The solubility of 40Ar in liquid hydrocarbons: implications for Titan's chemistry and evolution

The solubility of argon in liquid methane and ethane has been experimentally determined at 94 K. The solubilities are very large: 47% in methane and 15% in ethane, making the lakes of Titan an important potential reservoir of ⁴⁰Ar. The amount of argon in the Titan lakes can be several times the atmospheric amount. After describing the experimental results, we will compare them with available models for vapor-liquid equilibria in the CH₄-N₂-Ar system. Using the data obtained on the solubility of argon in ethane, we will also derive implications for calculating the vapor-liquid equilibria in the C₂H₆-N₂-Ar system. We eventually discuss the reasons for such high solubilities in terms of Hildebrand solubility parameters and the implications for Titan's surface chemistry and evolution.