Saturn and Its Moon Titan

Why does only Titan have such a massive atmosphere, in contrast to the other similarly sized Jovian moons (which are closer to the sun, but have an escape 

Studies carried out on Earth, for example, by the NASA infrared telescope on Mauna Kea (Hawaii), showed albedo variations which indicated the presence of holes in the Titanian cloud formations (Griffith, 1993). It is, however, still unclear as to whether these inhomogeneities result from differences in the surface composition. Lorenz et al. (1997) reported large variations in Titan s atmosphere due to photochemical processes. The methane contained in the dense nitrogen atmosphere is decomposed by solar and thermal radiation, and its content may be replenished from methane lakes or from clathrates. 

The common properties of Titan and our Earth have led to great scientific interest in this Saturnian satellite, which can be considered as a type of extraterrestrial laboratory in which a series of chemical and physical processes occur which are similar to those involved in chemical evolution on the primeval Earth. 

Several laboratories, including that of F. Raulin in Paris (Coll et al., 1998) and of J. Ferris in the USA (Clarke and Ferris, 1997) have carried out experiments on simulated Titan atmospheres these indicate that methane and nitrogen can exist side by side (Table 3.1). 

While the presence of methane indicates a reducing atmosphere, that of nitrogen fits better into a (weakly) oxidising environment. It is believed that the present composition of Titan s atmosphere is the result of chemical or radiation-induced reactions. 

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Another occasional use of hydrogen during space missions is as a reference gas with specific scientific instruments. One example of this application involves the Cassini-Huygens Mission to Saturn and its moon Titan that was launched in October 1997 and arrived at its destination during the summer of 2004 [106]. 

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