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Sharp Saturn Ring Images Dazzle Scientists - 2004-07-01

Scientists are being dazzled by the sharp, detailed images of the rings of Saturn transmitted to Earth soon after the U.S. Cassini spacecraft began orbiting the giant planet. They say that understanding the rings can expand our knowledge of the evolution of the solar system and other planetary systems.

Saturn's shimmering rings have intrigued astronomers for centuries, but no one has seen them as closely and sharply as Cassini has just seen them.

After successfully entering orbit around Saturn, the spacecraft immediately began taking pictures from above the rings as they were backlit by the sun. Then it descended through them for images from the illuminated side. It was the best opportunity the spacecraft will get in its four year mission because it will never be any closer.

A deputy chief of the U.S. space agency NASA, Ed Weiler, revealed the photographs just hours after Cassini began transmitting them.

"Citizens of Earth, I would like to present the majestic rings of Saturn," he said.

The highly detailed images have stunned Saturn ring specialists like Carolyn Porco, the head of the Cassini imaging team from the Space Science Institute in Boulder, Colorado. In her words, they are utterly remarkable in their beauty and clarity.

"They are shocking to me," she said. "They are so shocking I thought that my team here was playing tricks on me and showing me a simulation of the rings and not the rings themselves."

Ms. Porco says Cassini's steadiness allows for extremely crisp images, like a tripod in space. The photos show better details of well known ring phenomena photographed by the two Voyager missions that flew by Saturn in the 1980s. For example, one sees the scalloped or wavy inside edges of certain ones, an indication that the gravity of some of Saturn's 31 moons is tugging on the icy dust that makes them up. Other rings have smooth edges.

The pictures also portray finer detail of smooth, flat rings that vary in particle density, as indicated by how much sunlight passes through, and rings that are rippled like corrugated cardboard, caused by differing positions of particles under influence of Saturn's moons.

"These are characteristics that ring scientists read like a book to discern what kind of properties the particles have, how densely they are packed, and so on," she explained.

But Ms. Porco is also excited by novelties not apparent in previous ring images. In one case, the shape and alignment of particles make segments of one of Saturn's rings look like clumps of straw.

"I don't know what this is. We think it's real. There may be processes going on that make the particles clump on scales you're seeing here," she noted.

Scientists will spend years poring over the ring pictures and learning their structure. Cassini mission researchers say studying them is one of the best ways to understand how our solar system formed. NASA's Ed Weiler explains that planets form from similar flat disks of gas and dust around stars.

"This process is not going on around just Saturn," he added. "With the Hubble Telescope and other systems, we have discovered not ring systems, but disc systems around many, many, many young stars. This is the process of planet formation, these disks. So the studies we're doing on Saturn go well beyond the understanding of ring systems. They could tell us a lot about how planets form around other stars."

Cassini is the first spacecraft ever to orbit Saturn and will spend at least four years touring the planet and eight of its many moons.

While the first results are stunning, mission manager Robert Mitchell is braced for a lot more new information about the second largest planet in the solar system.

"These kinds of pictures, I think, are going to excite a lot of people," he said.