15 Facts About the Mariana Trench

We have mapped the surface of the moon and sent rovers trundling across Mars, and yet the deepest part of our own oceans remain among the least explored places. So let's take a look at 15 incredible things about the Mariana Trench. Starting with number 15, it's the deepest place on Earth. So we're going to begin with pretty much the single most important fact about the Mariana Trench. It's the one from which everything else is going to follow. It's quite simply the deepest place anywhere on planet Earth. At its lowest point, a spot known as the Challenger Deep, this trench goes down to a depth of nearly 11 kilometers beneath the surface of the ocean. A figure so large that it is difficult for us to really grasp it. The exact depth is really hard to measure though. Estimates have been refined over the years using sound waves that are bounced off the seafloor, but it lies somewhere close to 11,000 meters. It's deeper than any other point in any ocean on Earth. Now to truly appreciate just how deep this is, take the tallest mountain, Mount Everest. It stands about 8,849 meters. Its summit is scraping the edge of the sky, and yet if you could somehow just pick it up and drop it into Challenger Deep, the peak would still have two kilometers of water above it. The deepest point in the ocean is, other words, comfortably deeper than the highest mountain is tall. But the trench itself forms part of what scientists call the Hadal Zone. This is the very deepest region of the ocean, a realm that's so remote and hostile, it's one of the last great frontiers of exploration on our own planet. While we've gazed upon distant galaxies and landed spacecraft on other worlds, this void beneath the waves has only been visited by a tiny handful of people. Figures, of course, do vary in depth slightly from one source to another, all of them hovering close to the mark of 11 kilometers. But to place that in context, the average depth of the world's oceans is only around 3,700 meters, meaning Challenger Deep goes down nearly three times deeper than the typical seabed. As the deepest point known anywhere on our planet, a place whose very depth has taxed the ingenuity of generations of scientists, the Challenger Deep sets the stage for everything else that's going to come. 14. The Pressure Down There Would Just Crush You If the depth of the Mariana Trench is hard to imagine, then the conditions at the bottom are even harder still. Chief among them is a pressure so immense it would destroy an unprotected human being in the blink of an eye. At the very bottom, the weight of nearly 11 kilometers of water pressing down from above creates a pressure roughly a thousand times greater than which we experience at the surface. It's unimaginable, it's just bearing down on every single point. Now, to put this in some kind of perspective, the pressure at the bottom is often compared to the weight of dozens of large jumbo jets that were stacked on top of you, or having many tons of force pressing down upon every square inch of your body. A human being that was descending unprotected into the condition would just be crushed instantly. For this reason, the vessels that go down there have to be engineered to almost superhuman standards, built with an immensely thick strong hull, often spheres of titanium or steel. They're capable of resisting a force that would just flatten an ordinary submarine like a tin can. Remarkably though, despite these crushing conditions, certain creatures not only survive, they thrive down there. Their bodies cleverly adapted to the pressure by doing away with the air-filled spaces that would otherwise be crushed. As one of the most extreme environments anywhere on Earth, where the pressure alone is enough to kill, the deep trench is a place of wonder, and its ability to defy human survival is one of its most remarkable qualities. There is an interesting, simple experiment that really demonstrates the power of the pressure. It's become something of a tradition among the deep-sea researchers. When ordinary polystyrene foam cups are attached to the outside of a submersible and then sent down to the bottom of the trench, the immense pressure squeezes all the air out of the foam, compressing the cups until they emerge, hours later, shrunken to a fraction of their original size, some of them no bigger than your thumb. It's an eerie illustration of a force that would do the very same thing to your body, only far more violently. The reason the pressure grows so intense though is that every 10 meters of depth adds about the equivalent of an entire atmosphere's worth of weight, so by the time you reach the bottom of Challenger Deep, the accumulated weight of all the water becomes a staggering thing. But the creatures down there that make their home, by contrast, have solved the problem in the opposite way. They do away entirely with any air-filled spaces and rigid structures that a pressure would destroy, so their soft, water-filled bodies are able to withstand a squeeze that no machine of comparable size could survive. 