text: Uranus has an active methane cycle. Methane is converted to hydrocarbons through photolysis which condenses and as they are heated, release methane which rises to the upper atmosphere.
  Studies by Grundy et al. (2006) indicate active carbon cycles operates on Titania, Umbriel and Ariel and Oberon through the ongoing sublimation and deposition of carbon dioxide, though some is lost to space over long periods of time.