Thermococcus gammatolerans is an archaea extremophile and the most radiation-resistant organism known to exist. Discovered in 2003 in a submarine hydrothermal vent in the Guaymas Basin about 2,000 meters deep off the coast of California, Thermococcus gammatolerans thrives in temperatures between 55–95 °C with an optimum development at approximately 88 °C. The optimal growth pH is 6, favoring the presence of sulfur (S), which is reduced to hydrogen sulfide (H2S). It is the organism with the strongest known resistance to radiation, supporting a radiation of gamma rays from 30,000 gray (Gy).