The Cassini spacecraft, a joint venture between NASA and the European and Italian Space Agencies, positioned itself on the far side of Saturn's rings and beamed radio signals at 0.94 (Ka-band), 3.6 (X-band), and 13-cm (S-band) toward Earth.
The signals were received and deciphered to reveal a distribution profile of ring material. Red, for example, represents regions with particles larger than 2 in. in diameter. Green and blue shades indicate regions where particles are smaller than 2 in. and 0.33 in, respectively. NASA scientists note that the Keeler Gap, the faint black ring near the outer edge, is filled with shades of blue. They theorize that frequent collisions between larger particles in this active region fragment them into more numerous smaller ones.