Challenger Deep

Challenger Deep, series of three seafloor basins located at the bottom of a steep-walled submarine valley in the Mariana Trench of the western Pacific Ocean, at 11°22′ N 142°35′ E. The Challenger Deep is the lowest point of the oceans and Earth’s lowest point with respect to surface elevation, plunging to an estimated 10,935 meters (35,876 feet, or roughly 6.8 miles) below sea level. The site is named for the HMS Challenger, an oceanographic survey ship that first charted the depth of the ocean in the region in 1875 (see also Challenger Expedition). It was first explored by Swiss oceanographer Jacques Piccard and U.S. Navy officer Don Walsh in 1960.

The Challenger Deep, which lies within the territory of the Federated States of Micronesia, is divided into the eastern, central, and western basins formed by the subduction of the Pacific Plate beneath the Philippine Plate (see also plate tectonics). Located within the southern arc of the Mariana Trench roughly 322 km (200 miles) southwest of Guam, the basins occur across a 40-km (roughly 25-mile) axis. Researchers have yet to identify conclusively which of the three is the deepest, but there is general agreement that hydrostatic pressures measured near the bottom of these basins are greater than 1,089 standard atmospheres (16,000 pounds per square inch).

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Piccard and Walsh were the first human beings to journey to the Challenger Deep, completing their descent and return aboard the bathyscaphe Trieste on January 23, 1960. The descent, which reached 10,916 meters (35,814 feet) below sea level, took five hours and resulted in a cracked plexiglass exterior window. People would not visit the Challenger Deep again until 2012, when Oscar-winning Canadian director and explorer James Cameron reached a depth of 10,898 meters (35,756 feet) in a solo dive aboard the submersible Deepsea Challenger.

Between April 2019 and the end of 2022, there were 20 crewed visits to the Challenger Deep to survey the three basins. The list of people making descents includes Kelly Walsh (Don Walsh’s son), American oceanographer and astronaut Kathryn Sullivan, and American investor-adventurer Victor Vescovo, who visited the Challenger Deep a record 15 times between April 2019 and July 2022. In addition, several probes and autonomous submersibles have explored the Challenger Deep.