Circling the orange-and-yellow planet of Saturn are more than 100 of what the poets call rings and the scientists more prosaically term "concentric features."

The Voyager spacecraft, still more than 2.7 million miles away but rapidly approaching Saturn, is photogaphing the planet's dazzling rings in such brilliant detail that it has revealed the shadow the three largest rings cast on the planet's surface, according to scientists at the Jet Propulsion Laboratory here, where Voyager is being directed.

"We're not calling them rings yet, but there's no question there are more than 100 distinct concentric features orbiting the planet," Voyager Project scientist Edward C. Stone said today. "There features are very discrete."

The rings of Saturn are so prominent that the shadow they cast across the planet's surface is as wide as the Earth is round.

Now almost one billion miles from Earth, Voyager will pass as close as 77,000 miles from Saturn at 6:46 p.m. EST Wednesday. The 1,800-pound spacecraft will be so far away its radio transmissions will take almost 1 1/2 hours to reach the Earth at the time it encounters Saturn.

While the number of rings came as no great revelation, features never seen before with the rings have taken Voyager scientists by complete surprise. There are at least two clumps inside the outermost ring that are so big that scientists thought they were moons. One clump measures more than 140 miles across and may be the source of the icy balls that make up the ring.

The origin of Saturn's rings is still a mystery, though most scientists believe they were formed when the planet collapsed to its present size at the dawn of time. The outermost of the three largest rings is bluer than the other rings, suggesting it may have formed later, but scientists believe it was formed the same way as the others.

"Maybe we're talking about 100 million years' difference," Stone said, "but we're not talking about a different kind of formation. We think all the rings came from the ice that formed when the gassy envelope around the planet cooled off."

The most puzzling features found by Voyager so far are the half-dozen "fingers" that reach out from the planet's surface to the middle of the three largest rings. The fingers appear, then disappear after a few days only to reappear again in different parts of the middle ring.

"The biggest mystery is what supplies the energy to get the fingers up from the planet," Stone said. "It's like lauching a rocket from Earth. It takes a mighty big engine to do it."

Titan, the largest of the 15 moons of Saturn, is still showing up in Voyager photographs wrapped in a yellow-and-orange haze that may be nothing more than smog. On Monday, Voyager will pass Titan at a distance of about 2,500 miles. The moon has an atmosphere of almost pure methane, thicker than the atmosphere of Mars, and is bitterly cold. But even so, some scientists believe there may be a primitive form of life in its atmosphere or on its surface.

Saturn is showing up in the Voyager pictures in rich orange-and-yellow bands, looking much like Jupiter without the Great Red Spot. Brown-and-white balls can be seen in the bands that circle the planet near its north and south poles, suggesting they are enormous clouds that go whizzing around the planet at the top of its atmosphere at hundreds of miles an hour.