13. It's a Realm of Eternal Darkness and Near-Freezing Cold So, beyond the crushing pressure, the Mariana Trench is defined by two further conditions that make it feel like an alien world. Absolute, unending darkness, and a cold that hovers just above freezing. Now, sunlight, which sustains almost all life on the surface of our planet, can penetrate only a limited distance into the ocean. It fades away entirely at a depth of around a kilometer, below which lies a region of total and permanent blackness. The Challenger Deep, down at 11 kilometers, has never known a single ray of sunlight in all of its existence. It's cloaked forever in absolute darkness. And the water at that depth is bitterly cold. It's just a few degrees above freezing, and yet it doesn't turn to ice. It's kept liquid by the combination of its saltiness and the tremendous pressure. This deepest zone of the ocean is known to scientists as the Hadal Zone. That's a name derived from Hades, the ancient Greek god of the underworld. A fitting title for such a dark and forbidding realm. But because no sunlight can reach down there, there's no plants and no photosynthesis. That's the process at which life at the surface captures the energy of the sun. Instead, the creatures down there must rely on other sources of sustenance, feeding either on the constant drizzle of dead organic matter that sinks down from the sunlit water above. It's poetically known as marine snow. Or on the strange chemical energy released from within the earth. This is a realm of eternal night and perpetual cold. And yet, as we'll see, it's far from lifeless. In this world of absolute dark, many of the creatures that live in the ocean there have evolved a remarkable ability to produce their own light through a process called bioluminescence. They generate an eerie glow to attract prey, to communicate, or to confuse predators. So that the blackness is occasionally pierced by tiny living sparks of light. And as for the sustenance with no sun to power the growth of plants, the entire food web of the deep depends on scraps drifting down from the world above. Some organisms reliance then on the chemical energy welling up from within the earth, thriving in the total absence of light. But as a place of eternal darkness and bitter cold and perpetual silence, sustained only by the faint snowfall of the dead from above, the deep trench is one of the most otherworldly places imaginable. 12. Yet Against All Odds, Life Does Thrive Down There Given the crushing pressure, the perpetual dark, and the near-freezing cold, you might reasonably assume that the bottom of the Mariana Trench would be utterly barren and devoid of life. And yet, in one of the most astonishing facts about this place, it's home to a whole community of strange and hardy creatures, an entire ecosystem existing in conditions that would seem to make life impossible. Among the most common things down there are amphipods. These small shrimp-like scavengers that swarm through the depths feeding on the organic matter that drifts down. Some of these will grow to surprisingly large sizes. They're known as supergiants. And then there's the Xenophyphors. These are truly bizarre organisms. They're among the largest single-celled living things known to science. They grow to around 10 centimeters across, despite being, in essence, one giant cell. Crawling along the muddy bottom are the Deep-Sea Cucumbers. These include a curious creature affectionately nicknamed the Sea Pig, which snuffles through the ooze in search of food, while translucent, ghostly fish glide through the water higher up in the trench walls. These creatures survive thanks to remarkable adaptations, most notably the absence of any air-filled spaces in their bodies that allows them to withstand the pressure. In the years since scientists first began exploring down there, they've been repeatedly amazed to discover just how much life is there, overturning an old assumption that the deep trenches were just empty deserts. As a place where life flourishes in defiance of everything the environment throws at it, the Mariana Trench shows us the sheer tenacity of living things and the wonder of the natural world. The Xenophyphors, in particular, are among the most extraordinary found anywhere in the trench. The idea of a single cell growing to the size of your fist is genuinely challenging our everyday understanding of what a living cell is. These curious little beings gather particles from their surroundings to construct elaborate structures, and in some of the deepest and most barren stretches of the trench, they're among the dominant life forms. Beyond the larger, visible creatures, the trench does also swarm with an unseen world of microbial life. Researchers who have analyzed the mud from its floor have identified hundreds of different kinds of microscopic organisms, many of them entirely new to science. And what makes all these discoveries so profound and exciting extends far beyond our planet. If life can survive but flourish down there in the crushing pressure and total darkness, then it becomes far easier to imagine that life might exist in the similarly hostile environments found elsewhere in our solar system. So, in this way, the little humble creatures of the Mariana Trench offer a tantalizing clue about the great search for life beyond Earth. 