The Origin and Evolution of Titan

Titan was formed as a regular satellite in a disk that was the outgrowth of the formation of Saturn itself. Unlike the Jovian system, Titan is alone in terms of its size and mass, notart of a system gradational in density and hence rock abundance,erhaps reflecting a smaller disk and greater importance of stochastic events during satellite assembly. Accretional heating of Titan was enough to melt an outer layer of water (a water “magma ocean”) and sustain for a shorteriod an environment in which exposed water or water-ammonia liquid was in contact with organic molecules. Initial warm surface conditions are supported by direct samplings of Titan's atmosphere by the mass spectrometers on board Cassini and Huygens, whichrovide circumstantial evidence that ammonia (NH₃) is therimordial source of Titan's atmospheric molecular nitrogen. Ammonia can be extracted from the liquidhase only if the surface temperature is above the meltingoint of the mixture, thus implying warm accretion.