Giant Dust Ring Discovered Around Saturn . ... Credit Copyright: NASA / JPL-Caltech / Univ. of Virginia Explanation: What has created a large dust ring around Saturn? At over 200 times the radius of Saturn and over 50 times the radius of Saturn's expansive E ring , the newly discovered dust ring is the largest planetary ring yet imaged. ... A leading hypothesis for its origin is impact material ejected from Saturn's moon Phoebe , which orbits right through the dust ring 's middle. ...