Although the hadal zone covers a significant swath of the planet, it remains a largely mysterious place.
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At that point, submariners enter what oceanographers call the Hadal Zone, derived from Hades – the Ancient Greek underworld.
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It was to be Stewart's first dive, making her the first woman to travel to the Hadal Zone.
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The Pacific's Mariana Trench, the deepest part of any ocean, is in the hadal zone (for Hades, the underworld).
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Orpheus has yet to enter the hadal zone, but the robot's small, nimble frame is designed to survive the pressure here, unlike most ROVs.
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Since then, Dr Cui has set his eyes on the hadal zone in general, and in particular on the bottom of the Mariana trench.
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The Hadal Zone makes up less than 1% of the ocean by area, but, viewed in cross-section, it accounts for almost half the depth.
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Over the next five years, China has stated plans to build both manned and unmanned submersibles able to surpass the hadal zone—the deepest parts of the ocean.
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Though the trenches ranged in location from Japanese to Chilean waters, all of them were within the "hadal zone," meaning they were at least 6,000 meters under the sea.
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On Earth, Orpheus is designed to plunge into the extreme pressures and pitch dark of the ocean's hadal zone — which ranges from depths of 220,236 to 2000,1003 meters (2100,219 to 22023,000 feet) beneath the surface.
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But at the First International Summit on Hadal Zone Exploration, held in Shanghai in June—a few weeks before Zhang Jian set sail—the cruise still had no scientific plan beyond putting the unmanned submersibles through their paces.
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The latest example comes from China, where a scientific adventurer called Cui Weicheng hopes to reap glory for himself and his country by organising routine manned expeditions to the hadal zone—the deepest part of the ocean, defined as anything below 6,000 metres.
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The area below the abyssal zone is the sparsely inhabited hadal zone. The zone above is the bathyal zone.
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The hadal zone – which includes the oceanic trenches, lies between 6,000–11,000 metres (20,000–36,000 ft) and is the deepest oceanic zone.
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At such depths, the pressure in the hadal zone exceeds . Lack of light and extreme pressure makes this part of the ocean difficult to explore.
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Giant tube worms chemosynthesize near hydrothermal vents The abyssal zone remains in perpetual darkness at a depth of . The only organisms that inhabit this zone are chemotrophs and predators that can withstand immense pressures, sometimes as high as . The hadal zone (named after Hades, the Greek god of the underworld) is a zone designated for the deepest trenches in the world, reaching depths of below . The deepest point in the hadal zone is the Marianas Trench, which descends to and has a pressure of .
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The mesopelagic zone extends from to . The bathyal zone extends from to . The abyssal zone extends from to or , depending on the authority. The hadal zone refers to the greatest depths, deeper than the abyssal zone.
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The hadal zone (named after the realm of Hades, the underworld in Greek mythology), also known as the hadopelagic zone, is the deepest region of the ocean lying within oceanic trenches. The hadal zone is found from a depth of around , and exists in long but narrow topographic V-shaped depressions. The cumulative area occupied by the 46 individual hadal habitats worldwide is less than 0.25 percent of the world's seafloor, yet trenches account for over 40 percent of the ocean's depth range. Most hadal habitat is found in the Pacific Ocean.
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The only known primary producers in the hadal zone are certain bacteria that are able to metabolize hydrogen and methane released by rock and seawater reactions (serpentinization), or hydrogen sulfide released from cold seeps. Some of these bacteria are symbiotic, for example living inside the mantle of certain thyasirid and vesicomyid bivalves. Otherwise the first link in the hadal food web are heterotroph organisms that feed on marine snow, both fine particles and the occasional carcass. The hadal zone can reach far below deep; the deepest known extends to .
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Coryphaenoides is a genus of rattails which is found in all oceans of the world. They are found in deep waters and C. yaquinae, recorded to , is the only member in the family known from the hadal zone.
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Similar to other depth ranges, the fauna of the hadal zone can be broadly placed into two groups: the hadobenthic species (compare benthic) living on or at the seabottom/sides of trenches and the hadopelagic species (compare pelagic) living in the open water.
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Cameras and manipulators on submersibles allow researchers to observe and take samples of sediment and organisms. Failure of submersibles under the immense pressure at hadal zone depths have occurred. HROV Nereus was thought to have imploded at a depth of 9,990 meters while exploring the Kermadec Trench in 2014.