11. A Huge Crescent-Shaped Scar In The Pacific When you picture the Mariana Trench, you often imagine a single deep hole maybe in the seabed, but the reality is far grander. The trench is, in fact, an enormous crescent-shaped scar carved across the floor of the western Pacific Ocean. It stretches for about 2,500 kilometers in length and it averages around 69 kilometers in width. It is a colossal feature, curving gracefully through the deep like a great scimitar slashed into the ocean. Just to put that length into perspective, it does dwarf the Grand Canyon many times over. The trench lies to the east of the Mariana Islands. This is a chain of volcanic islands in the western Pacific that includes Guam and Saipan, and it's from these islands that the trench takes its name. Its deepest point, the Challenger Deep, is tucked away near the southern end of the trench. It's not far from the island of Guam, and it's here that the seabed plunges to the very greatest depth. But the Mariana Trench is also part of a much larger network of these deep ocean trenches that ring the edges of the Pacific. It's a region famously known as the Ring of Fire on account of its intense volcanic and earthquake activity. These trenches mark some of the most geologically dramatic places on the planet, where the very crust of the Earth is being reshaped, and the Mariana Trench is the deepest of them all. As a gigantic chasm carved into the floor of the Pacific, far larger than most people realize, this trench is a monumental feature of our world. But the Mariana Trench doesn't exist in isolation. It forms a huge network of these deep trenches that traces the edge of the Pacific, marks the boundaries of the Great Plates. But despite the scale of it, one of the most curious things about it is how utterly hidden it remains. Anyone sailing across the surface of the ocean directly above it, you just wouldn't see anything but open water stretching to the horizon. As one of the grandest and most dramatic features on the face of our planet, it's hidden entirely beneath the waves. The Mariana Trench is a monumental wonder. 10. Born Where Two Tectonic Plates Collide So, one of the most natural questions you can ask about the Mariana Trench is how such a deep feature could have even come to exist. And the answer lies in the slow titanic forces that shape the surface of our planet. The trench sits at what geologists call a subduction zone. This is a place where two of the Earth's tectonic plates, those slabs of rock that make up its outer shell, meet and grind against one another, with one plate being forced down beneath the other. It's this collision, unfolding over huge spans of time, that's given birth to the At the trench, the Pacific Plate is diving down beneath the smaller Mariana Plate. It plunges into the hot interior of the Earth in a process that's continued on for millions of years. As the heavy oceanic crust of the Pacific Plate bends downward and sinks into the mantle, it drags down with it the seabed, carving out the deep, steep-sided trough that forms the trench. This is not a sudden event, it's an agonizingly gradual one. The plates are creeping past each other at roughly the speed at which fingernails grow, relentlessly deepening the chasm over eons. Part of the reason the trench is so deep is in the nature of the crust involved. The Pacific Plate here is among the oldest oceanic crust anywhere on the planet, and older crust is colder, denser, and heavier, meaning it sinks more steeply and to greater depths than the younger crust would. The same forces that created the trench also make the surrounding region intensely active, giving rise to earthquakes and the volcanic islands that lie nearby. The process unfolding at the trench is one of the cycles of the planet. It's just a continuous recycling of the Earth's crust that has shaped the surface of our world over billions of years. As the Pacific Plate is dragged down into the Earth at the trench, the ancient rock is just gradually consumed by the mantle. The reason this particular trench is the deepest of all is thought to lie partly in the age of nature of the crust being subducted there. It is old, but all of this unfolds over spans of time so long as to almost be beyond our comprehension. As a living demonstration of the geological force that continue to shape our planet, the Mariana Trench is an awe-inspiring feature. 