Picture a place deeper than Mount Everest is tall, with crushing pressure, total darkness, and freezing temperatures. Humanity assumed it had to be a barren wasteland. Instead we found it teeming with bizarre life and our own garbage.

This episode uncovers the human achievements required to reach the bottom of the Mariana Trench, the strange organisms that thrive there, and what this hidden world reveals about our connection to the planet. From weighted ropes to gasoline-filled bathyscaphes, it traces how we mapped the abyss and confronts the sobering truth that no true wilderness remains on Earth.

• How subduction of 170-million-year-old crust and flux melting forged the trench and fuels its volcanoes
• The 1960 Trieste descent by Walsh and Picard, and the disputed flatfish that was likely a sea cucumber
• Grapefruit-s ...