Saturn’s spectacular rings are just 400 million years old – less than a tenth the age of the planet, according to new research.
They are much younger than previously believed – solving a mystery that has puzzled astronomers for centuries.
A US team came up with the answer by studying dust. They likened it to analysing a carpet in an unvacuumed room.
Lead author Professor Sascha Kempf explained: ‘Think about the rings like the carpet in your house.
‘If you have a clean carpet laid out, you just have to wait. Dust will settle on your carpet. The same is true for the rings.’
It is the first time a definitive age has been put on Saturn’s iconic rings. Some experts have argued the stunning loops of icy particles formed along with the planet itself.
Others suggested they were a recent phenomenon – perhaps the crushed up remains of a moon or a passing comet that was involved in a collision.
The University of Colorado Boulder team decided to resolve the dispute. They peg their age at ‘no more than 400 million years old’.
Professor Kempf said: ‘That makes the rings much younger than Saturn itself, which is about 4.5billion years old.
‘In a way, we have closure on a question that started with James Clerk Maxwell.’
The famous Scottish physicist first showed they must consist of countless particles. The Maxwell Gap within Saturn’s C ring is named after him.
Tiny grains of rocky material wash through Earth’s solar system on an almost constant basis. In some cases, this flux can leave behind a thin layer of dust on planetary bodies, including on the ice that makes up Saturn’s rings.
Professor Kempf and her colleagues studied how rapidly this layer builds up – a bit like telling how old a house is by running your finger along its surfaces.
They used an instrument called the Cosmic Dust Analyzer aboard Nasa’s Cassini spacecraft to analyse orbiting specks between 2004 and 2017.
Over those 13 years, the researchers collected just 163 grains that had originated from beyond the planet’s close neighbourhood.
They were enough to suggest the rings have been gathering dust for only a few hundred million years.
In other words, they are a new phenomena, arising, and potentially even disappearing, in what amounts to a blink of an eye in cosmic terms.
Professor Kempf said: ‘We know approximately how old the rings are, but it doesn’t solve any of our other problems. We still don’t know how these rings formed in the first place.’
Scientists have been captivated by the seemingly-translucent rings for more than 400 years.
In 1610, Italian astronomer Galileo Galilei first observed the features through a telescope, although he didn’t know what they were.
His original drawings make the rings look a bit like the handles on a water jug. In the 1800s, Maxwell concluded the rings couldn’t be solid but were, instead, made up of many individual pieces.
It is now known Saturn hosts seven rings comprised of countless chunks of ice, most no bigger than a boulder on Earth.
Altogether, this ice weighs about half as much as Saturn’s moon Mimas and stretches nearly 175,000miles from the planet’s surface.
For most of the 20th Century, it was assumed the rings likely formed at the same time as Saturn.
But they sparkle. Observations suggest they are made up of 98% pure water ice by volume, with only a tiny amount of rocky matter.
Cassini first arrived at Saturn in 2004 and collected data until it was purposefully crashed into the planet’s atmosphere in 2017. The Cosmic Dust Analyser, which was shaped a bit like a bucket, scooped up small particles as they whizzed by.
Engineers and scientists have designed and built a much more sophisticated version for Nasa’s upcoming Europa Clipper mission, scheduled to launch in 2024.
The team estimated that this interplanetary grime would contribute far less than a gram of dust to each square foot of Saturn’s rings every year – a light sprinkle, but enough to add up over time.
Previous studies had also suggested the rings could be young but didn’t include definitive measures of dust accumulation.
And they might already be vanishing. In a previous study, Nasa scientists reported that the ice is slowly raining down onto the planet and could disappear entirely in another 100million years.
That these ephemeral features existed at a time when Galileo and the Cassini spacecraft could observe them seems almost too good to be true.
Professor Kempf said: ‘If the rings are short lived and dynamical, why are we seeing them now? It is too much luck.’
The study is published in the journal Science Advances.
MORE : Saturn’s rings are disappearing – and astronomers don’t know how long they have left
MORE : This ‘robot snake’ could probe Saturn’s moon in search for alien life
