Feeling under pressure? Try being a mile underwater.
More than 70 percent of the earth is ocean floor, an environment as lethal to human life as outer space. With pressures hundreds of times stronger than on the surface, no sunlight, and near freezing temperatures, it is hard to imagine that anything could survive on the bottom of the ocean.
Dr. Craig McClain, a marine biologist at the National Center for Evolutionary Synthesis, has taken robot submersibles to the ocean floor. He discovered an astonishing number of species thriving on the seafloor: a comparable number of animals to what is found in a tropical rainforest or a coral reef. He discusses what makes it possible for so many species to coexist in such a hostile environment.