2023-05-13 01:42:31
A study just published in the journal ‘Science Advances‘ and led by physicist Sascha Kempf of the University of Colorado Boulder, has revealed the strongest evidence to date for the age of Saturn’s rings, a question that has puzzled scientists for decades. The research determines that this conglomerate of rocks, ice and dust would not be more than 400 million years old, which means that they are significantly younger than their planet (which was created 4.5 billion years ago). To reach this conclusion, the scientists looked at something that might seem trivial: dust.
Kempf explains that our Solar System has a constant flow of dust that, in some cases, settles on bodies and leaves a thin layer, even on the ice that forms Saturn’s rings. In the new study, the team set out to date Saturn’s rings by studying how quickly this layer of dust accumulates, sort of like checking the age of a house by running your finger over furniture. “Think of the rings as the rug in your house,” Kempf explains. “If you have clean carpet, you just have to wait for these particles to settle. The same goes for the rings.”
It was an arduous process: From 2004 to 2017, the team used an instrument called the Cosmic Dust Analyzer, aboard NASA’s latest Cassini spacecraft, to analyze dust specks flying around Saturn. During those 13 years, the researchers collected just 163 grains that originated beyond the immediate neighborhood of the planet. But it was enough. Based on their calculations, Saturn’s rings have likely been collecting dust for only a few hundred million years.
The planet’s rings, in other words, are new phenomena that arise (and potentially even disappear) in what amounts to the blink of an eye in cosmic terms. “We know roughly how old the rings are, but it doesn’t solve any of our other problems,” says the physicist. “We still don’t know how these rings formed in the first place.”
From Galileo to Cassini
Researchers have been captivated by these seemingly translucent rings for more than 400 years. In 1610, the Italian astronomer Galileo Galilei first observed the features through a telescope, although he did not know what they were. In the 1800s, Maxwell, a scientist from Scotland, concluded that Saturn’s rings could not be solid, but were made up of many individual pieces.
Today, scientists know that Saturn is home to seven rings made up of countless chunks of ice, most no bigger than a rock on Earth. In total, this ice weighs about half that of Saturn’s moon Mimas and extends nearly 280,000 kilometers from the planet’s surface.
Kempf added that for most of the 20th century, scientists assumed that the rings probably formed at the same time as Saturn. But that idea raised some problems: The rings are sparkling clean. Observations suggest that these features are made up of about 98% pure water ice by volume, with only a small amount of rocky matter. “It’s almost impossible to end up with something that clean,” Kempf said.
Cassini first arrived at Saturn in 2004 and collected data until it deliberately crashed into the planet’s atmosphere in 2017. Shaped like a bucket, the Cosmic Dust Analyzer picked up tiny particles as they whizzed by.
LASP engineers and scientists designed and built a much more sophisticated dust analyzer for NASA’s upcoming Europa Clipper mission, scheduled for launch in 2024.
The team estimated that this interplanetary debris would contribute much less than a gram of dust to each square foot of Saturn’s rings each year: a small amount, but enough to accumulate over time. Previous studies also suggested that the rings might be young, but did not include definitive measurements of dust accumulation.
Stroke of luck
The rings may already be disappearing. In an earlier study, NASA scientists reported that ice is slowly falling on the planet and could disappear completely in another 100 million years.
That these short-lived features existed at a time when Galileo and the Cassini spacecraft could observe them seems almost too good to be true, Kempf said, calling for an explanation of how the rings formed in the first place. Some scientists, for example, have postulated that Saturn’s rings may have formed when the planet’s gravity tore at one of its moons.
“If the rings are short-lived and dynamic, why are we seeing them now?” he says. “It’s too lucky.”
#million #years #cosmic #sigh