Deeper Than Everest is Tall

At its deepest point—the Challenger Deep—the Mariana Trench plunges nearly 11,000 meters (36,000 feet) beneath sea level. To put that in perspective: if Mount Everest were dropped into the trench, its peak would still be over a mile underwater.

Located east of the Mariana Islands, this abyss is the result of tectonic forces. Here, the Pacific Plate is slowly sliding beneath the smaller Philippine Sea Plate, a process known as subduction. Over millions of years, this collision has carved out one of the most extreme environments on Earth.

Life in the Pressure Cooker

This is the realm of extremophiles—organisms that challenge what we think life needs to survive. Some scientists believe similar life forms might exist on icy moons like Europa or Enceladus, where oceans lie beneath frozen crusts.

The crushing pressure is over a thousand times what we feel at sea level, the surroundings are not dark but black, and the temperature is near-freezing. Yet, against all odds, an array of remarkable creatures have adapted to thrive there. One of the most iconic is the Mariana snailfish, a ghostly, translucent animal with a soft, scaleless body and paddle-like fins. Delicate and almost formless, it looks more like a drifting jelly sculpture than a fish—perfectly evolved to withstand pressures that would crush a submarine. 

Scavenging the seafloor are swarms of amphipods, shrimp-like crustaceans with hard, segmented shells that flash with a pale iridescence. Some are nearly an inch long, others no bigger than a grain of rice, yet all are tireless recyclers, feeding on sunken debris from the surface world—including fallen whales, and disturbingly, plastic microfibres. 

Hovering just above the trench floor are holothurians, or deep-sea sea cucumbers—bloated forms with gelatinous sails or legs, some trailing luminous threads like slow-moving jellyfish. And scattered through the mud are the surreal xenophyophores, giant single-celled organisms that build intricate, shell-like casings from sand grains and minerals. They resemble miniature coral reefs, unmoving but teeming with microbial life. 

And then there are the microbes, tiny lifeforms that feast on chemicals leaching from rocks or even oil and methane seeping from the seafloor.

Together, these strange and spectral beings form a living mosaic of adaptation, persistence, and mystery—testament to life’s refusal to yield, even in the blackest depths of the Earth.

A Deep Well of Mysteries

Despite a handful of crewed descents and robotic missions, most of the trench remains unexplored. Every visit uncovers new questions:

• What other strange creatures still lurk in the darkness?
• Could unknown species hold secrets beneficial to medicine or biotechnology?
• How does deep Earth geology interact with these extreme marine ecosystems?
• And perhaps most shockingly—how did human-made plastic waste and toxic pollutants like PCBs end up even here, in one of the most remote places on Earth?

Why It Matters

Studying the Mariana Trench is not just about satisfying curiosity. It helps us understand the limits of life, the inner workings of our planet, and the far-reaching consequences of human activity. It’s a reminder that the ocean is not only vast and very beautiful, but also deeply connected to our future.

The trench is more than a geological oddity. It’s a living, breathing mystery that still guards its secrets with the deepest silence.

Stay tuned for the next instalment in our Ocean Mysteries series, where we’ll dive into the ghostly glow of bioluminescent life in the deep sea.

(c) Ila France Porcher

author of The True Nature of Sharks