Saturn’s rings are disappearing, a phenomenon never before seen 

Saturn’s rings are disappearing, evidenced by an excess of ultraviolet radiation and the erosion of the planet’s upper atmosphere.

Using observations of Saturn from NASA’s Hubble Space Telescope and the retired Cassini probe, in addition to the Voyager 1 and 2 spacecraft and the retired International Ultraviolet Explorer mission, NASA was able to ascertain that Saturn’s vast ring system is heating the giant planet’s upper atmosphere.

Scientists have known about the erosion of Saturn’s innermost rings since the 1980s, according to Space.com. The downpour is so great that an Olympic-sized swimming pool of water rains on the gas giant daily.

The telltale evidence is an excess of ultraviolet radiation, seen as a spectral line of hot hydrogen in Saturn’s atmosphere. The bump in radiation means that something is contaminating and heating the upper atmosphere from the outside.

“Though the slow disintegration of the rings is well known, its influence on the atomic hydrogen of the planet is a surprise. From the Cassini probe, we already knew about the rings’ influence. However, we knew nothing about the atomic hydrogen content,” said Lotfi Ben-Jaffel of the Institute of Astrophysics in Paris and the Lunar & Planetary Laboratory, University of Arizona, author of a paper published on March 30 in the Planetary Science Journal.

“Everything is driven by ring particles cascading into the atmosphere at specific latitudes. They modify the upper atmosphere, changing the composition,” said Ben-Jaffel. “And then you also have collisional processes with atmospheric gasses that are probably heating the atmosphere at a specific altitude.”

Needless to say, scientists are still trying to figure out exactly what is involved in this strange phenomenon. This is why they are using all the observations from Hubble, the Cassini, and Voyager missions.

Ben-Jaffel brought all the data together and calibrated it. He found that there was no difference in the level of UV radiation found in all the missions.

“At any time, at any position on the planet, we can follow the UV level of radiation,” he said. This points to the steady “ice rain” from Saturn’s rings as the best explanation.

Exactly how fast are the rings eroding?

While Saturn’s rings may seem timeless and eternal, they are actually relatively young in cosmic terms, with some experts estimating that they could be only 100 million years old.

“We’re still trying to figure out exactly how fast they are eroding,” James O’Donoghue, a planetary scientist at the Japan Aerospace Exploration Agency who will lead the new effort to pin down how long Saturn’s rings will last, said in a statement published Monday (April 17).

“Currently, research suggests the rings will only be part of Saturn for another few hundred million years. This may sound like a long time, but in the history of the universe, this is a relatively quick death. We could be very lucky to be around at a time when the rings exist.”

Because of the interest and number of questions concerning the planet’s eroding rings, the James Webb Space Telescope and the Keck Observatory in Hawaii will be part of a long-term observation campaign to study the planet. 

The telescopes will help monitor how the “ring rain” phenomenon fluctuates during one full season on the gas giant, which lasts about seven Earth years thanks to its orbit far away from the sun.

Human beings are a curious lot, and we are still trying to figure out how and when the planet’s rings were born in the first place. Various models had shown that the rings had been a permanent structure around Saturn since 4.5 billion years ago.

However, data from the Cassini spacecraft painted a more youthful picture, aging them at just 10 million to 100 million years old. The discrepancy arose because older rings are often darker, but Cassini had captured Saturn’s rings to be bright, hinting at their youth.