Vertical variations of mole fractions (denoted x_i) of the main components (i.e., N₂, C₂ H₆ and CH₄) of Titan’salkanofer liquid. This figure depicts a scenario where the icy crust undergoes a geophysical thermal gradient derived from a model based on Sohl et al. (2014). While at the surface the temperature is T = 90 K and the pressure has the ground value of 1.5 bar, at a depth of 10 km the pressure varies between 1.5 bar at the surface (z = 0) and around 130 bar at the bottom of the simulated system (depth of z = −10 km). The three panels correspond to different surface compositions, expressed in mole fractions: (a) N₂: 0.05, C₂H₆: 0.20, CH₄: 0.75; (b) N₂: 0.20, C₂H₆: 0.20, CH₄: 0.60; (c) N₂: 0.20, C₂H₆: 0.30, CH₄: 0.50. For all computations, the porosity of the water ice matrix has been fixed to 5%, the diffusion theory formalism follows Ghorayeb & Firoozabadi (2000), the water-ice EoS is provided by Feistel & Wagner (2006), while the thermodynamic properties of liquids are computed using PC-SAFT. For comparison, the results of Fig. 1 are added in thin gray lines.