Mass versus the scaled density for observed (dots) and modelled planets (lines). Scaled density is defined as ρ/ρ_⊕, where ρ_⊕(M) is the density of a planet with the same interior structure and composition as Earth at a given mass (M). The radii of the modelled planets are based on the radius of the photosphere, which was averaged over the Kepler bandpass. The curves for atmosphere-bearing planets are computed for endmember cases (ξ = VIBSE, SOLAR; ΔIW = −3, +3; T_irr = 1250 K, 2500 K, at constant Ψ_VMF =0). Curves for two atmosphere-free cases (a coreless planet; CORL and a BSE-like planet, BSE) are also shown. The points denote a collection of measured masses and radii for planets R ≤ 4 R_⊕, M ≤ 10 M_⊕ and T_irr ≥ 1000 K, obtained from the NASA Exoplanet Archive; we omit objects with an uncertainty σ_ρscaled > 0.25 from the plot.