Evolution of atmosphere (a, b, c) Case 3, (d, e, f) Case 7. A case suffix of “v” denotes variable mixing length, “c” constant mixing length, and “s” gravitational separation. (a, d) Global melt fraction ϕ_g, (b, e) partial pressure of CO₂, (c, f) partial pressure of H₂O. For a constant mixing length, cases with and without gravitational separation are visually indistinguishable and therefore plotted together.