Saturn’s rings are breaking apart and heating up planet’s thin atmosphere, study finds

Saturn’s rings are disintegrating and heating up the gas giant’s upper atmosphere, according to a new study whose findings may help predict if planets around other stars have ring systems.

The phenomenon, never before seen in the Solar System, is an unexpected interaction between Saturn and its rings, say astronomers, including those from Nasa’s Goddard Space Flight Center in the US.

In the new study, published on Thursday in the Planetary Science Journal, scientists reported an excess of ultraviolet radiation in Saturn’s atmosphere, indicating that the planet’s upper atmosphere is being contaminated and heated up from the outside.

They say it could be due to the impact of micrometeorites, solar wind particle bombardment, solar ultraviolet radiation, or electromagnetic forces picking up electrically charged dust - all of which could be pulled towards the gas giant due to the gravitational field pulling particles into the planet.

Researchers say the most feasible explanation for the observed phenomenon is that icy ring particles are raining down onto Saturn’s atmosphere and causing the heating.

Nasa’s Cassini probe had previously measured the atmospheric constituents of Saturn in 2017 as it plunged into the planet’s atmosphere and confirmed that many particles are falling in from the rings.

“Everything is driven by ring particles cascading into the atmosphere at specific latitudes. They modify the upper atmosphere, changing the composition,” said study co-author Lotfi Ben-Jaffel.

Researchers suspect processes involving the collision of the particles with atmospheric gasses are likely heating the atmosphere at a specific altitude.

In the study, scientists assessed archival ultraviolet-light (UV) observations from four space missions that studied Saturn, including those from two Nasa Voyager probes that flew by the planet in the 1980s.

“When everything was calibrated, we saw clearly that the spectra are consistent across all the missions,” Dr Ben-Jaffel said.

“It was really a surprise for me. I just plotted the different light distribution data together, and then I realized, wow – it’s the same,” he added.

Based on the UV data covering four decades of solar cycles, astronomers could analyse the Sun’s seasonal effects on Saturn.

The data revealed that there is no difference in the level of UV radiation, suggesting steady “ice rain” from Saturn’s rings is the “best explanation” for the planet’s upper atmosphere heating up.

“We are just at the beginning of this ring characterisation effect on the upper atmosphere of a planet. We eventually want to have a global approach that would yield a real signature about the atmospheres on distant worlds,” Dr Ben-Jaffel said.

“One of the goals of this study is to see how we can apply it to planets orbiting other stars. Call it the search for ‘exo-rings’,” he added.