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.
Images from NASA’s Cassini spacecraft have revealed half-mile-sized (kilometer-sized) objects punching through parts of Saturn’s F ring, leaving glittering trails behind them. These trails in the rings, which scientists are calling “mini-jets,” fill in a missing link in our story of the curious behavior of the F ring.
Credit: NASA
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.
This set of six images obtained by NASA’s Cassini spacecraft shows 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).
Credit: NASA/JPL-Caltech/SSI/QMUL
The trails are also called “mini-jets” by Cassini scientists. Scientists believe they were originally formed by the pull of the moon Prometheus, which averages about 53 miles or 86 kilometers across, on tiny F ring particles.
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.
The constant change in Saturn’s wavy, wiggly F ring is on display in this set of images obtained by NASA’s Cassini spacecraft. . The images show a view looking directly down onto the ring with the planet removed from the center. The radial distance from the center of the F ring has been exaggerated by a factor of 140 to make the wiggles and other radial structures more visible. The regular patterns here primarily occur because of the gravitational pull of the moon Prometheus, which averages about 53 miles or 86 kilometers in diameter. Prometheus can create channels and snowballs as they part and push together icy F ring particles. These regular wiggles are about 65 miles (100 kilometers) from top to bottom.
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Image credit: NASA/JPL-Caltech/SSI/QMUL
“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.
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| Animation 1 | Animation 2 (closeup) |
Click on an individual image the movie
One of the glittering trails caused by small objects punching through Saturn’s F ring is highlighted in this movie from NASA’s Cassini spacecraft. These trails show how the F ring, the outermost of Saturn’s main rings, is constantly changing.
This movie covers seven hours and 23 minutes on Jan. 30, 2009. The moon Prometheus, which averages 53 miles or 86 kilometers across, is the bright body in the middle of the frames. The delicate F ring is the collection of lines initially on the left; the A ring is visible as the denser set of lines initially on the right.
The trail, made of icy particles dragged out of Saturn’s F ring, is highlighted in a box that starts at the bottom left. When it first appears, it is about 47 miles (75 kilometers) long. By the end of the sequence, it has stretched to about 155 miles (250 kilometers) long. The object that created the trail is about a half mile (1 kilometer) in diameter. The F ring has a radius of about 87,129 miles (140,220 kilometers).
Also available are a close-up video of the trail and a web video explaining these trails.
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 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).#LInk
The images for the video were obtained by Cassini’s narrow-angle imaging camera. A longer version of these images with a different projection that focuses on Prometheus, can be seen PIA15501. Other examples of trails like this are available atPIA15502, PIA15503 and PIA15504.
Contacts and sources:
Jia-Rui C. Cook
Jet Propulsion Laboratory, Pasadena, Calif.
