The largest moon of the ring-planet Saturn is named Titan. And like the size of its mythological namesakes - the giants - implies, calling it a moon hardly does it justice. Titan is larger than the planets Mercury and Pluto. But truly unique among the moons of the solar system is its dense atmosphere, which is even 50% more massive than Earth's. Thick and opaque for visible light this atmosphere - predominantly nitrogen - resembles conditions on ancient Earth, billions of years ago when life itself started. Despite very low temperatures around 94 degrees Kelvin chemical reactions take place frequently and intensively, where complex organic molecules are formed. Those drift suspended as aerosols and dark smog in the atmosphere, maybe even raining down on the surface, which should be partially covered by liquid ethane. Most probably lightning flashes through this smog, originating from huge, quickly forming thunderclouds and providing the necessary energy for chemical reactions. Titan is rotationally bound to Saturn and without an intrinsic magnetic field it is directly exposed to the solar wind or plasma in the Saturn system. Some of these fascinating discoveries have been made by Voyager 1. The US/ESA mission Cassini/Huygens, however, will deliver much more data as it started to orbit Saturn in 2004. After deploying the European landing probe Huygens it will pass Titan about four dozen times. The Space Research Institute of the Austrian Academy of Sciences is involved in the Cassini/ Huygens mission in many different ways.

Further information on Titan is found at The Nine Planets.