Have you ever seen what lives in the Mariana Trench? Only three people have ever been deep enough, 11 kilometers actually, to take a look. The Mariana Trench is so deep that the pressure felt at such depths is 1000x greater than sea level, with temperatures reaching freezing.
Even though the trench is so cold and dark, life is still plentiful. Scientists have found arthropods, sea cucumbers, microorganisms, and various types of bacteria. All of these animals are unique and different from their sea level cousins since they have evolved to survive the harsh conditions of the deep ocean. In addition to the knowledge gained from learning about the variation in animal species in extreme environments, deep underwater life gives us an idea of what kinds of different life forms we might look for on other planets.