Story of Saturn's rings

L-R: Saturn's icy rings could be the leftover mantle of a huge moon. Saturn

There has always been a great deal of interest about Saturn's mystifying yet magnificent set of rings. In fact, the formation of the nine rings of this sixth and the second largest planet of our solar system has always intrigued astronomers for ages. But a recent study conducted by the Southwest Research Institute (SwRI), USA, is shedding some conclusive light on the origins of Saturn's majestic rings. The study has been published in details in Nature's Advance Online Publication of December 12.
About 4.5 billion years ago, around the time when our Earth was formed, a moon about the size of Titan (Saturn's largest satellite) violently coiled into the massive planet braving a large disk of hydrogen gas that circled the Saturn. And as the event took place, Saturn's powerful gravity simply stripped off the fated moon's icy outer layers and thus dawned the planet's stellar icy rings. Previous theories suggested that Saturn's many moons (62 known moons and hundreds of moonlets) either crashed into each other or an asteroid collided with some of them leaving a trail of debris that would eventually form the rings. But according to Dr. Robin M. Canup, associate vice president of SwRI and author of the paper, this wasn't the case after all. And in her own words, "This scenario would have likely resulted in rings that were a mixture of rock and ice, rather than the ice-rich rings we see today". Saturn's rings are 90 to 95 % water-ice.
And since cosmic dust and debris from rocky meteoroids have polluted the rings after their formation, it is believed that these rings were actually consisted of pure ice. This means that if the rings were formed by a moon-on-moon crash or asteroid-on-moon collision, then there would have been more space rocks in the rings. And this clearly strengthens Dr. Canup's particular hypothesis on Saturn's ring formation.
This ring formation theory also links to the deceased satellites of Saturn. Today, as we all know, Saturn has only one true gigantic moon, Titan. But it is believed that during the early days of formation of our solar system, several Titan-size satellites orbited the planet. And it was those fateful moons which one after another collided with Saturn in the span of billions of years. Interestingly, each collision created a ring system which was subsequently destroyed by the collision of another moon which in effect formed another ring around the magnificent planet. And now Titan is the sole giant satellite of the planet, thanks to Saturn's powerful gravitational pull. It is to be noted that the water-ice around Saturn used to be 10 to 100 times more massive than the ones we see today. And this is due to the fact that these icy rings had shrink with the passage of time. So, the ring around Saturn today is very likely the ruins of the last moon that collided with the planet. Experts believe in the near future NASA's Cassini aircraft, which entered the orbit around Saturn back in 2004, would be able to measure the rings' mass and the pollution rate. And at the same time it'll also be able to provide information about the rings' age.

The contributor is a freelance science writer.