Challenger Deep and the Mariana Trench

Located in an arc sweeping to the east and south of the Mariana Islands and Guam is the deepest part of the ocean, the Mariana Trench. Running over 2,500 kilometers or 1,200 miles, the very deepest part of the trench is known as Challenger Deep. At the very bottom of the sea, there is no light, temperatures are almost freezing, and the pressure is enough to crush almost anything that might make it down there. It's so inhospitable that the number of people who have ever been there is about the same number who have visited the moon. Learn more about the Mariana Trench and Challenger Deep on this episode of Everything Everywhere Daily. As a podcaster, I'm often asked what podcasts I listen to. One of the shows I subscribe to and listen to every week is the Jordan Harbinger Show. The Jordan Harbinger Show is the top podcast that was named Best of Apple in 2018. One of my recent favorite episodes from this summer was the interview he did with Atassa Araxa Abrahimian, who explained how wealthy people can buy second passports overseas. On the show, Jordan dives into the minds of fascinating people, including everyone from athletes, authors, scientists, mobsters, spies, and hostage negotiators. If you like this podcast, you'll probably like the variety and in-depth interviews on the Jordan Harbinger Show. You can't go wrong with adding the Jordan Harbinger Show to your rotation. It's incredibly interesting and there's never a dull show. Search for the Jordan Harbinger Show. That's H-A-R-B as in boy, I-N as in Nancy, G-E-R on Apple Podcasts, Spotify, or wherever you listen to podcasts. I'm David Remnick, host of the New Yorker Radio Hour. There's nothing like finding a story you can really sink into that lets you tune out the noise and focus on what matters. In print or here on the podcast, the New Yorker brings you thoughtfulness and depth and even humor that you can't find anywhere else. So please join me every week for the New Yorker Radio Hour wherever you listen to podcasts. I've done previous episodes on some of the most extreme places on earth. None however comes close to being as extreme as the Mariana Trench and Challenger Deep. The Mariana Trench is an approximately 2,500 kilometer or 1,200 mile long crescent on the floor of the Western Pacific Ocean, south and east of Guam in the Mariana Islands. Its lowest point is Challenger Deep, a set of three adjacent sub basins at the southern end of the trench. Recent bathymetry and submersible surveys shows Western, Central, and Eastern pools each more than 10,850 meters deep, with the deepest surroundings in the Western and Eastern pools. Getting an exact measurement of the deepest point is actually kind of tricky. High resolution mapping in 2020 refined the picture somewhat. The problem is that even just the Challenger Deep section of the trench is rather large. So knowing you found the deepest spot rather than a deep spot is difficult. The most recent paper from the 2020 measurements puts the deepest point at 10,935 meters with an error of plus or minus 6 meters at a 95% confidence interval. In American units that converts to 35,876 feet. To put that into perspective, it is further below the sea level than the top of Mount Everest is above sea level by about 6,000 feet or 2,000 meters. So how did such an incredibly deep trench get created on the ocean floor? The trench formed through a geological process known as subduction, where two tectonic plates converge. Specifically, the Pacific plate is being pushed beneath the smaller Mariana plate, which is part of the Philippine sea plate, at a rate of about 2 to 3 inches per year. As the denser oceanic Pacific plate descends into the Earth's mantle, it creates this deep depression in the ocean floor. This subduction zone is also responsible for the volcanic Mariana Islands arc that runs parallel to the trench. This process has been ongoing for millions of years. The Mariana trench began forming approximately 50 to 60 million years ago during the Eocene epoch. There are multiple subduction zones around the world, especially in the Ring of Fire, and this just happens to be the deepest of them. The deepest part of the trench, Challenger Deep, is named after the HMS Challenger, a British Royal Navy survey ship that conducted the first systematic study of the world's oceans from 1872 to 1876. In 1875, the crew used weighted sounding lines and discovered an exceptionally deep area in the trench, which they measured at 8,184 meters or 26,850 feet, though this was significantly underestimated with their primitive equipment. This deep point was later named Challenger Deep in honor of the ship that made the first measurement. The next attempt to measure Challenger Deep didn't take place until 76 years later in 1951 when the HMS Challenger 2, named after the original, returned to the area and used echo sounding to measure a depth of 10,863 meters or 35,640 feet, coming much closer to the currently accepted depth. In August of 1957, a Soviet vessel named Vitziaz measured a depth of 11,034 meters or 36,201 feet, which remained the accepted depth for many years, though modern measurements suggest that this was slightly overestimated. Of course, once the deepest point on earth has been measured and identified, the next logical step would be for someone to visit. Here I should note that many people have commented that more people have been to space than have visited the bottom of the sea, and they often state this in a way that implies that it's the opposite of how it should be. Somehow, because Challenger Deep is on the planet earth, it should be easier to go there than to go into space. In many respects, going into space is actually easier. While a sufficiently wealthy person could probably more easily mount a mission to go to the bottom of Challenger Deep than space, from a pressure standpoint, being in space is actually much easier. Once pressure gets down to zero, that's it. However, pressure can theoretically keep increasing until you reach a black hole. The most famous early exploration occurred on January 23rd, 1960, when Swiss engineer Jacques Picard and US Navy Lieutenant Don Walsh descended to the bottom of Challenger Deep in the bath escape, Trieste. The dive was conducted under the auspices of the US Navy, which had purchased the Trieste from Auguste Picard, Jacques' father, and modified it for extreme depths. The Trieste was not a typical submarine. It was a bath escape, which is a free-diving, deep-sea craft designed for vertical descent, not horizontal travel. The crew sat inside of a seven-foot diameter steel sphere at the bottom of the craft, capable of withstanding the immense pressures of the deep. The walls of the sphere were 12.7 centimeters or five inches thick. There was barely enough room for two men and equipment. The pressure inside the sphere was kept at one