Seven Miles Down | Mariana Trench – The Season Finale

This is as far down as we go.Nearly seven miles below the surface of the Pacific Ocean, in a place named after the god of the underworld, lies the deepest point on Earth. The pressure at the bottom of Challenger Deep is more than 1,000 times what you feel on a normal day — enough to crush the air from human lungs in a fraction of a second. For most of human history, we assumed nothing could survive here.We were wrong. And in this season finale, we go all the way to the bottom to find out what's there.First, we meet the hadal snailfish — a pale, translucent, gelatinous fish that looks like it's falling apart, and is in fact one of the most sophisticated pressure-adapted organisms ever discovered. We break down the molecular secret that keeps its proteins from deforming under crushing weight, why that secret has a hard biological limit at 8,000 meters, and why that limit means even this fish can't reach the very bottom.Then we look at what feeds a world with no sunlight. The answer is a perpetual slow-motion blizzard — marine snow, falling every second of every day from the world above — funneled by the trench's steep walls into a thick, ancient ooze at the bottom. And we meet the creatures that live in that ooze: including the xenophyophore, the largest single-celled organism on Earth, the size of a mango, absorbing toxic heavy metals from the sediment and hosting an entire microbiome inside and around a single cell.And then, the hardest part. In 2019, the first person to reach the deepest measured point in Challenger Deep photographed a plastic bag in the sediment. A 2019 study found that 100 percent of amphipods sampled from the Mariana Trench contained plastic fibers in their digestive systems. Industrial chemicals banned in the 1980s are accumulating in trench animals at concentrations comparable to some of the most polluted coastal waters on Earth.The depth that took machines, engineering, and enormous courage to reach has been reached by a candy wrapper. Effortlessly. Simply by sinking.This episode ends where the season began: with the question of what life is, and where it ends. The Mariana Trench has an answer. There is no edge. There is no bottom. There is only what we choose to send there.Secrets of Earth is a nature documentary podcast for all ages, exploring the why and how behind the planet's most extraordinary life.