Derived allowed values for the ice coverage for (a) Themis and (b) Cybele as a function of the Bond albedo of surface ice. The solid curve represents the Q(H2O) constraint derived for each asteroid. Acceptable solutions must lie on or below this curve, as otherwise, gas production through sublimation would have been large enough for detection by HIFI. The dotted curves reflect the albedo constraint (see text) for geometric albedos of surface dust only pv(dust) in the range 0.02–0.04 for Themis and 0.02–0.03 for Cybele. Acceptable solutions for the areal mixing case must lie along or between these dotted curves to guarantee the area-averaged albedo matches our modeled TPM value. The purple stars represent the positions of the corresponding intimate mixing results.