atmosphere, so no decompression was needed after the dive. Above the sphere, there was a 15-meter long float that was filled with gasoline. Gasoline was used because it's less dense than water and incompressible, making it ideal for buoyancy even under high pressures. The craft carried iron pellets as ballast. These were released magnetically at the end of the dive to allow the Trieste to rise. It took four hours and 48 minutes to go from the surface to the bottom of the seafloor, sinking at a rate of a little under one meter or three feet per second. They spent about 20 minutes at the bottom before releasing their ballast and rising to the surface. The ascent took another three hours and 15 minutes. So just how strong is the pressure at Challenger Deep? It's approximately 1,100 atmospheres or about 16,000 pounds of pressure per square inch. It would be the equivalent weight of the entire Empire State Building being put on an area the size of your foot. An average naval submarine is only rated to dive about 3% of the depth of Challenger Deep. No one else would make the trip to the bottom of Challenger Deep for another 52 years. The next person to do it was Director James Cameron, who descended in the Deep Sea Challenger in 2012. He spent three hours at the bottom and recorded what he saw in high-definition video. As of the recording of this episode, 27 people have been to Challenger Deep, whereas only 24 people have ever landed on or have been in orbit around the moon. A special note is Victor Vescovo. He made the third ever dive in 2019 and has completed a total of 15 Challenger Deep descents. Two astronauts have been to Challenger Deep. Catherine Sullivan went in 2020 and Richard Garriott, the creator of the Ultima game series, who went in 2021. So what's it like down there? Challenger Deep lies in what is known as the "Hattle Zone." The "Hattle Zone" gets its name from the word "Hades." For starters, there's a whole lot of nothing. People who have been there have described it as being like on an enormous salt flat. It's mostly sediment with few recognizable features. It's also totally dark. There is no light in the ocean that goes beyond 300 meters, so Challenger Deep is basically like being inside of a cave in terms of light. The temperature of the water is about 34 degrees Fahrenheit or 1 degree Celsius, just above freezing. This extremely cold, dense water originally sank near the poles, mainly in the southern ocean around Antarctica and in the North Atlantic, where surface water becomes cold and salty enough to sink to the ocean floor. Once that water sinks, it spreads slowly along the bottom of the world's oceans following gradients in temperature, salinity, and seafloor topography. It creeps along like an invisible current system thousands of meters below the surface. At the depth of Challenger Deep, circulation is extremely sluggish. Water there is the oldest in the world's oceans because it's the endpoint of the conveyor belt. Because it's isolated from most bottom currents, water in Challenger Deep may be 2,000 years old or more before being replaced. Vertical mixing of water is weak but not non-existent. Occasional deep interval waves, earthquake induced turbulence, and density-driven microcurrents will allow some exchange of water and dissolved gases between the trench and the adjacent abyssal plane. Water also acts differently with this much pressure. Under normal circumstances, water doesn't compress. This is why hydraulics work. However, at Challenger Deep, water does slightly compress. At the surface, seawater density averages about 1.027 grams per cubic centimeter. At the bottom of Challenger Deep, it's 1.071 grams per cubic centimeter. That's about a four to five percent increase in density compared to surface seawater, which is actually an enormous amount for water. As a result, the speed of sound is considerably faster at around 1,500 to 1,550 meters per second. With these extreme conditions, many of you are probably wondering, is their life this far down? The answer is yes, though it's unlike anything we encounter at the surface. The problem is that there is no light and very little dissolved oxygen in the water. There are a fair number of species of microbes at this level that have been discovered in multiple missions to Challenger Deep. Many of these are piezofiles, which means pressure-loving. These microbes metabolize carbon, nitrogen, sulfur, and even methane, forming the base of the Haddle food chain. Among multicellular creatures, there are amphipods, small shrimp-like crustaceans that have been observed. They survive by scavenging organic detritus that sinks down from above. Nematodes and secucumbers have also been observed in sediment samples. One thing that has never been observed at Challenger Deep are fish or other vertebrates. The deepest known fish, the Haddle snailfish, lives on the trench slopes up to about 8,200 meters, but no deeper. It's likely because cellular membranes and enzymes can't function properly beyond about 8,400 or 8,600 meters. There is one other thing that has been found at the deepest point on Earth - garbage. When explorers first reached Challenger Deep in 1960, they reported seeing only pale sediments and a few solitary creatures. At the time, it was considered a pristine environment untouched by any human activity. In 2019, during the Five Deeps expedition, Victor Viscovo filmed what appeared to be a plastic bag and several candy or food wrappers lying on the seafloor at nearly 10,900 meters. Later dives found other fragments of plastic and fabric mixed into the sediment. Similar findings were reported by Chinese expeditions in 2020 and 2021, which retrieved samples containing microplastic fibers, even from the most remote part of the trench. Laboratory analysis of amplifods collected from Challenger Deep revealed that their bodies contained traces of persistent organic pollutants, some of which had been banned decades ago. Because water at this level moves so slowly, whatever makes it this far down will remain there potentially for thousands of years. Challenger Deep is the most extreme environment on planet Earth. It's extremely difficult to get to and once you're there, you can't stay very long. Yet despite being so inhospitable, life manages to find a way. Life and garbage. The executive producer of everything everywhere daily is Charles Daniel. The associate producers are Austin Otkin and Cameron Kiefer. My big thanks go to everyone who supports the show over on Patreon. Your support helps make this podcast possible. And I also want to remind everyone about the community groups on Facebook and Discord. That's where everything happens that's outside the podcast and links to those are available in the show notes. As always, if you leave a review on any major podcast app or in the above community groups, you too can have it read in the show.