape, which involved in quite a few human diseases. Well, look, thank you all very much. This has been absolutely fascinating. Really appreciated. Simon. Does anyone want teal coffee or rum? No, I'm alright. The chances of finding a glass of rum in the BBC are actually less than zero. Thank you very much. Thank you. Really? Thank you. Thank you. In our time with Misha Gleini is produced by Simon Tilletson and it's a BBC studio's production. I'm Paul Kenyon and for Radio 4 and the History Podcast, this is Two Nottingham Lads. When the invasion happened, it was completely hell on earth with the sounds. The sad thing about war is people lose their empathy and their humanity. I want to know how two men from Nottingham ended up on opposite sides in the war in Ukraine. And what became of them after a chilling encounter in a prison in Dunyetsk. Out of all the places in the world where I meet someone from Nottingham, it's in captivity on two sides of the conflict. It's a story about hell and why you pick a side in a war that's not your own. You can listen to Two Nottingham Lads first on BBC Sounds.