They seem to be the same age as their parent planet, but is there evidence that Saturn’s rings are younger than their parent planet?
By: Ringo Bones
Conventional wisdom suggests that Saturn’s rings are the same age and therefore always been a permanent fixture of the planet itself but research done since 1984 have seem to prove otherwise. Many scientists have been forced to abandon the long-established notion that the rings of Saturn are as ancient and as enduring as the solar system itself. It now appears that the rings could not have formed along with the planet 4.5 billion years ago. Rather, they are a recent addition – as in no more than 100 million years old. Furthermore, the same processes that created them are already sowing the seeds of their destruction. This makes Saturn’s rings a “passing fancy” that will disappear before the next 100 million years go by. In all likelihood, Saturn has “fathered” several generations of rings over the course of the planet’s lifetime.
“I’m interested in all the ring systems,” says Jeffrey Cuzzi of NASA’s Ames Research Center in Mountain View, California, who was drawn to his work by the confounding mystery and beauty of Saturn’s rings. What we currently know about the astrophysical principles behind planetary ring formation theory suggest they are primarily created by the breakup of a planet’s own moons going to pieces or captured comets caught on the fly and then torn to shreds by competing gravitational forces. If you scoop up all the scattered particles of ice and dust glittering Saturn’s ring system – or other planetary ring systems – and pack them together, you could mold a moon about the size of Saturn’s moon Mimas – a little under 250 miles in diameter. Such a satellite probably existed quite close to the planet Saturn about 100 million years ago. Then came along a comet or another big celestial body on a collision course and blasted this ancient moon to bits.
This ill-fated moon, more likely, lay within Saturn’s Roche Limit – named for the 19th Century French mathematician Edouard Roche and defined the region close to a planet where where competing gravitational forces are strong enough to shatter unstable satellites or prevent them from forming in the first place. Within the Roche Limit, the destructive tidal forces dominate other effects. Tidal forces pull those parts of an orbiting body that are relatively close to the planet more strongly than the parts farther away; as a result, the satellite – held together only by the weak glue of its own gravity – may literally be pulled to pieces. Though not all orbiting bodies must submit to tidal forces – NASA’s fleet of space shuttles and the International Space Station, for example, orbits well within planet Earth’s Roche Limit yet does come undone, because its constituent parts are held together by nuts, bolts and the fierce crystal cohesion of the molecules of its metallic parts.
“The ring systems are a little bit like poppies on a hill,” muses Cuzzi, “You come back next year to the same place, and you’ll still see poppies on the hillside, but they’re not the same poppies you saw last year. In the same way, the rings of the planets may not be the same rings that were there a million years ago – or 10 million or 100 million years ago. They’re just the most recent incarnation. And the process just keeps on going.” Sadly, there's probably only a very small handful in the global astronomical community who is accommodating to the theory that Saturn's rings might not be more than 100 million years old.