KCS

Titan, a natural satellite of Saturn, has been shrouded in mystery since its discovery by Christian Huygens in 1655. Titan’s surface was hidden from Voyagers 1 and 2, but the Cassini/Huygens data has begun to reveal some details. Titan’s atmosphere is a classical greenhouse troposphere overlain by a stratosphere consisting of mostly molecular nitrogen, with an admixture (2-10%) methane. Methane is condensed out in the troposphere by low temperature (95 K surface, 70 K @ 50 km), while it is photolytically converted to higher hydrocarbons in the stratosphere by ultraviolet photons from the Sun. Previous modeling had inferred an ethane-methane ocean on Titan, but so far, no liquid has been observed on the surface. However, it still appears that organics must be present on the surface and a source of methane must also be there. Understanding the generation of the organic molecules and the fate they undergo is key to understanding the chemistry on Titan. Cassini data will help elucidate this chemistry.