The Oklo Natural Nuclear Reactor: A 2-Billion-Year-Old Mystery Solved

In 1972, a peculiar discovery at the Oklo uranium mine in Gabon baffled scientists: the uranium ore contained a lower-than-expected proportion of uranium-235. Investigations revealed a naturally occurring nuclear fission reaction dating back over two billion years. The high uranium concentration, coupled with groundwater acting as a moderator, allowed a sustained chain reaction. This astonishing find demonstrates that natural nuclear reactors can exist, with Oklo remaining the only known example preserved to this day.