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Saturn’s rings may be a recent development

Saturn may have existed for billions of years before acquiring its famous rings according to a new study.

An Italian-led team found that the planet’s primary rings appear to be just 10 million to 100 million years old, comparatively recent compared to the estimated age of Saturn at 4.5 billion years.

The findings are based on data collected by Nasa’s Cassini spacecraft while repeatedly diving between Saturn and its rings in 2017, shortly before the craft's demise

The discovery challenges the notion favoured by some astronomers that the rings developed soon after Saturn’s formation along with the other planets including Earth. Others felt the rings were much younger, but lacked crucial data like their mass to estimate their age reliably.

By estimating the mass of the rings through gravity measurements, the researchers gauged the age of the three main rings: A, B and C.

It is still a mystery, though, how these icy rings formed. Scientists suspect a collision between two of Saturn’s many moons or perhaps a moon and comet.

The rings are made mostly of ice while the remaining 1 per cent is dust and possibly organic contaminants.

Overall, the material ranges in size from tiny particles to pebbles, to boulders.

Lead researcher Luciano Iess, a planetary scientist at Sapienza University in Rome, said orbital motion sprayed the dust and other contaminants onto the icy rings at a constant rate.

“I like the rings and their fascinating dynamics, whether they are young or old,” he said.

His team calculated the length of time it would take for the contaminants to accumulate; it turned out to be a “short” 10 million to 100 million years.

It is possible the rings were originally denser than they are now and have thinned over time, which would put them more in line with Saturn’s age.

But Iess said there was little consensus for that theory. He said Nasa’s Voyager spacecraft, as well as Cassini, had already provided clues that the rings had not formed with Saturn.

“But now we have much more concrete evidence, which was only possible to obtain during the final phase of the mission, called the Grand Finale,” he wrote in an email.

The only spacecraft to ever orbit Saturn, Cassini burned up as it plunged through the planet’s atmosphere.

The masses of Saturn’s fainter D, F, G and E rings are considered negligible, the researchers wrote.

Saturn’s E ring, meanwhile, has its own unique source: plumes of water vapour streaming into space from the moon Enceladus, believed to harbour an ocean beneath its surface.

Iess noted the latest findings are “another gift we received from this beautiful mission”.

“Cassini, like all giants, has left a legacy that will last for a long time,” he said.

Cassini was launched from Florida in 1997. It carried the European probe named Huygens, which separated and landed on Saturn’s moon Titan in 2005.

Meanwhile, Nasa research released in December 2018 confirmed that Saturn is losing its famous rings at the maximum rate estimated from Voyager 1 & 2 observations originally made decades ago.

The rings are being pulled into Saturn by gravity as a dusty rain of ice particles under the influence of the planet’s magnetic field. According to the research, Saturn’s rings have less than 100 million years to live. This is relatively short, compared to Saturn’s age of over four billion years.

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