Cracks up to 3,000 kilometers long and 30 kilometers wide streak across Europa's icy surface. They appear to have been filled by muddy, icy material from beneath the crust. This Galileo spacecraft image has been processed to enhance the surface's colour differences. Reddish brown indicates ice contaminated with mud and possibly bacteria. The blues indicate uncontaminated water-ice; light blue for areas of fine-grained ice and dark blue for coarse-grained ice.