9. Named After A Victorian Survey Ship The deepest point of the Mariana Trench, and indeed the deepest point of the entire planet, bears a rather charming name, with a history behind it. The Challenger Deep is named in honor of a Victorian-era British survey ship, the HMS Challenger. In the 1870s, this vessel undertook one of the most important voyages ever attempted, an expedition that circled the globe over the course of several years and laid the very foundations of modern science of oceanography. It was during this expedition in the mid-1870s that the crew of HMS Challenger first plumbed the depths of the trench, using the technology of the day, which meant lowering a weighted rope over the side of the ship and measuring how much line was played out before it struck the bottom. To their amazement, they recorded a depth far greater than anything previously known, and it offered humanity its first tantalizing hint of just how deep this part of the ocean was. Many decades later, in the 1950s, another British survey vessel returned to the same spot, this time armed with modern echo-sounding equipment that could measure depth by bouncing sound waves off the seafloor, and it confirmed that this was indeed the deepest known point in all the oceans, going down nearly 11 kilometers. In recognition of those pioneering voyages, the deepest point was named the Challenger Deep after the ships that had revealed it. It's a wonderful thought that the deepest place on Earth carries the name of a Victorian research vessel, and even the deepest-dwelling fish down there in the trench are named after the original expedition's crew members. This is a place steeped in the history of ocean exploration, and the Challenger Deep is a fitting tribute to the pioneers who first dared to measure the unfathomable. The voyage of the HMS Challenger in the 1870s was truly an undertaking. It lasted some four years and covered an immense distance as the ships crisscrossed the globe. It's widely regarded as the expedition that gave birth to the modern science of oceanography. Over the course of voyage, the scientists aboard gathered an astonishing wealth of data about the temperature, chemistry, and currents of the oceans, and discovered thousands of species of marine life that had never before been known to science. All of this was achieved with the relatively primitive tools of the Victorian age, and the measurement of the ocean in particular was a painstaking business, requiring the crew to lower a weighted line hundreds or thousands of meters over the side and just wait patiently for it to reach the bottom. It was a slow and imperfect method that nonetheless yielded the first inkling of the trench's depth. It's a fitting legacy for a voyage that did so much to open our eyes to the wonders of the deep. As the place that carries the name of this ship, and even lends the name to its deepest dwelling fish, the Challenger Deep is a lasting monument to the dawn of ocean science. 8. Even the Deepest Place on Earth is Polluted Well, you might imagine the deepest, most remote, and least accessible place on the entire planet would remain forever pristine, like an untouched wilderness. Sadly, though, this is not the case. In one of the more sobering facts about the trench, human pollution has managed to find its way down there. The trench, it turns out, is not the unspoiled sanctuary you might have hoped for. Plastic waste, the most persistent of the modern pollutants, has been discovered at an astonishing depth within the trench. There was a discarded plastic bag ranking among the deepest pieces of human debris ever recorded anywhere in the ocean, and when one modern explorer descended to the bottom of Challenger Deep in recent years, he reported the disheartening sight of what appeared to be a plastic wrapper resting on the seafloor. That was an unwelcome reminder that our rubbish had reached the deepest point even before he did. Maybe even more troubling than the visible plastic is what scientists have found hidden within the bodies of the trench's tiny little inhabitants. When researchers examined the shrimp-like amphipods living in the depths, they discovered a high concentration of toxic man-made chemicals, industrial pollutants that were banned decades ago, yet of which lingered on in the environment. These substances have gradually sunk through the ocean and accumulated in the creatures of the deep, making some of the most remote animals on the planet also among the most contaminated. This is a stark illustration of just how far-reaching the effects of pollution are, touching even the deepest corner of our planet. The way in which these pollutants really came to accumulate in the deepest place is troubling, but it is a revealing process. Many toxic man-made chemicals don't readily break down, and once they enter the environment, they tend to cling to particles that eventually sink through the water, drifting down along with the marine snow that feeds the creatures of the deep. As the scavengers in the trench consume this falling material, the harmful substances become concentrated in their bodies, and because these chemicals build up over time, they pass from prey to predator, and