Saturn: The Story of the Rings

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For many of us, the planet Saturn is a subject of fascination, an entity that inspires the imagination. Its unique rings make it seem especially other-worldly. It attracts us with its beauty and mesmerizes us with its unique role in the solar system. How did the planet develop those magnificent rings? What do we know about Saturn, and what is left to discover?

Saturn is the sixth planet from the sun, the second largest of the four gas giants in the solar system. It also happens to be the lightest, measuring half the density of Jupiter. More than twenty moons orbit Saturn-four of them were discovered in the summer of 2000 alone. Despite the proliferation of moons, only nine of them are considered to be significant. Titan is the largest of these, with a diameter of 5, 150 kilometers. It is the only planetary satellite known to have an atmosphere. That atmosphere consists mainly of nitrogen.

Saturn’s system of rings is made up of icy particles which vary in size from pebbles to basketballs. From Earth, the rings seem to be distinct bands with spaces between them. Each ring, moreover, is named for the astronomer who discovered it. A Saturn ring is no more than 150 meters thick and is marked by incredibly low temperatures, -180 degrees C in sunlight and -200 degrees C in shade. A fascinating feature of Saturn is that a number of smaller moons can be found within the ring system, and those moons have been known to affect the rings.

The composition of the planet is similar to that of Jupiter. The silicate core is bounded by liquid hydrogen and a deep gaseous hydrogen atmosphere, which is cooler than Jupiter’s atmosphere. The atmosphere of Saturn reveals similar banding, but the color of those bands is less brilliant because of the large amount of ammonia crystals at the outer reaches. Saturn is known for its high winds; wind speeds of as much as 1400 km/hour have been noted, indicating extreme meteorological activity.

The Voyager 1 and 2 space missions revealed key information about Saturn, its satellites, and rings in 1980 and ’81. The Cassini probe, which began in October of 1997, will meet up with Saturn next year. Cassini has now left Jupiter and is set to arrive at Saturn July 1, 2004. The probe is named after the Italian-born French astronomer Giovanni Cassini (1625-1712), who discovered what has come to be known as the Cassini Division, a significant gap in Saturn’s rings.

And there is more exploration in store. The European Huygens probe attached to Cassini will break apart and parachute to the surface of Saturn’s Titan moon January 14, 2005. Many unanswered questions remain about Saturn, its history, and expectations about its future. Why did it become such a unique entity in the solar system? How did it develop, and what transformations will it make in the coming years? Are there surprises ahead for the astronomers who will examine the evidence gathered by the Cassini probe? Star-gazers have high hopes that the mission will shed new light on this intriguing planet.


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