The Triest and Challenger Deep

May 29, 2019

The crescent-shaped Marina Trench, nearly 1,600 miles long with an average wide of 43 miles, is just east of the Mariana Islands in the Pacific Ocean, just south of Japan. Near the southern end of the Trench is Challenger Deep, the deepest point in the Earth’s seafloor.

On January 23, 1960 Swiss engineer Jacques Piccard and Marine Technology Society member, U.S. Navy Lieutenant Don Walsh, traveled in the manned-submersible Triest to Challenger Deep. They were the first humans to journey to the bottom of the ocean.

On the trip down, they first crossed the mesopelagic (twilight) zone, approximately 3,300 feet below. Very dim light is visible at this level but not enough for plants to carry on photosynthesis and bioluminescent creatures begin to be observed.

The next depth zone crossed was the bathypelagic (midnight) zone. At 13,100 feet below the surface of the ocean there is no light penetration from the sun. The pressure is a crushing 5,850 pounds per square inch, the equivalent of positioning the average mid-size car on your body, one on every square inch.

Piccard and Walsh next passed through the abyssopelagic (abyssal) zone. Three-quarters of the ocean floor is found at this depth. It is pitch-black, water temperature is near freezing and the only creatures are a few invertebrates, such as basket stars and tiny squid.

Finally, the men in the Trieste reached the hadalpelagic (hadal) zone, named after the Greek god Hades, god of the Underworld. These forbidding, deepest points of the oceans are referred to as the trenches. Piccard and Walsh had reached the deepest point of the hadalpelagic zone, Challenger Deep, in the Mariana Trench.

The pressure was over 16,000 pounds pressing on each square inch of the Triest or about 1,099 times that of the ocean surface.

No one would visit Challenger Deep for another 50 years! In 1965, Don Walsh became one of the first members of the Marine Technology Society.

Excerpted from the book Advances in Marine Technology 1963-2013, published by the Marine Technology Society. For more information about MTS, visit


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