The Swiss-designed Trieste, bought by the US Navy in 1958, was essentially a steel crew sphere hung beneath a float filled with petrol, which is lighter than water. The descent into the Mariana Trench took almost five hours. At the bottom the two men spent about 20 minutes, reporting that they saw what looked like a flatfish, although scientists later doubted it. A cracked outer window pane had shaken the vessel on the way down. No one returned to the Challenger Deep until 2012.
The bathyscaphe was the invention of Jacques Piccard's father, the Swiss physicist Auguste Piccard, who had earlier set altitude records in a balloon of his own design. Its principle was simple: a heavy steel sphere for the crew, just over two meters across, suspended beneath a large float filled with petrol for buoyancy, with iron shot as ballast that could be released to rise.
On January 23, 1960, Trieste began its descent at about 8:20 a.m. At around 9,000 meters the men heard a loud crack as an outer plexiglass window cracked under the pressure, and the sphere shook, but they continued. They reached the bottom at 1:06 p.m. The water outside pressed on the hull with more than a thousand times the pressure at the surface. The sinking stirred up so much fine sediment that they could take no photographs.
The ascent took about three hours. The Navy's achievement, during the early space race, drew worldwide attention, and President Eisenhower awarded both men medals. The film director James Cameron made the next crewed dive to the Challenger Deep, alone, in 2012. Walsh, then 81, was on the support ship.
Key people: Jacques Piccard, Don Walsh