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Dust on Saturn’s rings reveal how old they are, study says

Using data from NASA’s late Cassini spacecraft and its accompanying Cosmic Dust Analyzer, researchers found that Saturn’s rings are billions of years younger than the planet and may eventually disappear.

(CN) — By studying space dust, researchers think they've managed to date the age of Saturn's seven rings.

They could be much younger than previously thought.

Saturn's rings have gathered dust for no more than 400 million years — making them far younger than the 4.5-billion-year-old gas planet, according to a study published Friday in Science Advances. Sascha Kempf, an associate professor in the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder, was chief author on the study.

Just like old furniture, planetary bodies like Saturn's rings get dusty if not cleaned regularly. And since presumably no one has been cleaning Saturn's rings, that dust can leave clues about how long those rings have been around.

Think of it like carbon dating, but for dust. In the study, researchers likened it to "telling how old a house is by running your finger along its surfaces."

“If you have a clean carpet laid out, you just have to wait" and "dust will settle on your carpet," Kempf was quoted as saying in the study. "The same is true for [Saturn's] rings.”

The rings of Saturn have been an enigma ever since Italian astronomer Galileo Galilei spotted them in 1610. In the 1800s, Scottish scientist James Clerk Maxwell realized that Saturn’s rings were not solid masses but instead consisted of individual pieces of smaller material.

Among that material, later scientists confirmed, were countless chunks of ice, most no larger than a boulder on Earth. Still, for most of the 20th century, researchers "assumed that the rings likely formed at the same time as Saturn," according to the study.

That idea was complicated by further observations — and in particular, the realization that the rings are made of "sparkling clean" water.

Given the nature of dust — which floats around constantly in space just as it does on Earth — "it’s almost impossible to end up with something so clean,” Kempf said.

Still, to test their hypothesis, Kempf and his researchers needed dust. For this, they relied on the late Cassini spacecraft, one of several space probes launched by NASA in its efforts to learn more about the gas giant.

From its 2004 arrival on Saturn until its purposeful crash in 2017, Cassini used its "Cosmic Dust Analyzer" to gather dust used by Kempf and his colleagues in their research. The analyzer was "shaped a bit like a bucket," researchers explained in their paper, and "scooped up small particles" from space as Cassini went by.

The arduous process yielded just 163 grains of dust. Still, that was enough for researchers to draw conclusions.

The researchers estimated that the interplanetary grime contributed a "light sprinkle" of dust (less than a gram) to each square foot of Saturn’s rings every year. From there, the researchers determined that Saturn’s rings likely gathered dust for no more than 400 million years, making them far younger than Saturn.

The ages of planets and other space bodies may seem ancient to observers on Earth — but by the standards of space, Kempf said, 400 million years ago is relatively recent.

The creation of the rings was "a pretty rare event," Kempf wrote in an email, adding that it was a "stroke of luck that this happened 'recently.'"

Relatively speaking, the rings may not be around much longer, either. Ice is slowly raining down on the planet from the rings, and they may disappear within 100 million years, according to the study.

Researchers admit they have much more to learn about the rings of Saturn. Among their top questions is how the rings formed in the first place.

They hope they will learn more through a newer, more sophisticated dust analyzer that will be part of NASA's upcoming Europa Clipper mission. That mission is set to launch in 2024.

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Categories / Environment, Science

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