Challenger Deep
Overview
 
The Challenger Deep is the deepest known point in the oceans, with a depth of 10902 metres (35,767.7 ft) to 10916 metres (35,813.6 ft) by direct measurement from submersibles, and slightly more by sonar bathymetry (see below). It is located at the southern end of the Mariana Trench
Mariana Trench
The Mariana Trench or Marianas Trench is the deepest part of the world's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about long but has a mean width of only...

 near the Mariana Islands
Mariana Islands
The Mariana Islands are an arc-shaped archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean between the 12th and 21st parallels north and along the 145th meridian east...

 group. The Challenger Deep is a relatively small slot-shaped depression in the bottom of a considerably larger crescent-shaped trench, which itself is an unusually deep feature in the ocean floor.
Encyclopedia
The Challenger Deep is the deepest known point in the oceans, with a depth of 10902 metres (35,767.7 ft) to 10916 metres (35,813.6 ft) by direct measurement from submersibles, and slightly more by sonar bathymetry (see below). It is located at the southern end of the Mariana Trench
Mariana Trench
The Mariana Trench or Marianas Trench is the deepest part of the world's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about long but has a mean width of only...

 near the Mariana Islands
Mariana Islands
The Mariana Islands are an arc-shaped archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean between the 12th and 21st parallels north and along the 145th meridian east...

 group. The Challenger Deep is a relatively small slot-shaped depression in the bottom of a considerably larger crescent-shaped trench, which itself is an unusually deep feature in the ocean floor. The closest land to the Challenger Deep is Fais Island
Fais Island
Fais Island is a raised coral island in the eastern Caroline Islands in the Pacific Ocean, and forms a legislative district in Yap State in the Federated States of Micronesia...

 (one of the outer islands of Yap
Yap
Yap, also known as Wa'ab by locals, is an island in the Caroline Islands of the western Pacific Ocean. It is a state of the Federated States of Micronesia. Yap's indigenous cultures and traditions are still strong compared to other neighboring islands. The island of Yap actually consists of four...

), 289 km (180 mi) southwest, and Guam
Guam
Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

, 500 km (311 mi) to the northeast. The depression is named after the British Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 survey ship HMS Challenger
HMS Challenger (1858)
HMS Challenger was a steam-assisted Royal Navy Pearl-class corvette launched on 13 February 1858 at the Woolwich Dockyard. She was the flagship of the Australia Station between 1866 and 1870....

, whose expedition of 1872–76
Challenger expedition
The Challenger expedition of 1872–76 was a scientific exercise that made many discoveries to lay the foundation of oceanography. The expedition was named after the mother vessel, HMS Challenger....

 made the first recordings of its depth.

The most recent (1 June 2009) sonar mapping of the Challenger Deep by the Simrad EM120 sonar multibeam bathymetry system for 300–11,000 m deep water mapping aboard the RV Kilo Moana, has indicated a spot with a depth of 10971 m (35,994 ft) (6.82 miles). The sonar system uses phase and amplitude bottom detection, with an accuracy of better than 0.2% of water depth (this is an error of about 22 m (72 ft) at this depth).

Only three descents have ever been achieved. The first and only manned descent was by Trieste
Bathyscaphe Trieste
The Trieste is a Swiss-designed, Italian-built deep-diving research bathyscaphe with a crew of two, which reached a record maximum depth of about , in the deepest known part of the Earth's oceans, the Challenger Deep, in the Mariana Trench near Guam, on January 23, 1960, crewed by Jacques Piccard ...

 in 1960. This was followed by the unmanned ROVs Kaikō
Kaiko
was a remotely operated underwater vehicle built by the Japan Agency for Marine-Earth Science and Technology for exploration of the deep sea. Kaikō was the second of only three vessels ever to reach the bottom of the Challenger Deep, as of 2010...

in 1995 and Nereus
Nereus (underwater vehicle)
Nereus is a hybrid autonomous underwater vehicle built by the Woods Hole Oceanographic Institution . Constructed as a research vehicle to operate at depths of up to , it was designed to explore Challenger Deep, the deepest surveyed point in the global ocean...

 in 2009. These expeditions measured very similar depths of 10,902 to 10,916 meters. In January 2010, marking the fiftieth anniversary of the Trieste descent, the X Prize Foundation
X Prize Foundation
The X PRIZE Foundation is a non-profit organization that designs and manages public competitions intended to encourage technological development that could benefit mankind....

 announced a $10 million prize for the first privately funded craft to make two repeat manned descents.

