Fig. 11. Influence of Terrain Type on Spectrum Slope on Ganymede.

In 11a, circle diameter increases linearly with the fraction of bright crater material in the field of view. The largest circles indicate a pure bright crater spectrum. Both Voyager1 and 2 data are shown but not distinguished: all the spectra with more than 25% bright crater material are from Voyager2, however. The small slope of the bright crater spectra is readily seen. 11b is similar except that the fraction of dark (cratered) terrain rather than bright crater material is indicated. Only Voyager2 data are shown, in order that the vague slope/terrain correlation visible here is not obscured by slight slope differences between the Voyager1 and 2 spectra. Spectra with more that 25% bright crater material have also been excluded, so that the smallest circles indicate pure light (mostly grooved) terrain spectra. The largest circles represent pure dark terrain spectra.
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