Panel A: dependence of the scaling factor K on the characteristic rigidity R ₀ of the EXP model for the depth of 1 g cm⁻² for different values of the effective energy E*, as denoted in the legend (in MeV). Panel B: same as A, but for the POW model with the index γ. Panel C: effective energy E* as a function of depth in lunar sample 64 455 for the EXP and POW models. Panel D: same as C, but for the best-fit scaling factor K; the hatched areas represent the full-range ΔK-values.