Challenger Deep - History of Depth Mapping From The Surface

History of Depth Mapping From The Surface

Over the years the search for the point of maximum depth has involved many vessels.

• The HMS Challenger expedition (December 1872 – May 1876) first sounded the depths now known as the Challenger Deep. This first sounding was made on 23 March 1875 at station 225. The reported depth was 4,475 fathoms (26,850 ft; 8,184 m) at 11°24′N 143°16′E / 11.4°N 143.267°E / 11.4; 143.267, based on two separate soundings.

• A 1912 book, The Depths of the Ocean by Sir John Murray, records the depth of the Challenger Deep as 31,614 ft (9,636 m), reporting the sounding taken by the converted navy collier USS Nero in 1899. Murray was one of the expedition scientists.

• In 1951, about 75 years after its original discovery, the entire Mariana Trench was surveyed by a second Royal Navy vessel, captained by George Stephen Ritchie (later Rear Admiral Ritchie); this vessel was also named HMS Challenger, after the original expedition ship. This survey recorded the deepest part of the trench using echo sounding, a more precise and easier way to measure depth than the sounding equipment and drag lines used in the original expedition. A depth of 5,960 fathoms (35,760 ft; 10,900 m) was measured at 11°19′N 142°15′E / 11.317°N 142.25°E / 11.317; 142.25.

• The maximum surveyed depth of the Challenger Deep was reported in 1957 by the Soviet vessel Vityaz recording a spot 11,034 metres (36,201 ft) ±50 m (164 ft) deep at 11°20.9′N 142°11.5′E / 11.3483°N 142.1917°E / 11.3483; 142.1917. It was dubbed the Mariana Hollow and is listed in many reference sources, including the Encyclopædia Britannica, articles in National Geographic and on maps. The pressure at this depth is approximately 1,099 times that at the surface, or 111 MPa (16,099 psi).

• In 1959 the US Navy research vessel RV Stranger using bomb-sounding surveyed a maximum depth of 10,915 m (35,810 ft) ±10 m (33 ft) at 11°20.0′N 142°11.8′E / 11.333°N 142.1967°E / 11.333; 142.1967.

• In 1962 the US Navy research vessel RV Spencer F. Baird using a frequency-controlled depth recorder surveyed a maximum depth of 10,915 m (35,810 ft) ±10 m (33 ft) at 11°20.0′N 142°11.8′E / 11.333°N 142.1967°E / 11.333; 142.1967.

• In 1975 and 1980 the US Navy research vessel RV Thomas Washington using a precision depth recorder with satellite positioning surveyed a maximum depth of 10,915 m (35,810 ft) ±10 m (33 ft) at 11°20.0′N 142°11.8′E / 11.333°N 142.1967°E / 11.333; 142.1967.

• In 1984, the survey vessel Takuyo from the Hydrographic Department of Japan, used a narrow, multi-beam echo sounder to take a measurement of 10,924 m (35,840 ft) ±10 m (33 ft) at 11°22.4′N 142°35.5′E / 11.3733°N 142.5917°E / 11.3733; 142.5917.

• In 1998 a regional bathymetric survey of the Challenger Deep was conducted by the Deep Sea Research Vessel RV Kairei, from the Japan Agency for Marine-Earth Science and Technology, using a SeaBeam 2112 multibeam echosounder. The regional bathymetric map made from the data obtained in 1998 shows that the greatest depths in the eastern, central, and western depressions are 10,922 m (35,833 ft) ±74 m (243 ft), 10,898 m (35,755 ft) ±62 m (203 ft), and 10,908 m (35,787 ft) ±36 m (118 ft), respectively, making the eastern depression the deepest of the three.

• In 1999 and 2002 the RV Kairei revisited the Challenger Deep. The cross track survey in the 1999 RV Kairei cruise shows that the greatest depths in the eastern, central, and western depressions are 10,920 m (35,827 ft) ±10 m (33 ft), 10,894 m (35,741 ft) ±14 m (46 ft), and 10,907 m (35,784 ft) ±13 m (43 ft), respectively, which supports the results of the 1998 survey. The detailed grid survey in 2002 showed that the deepest site is located in the eastern part of the eastern depression around 11°22.260′N 142°35.589′E / 11.371°N 142.59315°E / 11.371; 142.59315, with a depth of 10,920 m (35,827 ft) ±5 m (16 ft), about 290 m (950 ft) southeast of the deepest site determined by the survey vessel Takuyo in 1984 and about 240 m (790 ft) east of the deepest place determined by the 1998 RV Kairei survey.

• On 1 June 2009 sonar mapping of the Challenger Deep by the Simrad EM120 sonar multibeam bathymetry system for deep water (300 – 11,000 metres) mapping aboard the RV Kilo Moana (mothership of the Nereus vehicle) indicated a depth of 10,971 m (35,994 ft). The sonar system uses phase and amplitude bottom detection, with an accuracy of better than 0.2% of water depth across the entire swath.

• Further sonar mapping of the Mariana Trench, conducted by the US Center for Coastal & Ocean Mapping, was reported in December 2011 at the annual American Geophysical Union fall meeting. Using a similar multibeam echo sounder system, from over 400 individual soundings the CCOM team determined that the Challenger Deep has a maximum depth of 10,994 m (36,070 ft), with vertical precision of ±40 m (130 ft).

The latter 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 the four expeditions which have reported from the bottom, have fixed depths in a narrow range from 10,916 m (Trieste) to 10,911 m (Kaikō), to 10,902 m (Nereus) to 10,898 m (Deepsea Challenger) 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.