History of depth mapping from the surface

  • The HMS Challenger expedition
    Challenger expedition
    The Challenger expedition of 1872–76 was a scientific exercise that made many discoveries to lay the foundation of oceanography. The expedition was named after the mother vessel, HMS Challenger....

     (December 1872 – May 1876) first sounded
    Sounding line
    A sounding line or lead line is a length of thin rope with a plummet, generally of lead, at its end. Regardless of the actual composition of the plummet, it is still called a "lead."...

     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 fathom
    Fathom
    A fathom is a unit of length in the imperial and the U.S. customary systems, used especially for measuring the depth of water.There are 2 yards in an imperial or U.S. fathom...

    s (26,850 ft, 8,184 m), 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 31614 ft (9,636 m), reporting the sounding taken by the converted navy collier, USS Nero
    USS Nero (AC-17)
    USS Nero , a steel steam collier, was built in 1895 as steamer Whitgift by J.L. Thompson & Son. Ltd., Sunderland, England; purchased on 30 June 1898 from McCondray and Co...

    , in 1899. Murray was one of the expedition scientists, a young man at the time.

  • In 1951, about 75 years after its original discovery, the entire Mariana Trench was surveyed by a second Royal Navy
    Royal Navy
    The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

     vessel, captained by George Stephen Ritchie
    George Stephen Ritchie
    George Stephen Ritchie CB DSC is a former British admiral noted for his cartographic and hydrographic work.-Naval career:Ritchie was born in Burnley, 1914, of Scottish parents, Sir Douglas Ritchie and Lady Margaret Stephen Ritchie. He was educated at the Royal Naval College, Dartmouth from the age...

     (later Rear Admiral
    Rear Admiral
    Rear admiral is a naval commissioned officer rank above that of a commodore and captain, and below that of a vice admiral. It is generally regarded as the lowest of the "admiral" ranks, which are also sometimes referred to as "flag officers" or "flag ranks"...

     Ritchie); this vessel was also named HMS Challenger
    HMS Challenger (1931)
    HMS Challenger was a survey ship of the United Kingdom's Royal Navy. She was laid down in 1930 at Chatham Dockyard and built in a dry dock. After that, the ship was moved to Portsmouth for completion and commissioned on 15 March 1932.-Service history:...

    , after the original expedition ship. This survey recorded the deepest part of the trench using echo sounding
    Echo sounding
    Echo sounding is the technique of using sound pulses directed from the surface or from a submarine vertically down to measure the distance to the bottom by means of sound waves. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes...

    , a much more precise and vastly easier way to measure depth than the sounding equipment and drag lines used in the original expedition. A depth of 5,960 fathom
    Fathom
    A fathom is a unit of length in the imperial and the U.S. customary systems, used especially for measuring the depth of water.There are 2 yards in an imperial or U.S. fathom...

    s (10,900 m, 35,761 ft) was measured at 11°19′N 142°15′E.

  • The maximum surveyed depth of the Challenger Deep was reported in 1957 by the Soviet vessel Vityaz recording a spot 11,034 m (36,201 ft) deep. It was dubbed the Mariana Hollow and is listed in many reference sources, including the Encyclopedia Britannica, articles in National Geographic
    National Geographic Society
    The National Geographic Society , headquartered in Washington, D.C. in the United States, is one of the largest non-profit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, the promotion of environmental and historical...

    and on maps. It equals 6.86 miles. The pressure at this depth is approximately 1,099 times that at the surface, or 111 MPa, roughly 16,155 psi
    Pounds per square inch
    The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...

    . The depth figure has not been confirmed by any later expedition. Considering that even in the early 21st century, the error margin for sounding out depressions in the sea floor at these depths is about 20 m, it is, however, reasonably close to a recent (2009, see below) measurement.

  • In 1984, a Japanese survey vessel used a narrow, multi-beam echo sounder to take a measurement of 10924 m (35,840 ft).

  • On 1 June 2009 sonar mapping of the Challenger Deep by the Simrad EM120 sonar multibeam bathymetry system for deep water (300 - 11,000 meters) mapping aboard the RV Kilo Moana (mothership of the Nereus vehicle), has indicated a spot with a depth of 10971 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.


