Saturn's Rings May Be Ancient, Thanks To Moon Recycling

It's a rare and pleasant day when you can say it's a big Saturn news day.

From researchers at NASA's Jet Propulsion Laboratory comes a new analysis of Saturn's rings, using data recently sent by the Cassini probe, that shows the rings may be much older than previously believed.

Observations by both the Voyager mission in the 1970s, and more recently from the Hubble telescope, had led to presumptions that Saturn's shimmering rings were relatively young, possibly created by a comet shattering a large moon around 100 million years ago.

These estimates were founded in part on the belief that if the rings were much older, they would be darker, due to the pollution of meteorite dust over long periods of time.

But more detailed study, using Cassini's instruments, is now convincing researchers otherwise. Ages of the different rings now appear to vary widely, with the ring material constantly being recycled into small moons, which are then broken again into ring particles.

"The evidence is consistent with the picture that Saturn has had rings all through its history," said Larry Esposito of the University of
Colorado's Laboratory for Atmospheric and Space Physics. "We see extensive, rapid recycling of ring material, in which moons are continually shattered into ring particles, which then gather together and re-form moons."

From the European Space Agency comes news that researchers are at last getting close to understanding the actual rotation speed of Saturn, after being puzzled for decades.

The giant gas planet rotations are tricky to measure from the start, since the surface of the planet is invisible under the atmospheric clouds. However, on Jupiter, scientists developed a way to measure the periodic variation of radio wave emissions, produced by electrically charged particles in the planet's magnetic field. As the planet's magnetic field sweeps around, the emissions change, leading researchers to the rotation time.

Naturally, they tried the same thing with Saturn. But they found a problem – Voyager found one answer, the Ulysses spacecraft 15 years later another, and Cassini agreeing with Ulysses, but still seeing odd variations. Clearly something was spoiling the measurements, since the planet was unlikely to have slowed down by 6 full minutes in the course of decades, as their data appeared to show.

Now studying the Cassini observations, researchers have realized that variations in the speed of the solar wind, as it impacts Saturn and affects the magnetic field, may be leading to the shifting measures.
They're correcting for this now, and hope at last to have a solid answer for the speed of the ringed planet's revolution soon.

Planetary scientists close in on Saturn’s elusive rotation[ESA]
Saturn's Rings May be Old Timers [NASA JPL]

(Image: Saturn, with moons near its rings, as seen by Cassini. Credit: NASA/JPL/Space Science Institute)