The Mariana Trench is the deepest place on Earth. It is located to the east of Mariana Islands, running for about 2550 kilometers but has a mean width of only 69 kilometers.
The deepest point, known as the Challenger Deep, which had hitherto been measured at 10919 meters, is now estimated to be 10994 meters.

From WikipediaThe Challenger Deep is the deepest known point in the Earth‘s sea floor hydrosphere, with a depth of 10,898 m (35,755 ft) to 10,916 m (35,814 ft) by direct measurement from submersibles, and slightly more by sonar bathymetry (see below). It is in the Pacific Ocean, at the southern end of the Mariana Trench near the Mariana Islandsgroup. The Challenger Deep is a relatively small slot-shaped depression in the bottom of a considerably larger crescent-shaped oceanic trench, which itself is an unusually deep feature in the ocean floor. Its bottom is about 11 km (7 mi) long and 1.6 km (1 mi) wide, with gently sloping sides. The closest land to the Challenger Deep isFais Island (one of the outer islands of Yap), 287 km (178 mi) southwest, and Guam, 304 km (189 mi) to the northeast. It is located in the ocean territory of the Federated States of Micronesia, 1 mi (1.6 km) from its border with ocean territory associated with Guam.

The depression is named after the British Royal Navy survey ship HMS Challenger, whose expedition of 1872–1876 made the first recordings of its depth. According to the August 2011 version of the GEBCO Gazetteer of Undersea Feature Names, the location and depth of the Challenger Deep are 11°22.4′N 142°35.5′E and 10,920 m (35,827 ft) ±10 m (33 ft).
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 indicated a depth of 10,971 metres (35,994 ft; 6.817 mi). The sonar system uses phase and amplitude bottom detection, with a precision of better than 0.2% of water depth; this is an error of about 22 metres (72 ft) at this depth.[4][5] Further soundings made by the US Center for Coastal & Ocean Mapping in 2011 are in agreement with this figure, placing the deepest part of the Challenger Deep at 10,994 m (36,070 ft), with a vertical precision of approximately 40 m (130 ft).
Only four descents have ever been achieved. The first descent by any vehicle was by the manned bathyscaphe Trieste in 1960. This was followed by the unmanned ROVs Kaikō in 1995 and Nereus in 2009. In March 2012 a manned solo descent was made by the deep-submergence vehicle Deepsea Challenger. These expeditions measured very similar depths of 10,898 to 10,916 metres (35,755 to 35,814 ft).”
The Challenger Deep is well, deep. Inverted it dwarfs Mt. Everest in comparison.

To put the figures into perspective;
The tallest mountain in the world, Mount Everest, is only 8848 meters.
The world record for scuba diving is 330 meters.
Image: whoi.edu
Let’s do some calculation.
Water pressure, P is given by hρg 
since h = 10994 m, g = 9.81 m/s^2, and  ρ = 1097 kg/m^3
Therefore P = 110763120.78 Pa, or 110.7 MPa. For those that are not as well versed in physics that is a LOT of pressure.  Bone crushing pressure.
So it’s really dark,  cold and pressurized down there. One might not expect to see any living organism here. Afterall life needs sunlight and something less than bone crushing pressures 24 hours a day- right?
Not here.  In the Challenger Deep, along with other deep water life biomes some life does exist.  Deep sea shrimp, seacucumbers, and a plentiful assortment of plankton and marine micro fauna exist.  Not unlike the deep sea hydrothermal vent zonesthere is life, for example the Vent Crab, and bacterias. Lots of them. These animals are kept alive probably by hydrothermal vents, which release hydrogen sulfide and other minerals, as well as heat.
Scientists are still not sure of the food chain in the Challenger Deep, but the abudnance of small shelled animals and a hierarchy of food chain organisms suggests life does just fine down there.
Pretty cool isn’t it?
info:
http://deepseanews.com/2011/12/deepest-trench-now-with-more-deep/
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