The equatorial Region of Ganymede

Caption NASA originale:"This picture is relevant to a Regione near the Equator of Ganymede, and has relatively subdued colors in the visible part of the spectrum. The most striking features are the bright ray craters which have a distinctly bluer color, appearing white against the redder background.
Ganymede's surface is known to contain large amounts of surface ice and it appears that these relatively young craters have spread bright fresh ice materials over the surface.
Likewise, the lighter color and reflectivity of the grooved areas suggest that here, too, there is cleaner ice. We see ray craters with all sizes of ray patterns, ranging from extensive systems, down to craters which have only faint remnants of bright ejecta patterns.
This variation suggests that, as on the Moon, there are processes which act to darken ray material - probably the so-called "gardening", by micrometeoroid impacts".