Hydrogen sulfide is a colorless and poisonous gas with a strong odor of rotten eggs and the formula H2S. It occurs in volcanic gases and natural gas and is produced by the breakdown of organic matter, commonly through the action of bacteria, and by liberation from sulfide minerals. H2S figures prominently in many origins of life models, especially those positing an origin near black smoker-type hydrothermal vents. It is found both in interstellar molecular clouds and in comets. The sulfanyl radical, SH, and the corresponding cation sulfaniumylidene (sulfanylium), SH+, have also recently been detected in the interstellar medium (Molecules in Space).