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About Saturn & Its Moons

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Rings - History

Despite all we've learned, scientists still aren't sure how long Saturn's rings have been around. They could be quite new, geologically speaking. Today, scientists are using Cassini to help determine whether the rings formed early in the planet’s history and are nearly as old as the Solar System, or whether they formed a only few hundred million years ago. The many fantastic sights Cassini has shared are part of a legacy of discovery going back four hundred years.

Galileo was the first person to observe Saturn with a telescope, in 1610. He was baffled by the rings, which through his crude telescope appeared to be two smaller bodies orbiting along with Saturn. When these features disappeared and then reappeared a few years later, he suggested they were arms or "cup handles" that mysteriously grew and disappeared periodically. We know now that the rings seem to disappear as our view of the ring plane shifts. When they are seen at an edge-on angle, the rings are virtually invisible.

However, Galileo’s confusion reigned until Christiaan Huygens, a Dutch astronomer, developed the concept of a planetary ring system in 1659. Huygens theorized the rings to be solid, thin, and flat. The new idea provided a model for astronomers of the day, who were then able to understand what they were seeing. In 1676, Giovanni Cassini, an Italian astronomer who eventually became a French citizen, was able to see the biggest gap within the ring system, now known as the Cassini Division.

Color-Enhanced Rings
Possible variations in chemical composition from one part of Saturn's ring system to another are visible in this Voyager 2 image as color variations that can be enhanced with special computer-processing techniques.
In the modern era, both the Pioneer and Voyager spacecraft completed flybys of Saturn in the 1970s and 1980s, revealing volumes of new information about the rings' structure and composition. After two decades of studying the Voyager data, and then studying more recent data from the Hubble Space Telescope, scientists developed a new set of questions for the Cassini mission to investigate. The quest to understand the rings’ origin, evolution, structure and composition continues with the Cassini Equinox Mission.

Read much more about the history of discoveries about Saturn's rings in the NASA publication Passage to a Ringed World (1.6 MB PDF).