Deep-sea exploration
Deep-sea exploration is the investigation of physical, chemical, and biological conditions on the ocean waters and sea bed beyond the continental shelf, for scientific or commercial purposes.
Scientific deep-sea exploration can be said to have begun when French scientist Pierre-Simon Laplace investigated the average depth of the Atlantic Ocean by observing tidal motions registered on Brazilian and African coasts circa the late 18th or early 19th century.
[2] From 1872 to 1876, a landmark ocean study was carried out by British scientists aboard HMS Challenger, a screw corvette that was converted into a survey ship in 1872.
The Challenger expedition covered 127,653 kilometres (68,927 nmi), and shipboard scientists collected hundreds of samples and hydrographic measurements, discovering more than 4,700 new species of marine life, including deep-sea organisms.
[citation needed] In the 20th century, deep-sea exploration advanced considerably through a series of technological inventions, ranging from the sonar system, which can detect the presence of objects underwater through the use of sound, to manned deep-diving submersibles.
In 1960, Jacques Piccard and United States Navy Lieutenant Donald Walsh descended in the bathyscaphe Trieste into the deepest part of the world's oceans, the Mariana Trench.
[6] On 25 March 2012, filmmaker James Cameron descended into the Mariana Trench in Deepsea Challenger, and, for the first time, filmed and sampled the bottom.
With more sophisticated use of fiber optics, satellites, and remote-control robots, scientists hope to, one day, explore the deep sea from a computer screen on the deck rather than out of a porthole.
[3] The extreme conditions in the deep sea require elaborate methods and technologies to endure, which has been the main reason why its exploration has had a comparatively short history.
Recovering sediment cores allows scientists to see the presence or absence of specific fossils in the mud that may indicate climate patterns at times in the past, such as during the ice ages.
[clarification needed] Deep-sea currents can be studied by floats carrying an ultrasonic sound device so that their movements can be tracked from aboard the research vessel.
[citation needed] The United States Navy acquired Trieste in 1958 and equipped it with a new cabin to enable it to reach deep ocean trenches.
For example, the American-built DSV Alvin, operated by the Woods Hole Oceanographic Institution, is a three-person submarine that can dive to about 3,600 m (11,811 ft) and is equipped with a mechanical manipulator to collect bottom samples.
The submarine is equipped with lights, cameras, computers, and highly maneuverable robotic arms for collecting samples in the darkness of the ocean's depths.
Alvin has also been involved in a wide variety of research projects, such as one where giant tube worms were discovered on the Pacific Ocean floor near the Galápagos Islands.
[32] Deep-sea exploration vessels must operate under high external hydrostatic pressure, and most of the deep sea remains at temperatures near freezing, which may cause embrittlement of some materials.
Regardless of the nature of the craft or the materials used, the pressure vessels are almost always constructed in spherical, conical, or cylindrical shapes, as these distribute the loads most efficiently to minimise stress and buckling instability.
This sphere is estimated to be able to withstand 23,100 psi of hydrostatic pressure, which is roughly equivalent to an ocean depth of 52,000 feet, far deeper than Challenger Deep.
About 5,200 photographs of the region were taken, and samples of relatively young solidified magma were found on each side of the central fissure of the rift valley, giving additional proof that the seafloor spreads at this site at a rate of about 2.5 centimetres (1.0 in) per year (see plate tectonics).
[38] For instance microbiological samples from the deep Tyrrhenian Sea collected in oceanographic campaigns of the Mediterranean Science Commission have confirmed the major contribution of marine bacteria and viruses to bathypelagic productivity and in particular the role played by autotrophic and ammonia-oxidizing Archaea in this regard.
Increasing interest of member states of the International Seabed Authority have led to 18 exploration contracts to be carried out in the Clarion–Clipperton fracture zone of the Pacific Ocean.
Various contractors in cooperation with academic institutions have acquired 115,591 km2 of high resolution bathymetric data, 10,450 preserved biological samples for study and 3,153 line-km of seabed images helping to gain a deeper understanding of the ocean floor and its ecosystem.
