1. Saturn's Rings
Saturn's rings backlit by the sun, as seen by the Cassini spacecraft
One: Lord of the Rings
There is nothing in the solar system quite like Saturn’s rings. They are not unique—Jupiter, Uranus and Neptune all have ring systems—but there is nothing to compare to their sheer magnificence and spectacle. The rings of the other planets are so dark and thin that they are invisible to even the most powerful telescopes—the existence of two of them was not even suspected until passing spacecraft photographed them. Saturn’s, on the other hand, are brilliant—the broad B ring is brighter even than the planet itself. This is because the rings of the other planets are made of dark rocky dust while Saturn’s rings are made of ice. And while the other planets’ rings are narrow bands as thin as smoke, Saturn’s are flat and wide, like a pizza or compact disk
The rings can be easily seen through even a small telescope. When the planet is at its maximum tilt toward or away from the Earth, the rings are a magnificent sight, appearing brilliant white against the pale yellow planet.
The rings are unbelievably vast. They cover an area of over 15 billion square miles (40 billion km 2 ), 80 times the total surface area of Earth. To travel from the inner edge of the rings to the outer edge, a space traveler would have to cover a distance equal to thirteen trips across the United States. Their full width from one side to the other is 70 percent that of the distance between Earth and the Moon. The thickness of the rings, however, rarely exceeds 33 feet (10 m). The rings are so thin that a sheet of paper the size of San Francisco would have the same proportions. If you were to make a model of the rings three feet (1 m) wide, it would have to be 10,000 times thinner than a razor blade.
The rings are divided into three distinct bands. The outer one, the A ring, and the broader, brighter B ring. Separating them is a narrow space called the Cassini Division (it only appears to be narrow because the rings are so large, the gap is actually large enough to drop the Earth’s Moon through!). Inside the B ring is the dim, translucent ring called the crêpe ring (or the C ring). Even before the advent of spacecraft, astronomers were aware of at least one additional very narrow outer ring and the Pioneer and Voyager probes discovered many more. There is now known to be at least seven distinct rings altogether. Additionally, Voyager found that the A and B rings were themselves made up of 500 to 1000 extremely narrow rings, like the grooves on an old-fashioned phonograph record.
The rings are made of billions of chunks of nearly pure water ice, something like the ice cubes you can buy in a bag at a convenience store. Some of the particles may be "dirty" or coated with dust. The ring particles are very small, ranging in size from grains of sugar to several feet. A few half mile- (kilometer-) sized bodies may also exist. If all of the material in the rings could be compressed into a ball, it would form a moon only 60 miles (100 km) across. Each ring particle is an individual moon and circles Saturn in its own orbit. It can be rightly said that Saturn is a planet with a billion moons.
There are many reasons for thinking that the rings are relatively young. One of these is how "clean" the ring particles are. The rings are so bright because the ice particles they are made of have not yet had time to be covered with dark dust. Another reason is that the gravitational effects of all of Saturn’s moons—the same forces that create the thousands of large and small gaps in the rings—make the rings unstable. They only look the way they do now because the moons haven’t had enough time yet to disrupt them. A few million years from now, however, the rings will start to fall in toward Saturn and the solar system will lose one of its greatest natural wonders.
Within Saturn's rings
