Astronomers reveal surprising age of Saturn’s rings
The mighty ring system is very young. And with that conclusion – perhaps – the ongoing debate truly comes to an end.
Scientists have been debating for years: how old are the rings of the sixth planet in our solar system? One says they’ve been around for billions of years, while the other is certain they didn’t come into existence until much later. A new research group has looked into the matter again and has come to a firm conclusion: the rings are much younger than Saturn itself.
Until recently, there were two theories. The first asserted that the rings formed at the same time as Saturn and must therefore be around 4.5 billion years old. According to the other theory, the rings would be very young. Some researchers have even suggested that the rings are less than 100 million years old – and may have formed as early as 10 million years ago.
For most of the 20th century, scientists believed that the rings were born at the same time as Saturn. However, this idea was later questioned. Because if they were very old, they would have been “much more polluted by meteoroid collisions”, the argument goes. Studies have suggested that the rings would have absorbed dusty material from the meteoroids and thus gradually darken. But if we look at Saturn’s ring system, we see that it looks very bright. They look sparkling clean. Observations suggest that the rings are made up of about 98% pure water ice, with only a small amount of rocky material. “It’s almost impossible to end up with something so beautiful,” says researcher Sascha Kempf.
He and his colleagues have now entered the rings of Saturn a new study scrutinized again. They studied the rate at which dust was accumulating – a bit like estimating the age of a house by running your finger over the layer of dust on the windowsill. “Think of the rings like the carpet in your house,” says Kempf. “If you have a new carpet lying around, the dust will accumulate over time. The same goes for the rings of Saturn.
Tiny grains of rocky material are constantly floating around in the solar system. And in some cases, a thin layer of dust can settle on planetary bodies, including the ice that makes up Saturn’s rings. Researchers studied data collected between 2004 and 2017 with the Cosmic dust analyzer, an instrument aboard NASA’s defunct Cassini spacecraft, to analyze dust particles flying around Saturn. THE Cosmic dust analyzer, which was shaped like a bucket, picked up particles as it passed. Over a period of thirteen years, the instrument collected 163 dust particles. Eventually, the team was able to determine the age of Saturn’s rings this way. And according to their calculations, the gas giant’s rings have only been gathering dust for a few hundred million years.
Final age determined
In other words, the planet’s rings are remarkably young. For example, they’re probably no more than 400 million years old, which is really a snap in cosmic terms. This makes the rings much younger than Saturn itself, which, as mentioned, is already 4.5 billion years old. “We now know roughly how old the rings are,” says Kempf. “But that doesn’t solve any of our other questions. For example, we still don’t know how these rings formed in the first place.
Under the spell of Saturn’s rings
Meanwhile, researchers have been fascinated by Saturn’s seemingly transparent rings for over 400 years. In 1610, Italian astronomer Galileo Galilei observed them for the first time through a telescope, although he did not know what they were (in Galileo’s original drawings, the rings look a bit like handles of a pitcher of water). In the 1800s, James Clerk Maxwell, a Scottish scientist, concluded that Saturn’s rings could not be massive, but made up of many separate parts. Today we know that Saturn is home to seven rings made up of countless chunks of ice, most of which are no bigger than a rock on Earth. In total, this ice weighs about half the weight of Saturn’s moon Mimas. The rings extend about 280,000 kilometers from the surface.
We may not have much time to find out. Because the rings may already be disappearing. A previous study suggested that ice rains slowly on the planet. And if this continues at the current rate, the rings have at most 100 million years to live.
Too good to be true
“So seeing Saturn’s rings at this precise moment, and Galileo and the Cassini spacecraft being able to see them, seems almost too good to be true,” Kempf says. This therefore calls for a conclusive explanation of how the rings formed in the first place. Some scientists believe the mighty ring system formed when the planet’s gravity crushed one of its moons. However, whether this is true remains to be investigated further.
While researchers now have an answer to a question that has puzzled scientists for more than a century, the final word on Saturn’s rings certainly hasn’t been said yet. “If the rings are short-lived, why do we see them now?” Kempf wonders aloud. “It’s too lucky.”
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