In this image, orange carbon spheres are straddled by purple-blue rod shaped cells named Candidatus Desulforudis. They were found in a fluid and gas-filled fracture 2.8 km beneath Earth’s surface at Mponeng Gold Mine near Johannesburg, South Africa. Surprisingly, they were the only lifeform there, making this deep ecosystem the first found on Earth with only one species. Image Credit: Greg Wanger (California Institute of Technology, USA) and Gordon Southam (The University of Queensland, Australia)