You can’t picture Saturn without its iconic rings — the two simply go together. But a new study based on data from NASA’s Cassini probe unveiled that the rings of Saturn may be a lot younger than previously believed, the space agency announced today.
According to the latest findings — which have been published in the journal Science — Saturn’s rings only date back a few tens of millions of years and were likely formed between 10 million and 100 million years ago. At that time, dinosaurs were still ruling Earth, notes NASA.
Meanwhile, Saturn was forged some 4.5 billion years ago, during the early days of the solar system. This means that there’s a considerable age difference between the gas giant and its emblematic rings.
The conclusion comes from a new analysis of gravity data gathered by the Cassini spacecraft — particularly measurements of the rings’ mass, performed by the NASA probe during its final and very close flybys of Saturn right before the end of its mission in September of 2017.
“In the final phase of the Cassini mission, the spacecraft dived between the planet and the innermost ring, at altitudes of 2,600 to 3,900 kilometers [1,615 to 2,425 miles] above the cloud tops,” the authors wrote in their paper.
“During six of these crossings, a radio link with Earth was monitored to determine the gravitational field of the planet and the mass of its rings.”
The mass of the gas giant and that of its rings was determined after researchers calculated Saturn’s gravitational pull on the Cassini spacecraft down to a fraction of a millimeter per second.
“Only by getting so close to Saturn in Cassini’s final orbits were we able to gather the measurements to make the new discoveries,” said study lead author Luciano Iess, a researcher at Sapienza University of Rome in Italy and a member of the Cassini radio science team.
“And with this work, Cassini fulfills a fundamental goal of its mission: not only to determine the mass of the rings, but to use the information to refine models and determine the age of the rings.”
This isn’t the first time that scientists have pointed to a connection between the mass of Saturn’s rings and their age. The planet’s icy rings are believed to have formed either from an earlier generation of frozen moons around Saturn or from a comet that wandered too close to the gas giant and was shredded by its massive gravitational pull.
Whichever may be the case, scientists have speculated that the brighter, less massive rings were the last to form, given that the darker, older ones had more time to accumulate debris and grow heavier. This suggests that Saturn’s lighter rings are younger than the more massive ones.
As Space points out, previous data from the Cassini orbiter showed that Saturn’s rings, which were originally made out of bright ice, are about 1 percent impure. By finding out their mass, Iess’ team was able to estimate the amount of time it took for the rings to gather interplanetary debris and reach that level of contamination. This ultimately helped reveal the age of the gas giant’s rings.
Up until now, the rings were estimated to weigh around 28 million billion metric tons, based on data from NASA’s two Voyager probes. However, the new Cassini data suggests that the rings are a lot lighter and only have a mass of about 15.4 million billion metric tons.
This, in turn, hints that the rings are a lot younger than initially thought and likely originated sometime between 10 million to 100 million years ago. By comparison, dinosaurs have held dominion over Earth up until 65 million years ago.
“Perhaps a big collision formed the rings around the age of the dinosaurs,” Iess told Gizmodo. “But for me, the real surprise was the interior structure.”
Saturn’s Core And Deep Atmosphere
Another revelation to come from the new data was the mass of Saturn’s core, which was found to weigh between 15 and 18 times the mass of planet Earth. In addition, the team also made an interesting discovery about the gas giant’s atmosphere, whose inner layers spin in synchrony the deeper they get.
The same phenomenon has been observed in the case of Jupiter’s atmosphere. However, Saturn’s layers only start rotating in synchrony at incredible depths of at least 5,600 miles, equivalent to 15 percent of the planet’s entire radius.
“That’s three times deeper than the same phenomenon at Jupiter,” notes NASA.
“The discovery of deeply rotating layers is a surprising revelation about the internal structure of the planet,” said Linda Spilker, a Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who wasn’t involved in the study.
“The questions are what causes the more rapidly rotating part of the atmosphere to go so deep, and what does that tell us about Saturn’s interior?”