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Sunday 17 February 2019

Saturn existed for billions of years before getting its rings, study says

An Italian-led team reckons the rings are only 10 to 100 million years old.

The planet Saturn, as seen from the Cassini spacecraft (Nasa/AP)
The planet Saturn, as seen from the Cassini spacecraft (Nasa/AP)

By Marcia Dunn, Associated Press

Saturn may have flown solo for billions of years, almost its entire existence, before getting its stunning set of rings, a new study suggests.

An Italian-led team has reported in the journal Science that Saturn’s primary rings appear to be just 10 million to 100 million years old.

The gas giant Saturn, on the other hand, is 4.5 billion years old, like all the other planets in our solar system.

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

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.

Cassini, like all giants, has left a legacy that will last for a long time Luciano Iess, scientist

The rings are made mostly of ice.

The remaining 1% 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.

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.

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The Earth as seen from Saturn appearing as a bright smudge with the fainter moon to its right (Nasa/JP Caltech/PA)

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

But Mr Iess said there was little consensus for that theory.

Mr Iess 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.

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Handout photo of Saturn and its rings from ESA (ESA/PA)

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.

Mr 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.

Press Association

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