the deepest ecosystems can end up harboring surprisingly high levels of contamination. The discovery of this pollution in the trench does carry a powerful message, that there's no longer any part of our planet, however remote or inaccessible, that's entirely beyond the reach of our human influence. What we release into the environment can, and does, find its way to the very bottom of the oceans. That's a sobering thought, and it's made the Mariana Trench an unexpectedly important place for studying the global spread of pollution. Moving on to number 7. Vents, Mud Volcanoes, and a Lake of Liquid CO2 So far from just being a simple featureless pit, the Mariana Trench and the region around it conceal an array of bizarre features that make it one of the most fascinating places. Among the most remarkable are these hydrothermal vents, their cracks in the seafloor from which superheated, mineral-laden water will gush forth, warmed by volcanic activity churning beneath the crust. These vents create oases of life in the deep, supporting an extraordinary community of creatures that cluster around them, drawing energy not from the sun, but from the chemicals pouring out of the earth. The region is also home to some mud volcanoes. These are strange formations where mud and fluids will erupt upwards from deep within the crust, building unusual structures on the seafloor, and offering scientists a rare window into the process taking place far below. Yet maybe the most astonishing feature of all is a particular vent in the area, sometimes called the Champagne Vent. It releases carbon dioxide not as a gas, but in liquid form. It sends droplets bubbling up through the water in a manner that's reminiscent of a glass of sparkling wine. It's believed to be the only known place on the entire planet where liquid carbon dioxide is found venting in this way. It is a genuinely unique phenomenon. But these remarkable features do transform the trench into a kind of natural laboratory, allowing scientists to study life in some of the most extreme conditions imaginable. The strange chemistry of the vents do support organisms there that thrive entirely without sunlight. And as a place of hidden vents, erupting mud volcanoes, and bubbling lakes of liquid carbon dioxide, the Mariana Trench is a treasure trove of wonders. And deep down there in the dark, entire communities of organisms are flourishing around these vents, sustained not by sun, but by a process known as chemosynthesis. And this is a very important discovery. It shows life can exist in complete isolation from the light of the sun, drawing its energy from the planet itself. Taken together, all these features make the Mariana Trench an invaluable natural laboratory, not just for understanding the deep ocean, but for exploring the tantalizing possibility that similar conditions, and maybe even similar life, might exist in the hidden oceans on distant worlds. 6. The Deepest Fish And A Hard Limit For All Fish Among the many creatures that call the trench home, one has a particularly impressive record. The deepest dwelling fish known anywhere in the world's oceans lives here. Discovered relatively recently, the Mariana Snailfish is a small, delicate creature measuring only a few centimeters in length, with a translucent, pinkish body devoid of scales that give it the appearance of a pale, overgrown tadpole. Found at a depth of around 8,000 meters, it glides along near the bottom of the trench, and despite its fragile looks, it does reign as the dominant predator in its zone. The snailfish has almost no need for any eyesight in the eternal darkness of the deep down there, but its whole body is exquisitely adapted to cope with the crushing pressure. But the interesting thing about this fish concerns not the depth at which it lives, but the depth beyond which it, and every other fish, simply can't survive. Scientists have come to believe that there exists a hard physical limit at a depth of around 8,200 meters, below which no fish can exist at all, a boundary that no known species is able to cross. The reason for this limit is thought to lie in the chemistry that the fish use to protect their bodies against the immense pressure of the deep. They rely on a special protective substance to keep their cells functioning, and below a certain depth, the pressure becomes so overwhelming that even that clever adaptation no longer copes. This means that the very deepest stretches of the Mariana Trench that go on for kilometers below the level where the snailfish swims are entirely beyond the reach of any fish whatsoever. The adaptations to allow the to survive where no other fish can are pretty remarkable. Their body is soft and gelatinous, it lacks the swim bladder full of gas that many other fish possess. Its bones are thin and flexible rather than hard and rigid, and most importantly of all, its cells are protected by a special chemical substance that helps stabilize them against the pressure. Scientists believe that a fish would need to accumulate even greater amounts of this protective chemical to survive at greater depths, until around 8,200 meters. The concentration required would reach a point at which the fish's biology couldn't simply function, setting a firm ceiling, or rather a floor, beyond which no fish can go. When scientists finally examined the pale, fragile fish, they realized they were looking at something never before brought up from the depths. Below a level where the snailfish swims, the deepest stretches of the trench belong entirely to the hardy invertebrates and microbes, a realm where no fish can follow. 