The Challenger Deep is 35,838 feet (about 11 kilometers) deep, which is deep enough to submerge Mount Everest and still have a mile of water left over. The approximately 6.8 miles worth of water creates a tremendous amount of pressure at the sea floor, far more than any human could withstand. The weight of the water would be the equivalent of about 50 747 airplanes. These depths have only been explored by specialized probes called bathyscaphes.
Incredibly, even at such high pressure and light-free depths, living organisms have been discovered. Thermal vents, which are like underwater geysers continuously pouring heat from the planet's core, create pockets of warmth that attract bacteria and keep them alive. In Challenger Deep, scientists have discovered single-celled organisms that build shells called foraminifera.
The depths were first mapped by a British ship named Challenger II in 1951, but the exact measurement of the bottom wasn't known until 1960, when the US Navy sent a bathyscaphe named the Trieste down to the bottom. The pilots, Don Walsh of California and Jacques Piccard of Switzerland, experienced no ill effects from the journey, though both men had to don warm clothing as the vessel descended thousands of feet below the farthest penetration of sunlight.
The deep water creates an extremely stable temperature at the surface. The Guinness Book of World Records lists the air above Challenger Deep as having an average year-round temperature of 85 degrees Fahrenheit, making it the "most equitable climate in the world." Challenger Deep is relatively nearby the US territory of Guam, and attracts vigorous scientific study.
