Challenger Deep

The Challenger Deep is the deepest known point in the Earth's seabed hydrosphere (the oceans), with a depth of 10,898 to 10,928 m (35,755 to 35,853 ft) by direct measurement from submersibles and slightly more by sonar bathymetry. It is located in the Pacific Ocean, at the southern end of the Mariana Trench near the Mariana Islands group. 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's bottom is about 11 km (7 mi) long and 1.6 km (1 mi) wide, with gently sloping sides. 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. It is located in the ocean territory of the Federated States of Micronesia, 1.6 km (1 mi) from its border with ocean territory associated with Guam. The depression is named after the British Royal Navy survey ship HMS Challenger, whose expedition of 1872–1876 made the first recordings of its depth. According to the August 2011 version of the GEBCO Gazetteer of Undersea Feature Names, the location and depth of the Challenger Deep are 11°22.4′N 142°35.5′E / 11.3733°N 142.5917°E / 11.3733; 142.5917 and 10,920 m (35,827 ft) ±10 m (33 ft). A 2014 study by Gardner et al. concludes that with the best of 2010 multibeam echosounder technologies a depth uncertainty of ±25 m (82 ft) (95% confidence level) on nine degrees of freedom and a positional uncertainty of ±20 to 25 m (66 to 82 ft) remains. The deepest point and its location recorded in the 2010 sonar mapping conducted by the US Center for Coastal & Ocean Mapping/Joint Hydrographic Center (CCOM/JHC) aboard USNS Sumner is 10,984 m (36,037 ft) at 11°19′48″N 142°11′57″E / 11.329903°N 142.199305°E / 11.329903; 142.199305 (11°19′47.650″N 142°11′57.498″E / 11.32990278°N 142.19930500°E / 11.32990278; 142.19930500). In November 2016 sonar mapping of the Challenger Deep area was conducted by the Royal Netherlands Institute for Sea Research (NIOZ)/GEOMAR Helmholtz Centre for Ocean Research Kiel aboard RV Sonne. Using a Kongsberg Maritime EM 122 multibeam echosounder system coupled to positioning equipment that can determine latitude and longitude the team determined that the Challenger Deep has a maximum depth of 10,925 m (35,843 ft) at 11°19′57″N 142°12′07″E / 11.332417°N 142.20205°E / 11.332417; 142.20205 (11°19.945′N 142°12.123′E / 11.332417°N 142.202050°E / 11.332417; 142.202050), with an estimated depth uncertainty of ±12 m (39 ft) (68% confidence level). The horizontal position of the grid point has an uncertainty of ±50 to 100 m (164 to 328 ft), depending on along-track or across-track direction. This depth (59 m (194 ft)) and position (about 410 m (1,345 ft) to the northeast) measurements differ significantly from the deepest point determined by the Gardner et al. (2014) study. The high water pressure at this depth makes designing and operating exploratory craft difficult. The first descent by any vehicle was by the manned bathyscaphe Trieste in 1960. This was followed by the unmanned ROVs Kaikō in 1995 and Nereus in 2009. In March 2012 a manned solo descent was made by film director James Cameron in the deep-submergence vehicle Deepsea Challenger. Between 28 April and 4 May 2019, the DSV Limiting Factor completed four manned dives to the bottom of Challenger Deep. Over many years, the search for the point of maximum depth has involved many different vessels. In 2014, a study was conducted regarding the determination of the depth and location of the Challenger Deep based on data collected previous to and during the 2010 sonar mapping of the Mariana Trench with a Kongsberg Maritime EM 122 multibeam echosounder system aboard USNS Sumner. This study by James. V. Gardner et al. of the Center for Coastal & Ocean Mapping-Joint Hydrographic Center (CCOM/JHC), Chase Ocean Engineering Laboratory of the University of New Hampshire splits the measurement attempt history into three main groups: early single-beam echo sounders (1950s-1970s), early multibeam echo sounders (1980s - 21st century), and modern (i.e., post-GPS, high-resolution) multibeam echo sounders. Taking uncertainties in depth measurements and position estimation into account the raw data of the 2010 bathymetry of the Challenger Deep vicinity consisting of 2,051,371 soundings from eight survey lines was analyzed. The study concludes that with the best of 2010 multibeam echosounder technologies after the analysis a depth uncertainty of ±25 m (82 ft) (95% confidence level) on 9 degrees of freedom and a positional uncertainty of ±20 to 25 m (66 to 82 ft) (2drms) remain and the location of the deepest depth recorded in the 2010 mapping is 10,984 m (36,037 ft) at 11°19′48″N 142°11′57″E / 11.329903°N 142.199305°E / 11.329903; 142.199305. The depth measurement uncertainty is a composite of measured uncertainties in the spatial variations in sound-speed through the water volume, the ray-tracing and bottom-detection algorithms of the multibeam system, the accuracies and calibration of the motion sensor and navigation systems, estimates of spherical spreading, attenuation throughout the water volume, and so forth. The 2009 and 2010 maximal depths were not confirmed by the series of dives Nereus made to the bottom during an expedition in May–June 2009. The direct descent measurements by several expeditions which have reported from the bottom, have fixed depths in a narrow range from 10,916 m (35,814 ft) (Trieste) to 10,911 m (35,797 ft) (Kaikō), to 10,902 m (35,768 ft) (Nereus) to 10,908 m (35,787 ft) (Deepsea Challenger) to 10,928 m (35,853 ft) ±10.5 m (34 ft) (DSV Limiting Factor). Although an attempt was made to correlate locations, it could not be absolutely certain that Nereus (or the other descents) reached exactly the same points found to be maximally deep by the sonar/echo sounders of previous mapping expeditions, even though one of these echo soundings was made by Nereus' mothership.