5. It's a Protected National Monument Given the extraordinary importance of the Mariana Trench and the unique ecosystems that it harbors, it will perhaps come as no surprise that a large portion of the region has been granted official protection. In 2009, the government of the United States established the Marianas Trench National Marine Monument. It's a huge marine area encompassing not only stretches of the trench itself, but also the hydrothermal vents, its mud volcanoes, and a great expanse of the surrounding water. It covers an area of hundreds of thousands of square kilometers, and it ranks among the largest protected marine areas anywhere on the entire planet. The trench falls under the jurisdiction of the United States because the nearby islands, including Guam and the Northern Mariana Islands, are American territories, giving the country responsibility for this underwater realm. By designating the area a national monument, the aim was to safeguard its exceptional natural wonders from potential threats like mining and commercial fishing, preserving the region in as pristine a state as possible for the benefit of science and future generations. The waters protected within the monument are ecologically valuable. Said to contain one of the greatest diversities of seamount and hydrothermal vent life known anywhere in the world, it's a treasure trove of often barely understood organisms. Protecting a place like this is no small matter. It represents a commitment to preserving an environment that we've only just begun to explore, and surely it still holds countless secrets waiting to be uncovered. As one of the largest protected marine areas on Earth, shielding a wealth of extraordinary life and geology from harm, the monument surrounding the Mariana Trench shows a growing recognition of just how precious this place is. The need to protect these places has grown more pressing in recent years as advancing technology has raised the prospect of mining the deep seafloor for valuable minerals, which are found in abundance in certain deep regions. And while these resources are tempting, the potential damage that mining could inflict upon these little-understood ecosystems is a matter of serious concern. Life down there in the cold dark tends to unfold at a leisurely pace, with many deep-sea organisms growing slowly and living for a very long time, which means that any damage done in a moment could take centuries or longer to heal. Enforcing a protection across so remote and enormous a stretch of ocean is no easy task, but the designation nevertheless represents an important commitment to safeguarding one of the 4. A Hollywood Director Dived It Alone In the history of attempts to reach the bottom of the Mariana Trench, one of the most famous and dramatic came in 2012. It was carried out by a rather unexpected figure, the celebrated Hollywood film director James Cameron, the creative force behind some of the highest-grossing films ever made. A lifelong ocean enthusiast as well as a filmmaker, Cameron descended entirely alone to the bottom of the Challenger Deep, becoming the first person in history ever to make a solo journey to the deepest point on Earth. This is a genuinely amazing undertaking. To achieve it, he piloted a specially-designed submersible known as the Deep-Sea Challenger, an unusual vertically-oriented craft that he had helped to develop over the course of several years, purpose-built to carry a single occupant safely to the crushing depths down there. The descent of the bottom took him little over two hours, and he plunged down through the dark until he reached the seafloor, 11 kilometers below the surface. He spent several hours exploring, filming, and collecting samples before beginning the long journey back up. The importance of this dive extended way beyond any personal achievement. It marked one of the first times in more than half a century, some 52 years, that any human had been traveling to the bottom of the Challenger Deep, the deepest point having remained unvisited by people since the very first descent. As both a serious scientific endeavor and a piece of documentary filmmaking, the dive captured the imagination of people around the world, and it brought fresh attention to the mysteries of the deep. By combining the resources of a Hollywood career with a genuine passion for exploration, James Cameron reminded the world that the deepest place