Relative abundances of the main hydrocarbons and comparison with their vapor pressure ratio: (a) Relative abundances of the main hydrocarbons (orange solid line with circles for CH₄, solid pink line for C₂H₂, purple dash-dotted line for C₂H₄ and brown dashed line for C₂H₆), and blue dotted line for HCN. (b) Relative abundances (solid lines) compared to the ratio of the vapor pressure, P_v, and the pressure, P, (dashed lines) depending on altitude for CH₄, the main C₂H_x, and HCN. When the curves of the P_v/P ratio and the abundance merge, this means that the species is condensing, as its abundance cannot be higher than this ratio.