Saturn Loosens its Belt
May 12, 2010

On August 25, 2003, NASA launched the Spitzer Space Telescope into an Earth-trailing, heliocentric orbit as part of the Great Observatories program. The Hubble Space Telescope, the Chandra X-ray observatory, and the Compton Gamma-Ray Observatory are the other three space-based platforms in the program, designed to resolve distant objects at various wavelengths. Spitzer is the infrared partner in the quartet—seeing objects in the 5.3 to 40 micron wavelength range.

One of the most intriguing new discoveries from Spitzer is the presence of another ring around Saturn, something completely unexpected. The new ring is canted 27 degrees from the main ring plane and is in a retrograde orbit around the giant gas planet. It is also quite large. As Anne Verbiscer from the University of Virginia commented: "This is one supersized ring. If you could see the ring, it would span the width of two full moons' worth of sky, one on either side of Saturn."

The vast belt of material ends at 18 million kilometers from the planet and is 12 million kilometers wide. It is also much thicker than the main rings: 2.5 million kilometers from top to bottom. The thickness measurement is an approximation, since the ring is so diffuse.

One of Saturn's moons, Phoebe, orbits within the new ring and is, itself, circling its parent in a retrograde orbit. Some scientists speculate that the ring is generated from Phoebe as its surface ices are eroded by impacts over millions of years.

Phoebe is another tiny moon, 220 kilometers in diameter, half the size of Enceladus. Its gravitational acceleration is a mere .05 meters per second squared. The majority of Saturn's other moons are highly reflective of visible light, but Phoebe is as black as coal, making it one of the darkest objects in the Solar System. NASA scientists describe Phoebe as "very strange" and probably a captured moon.

Many of Saturn's moons seem to be partially covered with reddish-black "soot." Iapetus, Dione and Hyperion are all dusted with the same dark reddish substance. In previous Picture of the Day articles, it was theorized that they were darkened by particles ejected from Phoebe.

The plasmasphere of Saturn electrifies its environment, causing dark-mode plasma discharges to impinge on its family of moons. Enceladus, Dione and Tethys are all electrically active, flinging vast quantities of charged particles into space. Each moon is connected to its parent and to one another through cosmic electrical circuits.

Planets with magnetic fields can trap fast-moving particles to form giant electrified clouds, more accurately called electric currents. NASA scientists have noted that Saturn's magnetic field bends around Enceladus "due to electric currents generated by the interaction of atmospheric particles and the magnetosphere of Saturn." Further flattening of the plasma torus on the sunward side demonstrates an electrical (not mechanical) effect is occurring between Saturn and the Sun.

Bodies immersed in plasma are not isolated, they are connected by circuits, just as Phoebe is connected to Saturn. Most of the time they are not in equilibrium because they are in unstable conditions. The majority of them are moving across the plasma filaments that exist in the Solar System and in the plasmaspheres around planets. Currents in plasma contract into filaments and the force between filaments is linear, so the electromagnetic fields created by them are the most powerful long-range attractors in the Universe.

The simplest, most straightforward explanation for the new ring is charged particles spewing from Saturn's moons. There is no need to conjure numerous impact events over the eons. We predict that investigation over time will show that the active sources of charged particle streams from Enceladus, Tethys, Dione, and Phoebe all move across their surfaces.

Stephen Smith