Beginner 8 minutes
Deep-sea exploration: going where no one can dive
Bathyspheres, bathyscaphes, submersibles and robots, and how much is still unexplored
A recreational diver reaches forty meters. A saturation diver, a few hundred. The ocean's average depth exceeds three thousand, and its deepest point passes ten thousand. For almost the entire ocean, diving isn't an option: you have to go inside something.
In this article you'll see how the part of the ocean where you can't dive was explored, from the first spheres hanging on a cable to today's robots, which discoveries changed our idea of life, and how much is still left to look at.
It's the context that gives scale to everything else in this encyclopedia: diving occupies an extremely thin band of the water column, and what lies beneath it is known far worse than the surface of other planets.
The first spheres
The first real solution to going down wasn't to try to breathe the gas outside: a steel sphere at interior atmospheric pressure, hung on a cable from a ship. In the 1930s, William Beebe and Otis Barton's bathysphere descended past nine hundred meters with two people inside.
The observations from those descents were astonishing for the time: abundant bioluminescence, unknown organisms, and confirmation that the lightless zone was densely inhabited, something net sampling hadn't been able to show.
The problem with the cable is obvious: the sphere can't move or go deeper than the cable itself can bear. The solution came with the bathyscaphe, a vehicle with its own buoyancy based on a float filled with a liquid less dense than water and droppable ballast.
In 1960, the bathyscaphe Trieste, with Jacques Piccard and Don Walsh on board, reached the bottom of the Mariana Trench, below ten thousand meters. It was the deepest point ever reached by human beings, and it wouldn't be repeated for decades.
That descent settled a question that had been open: yes, there is life at the deepest point of the ocean. The pressure there exceeds a thousand atmospheres.
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