Specific surface area as a maturity index of lunar fines

Mature surface fines have an equilibrium specific surface area of about 0.6 m²/g, the equivalent mean particle size being about 3 μm. The adsorption behavior of inert gases (reversible isotherms) indicates that the particles are also non-porous in the size range of pores 10–300Å. Apparently in mature soils there is a balance in the forces which cause fining, attrition, pore filling and growth of lunar dust grains. Immature, lightly irradiated soils usually have coarser grains which reduce in size as aging proceeds. The specific surface area, determined by nitrogen or krypton sorption at 77°K, is a valuable index of soil maturity.