The Mariana Trench is named for the nearby Mariana Islands in turn named Las Marianas in honor of Spanish Queen Mariana of Austria, widow of Philip IV of Spain. The islands are part of the island arc that is formed on an over-riding plate, called the Mariana Plate also named for the islands, on the western side of the trench.

The Mariana Trench is part of the Izu-Bonin-Mariana subduction system that forms the boundary between two tectonic plates. In this system, the western edge of one plate, the Pacific Plate, is sub ducted (i.e., thrust) beneath the smaller Mariana Plate that lies to the west. Crustal material at the western edge of the Pacific Plate is some of the oldest oceanic crust on earth (up to 170 million years old), and is therefore cooler and more dense; hence its great height difference relative to the higher-riding (and younger) Mariana Plate. The deepest area at the plate boundary is the Mariana Trench proper. The movement of the Pacific and Mariana plates is also indirectly responsible for the formation of the Mariana Islands. These volcanic islands are caused by flux melting of the upper mantle due to release of water that is trapped in minerals of the sub ducted portion of the Pacific Plate.

From the cold to the never-ending darkness and the unimaginable pressure, life in the deep is by no means easy. Some creatures, such as the dragonfish, produce their own light in order to attract prey, mates, or both. Others like the hatchet fish have evolved enormous eyes in order to try and catch as much of the scarce light that makes it that deep. Some creatures simply try and be avoided, which normally means either becoming translucent or red, because this absorbs any blue light that has managed to make its way down to the depths. Then they also have to deal with the pressure and the cold, which in effect “sets” the fat that forms the membranes of the body’s cells. If left unchecked, it would cause the membranes to crack and break, so in order to get around this, deep sea creatures have lots of unsaturated fat in their membranes, which help to keep them fluid.

OR Sample collection.

Deep-sea sediment samples were collected from the Mariana Trench, Challenger Deep (11°22.109N, 142°25.859E), at a depth of 10,898 m, by means of sterilized mud samplers, with the unmanned submersible Kaiko. At the bottom of the Mariana Trench, brown soft sediment was widespread and no rock was observed. Several deep-sea animals were observed, suggesting the presence of a large community of deep-sea invertebrates. The deepest mud samples were taken by Kaiko’s manipulator and put into the sample holder of the sterilized sampler, and then the samples were carried to the sea surface without any change in temperature but were subject to changes in pressure. A part of each of the samples employed for isolation of barophilic bacteria was pressurized at approximately 100 MPa in a pressure vessel which was placed in a refrigerator(2 to 4°C) on the support ship M. S. Yokosuka