Darkening of powdered basalt by simulated solar-wind bombardment

The differences between the reflective properties of the lunar surface and terrestrial materials have been the subject of much recent study. The lunar surface is characterized by a low albedo, strong backscatter, and the absence of color. Hapke and Van Horn [1963] found that a surface must be underdense and very complex to duplicate these properties. Long-duration solar-wind bombardment has been simulated on a much accelerated scale with a low-pressure hydrogen plasma [Wehner et al., 1963a, b].