... Credit: Cassini Imaging Team , ISS , JPL , ESA , NASA Explanation: What's causing those strange dark streaks in the rings of Saturn? Prometheus . Specifically, an orbital dance involving Saturn's moon Prometheus keeps creating unusual light and dark streamers in the F-Ring of Saturn. ... Prometheus' gravity then pulls the closest ring particles toward the 80-km moon. ... Since Prometheus orbits faster than the ring particles, the icy moon pulls out a new streamer every pass. ...