Pure and Applied Chemistry

Abstract: Thermodynamic principles can be applied for describing the atmospheres and the internal structure of celestial bodies using Saturn's moon Titan as a most appropriate example. Some basic physical data of Titan such as the measured temperature and pressure on its surface, the atmospheric composition, Titan’s density and diameter, and other information allow us to predict further properties which have not been determined directly by measurements. The existence of a liquid phase covering smaller parts of the surface can be confirmed, and the composition of the liquid can be predicted. The change of temperature with the height over the surface and the appearance of clouds and rainfall in the atmosphere consisting essentially of CH₄ + N₂ mixtures can also be predicted. By developing a new method of calculation of atmospheric scenarios, the chemical history of Titan’s surface and atmosphere can be roughly reconstructed taking into account the known rate of methane destruction caused by radiative absorption of sunlight. Finally, some estimations concerning the material structure and the pressure behavior of Titan’s interior can be made. Only basic knowledge of thermodynamics and physics is required to understand essential features in a strange world that is more than one billion kilometers away from us.