Titan, the largest moon of planet Saturn is covered by a dense 1.5 bar methane and nitrogen atmosphere and haze particles. Titan taken in the image of NASAs Voyager-1 spacecraft showed a featureless orange body. Infrared spectroscopic observations revealed also ethane and several complex organic molecules in Titan's atmosphere. The detection of hydrogen cyanid (HCN), which is a critical building block for more complex organic molecules of life, and therefore a great significance for exobiology, confirmed the unique nature of Titan in the Solar System.
Titan provides a unique milieu to study, in-situ the products of fundamental physical and chemical interactions driving planetary organic chemistry and serves as a reference laboratory to study by default, the role of liquid water in exobiology. Several atmospheric energy sources like solar UV light, energetic electrons from Saturn's magnetosphere, cosmic rays and electrical discharges, allow an efficient transformation of the main atmospheric constituents into more complex compounds.
In 2004 the Cassini/Huygens spacecraft will allow the moon's organic chemistry to be studied in an environment thought to be similar to that prevailing on Earth 4.5 billion years ago before life began.
Huygens is the ESA-provided Titan-probe of NASA's Cassini spacecraft. Released from the mothership after a seven year-long interplanetary journey to Saturn, the probe is designed to enter in Titan's atmosphere in order to parachute a robotic laboratory down to the moon's surface. The Huygens probe will analyse in detail Titan's meteorology, prebiotic chemistry, atmospheric constituents and its exotic surface.
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