How previous are Saturn’s rings? Far youthful than as soon as thought, in line with new examine | CU Boulder Right this moment
Saturn’s rings partially in shadow as seen by NASA’s Cassini spacecraft. (Credit score: NASA/JPL/House Science Institute)
A brand new examine led by physicist Sascha Kempf at CU Boulder has delivered the strongest proof but that Saturn’s rings are remarkably younger—probably answering a query that has boggled scientists for effectively over a century.
The analysis, published May 12 in the journal Science Advances, pegs the age of Saturn’s rings at not more than 400 million years previous. That makes the rings a lot youthful than Saturn itself, which is about 4.5 billion years previous.
“In a approach, we’ve gotten closure on a query that began with James Clerk Maxwell,” mentioned Kempf, affiliate professor within the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder.
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Saturn’s rings could get their striated colours from the small concentrations of contaminates that turn into trapped within the rings’ ice. (Credit score: NASA/JPL/House Science Institute)
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Artist’s depiction of NASA’s Cassini throughout its 2017 “grand finale,” by which the spacecraft dove between Saturn and its rings a number of instances earlier than purposefully crashing into the planet’s environment. (Credit score: NASA/JPL-Caltech)
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The Europa SUrface Mud Analyzer (SUDA), designed and constructed at LASP, will gather grains of mud as a part of NASA’s flagship Europa Clipper mission. (Credit score: Glenn Asakawa/CU Boulder)
The researchers arrived at that closure by learning what would possibly seem to be an uncommon topic: mud.
Kempf defined that tiny grains of rocky materials wash by means of Earth’s photo voltaic system on an virtually fixed foundation. In some circumstances, this flux can go away behind a skinny layer of mud on planetary our bodies, together with on the ice that makes up Saturn’s rings.
Within the new examine, he and his colleagues got down to put a date on Saturn’s rings by learning how quickly this layer of mud builds up—a bit like telling how previous a home is by operating your finger alongside its surfaces.
“Take into consideration the rings just like the carpet in your own home,” Kempf mentioned. “When you have a clear carpet laid out, you simply have to attend. Mud will settle in your carpet. The identical is true for the rings.”
It was an arduous course of: From 2004 to 2017, the group used an instrument referred to as the Cosmic Dust Analyzer aboard NASA’s late Cassini spacecraft to research specks of mud flying round Saturn. Over these 13 years, the researchers collected simply 163 grains that had originated from past the planet’s shut neighborhood. Nevertheless it was sufficient. Primarily based on their calculations, Saturn’s rings have possible been gathering mud for only some hundred million years.
The planet’s rings, in different phrases, are new phenomena, arising (and probably even disappearing) in what quantities to a blink of a watch in cosmic phrases.
“We all know roughly how previous the rings are, however it doesn’t resolve any of our different issues,” Kempf mentioned. “We nonetheless don’t know the way these rings fashioned within the first place.”
From Galileo to Cassini
Researchers have been captivated by these seemingly translucent rings for greater than 400 years. In 1610, Italian astronomer Galileo Galilei first noticed the options by means of a telescope, though he didn’t know what they have been. (Galileo’s authentic drawings make the rings look a bit just like the handles on a water jug). Within the 1800s, Maxwell, a scientist from Scotland, concluded that Saturn’s rings couldn’t be strong however have been, as an alternative, made up of many particular person items.
Right this moment, scientists know that Saturn hosts seven rings comprised of numerous chunks of ice, most no greater than a boulder on Earth. Altogether, this ice weighs about half as a lot as Saturn’s moon Mimas and stretches practically 175,000 miles from the planet’s floor.
Kempf added that for many of the twentieth Century, scientists assumed that the rings possible fashioned similtaneously Saturn.
However that concept raised a number of points—specifically, Saturn’s rings are glowing clear. Observations recommend that these options are made up of roughly 98% pure water ice by quantity, with solely a tiny quantity of rocky matter.
“It’s virtually unattainable to finish up with one thing so clear,” Kempf mentioned.
Cassini provided a possibility to place a definitive age on Saturn’s rings. The spacecraft first arrived at Saturn in 2004 and picked up knowledge till it purposefully crashed into the planet’s atmosphere in 2017. The Cosmic Mud Analyzer, which was formed a bit like a bucket, scooped up small particles as they whizzed by.
Engineers and scientists at LASP designed and constructed a much more sophisticated dust analyzer for NASA’s upcoming Europa Clipper mission, which is scheduled to launch in 2024.
The group estimated that this interplanetary grime would contribute far lower than a gram of mud to every sq. foot of Saturn’s rings yearly—a lightweight sprinkle, however sufficient so as to add up over time. Earlier research had additionally suggested that the rings could be young however didn’t embody definitive measures of mud accumulation.
Stroke of luck
The rings would possibly already be vanishing. In earlier analysis, NASA scientists reported that the ice is slowly raining down onto the planet and will disappear solely in one other 100 million years.
That these ephemeral options existed at a time when Galileo and the Cassini spacecraft might observe them appears virtually too good to be true, Kempf mentioned—and it begs a proof for a way the rings appeared within the first place. Some scientists, for instance, have posited that Saturn’s rings could have fashioned when the planet’s gravity tore aside certainly one of its moons.
“If the rings are brief lived and dynamical, why are we seeing them now?” he mentioned. “It’s an excessive amount of luck.”
Co-authors on the brand new examine embody Nicolas Altobelli of the European House Company; Jürgen Schmidt of the Freie Universität Berlin; Jeffrey Cuzzi and Paul Estrada of the NASA Ames Analysis Heart; and Ralf Srama of the Universität Stuttgart.