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See Mint Mobile for details. 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 1200 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 subbasins at the southern end of the trench. Recent bathymetry and submersible surveys show 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 35,876ft. To put that into perspective, it is further below the sea level than the top of Mount Everest is above sea level by about 6,000ft 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 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 8,100 184 meters, or 26,850ft. 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 of 10,863 meters, or 35,640ft. Coming much closer to the currently accepted depth, In August of 1957, a Soviet vessel named Vitsyaz measured a depth of 11,034 meters or 36,201ft, 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 23, 1960 when Swiss engineer Jacques Piccard and naval lieutenant Don Walsh descended to the bottom of Challenger Deep in the Bathyscape Trieste. The dive was conducted under the auspices of the US Navy which had purchased the Trieste from Auguste Picard, Jacques's 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 7 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 5 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 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 4 hours and 48 minutes to go from the surface to the bottom of the seafloor, sinking at a rate of a little under 1 meter or 3ft 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 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. Of 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. Kathryn Sullivan, who 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 Hadal Zone. The Hadal 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 sea floor 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 2000 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 plain. 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 4 to 5% 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 1500-1550 meters per second. With these extreme conditions, many of you are probably wondering, is there 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 piezophiles, which means pressure loving. These microbes metabolize carbon, nitrogen, sulfur and even methane, forming the base of the hadal 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 sea cucumbers 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 8200 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 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 Vescovo 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 and even from the most remote part of the trench. Laboratory analysis of amphiphods 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 on the show.
