A bacterial colony was recently discovered 4,500 ft below the earth's surface, surviving apparently on only rock and water. The cluster was found in an aquifer near the river Columbia (close to the Hanford nuclear facility), in the state of Washington, US, by microbiologist Todd Stevens and geochemist James McKinley, from the Pacific Northwest National Laboratory. The bacterial population may help solve the mysteries about the forms of life that thrived before photosynthesising microbes came into existence. These bacteria have been identified as methonogens (Discover, Vo117, No 3).