Where did Saturn’s rings come from?

Saturn without its rings is really boring. See the picture below of “Jason Kottke” (Jason Kottke) blogger; Saturn has the simplest appearance in the solar system. Of course, there is a hexagonal storm and some attractive cyclones at the poles, but the pale appearance of the planet has neither the coloring of Jupiter, nor the attractive blue of Neptune, nor the stifling gloom of Venus.

Rings of Saturn
Saturn without rings
When the Cassini spacecraft photographed above Saturn’s poles in 2013, its rings did not collide with the planet. If we remove the rings from the image, the planet’s visual appeal is significantly reduced.

Even Rusty Mars is more interesting than this. Fortunately, somewhere in the last 4.5 billion years the universe updated this neighbor of ours; With a large, bright icy ring system around it. But scientists do not agree on the formation time of these rings; Also how they came about. This problem has existed for decades; It seems that the origins of one of the most special phenomena of the solar system is an unsolved mystery.

Maryame El Moutamid, an astrophysicist at Cornell University, said, “The planet formed at some point during the formation of the solar system, and we don’t know if the rings were found then or later.” “The reason it’s interesting is not just knowing the answer, but understanding the Saturn system—we have a planet, a ring system, and a lunar system, and we think there’s a connection between the rings and the moons.”

This puzzle has a unique appeal. For the most part, scientists have a good knowledge of the origins of the Solar System’s spectacular phenomena: the notch on Mars that the Grand Canyon pales against, the Great Red Circle on Jupiter, and the Great Blue Basin south of the Moon. But Saturn’s rings remain an unsolved mystery.

“Saturn’s rings are unique,” said Jeff Cuzzi of NASA’s Ames Research Center. They are just very, very bright large rings that are very unusual. This is the mystery we are facing.”

Galileo painting of Saturn
Images of Saturn have come a long way since their first drawings: what Galileo saw in 1610 (left) and what he observed with a better telescope in 1616 (right).
Cassini drawing of Saturn
An image drawn by the astronomer Giovanni Cassini and published in 1676.

Scientists dealing with this puzzle usually fall into two groups. The first group says that Saturn’s rings were eternal; It means that more than four billion years have been formed together with the planet itself, and Saturn has never been a dull planet.

The second group believes that the rings are much younger and formed in the last few hundred million years. According to this theory, the rings are so young that if the dinosaurs had a space program, they would have seen a ring-less Saturn with their telescopes (and perhaps could have prevented that asteroid impact).

“Both scenarios have strong reasons, but they also have weaknesses,” Al-Motamid says.

Although these two stories are billions of years apart, they have one thing in common: violence. The formation of the rings required the destruction of an ice mass; Maybe a comet or a moon. The object approached Saturn incognito, and the planet’s gravity turned it into tiny chunks of ice. A few of these pieces are a little bigger than a house, but the rest are very small. Most of them are bright clear frozen waters, but a band in the rings is slightly darker. Over time, these fragments arranged themselves into the ring system we see today, which is about 275,000 km wide and only about 10 meters thick.

Rings of Saturn
Disc rings
The different rings are named alphabetically according to the time of their discovery, while the gaps and boundaries between them are named after astronomers. Tiny “shepherd” moons such as Pan, Atlas, Prontheus, and Pandora, orbiting within bright rings, hold the boundaries.

The Old Rings group says the destruction occurred in Saturn’s early days (it’s scientifically more likely that a stray object entered a planet’s gravitational cavity during the solar system’s youth). One version of this story is that the giant planets were not born where we see them today; Rather, they migrated to their current position and created a wave of instability in smaller objects that caused them to scatter everywhere like celestial ping-pong balls.

During the solar system’s infancy, it was not difficult for an icy body to form rings around Saturn. The old ring theory also predicts that Saturn’s moons are composed of detached ring fragments that have been far enough from the planet to form a separate mass on their own. So some of the moons that orbit the edges of the rings today are made of the same material.

“Truthfully, without trying to be impartial, the old rings theory makes more sense to me than the new rings theory,” al-Matimad says. This has been my belief until now, but I will be happy if someone changes my opinion.”

The problem is that the ice rings are too white to be billions of years old; At least that’s one of the arguments that the Young Circles group focuses on. This problem, called the contamination argument, relies on the rate at which dark dust from the outer solar system collides with the rings and dilutes them. Simply put, nearly four billion years of cosmic gray rain should have made Saturn’s rings as dirty and insignificant as Jupiter’s rings; Unless the rings are heavy or young.

In 2017, scientists using the Cassini spacecraft measured the mass of Saturn’s rings and found that there is not enough material to absorb dust as old as the Solar System and stay clean. Cassini also collected data on the amount of dust entering the Saturn system, which also supports the idea that the rings are young.

However, it is highly unlikely that an object large enough to form the rings would have approached Saturn’s region (unless in the chaos of the early solar system).

The first image of Saturn
The first picture of Saturn was taken by Voyager 1 in 1980.

What if Saturn destroyed one of its moons instead of ripping apart an exoplanet? Two new theories suggest that just like the bloody masterpiece of the Spanish painter, Francisco de Goya, Saturn actually swallowed one of his own children.

The number one theory, presented in 2016, says that roughly a hundred million years ago, the Saturn system entered a position where the Sun’s gravity sent the planet’s inner moons into collisional orbits that eventually created the debris ring. This idea also explains the young appearance of the surface of some of Saturn’s moons, as the ring-forming event could have destroyed some moons and created others.

Theory number two, from late 2022, blames the rings on Saturn’s supermoon, Titan, which is slowly drifting away from its home planet. About two hundred million years ago, the moon’s slow migration brought it into resonance (exerting a gravitational effect) with a hypothetical moon that scientists call Chrysalis. As a result, the chrysalis was thrown towards Saturn and turned into a ring. (This theory also explains Saturn’s interesting orbital angle: the effect of a gravitational interaction with Neptune’s orbit.)

Needless to say, we don’t accept either scenario so easily, but in Casey’s opinion, “controversy is good for science; It’s not bad that not everyone is convinced.”

Young Saturn’s rings challenge our simplistic idea of ​​cosmic continuity (even with exploding stars and meteors crashing into our sky). It’s exciting that perhaps one of the most familiar sights in the solar system, Saturn’s amazing rings, hasn’t always been this way; Just like when Gemini became extremely dim and changed the pattern of the Orion constellation; As Cazi says, “The things we know and love in the night sky aren’t going to change like this.”

However, young Saturn’s rings also show that life on Earth has been very lucky. Coincidentally, our evolution (the species that can build telescopes) coincided with Saturn’s amazing cosmic view.

During the human lifetime, the night sky may not change much

Planets move in predictable orbits, constellations rise and set according to schedule, the passage of time can be marked by the changing face of the moon; This is reassuring because it shows that little beings like us, adrift in the endless sea of ​​space on a green island, have attained a degree of celestial knowledge.

We have deciphered the order of planetary motions; We can accurately calculate the occurrence of a magical phenomenon such as the sun darkening in the middle of the day, and we know to some extent how things (except ourselves) came to be. In an infinite universe, we cling to what we know.

“Your mind just wants things to be permanent,” says Jeff Causey. Heavenly objects are not supposed to change before our eyes. But that’s what the Cassini spacecraft showed us when it got to Saturn… We know what’s showing up there on all the time scales. This is a useful change of perspective for us.”

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