A brief introduction to Titan

Titan is the only known moon with a substantial atmosphere. Ten times thicker than Earth's, Titan's atmosphere is N2 based and possesses a rich organic chemistry, including, most likely, amino acids and nucleotide bases. The organic material results largely from methane (the second most abundant constituent), which is irreversibly destroyed by photolysis, and thus must be recently supplied. Its presence in the atmosphere points to a geologically active planet. However, rather than being scarred by volcanic features, Titan's surface is shaped largely by liquid and wind erosion, with dunes, lakes, and drainage systems that weave downhill. Like the terrestrial hydrological cycle, Titan has a methane cycle, with methane clouds, rain, and seas that evolve following the processes that govern Earth's biosphere.

Presently, as a result of the ongoing international Cassini-Huygens mission, there is a revolution in our understanding of Titan. The Cassini-Huygens spacecraft, launched in 1997, is the largest, most expensive mission sent to the outer solar system. Sixteen European countries, through the European Space Agency (ESA) and the Italian Space Agency (ASI) and the United States, through the National Aeronautics and Space Administration (NASA), designed, built, and now operate the Cassini-Huygens mission. Equipped with an orbiter (Cassini) and a lander (Huygens probe), the spacecraft entered into orbit about Saturn in 2004. The Huygens probe descended into Titan's atmosphere on January 14, 2005 and made the first landing in the outer solar system. The Cassini orbiter and its twelve instruments are orbiting Saturn and flying by Titan every several weeks. The mission will continue until 2017.