Facts And Discovery

                                                           Mariana Trench 

                                     The Mariana Trench or Marianas Trench is located in the western Pacific Ocean approximately 200 kilometres (124 mi) east of the Mariana Islands, and has the deepest natural point in the world. It is a crescent-shaped trough in the Earth's crust averaging about 2,550 km (1,580 mi) long and 69 km (43 mi) wide. The maximum known depth is 10,994 metres (36,070 ft) (± 40 metres [130 ft]) at the southern end of a small slot-shaped valley in its floor known as the Challenger Deep. However, some unrepeated measurements place the deepest portion at 11,034 metres (36,201 ft).  For comparison: if Mount Everest were dropped into the trench at this point, its peak would still be over 2 kilometres (1.2 mi) under water. At the bottom of the trench the water column above exerts a pressure of 1,086 bars (15,750 psi), more than 1,000 times the standard atmospheric pressure at sea level. At this pressure, the density of water is increased by 4.96%, so that 95.27 litres of water under the pressure of the Challenger Deep would contain the same mass as 100 litres at the surface. The temperature at the bottom is 1 to 4 °C (34 to 39 °F).   

                           
The depths of the Mariana Trench were first plumbed in 1875 by the British ship H.M.S. Challenger as part of the first global oceanographic cruise. The Challenger scientists recorded a depth of 4,475 fathoms (about five miles, or eight kilometers) using a weighted sounding rope. In 1951, the British vessel H.M.S. Challenger II returned to the spot with an echo-sounder and measured a depth of nearly 7 miles (11 kilometers)

The majority of the Mariana Trench is now a U.S. protected zone as part of the Marianas Trench Marine National Monument, established by President George W. Bush in 2009. Permits for research in the monument, including in the Sirena Deep, have been secured from the U.S. Fish and Wildlife Service. Permits for research in the Challenger Deep have been secured from the Federated States of Micronesia.

HISTORIC DIVE

Because of its extreme depth, the Mariana Trench is cloaked in perpetual darkness and the temperature is just a few degrees above freezing. The water pressure at the bottom of the trench is a crushing eight tons per square inch—or about a thousand times the standard atmospheric pressure at sea level. Pressure increases with depth.

                The first and only time humans descended into the Challenger Deep was more than 50 years ago. In 1960, Jacques Piccard and Navy Lt. Don Walsh reached this goal in a U.S. Navy submersible, a bathyscaphe called the Trieste. After a five-hour descent, the pair spent only a scant 20 minutes at the bottom and were unable to take any photographs due to clouds of silt stirred up by their passage