This image obtained by NASA's Cassini spacecraft around the time it went into orbit around Saturn in 2004 shows a short trail of icy particles dragged out from Saturn's F ring. While scientists did not notice the trail then, a re-examination of over 20,000 images turned up about 500 examples of such glittering trails, including this one from July 1, 2004. The images show that these trails have actually occurred frequently during Cassini's visit to Saturn.
Scientists think the trails, also called "mini-jets" by Cassini scientists, are created when small objects about half a mile (1 kilometer) in diameter punch through the F ring and drag icy ring particles behind them. The objects creating the trails were likely originally formed by the pull of the moon Prometheus, which averages 53 miles or 86 kilometers across, on tiny F ring particles.
As the moon works its way around Saturn, its gravitational attraction sometimes parts channels in the icy particles of Saturn's F ring and sometimes pushes together sticky snowballs. The moon's continued progress around Saturn pulls some of the snowballs apart over time and adds material to others. These trails appear to be the telltale signs of surviving, evolved snowballs that strike through the F ring on their own. Scientists have been able to use Cassini images to track the objects and be sure they have different orbits from the F ring. The collisions occur at gentle speeds, on the order of 4 mph (2 meters per second). The F ring is the outermost of Saturn's main rings, with a radius of about 87,129 miles (140,220 kilometers).
The trail here is about 35 miles (55 kilometers long).
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.