Saturn’s Majestic Rings are Extremely Young–and Might Not Be Around for Much Longer

Newly-analyzed data from the Cassini space probe has revealed that Saturn is losing material from its visually stunning ring system at a rapid rate, due to an effect cased by the planet’s wide-reaching magnetic field that produces what NASA is calling “ring rain”. The rapid loss of material has also illustrated that Saturn’s rings are extremely young–and that they may not be around for much longer.

But don’t worry about having to pine over the good ‘ol days back when Saturn used to have rings, as they’re estimated to last for another 300 million years. That might be a long time for us, but that’s the blink of an eye for a planet that has been around for 4.5 billion years, just 1/15th of Saturn’s existence. The discovery of this rapid material loss also places a limit on how far into the past the rings could have formed, and at less than 100 million years old, they’re incredibly young for a planetary feature. This new finding settles the long-standing question as to whether Saturn’s rings formed at the same time as the rest of the planet, or if it acquired them later in life, perhaps as the as the leftover debris of moons that were obliterated in a long-ago collision.

Saturn’s rings are made up mostly of chunks of water ice, ranging in size from microscopic dust to 30-foot-wide boulders. Ultraviolet radiation from the Sun ionizes the particles, allowing them to be carried away by the planet’s magnetic field. Saturn’s gravity then causes them to fall as a dusty rain into its atmosphere–and at a surprisingly rapid rate. 

“We estimate that this ‘ring rain’ drains an amount of water products that could fill an Olympic-sized swimming pool from Saturn’s rings in half an hour,” explains James O’Donoghue of NASA’s Goddard Space Flight Center. “From this alone, the entire ring system will be gone in 300 million years, but add to this the Cassini-spacecraft measured ring-material detected falling into Saturn’s equator, and the rings have less than 100 million years to live. This is relatively short, compared to Saturn’s age of over 4 billion years.”

Clues to this phenomenon were first noticed by the Voyager probes as odd variations in Saturn’s electrically charged upper atmosphere, density variations in the planet’s rings, and three narrow dark bands that circle the planet at northern mid-latitudes, where the ring rain has now been confirmed to be falling. Further measurements were made by Cassini during its 13-year study of the ringed planet, confirming suspicions raised by its predecessors’ flybys.

“We are lucky to be around to see Saturn’s ring system, which appears to be in the middle of its lifetime. However, if rings are temporary, perhaps we just missed out on seeing giant ring systems of Jupiter, Uranus and Neptune, which have only thin ringlets today!” O’Donoghue adds.