Modelled regolith properties versus grain size R (a) Bolometric Bond albedo A (Eq. (9)) versus grain size, R, for various tholins fractions (0%, 5%, 20%). The range of bolometric Bond albedos for Saturn’s icy moons is marked as horizontal dotted lines (Pitman et al. 2010). (b) Average hemispherical emissivity versus grain size, R, for various tholins fractions (0%, 5%, 20%) and surface temperature T_S = 80 K (Eq. (11)). The error bars figure the dispersion of when T_S varies from 50 K to 110 K for a tholins fraction of 5% in crystalline water ice grains. The curves are similar in cases of amorphous water ice (Eq. (11)). (c) Typical surface temperature T_slow of a plate covered with regolith of grain size, R, for various tholins fractions (0%, 5%, 20%) in the case of a slowly rotating moon.