Pressure follows the barometric formula P(h) = P0·exp(−h/H), plotted on a log axis for each world using its own scale height H = kT/(m·g). Surface temperature is the radiative-equilibrium value T_eq = (S(1−α)/4σ)^(1/4) plus a greenhouse increment that grows logarithmically with CO₂. Atmospheric retention is judged with the Jeans escape parameter:
λ = v_esc² · m_gas / (2 · k_B · T)
Large λ (roughly above 15–30) means a gas is well bound; small λ means it leaks to space over geological time — the reason low-gravity Mars and the Moon lost most of their air while Venus, despite its heat, keeps a thick CO₂ blanket.