Nereus (underwater vehicle)
Encyclopedia
Nereus is a hybrid autonomous underwater vehicle (HROV, a type of remotely operated underwater vehicle) built 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...
(WHOI). Constructed as a research vehicle to operate at depths of up to 36000 feet (10,972.8 m), it was designed to explore Challenger Deep
Challenger Deep
The Challenger Deep is the deepest known point in the oceans, with a depth of to by direct measurement from submersibles, and slightly more by sonar bathymetry . It is located at the southern end of the Mariana Trench near the Mariana Islands group...
, the deepest surveyed point in the global ocean
World Ocean
The World Ocean, world ocean, or global ocean, is the interconnected system of the Earth's oceanic waters, and comprises the bulk of the hydrosphere, covering almost 71% of the Earth's surface, with a total volume of 1.332 billion cubic kilometres.The unity and continuity of the World Ocean, with...
. Nereus, named for Greek sea titan Nereus
Nereus
In Greek mythology, Nereus was the eldest son of Pontus and Gaia , a Titan who with Doris fathered the Nereids, with whom Nereus lived in the Aegean Sea. In the Iliad the Old Man of the Sea is the father of Nereids, though Nereus is not directly named...
(who has a man's torso and a fish-tail) through a nationwide contest of high school and college students, began its deep sea voyage to Challenger Deep in May 2009 and reached the bottom on May 31, 2009.
On this dive the Nereus reached a depth of 35768 feet (10,902.1 m), making the Nereus the world's second deepest-diving vehicle currently in operation, and the first since 1998 to explore 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...
, the deepest part of the ocean known.
Hybrid design
Being a hybrid ROV means that the vehicle can operate untethered, when near the surface, in order to explore large areas. To descend to great depths, however, it is tethered with a thin optic fiber cable, operated by pilots aboard the ship. This enables it to make deep dives while being highly maneuverable. The optic fiber tether has the approximate diameter of a human hair, and can bear only 4 kilograms (8.8 pounds). It is made up of a thin layer of plastic surrounding a slender glass fiber core. The vehicle carries approximately 40 kilometres (24.9 mi) of cable wound in two small canisters that play out the fiber as the vehicle descends. This slim tether is smaller, lighter, and more cost effective than cable.Nereus weighs approximately 3 tons in air and is about 4.25 meters (14 feet) long and 2.3 meters (8 feet) wide. Approximately 2,000 lithium-ion batteries provide its power. The vehicle makes use of two precisely designed ceramic spheres or hulls for flotation devices, rather than using the much heavier syntactic foam
Syntactic foam
Syntactic foams are composite materials synthesized by filling a metal, polymer or ceramic matrix with hollow particles called microballoons, "syntactic" meaning "put together"...
that is typically used for submersible vehicles. Each hull
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...
contains between 700 and 800 9-cm (3.5-inch) hollow spheres that are specifically designed to handle intense pressure. Nereus has a lightweight robotic manipulator arm to conduct the sample collecting that operates hydraulically and is able to perform under intense pressure.
As an alternative to the tether, the Nereus can be switched to a free-swimming mode and operated as an autonomous vehicle and hover, similar to a helicopter, over the ocean floor.
In designing the vehicle, the design team relied on previous experience in developing autonomous underwater vehicles (AUVs) and tethered robots to build a hybrid vehicle that could both fly like an aircraft to explore large areas of the ocean floor, but would be easily converted into a remotely operated vehicle (ROV) able to hover over the small areas to conduct experiments or collect samples of rocks and sea life.
Deepest dive
Challenger Deep
The Challenger Deep is the deepest known point in the oceans, with a depth of to by direct measurement from submersibles, and slightly more by sonar bathymetry . It is located at the southern end of the Mariana Trench near the Mariana Islands group...
is located in the Western Pacific Ocean near the island of 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...
in 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...
, the deepest known part of an ocean on earth, and the deepest known location on earth. The May 2009 dive by the Nereus achieved a depth of 10,902 meters (6.8 miles), making it the world's deepest-diving vehicle currently in operation, and the first since 1998 to explore the Mariana Trench. To accomplish this dive, the vehicle had to sustain pressures over 1,000 times the atmospheric pressure at the Earth's surface. It hovered over the trench for more than 10 hours and sent back live video to the mother ship.
Nereus is the third vehicle in the world to reach the bottom of the Pacific Ocean's Challenger Deep. The first was the manned Bathyscaphe 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 ...
, which carried U.S. Navy Lieutenant Don Walsh and Swiss engineer 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...
and made the voyage on January 23, 1960. This is the only manned voyage to the Challenger Deep on record. The Nereus dive aimed for the same spot. On 24 March 1995 a Japanese robotic deep-sea probe called 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...
made the first unmanned trip to the Challenger Deep.
Once at the bottom, Nereus collected liquid and rock specimens. Patricia Fryer, co-chief scientist of the expedition, said the following about the samples.
"We want to know how all of this relates to subduction around the globe, changes in the chemistry of the ocean in general and, therefore, potential effects those changes may have on ocean-atmosphere interactions and things like global climate change."
Future missions
The Mariana Trench is part of the Pacific Ring of FirePacific Ring of Fire
The Pacific Ring of Fire is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. In a horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements...
, a 25,000 mile area that is the location of most of the volcanic eruptions and earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s in the world and is the boundary between two tectonic plates. Here, the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
is subducted under the Mariana Plate
Mariana Plate
The Mariana Plate is a small tectonic plate located west of the Mariana Trench and forms the basement of the Mariana Islands. It is separated from the Philippine Sea Plate by a long divergent boundary with numerous transform fault offsets. The boundary between the Mariana and the Pacific Plate to...
. It is hoped that the Nereus missions will provide valuable information about plate tectonics.
The principal developer of the Nereus, Andy Bowen of 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...
said, "The trenches are virtually unexplored, and I am absolutely certain Nereus will enable new discoveries. I believe it marks the start of a new era in ocean exploration." He described the achievement of the Nereus in diving to such an extreme ocean depth as "the pinnacle of technical challenges".