Laboratory samples in P_min−α₀ (depth-width of NPB) space. Alumina samples are shown in Fig. 1. The numbers with units % are albedo values. “Silicate+Carbon” samples are connected by lines in the order of albedo. The arrows for “Pressed Albedo” indicate the increasing albedo for the pressed MgO and soot mixture sample given in the original publication. Ceres and Vesta are shown for comparison (see Fig. 3; b=0.30–0.45 µm).