Where Is Challenger Deep? Location, Depth and Who Has Been There

Where is Challenger Deep? It lies at the southern end of the Mariana Trench in the western Pacific Ocean, about 320 km (200 mi) southwest of Guam. The position is roughly 11 degrees 22 minutes north, 142 degrees 35 minutes east. It is the deepest known point of the seabed on Earth. The maximum measured depth is about 10,935 meters (35,876 ft) below sea level, quoted with an uncertainty of a few meters.

It is not a single pit. Challenger Deep is a series of three seafloor basins sitting at the bottom of a steep walled submarine valley within the trench, and modern surveys resolve them separately. The deepest sounding comes from the western basin.

How deep that really is

Some comparisons make the number usable. Mount Everest, at 8,849 meters (29,032 ft), would sit entirely below the surface if it were placed in Challenger Deep, with more than two kilometers of water still above the summit. Average ocean depth is about 3,682 meters (12,080 ft), so the trench floor is nearly three times deeper than the typical seabed a ship passes over.

The pressure at that depth is around 1,100 times atmospheric pressure at the surface, in the region of 1,086 bar or about 15,750 psi. Every square centimeter of a submersible hull carries roughly a metric ton of load. That is the engineering problem that kept the deepest point of the ocean visited fewer times than the surface of the Moon has been walked on.

Why a trench exists there at all

The Mariana Trench is a subduction zone. The Pacific Plate is being forced beneath the smaller Mariana Plate, and where the descending plate bends downward it creates a long, narrow, arc shaped depression in the seabed. The trench runs for well over 2,500 km (1,550 mi) with a characteristic crescent shape, and Challenger Deep sits at its southern extremity.

Subduction also explains the string of volcanic islands to the west of the trench. Material carried down with the descending plate releases water into the overlying mantle, lowering its melting point and feeding the volcanic arc that formed the Mariana Islands.

Where the name comes from

The feature is named after HMS Challenger, the Royal Navy corvette converted for the pioneering Challenger expedition of 1872 to 1876. Working a sounding line by hand, the ship recorded an exceptional depth in this area in 1875. That single sounding identified the location more than eighty years before anyone reached the bottom.

The name carried through to later survey work by HMS Challenger II in the 1950s, which refined the position and the depth using echo sounding.

Who has actually been to the bottom

Crewed descents to Challenger Deep remain rare events.

• 1960. Jacques Piccard and Don Walsh reached the bottom in the bathyscaphe Trieste, the first crewed descent, spending only a short time on the seafloor after their descent stirred up sediment.
• 2012. James Cameron made the first solo crewed descent in the submersible Deepsea Challenger, purpose built for the dive.
• 2019 onward. Victor Vescovo reached the deep in the submersible Limiting Factor as part of a project to visit the deepest point of each ocean, and repeat dives since have carried a number of scientists and guest divers, including landings by uncrewed and robotic vehicles.

Uncrewed landers and remotely operated vehicles have visited far more often, and they have done most of the useful science, returning sediment cores, water samples and observations of hadal amphipods and other life adapted to the pressure.

Jurisdiction and why the answer is not simple

Challenger Deep lies in an area of complex maritime jurisdiction in the western Pacific. Reference sources place it within the ocean territory associated with the Federated States of Micronesia, while the northern reaches of the Mariana Trench lie within United States jurisdiction connected to Guam and the Commonwealth of the Northern Mariana Islands, where the Mariana Trench Marine National Monument was established. Research expeditions therefore need to establish permissions carefully before working there.

What deep water means for ships passing over

A merchant ship crossing the region gets no useful reading from its echo sounder. Standard navigational echo sounders are designed for shallow water and shelf depths and simply lose the bottom in the open Pacific, so soundings on the chart in these areas come from dedicated hydrographic survey and satellite derived bathymetry rather than from passing traffic.

The wider point matters for anyone planning ocean passages. Large parts of the seabed remain poorly surveyed, which is what international projects such as Seabed 2030 exist to fix. Charted depths in remote deep water can rest on very sparse data, and uncharted seamounts have been found by ships hitting them. Deep water on a chart is not the same as surveyed water.

Our Navigation and Seamanship section covers chart source data, zones of confidence and passage planning in open ocean.

Charts are an inspection item, not a convenience. SOLAS Chapter V requires a ship to carry adequate and up-to-date charts and publications for the intended voyage, and port state control officers under the Paris MoU and Tokyo MoU check the corrections held on board. Charts uncorrected, or missing for the passage, is one of the deficiencies that draws a detention.

The failure this region is known for is a chart that was simply wrong. In January 2005 the submarine USS San Francisco struck an uncharted seamount at speed near Guam, killing one crew member and injuring dozens. Satellite derived bathymetry resolves broad shape rather than individual pinnacles, so a printed sounding in remote deep water can rest on no direct measurement at all.

Sources and further reading

• Challenger Deep
• Challenger Deep - Depth, Expeditions and Facts - Britannica
• Deepest Part of the Ocean - Geology.com
• The Mariana Trench - DEEPSEA CHALLENGE

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