Monday, May 07, 2012

Punching Holes in the F Ring

The above six images, obtained by NASA's Cassini spacecraft, show trails that were dragged out from Saturn's F ring by objects about a half mile (1 kilometer) in diameter. Scientists have seen more than 500 of these kinds of trails in over 20,000 images collected by Cassini from 2004 to 2011. The trails seen in this set are typical of the entire collection. From left to right in the top row, the trails in these images are 18, 85 and 96 miles long (29, 136 and 155 kilometers long). In the bottom row from left to right, the trails are 43, 129 and 32 miles long (69, 207 and 51 kilometers long). Image Credit: NASA/JPL-Caltech/SSI/QMUL

It seems that scientists were studying images from the Cassini spacecraft and discovered strange half-mile-sized (kilometer-sized) objects punching through parts of Saturn's F Ring and leaving glittering trails behind them. Folks are calling these trails "mini-jets" and they appear to answer some elusive questions about the F Ring. The results were presented during this year's meeting of the European Geosciences Union, which was held April 22 through 27 in Vienna, Austria.

The F Ring is the outermost discrete ring of Saturn and perhaps the most active ring in the solar system. Its features change a bit every few hours. The F ring It is located 3,000 km beyond the outer edge of the A Ring. It was discovered in 1979 by the Pioneer 11 imaging team. It is very thin, just a few hundred kilometers wide, and is held together by two shepherd moons, Prometheus and Pandora, which orbit inside and outside the ring.

Scientists knew that relatively large objects like the Saturnian moon Prometheus (as long as 92 miles, or 148 kilometers, across) could create channels, ripples and snowballs in the F Ring. But scientists didn't know what happened to these snowballs after they were created. Some were surely broken up by collisions or tidal forces in their orbit around Saturn, but now scientists have evidence that some of the smaller ones survive, and their differing orbits mean they go on to strike through the F ring on their own.

These small objects appear to collide with the F Ring at gentle relative speeds — something on the order of about 4 mph (2 meters per second). The collisions drag glittering ice particles out of the F ring with them, leaving a trail typically 20 to 110 miles (40 to 180 kilometers) long. Murray's group happened to see a tiny trail in an image from Jan. 30, 2009 and tracked it over eight hours. The long footage confirmed the small object originated in the F ring, so they went back through the Cassini image catalog to see if the phenomenon was frequent.

According to scientists, these mini-jets are so tiny that it took quite a bit of time and luck to find them. It is reported that they went through 20,000 images and were thrilled to find 500 examples of these rogues during just the seven years Cassini has been at Saturn.

In some cases, the objects traveled in packs, creating mini-jets that looked quite exotic, like the barb of a harpoon. Other new images show grand views of the entire F Ring, showing the swirls and eddies that ripple around the ring from all the different kinds of objects moving through and around it.

And now, the mission particulars...

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the mission for NASA's Science Mission Directorate, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colo. JPL is a division of the California Institute of Technology, Pasadena.

For information about Cassini, visit: and

New images and movies of the mini-jets and other peculiar F ring behavior are available at:

To learn more about the 2012 meeting of the European Geosciences Union, visit this link:

To learn more about the NASA Pioneer 10 and 11 missions, visit this link:


No comments: