Panels a and b: false-colors images (red, green, and blue correspond to filters 28, 23, and 24, centered at 743.7 nm, 535.7 nm, and 480.7 nm, respectively) obtained by the multispectral images. Panels c and d: spectral slope maps for the two datasets obtained with Eq. (2); the black boxes frame the same areas of fine material deposits; they show different spectral slope values.