"The sediments underneath Earth's seas are home to roughly 2.9 x 1029 microorganisms, which survive at depths of up to 2.5 km below the seafloor." The bulk of this deep subseafloor biosphere develops incredibly slowly in comparison to life on the top, with cell division estimated to occur once every 10-1000 years or so. Scientists are discovering new microscopic life sources further and deeper beneath the ocean than ever before. In March, a team of scientists announced that they had discovered remnants of bacteria (about 10 billion bacterial cells) in rocks 400 feet below the bottom, which was the deepest ever discovered.