The Earth’s deepest underwater trench is located in the Pacific Ocean, just east of the Mariana Islands. Formed by a process known as subduction, which is when a tectonic plate is submerged by another, the Mariana(s) Trench is crescent shaped and extends about 1500 miles long and 43 miles wide. In 2009, as a part of the Marianas Trench National Monument, the entire area became a US protected zone.

The trench’s maximum known depth is located within a small valley at its southern end, called the Challenger Deep. It was first measured in 1875 when scientists aboard the British ship HMS Challenger used a weighted sounding rope to record the depth. Their measurement of 5 miles remained until 1951 when the HMS Challenger II returned to the same spot and, using an echo-sounder, determined that it was actually 7 miles beneath the surface of the ocean.

The water pressure at this depth is about 1000 times the atmospheric pressure at sea level. In addition, the trench is also devoid of natural light and the temperature remains between 1 and 4° Celsius. These conditions make it hazardous for any human explorations to take place. Even so, there have been two people brave enough the journey.

In 1960, Jacques Piccard and Lt. Don Walsh descended in a US navy submersible. It took them 5 hours to get to the bottom, where they remained for only 20 minutes. As a result of the silt that was stirred up because of their submersion, they were unable to get any pictures of the underwater scenery. Their journey proved one very important fact; that life could exist at these depths, as their floodlights illuminated the waters enough for them to view various types of sea creatures within close proximity of their vessel.

Some scientists, at the time, maintained that what Piccard had identified as a flatfish might have been a form of sea cucumber. They argued that the pressure under that amount of water would be so great that calcium would not be able to exist in any solid form. This meant that the bones of all creatures in the trench would disintegrate. Unmanned subs sent to the depths proved them wrong, however, as they have recorded shrimp-like amphipods and unique translucent creatures, called holothurians. Scientists are still only able to speculate as to how the animals are able to survive here.

There is also the theory that studying the microorganisms which live in the trench might be able to shed light about the evolution of the species on our planet. Researchers believe that the conditions at the bottom of the ocean would have been ideal to facilitate the emergence of the first lifeforms. As the exploration continues and technology advances, they hope that more of these questions will be answered.