The grain size distributions of the three Mars regolith simulants have been added to the text in form of two additional tables (table 2: P-MRS and S-MRS; and table 3: JSC Mars-1A), as well as a new citation for the grain size distribution of JSC Mars-1A [8].
Three different Mars regolith simulants were used. The mineralogical composition is given in table, but not the grain size distribution. Knowing the grain sizes and assuming a homogeneous distributrion of cells and grains or a measurement of the real distribution an assessment can be made about the shading effect of the grains with respect to UV radiation.