On the Cover: Photographing Saturn's rings is only one way to study them. This image was generated by a computer using data gathered by Voyager 2's photopolarimeter while the rings occulted the star Delta Scorpii on August 25, 1981. The rings appear brightest where they are most opaque. The insert shows the F-ring with a resolution of one kilometer. This experiment, and the radio occultation experiment (pages 4–7), revealed details of the rings invisible to the spacecraft's cameras. Larry Esposito, University of Colorado, Boulder
4 Taking the Measure of Saturn's Rings: Len Tyler and Dick Simpson explains how we're beginning to understand planetary ring systems thanks to Voyager's encounters with Saturn.
10 Twenty-five Years of Searching: SETI Scientists Celebrate an Anniversary: Woodruff T. Sullivan, IIIlooks back on the history of the Search for Extraterrestrial Intelligence.
3 Q&A What are Syrtis Major and the other dark markings on Mars?
13 World Watch The Planetary Society's political advocacy efforts.
14 News & Reviews Echoes from a dead comet?
15 Society Notes "Steps to Mars" a success; dedicated volunteers help SETI.
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