With a new collaborative article with EPS Professor Burkhard Militzer published in Science today, gravity measurements collected during Cassini spacecraft’s Grand Finale point to an unexpectedly young age for Saturn’s rings. The first gravity measurement of the ring mass now tells us they contain only about 0.4 Mimas masses (2000 Mimas masses = 1 Earth moon) worth of material, which points to a surprisingly young ring age of only between 10 and 100 million years compared with the formation of the planet itself (4.5 billion years). Before that Saturn presumably did not have any rings. See “Saturn hasn’t always had rings” article in Berkeley News, by Robert Sanders, for further details.
A dramatic event must have occurred at Saturn in our recent solar system history. 100 million years ago, the dinosaurs still roamed on Earth. They disappeared when a giant impact occurred near the Yucatan peninsula 65 million years ago. Now we have evidence that a drastic event occurred near the Saturnian system that produced a gazillion piece of icy rubble that make up the rings today. This suggests that our solar system is not such a stable and happy place as one might think. We assume the rings are either the leftover debris from comets that were tidally disrupted by Saturn's extreme gravity just like the Shoemaker-Levy comet was pulled apart by Jupiter. Alternatively Saturn originally had multiple satellites, their orbits become unstable, and it came to a gigantic collision. We cannot tell which scenario is more likely but we not know something drastic must have happened in the Saturnian system fairly recently by astronomical standards.
(Note: This image has been brightened from the processed image, available here.) Image credit: NASA/JPL-Caltech/Space Science Institute)