Titan
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 [link to PDF-File from ESA-SP-1177, F. Raulin: Titan`s organic chemistry and exobiology, p. 219-231] 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 [link to PDF-File from ESA-SP-1177, T. Owen et al.,
The relevance of Titan and Cassini / Huygens to pre-biotic chemistry
and origin of life on Earth, p. 231] 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 [link to PDF-File from
ESA-SP-1177, J.I. Lunine, Titan surface-atmosphere interactions, p.
211-219].