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The hadal zone is the deepest part of the marine environment Marine life decreases with depth, both in abundance and biomass, but there is a wide range of metazoan organisms in the hadal zone, mostly benthos, including fish, sea cucumber, bristle worms, bivalves, isopods, sea anemones, amphipods, copepods, decapod crustaceans and gastropods. Most of these trench communities probably originated from the abyssal plains. Although they have evolved adaptations to high pressure and low temperatures such as lower metabolism, intra-cellular protein-stabilising osmolytes, and unsaturated fatty acids in cell membrane phospholipids, there is no consistent relationship between pressure and metabolic rate in these communities. Increased pressure can instead constrain the ontogenic or larval stages of organisms.
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Trophomera marionensis is a deep-sea nematode endoparasite of the family Benthimermithidae. They can be found in one of the deepest parts of the ocean, for example, in the hadal zone 7,000 to 10,000 meters below sea level. They exist in relentless darkness under immense water pressure. Marine invertebrates are their definitive hosts.
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The benthic zones are aphotic and correspond to the three deepest zones of the deep-sea. The bathyal zone covers the continental slope down to about . The abyssal zone covers the abyssal plains between 4,000 and 6,000 m. Lastly, the hadal zone corresponds to the hadalpelagic zone, which is found in oceanic trenches.
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Around the poles, the angle of the sunlight means it does not penetrate as deeply so the aphotic zone is shallower. If the water is turbid, suspended material can block light from penetrating resulting in a shallower aphotic zone. Temperatures can range from roughly to . The aphotic zone is further divided into the mesopelagic zone, the bathyal zone, the abyssal zone, and the hadal zone.
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The outcome of 2013's campaign would see the release of The Hadal Zone Express in March 2014. The album was a success, heavily influenced by 70s/80s glam with some very fast tracks such as "Danish Rush" and "Black Money". Michael Stalling of Metal.de called the album "Fun from beginning to end... each track has its own character and lets the album rock on".
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Some species are adapted to the cold, ocean depths. The spoon-armed octopus (Bathypolypus arcticus) is found at depths of , and Vulcanoctopus hydrothermalis lives near hydrothermal vents at . The cirrate species are often free-swimming and live in deep-water habitats. Although several species are known to live at bathyal and abyssal depths, there is only a single indisputable record of an octopus in the hadal zone; a species of Grimpoteuthis (dumbo octopus) photographed at .
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Although generally recognized, some have suggested that the record-breaking individual might have been caught with a non-closing net (a net that is open on the way up and down into the deep) and therefore perhaps caught shallower.Linley, T.D.; M.E. Gerringer; P.H. Yancey; J.C. Drazen; C.L. Weinstock; and A.J. Jamieson (2016). Fishes of the hadal zone including new species, in situ observations and depth records of Liparidae. Deep Sea Research Part I: Oceanographic Research Papers 114: 99–110.
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Notoliparis antonbruuni is a species of snailfish. It was described in 2005 from a single poorly preserved specimen collected in 1966 from the hadal zone off Callao, Peru. Despite its poor condition, this specimen clearly represents a distinct species although it was unclear which genus the species should be placed in. Notoliparis was chosen rather than Careproctus or Pseudoliparis due to the location the new species was collected being close to the distribution of other Notoliparis species.
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The species in these deepest records remain undescribed, but it has been referred to as the "ethereal snailfish". The deepest-living described species is Pseudoliparis swirei, also of the Mariana Trench, which has been recorded to . In general, snailfish (notably genera Notoliparis and Pseudoliparis) are the most common and dominant fish family in the hadal zone. There are indications that the larvae of at least some hadal snailfish species spend time in open water at relatively shallow depths, less than .
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Of these 11 species, two live exclusively in the hadal zone. The greatest number of monoplacophorans are from the eastern Pacific Ocean along the oceanic trenches. However, no abyssal monoplacophorans have yet been found in the Western Pacific and only one abyssal species has been identified in the Indian Ocean. Of the 922 known species of chitons (from the Polyplacophora class of mollusks), 22 species (2.4%) are reported to live below 2000 meters and two of them are restricted to the abyssal plain.
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Depths in excess of are generally in ocean trenches, but there are also trenches at shallower depths. These shallower trenches lack the distinct shift in lifeforms and are therefore not hadal. Although the hadal zone has gained widespread recognition and many continue to use the first proposed limit of , it has been observed that represents a gradual transition between the abyssal and hadal zones, leading to the suggestion of placing the limit in the middle, at . Among others, this intermediate limit has been adopted by UNESCO.
