Marianas Trench Descent

In January 1960, the bathyscaphe Trieste carried two men to the floor of the Challenger Deep, the deepest known point in the world's oceans. The dive, made by U.S. Navy Lieutenant Don Walsh and the Swiss oceanographer Jacques Piccard, reached a depth of roughly 10,900 meters (about 35,800 feet) in the western Pacific, near Guam. It remains one of the great feats of exploration, proving that humans could survive at the bottom of the sea's greatest abyss.

The Trieste was designed by Jacques's father, Auguste Piccard, a Swiss physicist who had earlier pioneered high-altitude balloon flights. He applied similar logic underwater: a small, thick-walled crew sphere hung beneath a large float filled with gasoline, which is lighter than water and resists compression. Iron shot served as ballast, released to rise. The first Trieste was built in Italy in the early 1950s and named for the city where it was constructed. In 1958 the U.S. Navy bought it, partly for its interest in deep-ocean research, and fitted it with a new, stronger crew sphere made in Germany. The Mariana Trench, formed where the Pacific Plate slides beneath another plate, was a natural target.

The dive took place on 23 January 1960. Walsh and Piccard descended for nearly five hours in a cramped sphere, in cold, dim conditions. Partway down, an outer window pane cracked under the pressure, shaking the vessel, but they continued. They spent only about twenty minutes on the bottom. They reported seeing a flatfish-like creature resting on the seabed, though scientists have since debated just what they saw and how clear the view was. Silt stirred up by the craft clouded the water, and they began the ascent without lingering. Their reading of the depth was later refined by other measurements, and modern estimates for the Challenger Deep vary slightly.

The dive's scientific value was real but modest. It suggested that life could exist at extreme depth and that deep water was not stagnant, which bore on debates about disposing of radioactive waste at sea. Its larger impact was symbolic. It came during the Cold War, as the United States and the Soviet Union competed in the race to space, and it showed that the ocean's depths were also reachable.

For decades afterward, no crewed vehicle returned to the bottom. In 2012 the filmmaker James Cameron made a solo dive in the Deepsea Challenger, and later expeditions, including those by Victor Vescovo beginning in 2019, have made repeated visits with modern submersibles. The Trieste's pioneering descent remains the first.