Atmospheric loss from planets between 0.5 and 10 Earth masses over 100 Myr with an initial H₂ atmosphere of 3 wt.% at 0.1 au around a young, Sun-like star. The dashed curve shows the contour of fixed Earth-like density of 5.5 g cm⁻³. Blue dots representing rocky bodies fall below this line due to compression at high mass. In both plots, the model was run with τ = 100 Myr, R_g = 4157 J kg⁻¹ K⁻¹, p_XUV = 5 Pa, F_XUV = 55 W m⁻², η = 0.1, and α = 0.03. The planets in plot (a) had an isothermal atmospheric temperature of T = 880 K (corresponding to the effective temperature at 0.1 au with a Bond albedo of 0), and the temperature was set to T = 1760 K in plot (b). In both cases, we see a sharp cutoff between rocky and gas-enveloped planets occurring in the 1.2 R_⊕ to 1.6 R_⊕ range.

(An animation of this figure is available.)

The video/animation of this figure is available in the online journal.