- The Washington Times - Wednesday, March 29, 2006

When the Voyager spacecraft passed Saturn in the 1980s, the valuable images it collected were gobbled up by space scientists.

So imagine the anticipation building over the Cassini-Huygens spacecraft, which entered an orbit around Saturn in 2004. It is slated to circle the ringed planet 75 times before its mission is accomplished.

By that time, scientists should have their best information about not just the sixth planet from the sun itself, but its magnificent ring structure as well.

Similar rings can be found on the other Jovian planets — Jupiter, Uranus and Neptune, grouped together because all are considered gas giants like Saturn — but only Saturn has such a large, extensive ring system. Its rings also are far brighter than the rings of other planets, making them pop out against the blackness of space, firing the imaginations of astronomers the world over.

The unmanned Cassini-Huygens craft made news recently when it revealed there may be water near the surface of the Saturnian moon Enceladus — the vessel sent back images of plumes that could be a variation on a geyser.

The verdict still may be out on whether Saturn itself has water on its surface, but Jeff Cuzzi, the interdisciplinary scientist for rings and dust on the Cassini-Huygens mission, says there’s little doubt that up to 90 percent if not more of the rings are made of water.

That accounts for their light color, but the rings also have a reddish tinge that scientists can’t fully explain, he says.

“Some think it’s organic materials like we see on Neptune’s big moon,” he suggests.

The Cassini-Huygens mission, a collaboration between NASA, the European Space Agency and the Italian Space Agency, marks the fourth such effort to reach out to Saturn. Pioneer 11 flew past in 1979, followed by Voyager 1 and its twin, Voyager 2, in 1980 and 1981, respectively.

William C. Parke, a physics professor at George Washington University, says such space probes provide the best shot for learning all we want to know about Saturn’s rings.

By studying the rings, Mr. Parke says, we also can learn more about our own planet.

“It’s an interesting way to understand how the solar system evolved,” he says. “Our own planets around the sun condensed out of materials that orbited the sun, like how the rings orbit Saturn.”

The rings first were observed in 1610 by Galileo, but his primitive viewing techniques left much to be desired.

The rings can appear hazy as seen from the Earth without the proper magnification, and they easily can slip away from sight entirely.

“When Saturn tilts at one point, you look straight across the rings, and they disappear because they’re so thin,” he says.

Ken Wilson, director of astronomy at the Science Museum of Virginia, says scientists have a broad understanding of Saturn’s rings, but many details are still being “puzzled out.”

One of those puzzles is a little closer to being solved, thanks to the Cassini-Huygens mission.

Last year, the craft confirmed an image that initially was suspected from details downloaded from the Voyager spacecraft, Mr. Wilson says.

“When light is above the rings, it looks like spokes,” he says. The spokes exist slightly above the rings and rotate at the same rate as the planet does, he adds. The particles that make up the spokes are so fine they’re controlled by both the planet’s magnetic field and by gravity.

The rings’ particles are far larger, and should they ever wane, there’s a fresh supply waiting at one of the planet’s many moons. Some of the smaller moons occasionally crash into each other, Mr. Wilson says. These collisions cause the moons to fracture and break apart, a process that releases more particles to be gathered by the rings.

“The rings are a recycling process,” Mr. Wilson says, adding that many moons aren’t constructed as solidly as the Earth’s moon. “It’s an ongoing phenomena; they’re constantly renewing themselves.”

The rings, which number in the hundreds and are grouped and classified by labels such as “E-ring,” are made of ice and rock and extend hundreds of thousands of miles away from the planet’s surface.

One mystery that remains open is just how the rings came to be.

Mr. Cuzzi says the rings may have formed along with the moons near the planet, or an outside force such as a comet may have sparked their creation.

Practically speaking, the rings don’t provide a function for Saturn any more than its moons do, says Mr. Cuzzi, a research scientist at NASA’s Ames Research Center in California.

The Earth at one point had a ring around it similar to Saturn’s, he says. The rubble in that ring eventually formed the moon we see each night, but Earth’s gravitational pull is weaker than Saturn’s, so the ring system disbanded after the moon’s formation.

Robert Mitchell, the Cassini-Huygens program manager, says the mission so far has solidified existing knowledge about Saturn’s rings, from their structure to their overall composition.

The data will help the layperson get a better handle on the ringed planet.

“They don’t have a lot of detailed knowledge about Saturn, but neither did scientists until very recently,” Mr. Mitchell says.

One eye-popping fact is that while the rings can be as thin as a kilometer, in vertical dimension they extend out more than 200,000 kilometers, he says.

The Cassini-Huygens mission represents the biggest advance in Saturn research.

“We’ve only just flown past Saturn with past missions. Now, it’s an extended visit,” he says.

Mr. Cuzzi says the current mission promises to be a “bonanza” for ring research.

“It’s gonna be tremendous in terms of helping us,” he says. “It has more instruments on it than Voyager, and better instruments.”



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