The latter maximal depths were not confirmed by the series of dives Nereus
Nereus (underwater vehicle)
Nereus is a hybrid autonomous underwater vehicle built by the Woods Hole Oceanographic Institution . Constructed as a research vehicle to operate at depths of up to , it was designed to explore Challenger Deep, the deepest surveyed point in the global ocean...

made to the bottom during the Challenger Deep Nereus May/June 2009 Expedition. The direct descent measurements by the three expeditions which have reported from the bottom, have fixed depths in a narrow range from 10,916 m (Trieste
Bathyscaphe Trieste
The Trieste is a Swiss-designed, Italian-built deep-diving research bathyscaphe with a crew of two, which reached a record maximum depth of about , in the deepest known part of the Earth's oceans, the Challenger Deep, in the Mariana Trench near Guam, on January 23, 1960, crewed by Jacques Piccard ...

) to 10,911 m (Kaikō
Kaiko
was a remotely operated underwater vehicle built by the Japan Agency for Marine-Earth Science and Technology for exploration of the deep sea. Kaikō was the second of only three vessels ever to reach the bottom of the Challenger Deep, as of 2010...

), to 10,902 m (Nereus
Nereus (underwater vehicle)
Nereus is a hybrid autonomous underwater vehicle built by the Woods Hole Oceanographic Institution . Constructed as a research vehicle to operate at depths of up to , it was designed to explore Challenger Deep, the deepest surveyed point in the global ocean...

). However, although an attempt was made to correlate locations, it could not be absolutely certain that Nereus (or the other two descents) reached exactly the same points found to be maximally deep by the sonar/echo sounders of previous mapping expeditions, even though the last of these echo soundings was made by the Nereus mothership.

Trieste

On 23 January 1960, the Swiss-designed, bathyscaphe
Bathyscaphe
A bathyscaphe is a free-diving self-propelled deep-sea submersible, consisting of a crew cabin similar to a bathysphere, but suspended below a float rather than from a surface cable, as in the classic bathysphere design....

 Trieste, originally built in Italy and acquired by the U.S. Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

, descended to the ocean floor in the trench manned by Jacques Piccard
Jacques Piccard
Jacques Piccard was a Swiss oceanographer and engineer, known for having developed underwater vehicles for studying ocean currents. He was one of only two people, along with Lt...

 (who co-designed the submersible along with his father, Auguste Piccard
Auguste Piccard
Auguste Antoine Piccard was a Swiss physicist, inventor and explorer.-Biography:Piccard and his twin brother Jean Felix were born in Basel, Switzerland...

) and USN Lieutenant Don Walsh
Don Walsh
Don Walsh is an American oceanographer, explorer and marine policy specialist. He and Jacques Piccard were aboard the bathyscaphe Trieste when it made a record maximum descent into the Mariana Trench on 23 January 1960, the deepest point of the world's ocean...

. Their crew compartment was inside a spherical pressure vessel which was a heavy-duty replacement (of the Italian original) built by Krupp
Krupp
The Krupp family , a prominent 400-year-old German dynasty from Essen, have become famous for their steel production and for their manufacture of ammunition and armaments. The family business, known as Friedrich Krupp AG Hoesch-Krupp, was the largest company in Europe at the beginning of the 20th...

 Steel Works of Essen, Germany, a company that had produced well over 100 U-boat
U-boat
U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

s during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Their descent took almost five hours and the two men spent barely twenty minutes on the ocean floor before undertaking the three-hour-and-fifteen-minute ascent. Their early departure from the ocean floor was due to their concern over a crack in the window caused by the intense pressure of their descent, and also because their landing on the sea bed had stirred up a cloud of silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...

 which reduced visibility to zero and showed no sign of settling. The measured depth at the bottom was 10916 m (35,814 ft).

Kaikō

On 24 March 1995, the Japanese robotic deep-sea probe Kaikō broke the depth record for unmanned probes when it reached close to the surveyed bottom of the Challenger Deep. Created by the Japan Marine Science and Technology Center (JAMSTEC), it was one of the few unmanned deep-sea probes in operation that could dive deeper than 6000 metres (19,685 ft). Its recorded depth of 10911 m (35,797 ft) for the Challenger Deep is believed to be the most accurate measurement taken yet. Kaikō also collected sediment cores containing marine organisms from the bottom of the deep. Kaikō made many unmanned descents to the Mariana Trench during three expeditions between 1995 and 1998.