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The exploration of the hadal zone requires the use of instruments that are able to withstand pressures of several hundred up to a thousand or more atmospheres. Few haphazard and non- standard tools have been used to collect limited, but valuable, information about the basic biology of a few hadal organisms. Manned and unmanned submersibles, however, can be used to study the depths in greater detail. Unmanned robotic submersibles may be remotely operated (connected to the research vessel by a cable) or autonomous (freely moving).
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They feed primarily on algae but also eat slow-moving or sessile animals. Their predators include sea otters, starfish, wolf eels, triggerfish, and humans. Like other echinoderms, urchins have fivefold symmetry as adults, but their pluteus larvae have bilateral (mirror) symmetry, indicating that they belong to the Bilateria, the large group of animal phyla that includes chordates, arthropods, annelids and molluscs. They are widely distributed across all the oceans, all climates from tropical to polar, and inhabit marine benthic (sea bed) habitats from rocky shores to hadal zone depths.
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Historically the hadal zone was not recognized as distinct from the abyssal zone, although the deepest sections were sometimes called "ultra-abyssal". During the early 1950s, the Danish Galathea II and Russian Vitjaz expeditions separately discovered a distinct shift in the life at depths of not recognized by the broad definition of the abyssal zone. The term "hadal" was first proposed in 1956 by Anton Frederik Bruun to describe the parts of the ocean deeper than , leaving abyssal for the parts at . The name refers to Hades, the ancient Greek god of the underworld.
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Pseudoliparis amblystomopsis, or the hadal snailfish, is a species of snailfish from the hadal zone of the Northwest Pacific Ocean, including the Kuril–Kamchatka and Japan Trenches. In October 2008, a team from British and Japanese institutes discovered a shoal of Pseudoliparis amblystomopsis at a depth of about in the Japan Trench. These were, at the time, the deepest living fish ever recorded on film. The record was surpassed by a type of snailfish filmed at a depth of in December 2014, and extended in May 2017 when another snailfish was filmed at a depth of .
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Pressure increases ten-fold as an organism moves from sea level to a depth of , whilst pressure only doubles as an organism moves from . Over a geological time scale, trenches can become accessible as previously stenobathic (limited to a narrow depth range) fauna evolve to become eurybathic (adapted to a wider range of depths), such as grenadiers and natantian prawns. Trench communities do, nevertheless, display a contrasting degree of intra-trench endemism and inter-trench similarities at a higher taxonomic level. Only a relatively small number of fish species are known from the hadal zone, including certain grenadiers, cutthroat eels, pearlfish, cusk- eels, snailfish and eelpouts.
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The deep-sea floor is called the abyssal plain and is usually about deep. The ocean floor is not all flat but has submarine ridges and deep ocean trenches known as the hadal zone. For comparison, the pelagic zone is the descriptive term for the ecological region above the benthos, including the water-column up to the surface. Depending on the water-body, the benthic zone may include areas that are only a few inches below water, such as a stream or shallow pond; at the other end of the spectrum, benthos of the deep ocean includes the bottom levels of the oceanic abyssal zone.
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There are more than 10,000 described species of polychaetes; they can be found in nearly every marine environment. Some species live in the coldest ocean temperatures of the hadal zone, while others can be found in the extremely hot waters adjacent to hydrothermal vents. Within the abyssal and hadal zones, the areas around submarine hydrothermal vents and cold seeps have by far the greatest biomass and biodiversity per unit area. Fueled by the chemicals dissolved in the vent fluids, these areas are often home to large and diverse communities of thermophilic, halophilic and other extremophilic prokaryotic microorganisms (such as those of the sulfide-oxidizing genus Beggiatoa), often arranged in large bacterial mats near cold seeps.
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The first specimen was found in Atlantic waters in August 1901 at a depth of in the hadal zone southwest of the Cape Verde Islands. It was caught during an oceanographic cruise by Princess Alice of Monaco using a fish trap designed by her husband Prince Albert I.Oceanographic Museum - the 1901 Trawl The genus to which this species belongs was initially named Grimaldichthys after the ruling family of Monaco. Other specimens of this fish were recorded later in the Pacific and the Eastern Indian oceans at depths between . For many decades it was thought to be the fish living at the greatest depth in the world until the species Abyssobrotula galatheae—one specimen of which was found at a depth of over —was described in 1977.
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