Fig. 6

Contour plot of thermal inertia (in units of J m⁻² s^−1/2 K⁻¹) as a function of particle diameter and porosity. The gray-filled region indicates the thermal inertia range estimated for Ryugu by ground-based observations (Müller et al. 2017). The regolith parameters assumed in the calculation are c_p = 758 J kg⁻¹ K⁻¹, T = 300 K, ρ_m = 3110 kg m⁻³, k_m = 0.0021 T + 1.19 W m⁻¹ K⁻¹, γ = 0.032 J m⁻², ν = 0.25, E = 78 GPa, ϵ = 1.0, ξ = 0.12, z = 0.01 m, and g = 1.8 × 10^–4 m s⁻², respectively. γ and ξ were optimized for experimental data of lunar regolith simulant JSC-1A (Sakatani et al. 2018)