Nereus

On 31 May 2009 the United States sent the Nereus hybrid remotely operated vehicle (HROV) to the Challenger Deep. Nereus thus became the first vehicle to reach the Mariana Trench since 1998 and the deepest-diving vehicle currently in operation. Project manager and developer Andy Bowen heralded the achievement as "the start of a new era in ocean exploration". Nereus, unlike Kaikō, did not need to be powered or controlled by a cable connected to a ship on the ocean surface.

Nereus spent over 10 hours at the bottom of the Challenger Deep and measured a depth of 10902 m (35,768 ft), while sending live video and data back to its mothership RV Kilo Moana
RV Kilo Moana (T-AGOR-26)
R/V Kilo Moana is a small waterplane area twin hull oceanographic research ship owned by the US Navy and operated by the University of Hawaii as a part of the University-National Oceanographic Laboratory System fleet. She was designed to operate in coastal and blue water areas...

at the surface and collecting geological and biological samples from the Challenger Deep bottom with its manipulator arm for further scientific analysis.

The Nereus is operated by the Woods Hole Oceanographic Institution
Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution is a private, nonprofit research and higher education facility dedicated to the study of all aspects of marine science and engineering and to the education of marine researchers. Established in 1930, it is the largest independent oceanographic research...

.

Lifeforms

The Summary Report of the HMS Challenger expedition lists radiolaria from the two dredged samples taken when the Challenger Deep was first discovered. These (Nassellaria and Spumellaria) were reported in the Report on Radiolaria (1887) written by Ernst Haeckel
Ernst Haeckel
The "European War" became known as "The Great War", and it was not until 1920, in the book "The First World War 1914-1918" by Charles à Court Repington, that the term "First World War" was used as the official name for the conflict.-Research:...

.

On their 1960 descent, the crew of the Trieste noted that the floor consisted of diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

aceous ooze and reported observing "some type of flatfish, resembling a sole
Sole (fish)
Sole is a group of flatfish belonging to several families. Generally speaking, they are members of the family Soleidae, but, outside Europe, the name sole is also applied to various other similar flatfish, especially other members of the sole suborder Soleoidei as well as members of the flounder...

, about 1 foot long and 6 inches across" lying on the seabed. The report has since been questioned, with suggestions that it may have been a sea cucumber. The video camera on board the Kaiko probe spotted a sea cucumber, a scale worm
Polynoidae
A family of scaled Polychaete worms known as the "scale worms". Short and flat, specimens reach as much as 20 cm in length and 10 cm width. An almost-constant number of small segments is the norm. They are covered by scales, technically termed elytra....

 and a shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

 at the bottom. At the bottom of the Challenger deep, the Nereus probe spotted one polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...

 worm (a multi-legged predator) about an inch long.

An analysis of the sediment samples collected by Kaiko found large numbers of simple organisms at 10900 m (35,761.2 ft). While similar lifeforms have been known to exist in shallower ocean trenches (> 7,000 m) and on the abyssal plain
Abyssal plain
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3000 and 6000 metres. Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth’s surface. They are among the flattest, smoothest...

, the lifeforms discovered in the Challenger Deep possibly represent taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 distinct from those in shallower ecosystems.

The overwhelming majority of the organisms collected were simple, soft-shelled foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

 (432 species according to National Geographic), with four of the others representing species of the complex, multi-chambered genera Leptohalysis and Reophax. Eighty-five percent of the specimens were organic, soft-shelled allogromiids, which is unusual compared to samples of sediment-dwelling organisms from other deep-sea environments, where the percentage of organic-walled foraminifera ranges from 5% to 20%. As small organisms with hard, calcareous shells have trouble growing at extreme depths because of the high solubility of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 in the pressurized water, scientists theorize that the preponderance of soft-shelled organisms in the Challenger Deep may have resulted from the typical biosphere
Biosphere
The biosphere is the global sum of all ecosystems. It can also be called the zone of life on Earth, a closed and self-regulating system...

present when the Challenger Deep was shallower than it is now. Over the course of six to nine million years, as the Challenger Deep grew to its present depth, many of the species present in the sediment died out or were unable to adapt to the increasing water pressure and changing environment. The species that survived the change in depth were the ancestors of the Challenger Deep's current denizens.

External links

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