on our own planet remains a frontier still waiting to be understood. That submersible that carried him to the bottom was a product of years of dedicated, secretive development. It was engineered specifically to overcome the immense challenges of reaching the deep. Rather than the horizontal shape of a conventional sub, the Deepsea Challenger was built to descend and descend vertically, plunging down through the water like a torpedo, standing on end. Cameron himself was closely involved in its creation, drawing on his lifelong fascination with the ocean, which had already led him to make numerous deep dives during the making of his films. The dive wasn't without its difficulties and dangers, as is inevitable when you're venturing into a hostile environment. The footage he captured shows findings from the expedition they were shared with the world through a documentary, bringing the wonders and mysteries of the deep trench to a huge global audience and inspiring fresh interest in ocean exploration. As a bold fusion of filmmaking artistry and a genuine scientific endeavor, James Cameron's solo journey to the bottom of the Mariana Trench was a landmark moment in the history of deep sea exploration. 3. A Modern Explorer Went Back Again And Again While the earliest journeys to the bottom of the Mariana Trench were rare and stuff of monumental one-off events, in 2019 a new era of deep sea exploration dawned, driven by American explorer Victor Vescovo. As part of an ambitious undertaking known as the Five Deeps Expedition, he aimed to reach the deepest point of each of the world's five oceans. Vescovo journeyed down to the bottom of the Challenger Deep and is submersible, the limiting factor, reaching a record-breaking depth and pushing even deeper than those who had gone before him. What set Vescovo's achievement apart wasn't just merely the depth he reached, but the fact that he became the very first person to ever descend to the bottom of the trench more than once, making a series of dives rather than just a single plunge. His submersible had been designed specifically to make repeated journeys to the deepest parts, unlike the earlier craft which had only made a single descent. And this one marked the beginning of a new age, in which the deepest point on Earth could be visited far more regularly than ever before. In a wonderful full circle moment that beautifully connected the pioneering past with the present day, one of the two men who had made the very first descent to the trench back in 1960 was present aboard Vescovo's surface support ship, watching on as a new generation carried the torch of exploration deeper. In the years that followed, still more people would make the journey, including the first women to ever reach the deepest point, as the explorer who transformed the bottom of the trench from an almost unreachable goal into a place that could be visited again and again, Victor Vescovo earns a distinguished place in our countdown. While the wider expedition, of which his Mariana Trench dives, formed a part which was genuinely historic, its goal was to reach the deepest point of each and every one of the world's five oceans, a feat that had never before been accomplished, and over the course of the expedition, Vescovo and his team journeyed to the bottom of one ocean after another, methodically ticking off the deepest points in the world. This marked a genuine turning point, it meant that the deepest reaches of every sea could now be visited far more routinely, and in the years that followed, the submersible carried a series of people down to the bottom. Alongside those descents, the expedition carried out valuable mapping and scientific work, and it added greatly to our knowledge of the deep ocean. As the explorer who ushered in a new era in which the bottom of the Mariana Trench could be reached again and again, Victor Vescovo has a distinguished place here. 2. More People Have Been To Space Than To The Bottom Of The Ocean So we come to a fact that maybe captures better than any other just how remote and unreachable the deepest point on Earth really is. Astonishing as it may sound, way more people have journeyed into the vastness of outer space than have ever descended to the bottom of the Challenger Deep. While well over 600 human beings have flown into space, and many thousands more have stood upon the summit of Mount Everest, the number of people who have reached the deepest point in the ocean is astonishingly small, numbering only a few dozen in all of history. For a stretch of more than 50 years, only two people had ever visited the bottom of the trench, the pioneers who first made the descent in 1960, and it wasn't until a famous solo dive in 2012 that a third person joined the ranks. Only in very recent years, with the advent of submersibles capable of making repeated journeys, has that number begun to climb. There's a cool detail that ties together humanity's two greatest frontiers. The first woman to ever reach the deepest point of the