Saturn's "Spokes" Once Again Visible

A strange radial phenomenon that cuts across the width of Saturn's rings is visible once more, prompting scientists to wonder about its origins.

When the Voyager spacecraft first flew by Saturn in the early 1980s, scientists got their first glimpse that Saturn's rings were not as consistent as they had thought. Strange ghostly shafts could be seen crossing along a portion of the rings, much like the spokes on a bike. Simply by observing the Voyager images, NASA scientists quickly determined that these mysterious radial shafts could not have been caused by gravitational interactions with the planet or ring material - shrouding the already enigmatic planet in new mystery.

In 2005, the Cassini unmanned spacecraft managed to snag pictures of these strange phenomena once again. Interestingly, the spokes were visible along portions of Saturn's outer B-ring when it was not illuminated by the Sun.

According to a 2005 NASA press release, these images betrayed something interesting. The timing of the appearances of the spokes had changed. NASA's Hubble Space Telescope had taken enough images of the spoke after the Voyager to indicate that they were comprised of tiny ice particles that had oddly aligned in a radial manner to coincide with changes in the gas giant's magnetic field. Another theory was that the "spoke" particles has been caused by asteroids streaking through the rings. However, if either of those theories were true, the timing of when these shafts would be visible would be predictable. But, since they were visible in 2005, that tells scientists that the rotation of the rings may have changed.

"Cassini has found that the Saturn Kilometric Radiation period has changed since Voyager, which though hard to believe, may mean that the rotation of Saturn's interior has changed," said Dr. Carolyn Porco, Cassini's imaging team leader at the Space Science Institute in Boulder, Colo. "That would be a finding of enormous consequence, so we'll be looking very closely to see if the frequency of spoke activity has changed too."

Now, new Cassini photos taken eight years after the original Saturn photos have identified new spoke activity, rousing the scientific community once more, NASA reports. A study of these new observations has already begun, with the hopes of unraveling more of the mystery that is Saturn's rings.

You can see the new Cassini image here.