When the astonishingly clear and detailed pictures of Saturn (search) and its rings came beaming in from the Cassini (search) spacecraft to the video monitors at the mission's control center, Carolyn Porco could not believe her eyes.

"They were so shocking I thought that my team was playing tricks on me and showing me a simulation of the rings and not the rings itself," Porco, leader of the mission's imaging team, said Thursday at NASA's Jet Propulsion Laboratory (search).

The 61 images were recorded late Wednesday after Cassini entered orbit around Saturn to begin a four-year study of the planet, its rings and many moons, including Titan (search), which will be visited in January by a probe launched from the spacecraft.

A Titan flyby Friday was the next major event on the mission schedule. Frozen Titan, with its thick hydrocarbon atmosphere, is thought to have chemical compounds resembling those on Earth billions of years ago before life appeared.

But Saturn's glimmering rings were the first stars of the mission.

Cassini photographed the rings from above — the dark side — and then dove through a gap and recorded bright images of the sun-illuminated side below.

The black-and-white images captured ring segments — wide, narrow and whispy thin, some with sharp edges and others with scalloped edges — and gaps in between in which little moons orbit, exerting influence on the adjacent particles.

"I'm surprised at how surprised I am at the beauty and the clarity of these images," Porco said.

One ring looked like corrugated cardboard to Porco. Another's structure resembled straw, she said.

"I think ring scientists are going to have a field day," she concluded.

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.

Saturn and its rings resemble the early solar system, when the sun was surrounded by a disk of dust and gas that eventually formed the planets.

Ed Weiler, NASA's associate administrator for space science, said telescopes have found disk systems around many young stars, and studying the Saturn system may go beyond understanding ring systems to showing how planets form around other stars.

"When I was growing up this kind of stuff was science fiction," Weiler said. "... This isn't science fiction. We actually did this. We're in orbit around another planet, taking these kinds of pictures with an incredible machine."

The $3.3 billion mission, funded by NASA and the European and Italian space agencies, took seven years to reach Saturn and is the first to orbit the giant planet. Previous visits were flybys by Pioneer 11 and Voyagers 1 and 2 between 1979 and 1981.

A check of subsystems after the orbit insertion maneuver showed no problems with the spacecraft, program manager Robert Mitchell said.