Scientists find turbulence in Saturn's rings

 

March 19, 2010|By David Perlman, Chronicle Science Editor

(03-19) 11:03 PDT SAN FRANCISCO — The ringed planet Saturn, brilliant jewel of the night sky, has revealed new insights into the behavior of its rings for scientists studying signals from the Cassini spacecraft still flying through the Saturnian neighborhood after six years in orbit.

"We now have the clearest view of the rings' beautiful crystalline structure pasted onto the real night sky," said Jeffrey Cuzzi of NASA's Ames Research Center in Mountain View, leader of the Cassini-Huygens mission. "Gazillions of icy particles are constantly colliding with each other up there as they orbit the planet ... moving as waves under the influence of moonlets we've discovered orbiting inside gaps between the rings."

The tumultuous nature of the particles in Saturn's seven main rings and the gaps between the planet's rings, where those tiny moonlets cause ring edges to wave like ripples on the shorelines of space, are being described today in the journal Science.

Saturn's rings, through even the best of telescopes, look like series of thin flat discs grooved like an old phonograph record. But that's far from the truth: From Cassini's images and data, researchers have determined that each ring is a turbulent collection of orbiting particles - 95 percent water ice glistening in sunlight and the rest some strange kind of rubble tinged in red-brown here and there.

"That color may be some kind of organic materials," said Cuzzi, "but to me it looks like just plain rust - iron oxide. How it got there we don't yet know."

The ice chunks range in size from a few inches to tens of yards. As they orbit the planet, gravity turns some into huge clumps and pulls others apart, and they batter each other chaotically.

Beyond Saturn's major rings, Cassini scientists report they have detected several other faint rings that seem to be composed of minute amounts rubble and "microscopic dust."

The physics involved in their evolution suggests they are similar to the "protoplanetary discs" of rubble that on a much larger scale mark the earliest stages in the formation of the planets in the solar system.

But just how long ago the rings of Saturn formed and where their material came from originally remains a mystery, the scientists say.

The rings and the icy matter they contain are far from stable in their orbits around the planet. Instead, they appear to be changing constantly.