The history and fate of Saturn's rings

The universe is a mysterious place. As much scientific knowledge we have, there is so much more that we do not know and much of those unknowns involve the study of the universe. It’s size is beyond comprehension, and because space technically goes on forever, it’s impossible to ever know everything about it.

We do, however, know much more about our own solar system, but even that holds a long list of mysteries that scientists are coming closer to solving every day. One of those mysteries and now at least partial discoveries involves the very recognizable and popular rings of Saturn. Saturn’s rings are one of those things that most people take for granted, but they are really strange when you stop and actually think about it. A recent study on the rings gets us just a little closer to understanding them.

What are they? 

Saturn's rings are relatively new in terms of astronomical history. The newest studies show that Saturn’s rings developed around the time of the dinosaurs. Saturn is not the only planet to have rings, it just so happens to have the most visible rings in our solar system. There are even a few moons that have very faint rings and scientists say that at one time the Earth may have had rings.

Most people know that Saturn’s rings are not solid (although there are some that don’t know that), but what many do not realize is just how thin those rings are. The average thickness of the rings is only about 30 feet. When you think about the huge sizes of planetary objects, this is extremely tiny. The reason why they are so thin can be explained in their formation.

Ring Formation

For a long time, scientists thought that the rings were made mostly of rock and dust. The rings do have rock and dust in them, but the vast majority of matter is in the form of ice. The long held belief is that one or more of Saturn’s moons broke apart or collided and the rings are the debris from the long-lost moon. This was a reasonable explanation until scientists found that the rings were made of mostly ice. This would not be the case if the rings were remnants of a moon.

Recently, a new idea has emerged that offers a better explanation for the amount of ice found in Saturn’s rings. This idea proposes that one of Saturn’s moons was formed too close to the giant planet. The intense gravity of Saturn pulled the water and ice off of the moon over time and that is the ice that is now circling the planet as rings. Eventually, Saturn’s gravity pulled the now dry moon into the planet in a spectacular collision. Some of the dust and rock from the collision also got caught up in the rings.

This explains why there is ice and some rock circling Saturn, but why are the rings so perfectly flat? This answer can be completely answered by physics. The greatest gravitational pull will occur along the planet’s equator. Therefore, the ice and rock will concentrate toward where the rings currently are. If the rings were thicker (which they once were) things would not be as stable. The material furthest north of the equator will be pulled south so its orbit will wobble both above and below the equator.

The material furthest south would do exactly the opposite. This process would cause material to crisscross and collide often. The collisions would make the material smaller and over time would concentrate closer and closer to the equator. This process has given us what we have now: a very thin ring aligned along the equator.

The Future of the Rings

As stated earlier, Saturn’s rings are relatively young and the newest research shows that they won’t be around that long either — at least in terms of astronomical time. Scientists have suspected that some of the ice caught in the rings is continually raining down on Saturn. This idea was confirmed when one of NASA’s probes detected the falling “ring rain.” Further studies have found that about 4,000 pounds of water are falling from Saturn’s rings to the surface of the planet every second! That’s a lot of water, but the rings contain a lot of water. It is estimated that the rings could run out of water (ice) in about 200 million years or so. Because the rings are made mostly of ice, this would be the end of us Earthlings seeing the rings.

Mike Szydlowski is the science coordinator for Columbia Public Schools.