Model of the mid-infrared brightness of the optically thick B ring of Saturn. (top) Hemispherical emissivity of a regolith of grains following a power-law size distribution with p = 2.8, a_max= 5 cm, and a_min=1 µm (solid line) or a_min=1 mm (dashed line). Water ice is crystalline (Ih90), and contaminants (AmC or Th) are intra-mixed with a fraction ƒ. The esa diffraction correction is used here and ξ = 0. (bottom) Corresponding modelled brightness temperatures T_b(K) of these regoliths on particles. The solar contribution is plotted for both contaminants in the case of a_min=1 mm (dotted line).