Challenger Deep (bathyscaphe Trieste)

Challenger Deep, in the Mariana Trench in the western Pacific, is the deepest known point of the sea floor. On 23 January 1960, two men became the first people to reach its bottom, in a deep-diving vessel called the bathyscaphe Trieste.

The pilots were Swiss oceanographer Jacques Piccard and US Navy lieutenant Don Walsh. They reached a depth of about 10,916 metres, in a dive that was the final goal of the US Navy's Project Nekton. The record dive was the final goal of Project Nekton, a series of US Navy dives in the Pacific Ocean near Guam. Trieste is now on show in the National Museum of the United States Navy in Washington, D.C.

What was the Trieste?

Trieste was designed by Jacques's father, the Swiss scientist Auguste Piccard, and built in Italy. A bathyscaphe is a vessel that dives and moves without a cable to a ship. It had a heavy steel crew sphere hanging under a hull of tanks filled with petrol, which is lighter than water and gave it buoyancy.

To sink, it dropped iron shot ballast and flooded water tanks. The hull was more than 15 metres long, and the sphere held two people.

After the record dive

The US Navy bought Trieste in 1958 for about 267,000 US dollars. It was taken out of service in 1966 and has been on show since the 1980s in the National Museum of the United States Navy in Washington, D.C.

Sources give slightly different depths for the 1960 dive, from about 10,911 to 10,916 metres, because measuring so deep is difficult.

On the globe

Find it on the globe in the western Pacific over the Mariana Trench and zoom in to open its card.