'Mind-blowing' images of Saturn's rings beamed back

PASADENA, Calif. - Hours after settling into orbit around Saturn, the Cassini spacecraft sent back "mind-blowing" photographs Thursday of the planet's shimmering rings that resembled a fine-grain piece of wood or a grooved phonograph record.

Scientists could not contain their excitement as the raw black-and-white pictures of the rings and the inky gaps between them arrived at NASA's Jet Propulsion Laboratory from more than 900 million miles away.

The photographs showed concentric bands - some dark, some light-colored, some broad, some extremely narrow. Some had wavy edges, some had sharp ones. Some had rippled surfaces, like corrugated cardboard. Some appeared smooth.

"Wow, look at that scallop on the inner edge. That's a beauty," said imaging scientist Jeff Cuzzi as a picture from the sunlit side of the rings was displayed.

Cassini, a spacecraft the size of a bus, passed between two of the rings late Wednesday and settled into orbit around the giant planet to begin the most detailed study ever of Saturn and many of its 31 moons. Imaging team leader Carolyn Porco watched the photographs stream in before dawn.

"It was beyond description, really, it was mind-blowing," she said. "I'm surprised at how surprised I am at the beauty and the clarity of these images. They are shocking to me."

The $3.3 billion mission is funded by NASA and the European and Italian space agencies. Cassini is the first spacecraft to orbit the solar system's second-largest planet. Pioneer 11 and Voyagers 1 and 2 made only fly-bys between 1979 and 1981.

Cassini passed through the rings unscathed and was in perfect condition, program manager Robert Mitchell said.

The rings, which have fascinated astronomers for centuries, were the mission's first priority in the minutes after achieving orbit because Cassini will never again be as close to them during its planned 76 orbits over four years.

Cassini images have five times higher resolution than the best Voyager pictures, Cuzzi said. He called the stream from Cassini "a very rich harvest of data."

The first images to arrive were dark and indistinct because Cassini photographed them from the side not illuminated by the sun. But they quickly became crisper.

"Look at that sharp edge. That brings tears to my eyes," Porco exclaimed.

The major rings, ranging in width from 30 miles to 188,000 miles, are named for the first seven letters of the alphabet - but in the order of discovery, not distance from Saturn. From closest to farthest they are D, C, B, A, F, G and E.

Subject to various vorces, including "shepherding" by Saturn's many moons, the rings have structures that scientists described with terms like "spiral waves," "density waves," "bending waves" and even "notes on a chord."

The causes of most of the observed structures are not known, Porco said.

The sharp edges, for example.

"Ring scientists love sharp edges. They have to be held sharp by some mechanism," Porco said. "We don't know the mechanism so we're intrigued by them."


On the Net:

Jet Propulsion Laboratory: http://www.jpl.nasa.gov


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