Growth of hydrocarbons in the atmosphere of Titan. Titan´s atmosphere contains an unexpected amount of larger hydrocarbons whose formation was so far not explained. A rationale based on the reactivity of hydrocarbon dications is presented. The large potential energy of dications, which can be formed either by photoionization of monocations or by collisions of neutral molecules with energetic particles, is utilized for the activation of methane and formation of larger hydrocarbon dications.