The research team has presented a new model of the origin of Saturn's rings based on the results of computer simulations. These simulations also apply well to the rings of other giant planets and explain the difference between the compositions of the rings of Saturn and Uranus.
The giant planets of the solar system have a variety of rings. Observations show that Saturn's rings are more than 95 percent ice particles, while Uranus and Neptune's rings are darker and contain a higher percentage of rocks.
In a new study, a team of astronomers led by Hyodo Ryuki of Kobe University, Japan, has built a model for the formation of Saturn's rings based on the assumption of the presence in the outer solar system, beyond the orbit of Neptune, during the Late Heavy Bombardment (about 4 billion years ago) of several thousand Kuiper belt objects roughly the size of Pluto. The researchers first calculated the likelihood of such objects passing close enough to giant planets to be destroyed by their tidal forces during the Late Heavy Bombardment era. Calculations showed that Saturn, Uranus and Neptune experienced multiple encounters with these large celestial bodies.
Further modeling showed that when large Kuiper belt objects approach the giant planets of the Solar System, these objects are fragmented under the influence of the gravity of giant planets, and in many cases fragments with masses from 0.1 to 10 percent of the mass of the original body are captured into orbit around the planet … The total mass of these fragments is quite sufficient to explain the existence of rings around Saturn and Uranus.
This model also explains the difference between the material compositions of the rings of Saturn and Uranus. Unlike Saturn, which has a relatively low average density of matter (0.69 g / cm3), Uranus, as well as Neptune, have higher average densities of matter, respectively 1.27 g / cm3 and 1.64 g / cm3, therefore large the debris can come closer to the centers of such planets than to the center of diffuse Saturn, where they experience a more powerful influence of the planet's gravity. More powerful tidal forces in the case of ice giants make it possible to destroy these objects entirely, including the rocky core, while in the case of Saturn, only the ice shell of the Kuiper belt object undergoes destruction and subsequent capture into orbit.