Scientists said that a calculation of the mass of the rings based on gravitational measurements of the planet collected by Cassini indicated they formed between 100 million and 10 million years ago in roughly the final 2% of Saturn's current age.
With Saturn clocking in at around 4.5 billion years old, it means the giant planet may have been without its distinctive halo for much of its life. That made it hard to separate the gravitational effect of the rings from the gravity of the planet and, in the process, find the rings' mass. Scientists have suggested that the mass of Saturn's rings is directly linked to their age, so that answer had to wait until Cassini's final days.
"I like the rings and their fascinating dynamics, whether they are young or old", said Sapienza University of Rome aerospace engineering professor Luciano Iess, lead author of the study published in the journal Science.
The rings of Saturn are among the famous sights in the solar system.
During NASA's Cassini spacecraft's Grand Finale, the craft dove between the planet and its rings.
His work determined that the rings respond to vibrations within the planet itself, acting similarly to the seismometers used to measure movement caused by earthquakes. And they most likely formed in the last 100 million years. "That turned out to be massive flows in the atmosphere at least 9,000 kilometers (5,592 miles) deep around the equatorial region".
They calculated the rings have much less mass than previously thought.
When Cassini zipped through Saturn's ring plane, mission managers allowed the planet, its rings and moons to gravitationally tug at the speeding spacecraft.
The global Cassini spacecraft has captured an image that shows the rainfall on the north pole of Titan, the largest of Saturn's moons.
Saturn's E ring, meanwhile, has its own unique source: plumes of water vapor streaming into space from the moon Enceladus, believed to harbour an ocean beneath its surface.
"The discovery of deeply rotating layers is a surprising revelation about the internal structure of the planet", Cassini project scientist Linda Spilker at NASA's Jet Propulsion Laboratory in Pasadena, California, who did not participate in the study, said in a statement.
The new mass value fits earlier estimates, which suggest that lower mass equals younger age.
The rotation rate of 10:33:38 that the analysis yielded is several minutes faster than previous estimates in 1981, which were based on radio signals from NASA's Voyager spacecraft. "The question is what causes the more rapidly rotating part of the atmosphere to go so deep and what does that tell us about Saturn's interior". Made up of heavy elements, the team found that the planet's core is about 15 to 18 Earth masses, or 15 percent of the total mass of the planet.