Challenger Deep is the deepest known point in Earth’s oceans, first reached by Trieste in 1960.
On 23 January 1960, Swiss oceanographer Jacques Piccard and U.S. Navy lieutenant Don Walsh descended in the bathyscaphe Trieste. They reached the floor of the Mariana Trench in the western Pacific, at a depth of roughly 10,900 metres, though modern measurements vary by method and location.
Challenger Deep is named after HMS Challenger, whose 19th-century expedition made important deep-ocean measurements. It consists of several small basins rather than one perfectly uniform pit.
The descent demonstrated that life could exist under extraordinary pressure. Modern crewed and uncrewed vehicles have returned to the site, but Trieste’s dive remains one of the defining achievements in ocean exploration.