I was as surprised as anyone to hear some very good environmental news coming out of the White House this week: the President has decided to set an enormous amount of marine real estate aside for protection -- more than any other person in history -- including a zone that includes the Marianas Trench. The area totals about 190,000 square miles of sea and sea floor, and would ban commercial fishing and mining. According to the BBC:
The areas covered include some of the islands most remote from the world's large populations centres, which have not so far encountered the intense fishing present across much of the oceans. They also encompass some of the most biologically diverse places on the planet, undersea volcanoes and hot seafloor vents, and submarine pools of sulphur thought to be unique on Earth.
By all accounts, however, the trench is one of the most fantastic features anywhere in the ocean. (The only thing holding it back seems to be its name, which evokes images of pasta sauce and WWI-era doughboys getting shot at.) It's the deepest part of the surface of the earth -- at more than 35,000 feet, it's farther below sea level than Mount Everest is above it, and would fit at least seven Grand Canyons vertically inside it. Lots of people have climbed Everest and descended into the Grand Canyon. Only two people have ever been to the bottom of the Marianas Trench.
Like the moon landing, the famous trench descent happened in the 60s. In 1961, the U.S. Navy bathyscaphe Trieste -- a self-propelled deep-sea-diving submersible manned by a small crew (in Greek, "bathys" means "deep" and "scape" means "ship") -- reached the deepest point on the earth's surface, known as the Challenger Deep. (The trench itself is enormously long; it can't all be called simply "the Marianas Trench.")
In 1995 an unmanned Japanese submersible probed the depths of Challenger Deep, but was lost at sea a few years later. There is no longer a craft in existence which can plumb the deepest parts of the Marianas Trench.
This 3D rendering from the geophysical data center gives you a good idea of the shape and structure of the trench: