Comparison of predicted PH₃ equilibrium abundance at high- and low-metallicity atmosphere. (a) Predicted PH₃ equilibrium abundance at high-metallicity atmosphere with [Fe/H] = 0.0. (b) Predicted PH₃ equilibrium abundance at low-metallicity atmosphere with [Fe/H] = −1.0. (c) Logarithmic difference of predicted PH₃ equilibrium abundance for [Fe/H] = −1.0 to [Fe/H] = 0.0. The red area represents the relative enrichment of PH₃, and the blue area represents the relative depletion of PH₃. All other symbols and curves are the same as those in Figure 2.