The icy particles of the rings fall onto the planet’s surface as “ring rain.” Recent analysis has shown that with the ring rain falling at the 11 tons per second, the 170,000 mile-wide rings will have been completely drawn to the planet’s surface within 100 million years.
“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,” said NASA’s James O’Donoghue, lead author of a study on Saturn’s ring rain that appeared in Icarus on Dec. 17.
“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.”
The research, published in Science Direct, helps answer a long-standing question: Did Saturn always have its characteristic rings, or did it acquire them later in life?
According to the research, the answer is clear: Saturn’s rings came long after it was born, and are likely less than 100 million years old.
“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 said.
Some data about Saturn’s ring rain was gathered in 2017 by the Cassini spacecraft on its final kamikaze mission as it plunged down through the planet’s icy, rocky ring particles, picking up data before it hit the edge of the atmosphere and was vaporized.
Scientists already thought that some particles in the rings become charged and are then whipped out along the spirals of a magnetic field towards higher altitudes where they fall as rain.
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But they were surprised that Cassini found ring rain also falling directly under the ring, with the overall rate being much higher than expected.
The latest research adds to Cassini’s data by using a telescope to analyze the mysterious dark bands in the higher latitudes of the planet.
The possibility of ring rain was first proposed in 1986, as an explanation for faint dark bands observed by Voyager 2 back in 1981 in the upper altitudes of the planet, far from the rings.
Jack Connerney of NASA Goddard proposed that those lines were formed by electrically charged ice particles flowing along invisible magnetic field lines, dumping water in Saturn’s upper atmosphere to create these bands.
The most recent research used the Keck telescope in Hawaii to tune into and map the signature wavelength of a tell-tale flow of ions released by the icy ring particles as they vaporize and react with Saturn’s ionosphere.
“Their observations revealed glowing bands in Saturn’s northern and southern hemispheres where the magnetic field lines that intersect the ring plane enter the planet,” said a NASA statement. “They analyzed the light to determine the amount of rain from the ring and its effects on Saturn’s ionosphere. They found that the amount of rain matches remarkably well with the astonishingly high values derived more than three decades earlier by Connerney and colleagues, with one region in the south receiving most of it.”
The next step for the researchers is to try to establish whether the icy rain is affected by shifting seasons through the Saturn year that lasts over 29 earth years.