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The Challenger Deep is the deepest known point of the seabed of Earth, located in the western Pacific Ocean at the southern end of the Mariana Trench, in the ocean territory of the Federated States of Micronesia. According to the GEBCO Gazetteer of Undersea Feature Names the depression's depth is 10,920 ± 10 m (35,827 ± 33 ft) at 11°22.4′N 142°35.5′E, although its exact geodetic location remains inconclusive and its depth has been measured at 10,902–10,929 m (35,768–35,856 ft) by deep-diving submersibles, remotely operated underwater vehicles, benthic landers, and sonar bathymetry. The differences in depth estimates and their geodetic positions are scientifically explainable by the difficulty of researching such deep locations. The depression is named after the British Royal Navy survey ships HMS Challenger, whose expedition of 1872–1876 first located it, and HMS Challenger II, whose expedition of 1950-1952 established its record-setting depth. The first descent by any vehicle was by the bathyscaphe Trieste in January 1960. In March 2012, a solo descent was made by film director James Cameron in the deep-submergence vehicle Deepsea Challenger. As of July 2022, 27 people have descended to Challenger Deep. Topography The Challenger Deep is a relatively small slot-shaped depression in the bottom of a considerably larger crescent-shaped oceanic trench, which itself is an unusually deep feature in the ocean floor. The Challenger Deep consists of three basins, each 6 to 10 km (3.7 to 6.2 mi) long, 2 km (1.2 mi) wide, and over 10,850 m (35,597 ft) in depth, oriented in echelon from west to east, separated by mounds between the basins 200 to 300 m (660 to 980 ft) higher. The three basins feature extends about 48 km (30 mi) west to east if measured at the 10,650 m (34,941 ft) isobath. Both the western and eastern basins have recorded depths (by sonar bathymetry) in excess of 10,920 m (35,827 ft), while the center basin is slightly less deep. The closest land to the Challenger Deep is Fais Island (one of the outer islands of Yap), 287 km (178 mi) southwest, and Guam, 304 km (189 mi) to the northeast. Detailed sonar mapping of the western, center and eastern basins in June 2020 by the DSSV Pressure Drop combined with manned descents revealed that they undulate with slopes and piles of rocks above a bed of pelagic ooze. This conforms with the description of Challenger Deep as consisting of an elongated seabed section with distinct sub-basins or sediment-filled pools. Surveys and bathymetry Over many years, the search for, and investigation of, the location of the maximum depth of the world's oceans has involved many different vessels, and continues into the twenty-first century. The accuracy of determining geographical location, and the beamwidth of (multibeam) echosounder systems, limits the horizontal and vertical bathymetric sensor resolution that hydrographers can obtain from onsite data. This is especially important when sounding in deep water, as the resulting footprint of an acoustic pulse gets large once it reaches a distant sea floor. Further, sonar operation is affected by variations in sound speed, particularly in the vertical plane. The speed is determined by the water's bulk modulus, mass, and density. The bulk modulus is affected by temperature, pressure, and dissolved impurities (usually salinity). 1875 – HMS Challenger In 1875, during her transit from the Admiralty Islands in the Bismarck Archipelago to Yokohama in Japan, the three-masted sailing corvette HMS Challenger attempted to make landfall at Spanish Marianas (now Guam), but was set to the west by "baffling winds" preventing her crew from "visiting either the Carolines or the Ladrones." Their altered path took them over the undersea canyon which later became known as the Challenger Deep. Depth soundings were taken by Baillie-weighted marked rope, and geographical locations were determined by celestial navigation (to an estimated accuracy of two nautical miles). One of their samples was taken within fifteen miles of the deepest spot in all of Earth's oceans. On 23 March 1875, at sample station number #225, HMS Challenger recorded the bottom at 4,475 fathoms (26,850 ft; 8,184 m) deep, (the deepest sounding of her three-plus-year eastward circumnavigation of the Earth) at 11°24′N 143°16′E – and confirmed it with a second sounding at the same location. The serendipitous discovery of Earth's deepest depression by history's first major scientific expedition devoted entirely to the emerging science of oceanography, was incredibly good fortune, and especially notable when compared to the Earth's third deepest site (the Sirena Deep only 150 nautical miles east of the Challenger Deep), which would remain undiscovered for another 122 years. 1951 – SV HMS Challenger II Seventy-five years later, the 1,140-ton British survey vessel HMS Challenger II, on her three-year westward circumnavigation of Earth, investigated the extreme depths southwest of Guam reported in 1875 by her predecessor, HMS Challenger. On her southbound track from Japan to New Zealand (May–July 1951), Challenger II conducted a survey of the Marianas Trench between Guam and Ulithi atoll, using seismic-sized bomb-soundings and recorded a maximum depth of 5,663 fathoms (33,978 ft; 10,356 m). The depth was beyond Challenger II's echo sounder capability to verify, so they resorted to using a taut wire with "140 lbs of scrap iron", and documented a depth of 5,899 fathoms (35,394 ft; 10,788 m). The Senior Scientist aboard Challenger II, Thomas Gaskell, recalled: [I]t took from ten past five in the evening until twenty to seven, that is an hour and a half, for the iron weight to fall to the sea-bottom. It was almost dark by the time the weight struck, but great excitement greeted the reading...In New Zealand, the Challenger II team gained the assistance of the Royal New Zealand Dockyard, "who managed to boost the echo sounder to record at the greatest depths". They returned to the "Marianas Deep" (sic) in October 1951. Using their newly improved echo sounder, they ran survey lines at right angles to the axis of the trench and discovered "a considerable area of a depth greater than 5,900 fathoms (35,400 ft; 10,790 m)" – later identified as the Challenger Deep's western basin. The greatest depth recorded was 5,940 fathoms (35,640 ft; 10,863 m), at 11°19′N 142°15′E. Navigational accuracy of several hundred meters was attained by celestial navigation and LORAN-A. As Gaskell explained, the measurement was not more than 50 miles from the spot where the nineteenth-century Challenger found her deepest depth [...] and it may be thought fitting that a ship with the name Challenger should put the seal on the work of that great pioneering expedition of oceanography.The term "Challenger Deep" came into use after this 1951–52 Challenger circumnavigation, and commemorates both British ships of that name involved with the discovery of the deepest basin of the worl.... Discover the Sally Fryer Dietz popular books. Find the top 100 most popular Sally Fryer Dietz books.