Bar plot showing reflectance, R, variation induced by laser and ion irradiation experiments. Each bar connects at the upper end the reflectance of the fresh material and at the lower end the reflectance of the material weathered to the level stated in the legend. The length of the bar thus shows the variation in the reflectance at the given wavelength, λ. Instead of showing bars at all measured wavelengths, we down-sampled the spectra to 50 nm intervals to enhance readability. H⁺ stands for hydrogen, He⁺ for helium, and Ar⁺ for argon ions.