This is a new low, even for life on Earth — geologists have found bacteria living 1.6 kilometers beneath the ocean floor, twice as deep as ever recorded before. The simple bugs (one cell pictured, at the end of the arrow) are related to the ones found at deep sea hydrothermal vents, but they represent a stunning new discovery in that they open up the possibility that as much as 2/3 of all the biomass on Earth could be buried beneath its surface. It also strengthens the possibility that life on other planets could be hiding out, just waiting to be found.
The project's lead scientist, John Parkes says the the discovery is just the beginning. The deeper in the Eath you go the hotter it gets, obviously, and the critters Parkes and his team found live in sediments that sit at about 100 degrees C, or the boiling point of water. That's from from the hottest environment bacteria have ever been found in, though, so he thinks life could survive even deeper as much as 5 or 6 kilometers down.