ocean was a former astronaut who had previously been in the weightlessness of space, thereby becoming the first person in history to have traveled to both the heights of orbit and to the very deepest place on Earth. That we've sent out so many more people upward into the sky than downward into the sea speaks volumes about how much of our own planet still lies beyond our reach, and it makes the rarity of these deep-sea journeys one of the most thought-provoking facts of all about the Mariana Trench. In some respects, reaching the bottom of the ocean poses challenges every bit as formidable as venturing into space. For a while, a spacecraft must withstand the emptiness of a vacuum. Deep-sea submersible has to resist the crushing pressure pushing inward from all sides, a force that grows more punishing with every meter of descent. Maybe the most striking measure of how little we've explored our own oceans is the fact that huge stretches of the seafloor are still unmapped in any detail. We possess better maps of the surfaces of other planets and moons than we do the bottom of our own oceans. This imbalance between our exploration of heights and depths just shows how much of our planet still awaits discovery just hidden beneath the waves. As a fact that lays bare the huge unexplored frontier lying right here on Earth, the rarity of journeys to the bottom of the Mariana Trench is among the most humbling of all. Number 1. The First Descent in 1960, and then the silence that followed. The single greatest chapter in the story of the Mariana Trench, the very first time human beings descended. On the 23rd of January 1960, two men achieved what many had thought impossible, journeying all the way to the bottom of the Challenger Deep and becoming the first people ever to set eyes upon the deepest place on the entire planet. Their names were Jacques Piccard, a Swiss oceanographer, and Don Walsh, an officer in the United States Navy, and their extraordinary feat is one of the greatest achievements in the history of exploration. The two men made their descent aboard a remarkable vessel called the Trieste, a type of deep diving craft which had been designed by Jacques Piccard's own father. The vessel was an ingenious contraption that consisted of a small, immensely strong steel sphere in which two men sat, suspended beneath a large float filled with gasoline to provide buoyancy, allowing it to sink slowly in the depths and then rise again. Squeezed together inside their cramped metal chamber, Piccard and Walsh began their long journey down to the darkness, a descent that would take them nearly five hours to complete. The voyage wasn't without its terrors. As the Trieste sank to tremendous depths, one of its outer window panes suddenly cracked with a loud bang that shook the entire vessel, a heart-stopping moment far beneath the waves. Undeterred, the two explorers pressed on, finally reaching the very bottom of the trench, where they came to rest upon the seafloor nearly 11 kilometers below the surface. Their arrival, however, had stirred up a great cloud of silt from the bottom, obscuring their view, and so they were able to spend only around 20 minutes at the deepest point on Earth before beginning the long ascent back toward the light. Even so, Piccard reporting glimpsing what he believed to be a fish, which was a tantalizing hint that life could exist even in this most extreme of places. The achievement of Piccard and Walsh, in its own way, is every bit as monumental as humanity's later journeys to the moon. This was a triumph of courage and engineering that carried human beings to the deepest point of their own world for the very first time. And yet, in a fact that speaks volumes about the difficulty and danger of this undertaking, no human being would return for 52 years. Yet there is something uniquely powerful about the presence of a human in such a place, seeing it with their own eyes, and for over half a century that experience belonged to Piccard and Walsh alone. Their claim to have glimpsed a living creature, though, at the bottom sparked some great excitement at the time. It suggested that even in the most extreme conditions imaginable, life could find a way. It stands alongside the great feats of mountaineering and space flights as one of the boldest journeys ever undertaken by human beings. And yet it remains far less celebrated than many lesser achievements. This is a triumph in the darkest depths of our world. The story of the Mariana Trench is ultimately a story about the limits of the human reach and the vastness of all that we've yet to discover. Even now, more than 60 years after Two Brave Men first touched its floor, this alien world of darkness, pressure, and cold is one of the least explored places anywhere in the universe. As we continue to gaze outward toward the distant stars, the deepest point of our own ocean stands as a humbling reminder that some of the greatest frontiers of all lie not far above our heads, but deep, deep beneath the waves.