Life finds a way

Two miles beneath the surface of the Earth, in a South African gold mine, scientists have discovered a bacterial ecosystem that needs no connection, not even indirectly, to the Sun. Sulfur and hydrogen, of geological origin, are the only nutrients required. Other "chemoautotrophic" ecosystems, like those at deep-sea vents, still use, at least in part, some nutrients that can be traced to the photosynthetic world. One of the discoverers, Douglas Rumble, observed, "It is possible that communities like this can sustain themselves indefinitely, given enough input from geological processes. Time will tell how many more we might find in Earth's crust, but it is especially exciting to ponder whether they exist elsewhere in the solar system."