From: Jet Propulsion Laboratory
Posted: Tuesday, April 24, 2012
Scientists working with images from NASA's Cassini spacecraft have discovered strange, half-mile-sized objects punching through one of Saturn's rings and leaving glittering trails behind them. The results will be presented tomorrow at the European Geosciences Union meeting in Vienna, Austria.
The penetration occurred in the outermost of Saturn's main rings, called the F ring, which has a circumference of 550,000 miles (881,000 kilometers). Scientists are calling the trails in the F ring "mini-jets." Cassini scientists combed through 20,000 images and found 500 examples of these rogues during the seven years Cassini has been at Saturn.
"Beyond just showing us the strange beauty of the F ring, Cassini's studies of this ring help us understand the activity that occurs when solar systems evolve out of dusty disks that are similar to, but obviously much grander than, the disk we see around Saturn," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
Scientists have known relatively large objects can create channels, ripples and snowballs, or clumps of icy material, in the F ring. However, scientists did not know what happened to these snowballs after they were created. Some were broken up by collisions or tidal forces in their orbit around Saturn. Scientists now have evidence some of the smaller ones survived, and their differing orbits mean they go on to strike through the F ring on their own.
"I think the F ring is Saturn's weirdest ring, and these latest Cassini results go to show how the F ring is even more dynamic than we ever thought," said Carl Murray, a Cassini imaging team member based at Queen Mary University of London, U.K. "These findings show us that the F ring region is like a bustling zoo of objects from a half-mile (0.8-kilometer) in size to moons like Prometheus a hundred miles (160.9 kilometers) in size, creating a spectacular show."
These small objects appear to collide with the F ring at gentle speeds about 4 mph (2 meters per second). The collisions drag glittering ice particles out of the F ring with them, leaving a trail of 20-110 miles (40-180 kilometers) long.
In some cases, the objects traveled in packs, creating mini-jets that looked exotic, like the barb of a harpoon. Other new images show grand views of the entire F ring and the swirls and eddies from the different kinds of objects moving through and around it.
Saturn's rings are comprised primarily of water ice. The chunks of ice that make up the main rings spread out 85,000 miles (140,000 kilometers) from the center of Saturn. Scientists believe the rings' average thickness is approximately 30 feet (10 meters).
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate in Washington. The imaging team is based at the Space Science Institute in Boulder, Colo.
New images and movies of the mini-jets are available at: http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20120423.html
For information about Cassini, visit: http://www.nasa.gov/cassini
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