The rings of Saturn are believed to be formed from the debris of Saturn’s moons. The moons were formed some 4.5 billion years ago, and over time, they failed to occupy stable orbits and spiraled into Saturn. The collision barely scraped the surface of the moons, leaving behind only the rocky cores. It has been estimated that after 10,000 years or so, the leftover cores might have also nosedived into Saturn, generating a huge amount of dust that also joined the “ring” bandwagon.
Someone once told me that when God created Saturn, he was so delighted with it that he decided to put a ring on it. However, that same someone also believed that a pigeon is just a mouse with wings. The former is outright false (Welcome to ScienceABC), while the latter is still being debated in some intellectual circles. So how did those rings on Saturn come into existence? Let’s find out.
Saturn is the second-largest planet in our solar system. It is so large, in fact, that it could hold almost 700 Earths inside it. It also has a remarkably beautiful set of rings around it. Due to its large size and distinct rings, Saturn can be quite easily identified by stargazers and astronomers alike. Furthermore, Saturn isn’t the only planet with rings. Jupiter, Uranus and Neptune are also decorated with rings, but they aren’t as dense or bright as Saturn’s.
When Galileo observed the planet for the first time in 1610, he mistook the rings for two moons aligned on opposite sides of the planet. Further observation showed him that the rings tended to change shape or disappear altogether due to their inclination and line of sight with respect to our planet. Since then, scientists have developed a fascination with studying this phenomenon and an eagerness to deconstruct its composition.
The rings of Saturn aren’t thick hoops of awesome space rock, but are actually comprised of matter – from finely grained sand to chunks the size of mountains. The rings are primarily made up of a combination of water and ice. The rings have also befriended chunks of rocks over the millennia due to a constant peppering of meteoroids throughout their existence.
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There are several theories that explain the formation of these rings.
One theory suggests that the rings are a consequence of meandering meteorites and asteroids in Saturn’s vicinity that were inadvertently torn to shreds when they succumbed to the inescapable gravitational pull of this massive planet. Some asteroids may have even jarringly crashed into the planet and the resulting dust and debris settled in its orbit and refused to leave.
It could also be that one catastrophe led to another, perpetuating a chain reaction of collisions, such that moderate-sized chunks broke down into smaller and smaller pieces until the system reached a steady state. Although this theory accounts for the rocky components in the rings, it doesn’t explain where the water-ice composition, which apparently covers 90 percent of the hollowed discs, actually comes from.
The Ice Cold Moons
Another possibility and the currently prevailing theory is that the rings are the remnants of Saturn’s moons. Saturn has a lot of moons in comparison to its neighbors — around 60! However, a large number of them – except Titan – are quite small. Only 13 of these moons have a diameter larger than 50 kilometers.
It could be that the primeval moons, formed some 4.5 billion years ago, failed to occupy stable orbits following their formation and eventually spiraled into Saturn. The collision barely scraped the moons of their surface, leaving behind only the rocky cores. It has been estimated that after 10,000 years or so, the leftover cores might have also nosedived into Saturn, generating a huge amount of dust that also joined the “ring” bandwagon.
Saturn’s moons – just like Jupiter’s – are known to consist of hard ice. Therefore, this theory could explain why the rings are mostly made of ice and water. The water is because the ice slowly melted, which implies that the rings became smaller in size.
Saturn isn’t confined by a single ring, but rather a multitude of distinct rings. The distinctions or divisions mean that the planet is surrounded by a family of thin rings known as ringlets. They are named alphabetically in the order of their discovery. Rings A, B and C were discovered first and form concentric circles of radii in decreasing order, respectively. Then Voyager 1, during its stride across the solar system, discovered the innermost D ring in 1980. The F ring lies just outside A, whereas G and E lie the farthest away from the planet.
The woeful moons that were robbed of their surface, but were fortunate enough to survive, still seem to affect the ring’s structure and the dynamics of its constituents. Cassini has shown that some moons distribute their material along their motion, which is evident in the formation of the G ring. Similarly, the moon Enceladus has contributed to the formation of the E ring.
Some of these observable activities can be explained by the above theories, whereas others still remain a mystery. Another anomaly is that even though the rings aren’t as thick as you might typically associate with an extraterrestrial object, the distance or gaps separating these rings is on the scale of thousands of miles.
Galileo pointing his telescope towards the twinkling sky above reflects the curiosity and deliberate effort that goes into such groundbreaking discoveries. His act of coursing through absolute darkness and finally landing his vision on a planet so magnificent has a numinous quality to it. To me, saying that it was God, whose generosity bestowed this planet upon us, translates this planet’s unique, gradual and beautiful process of creation into a black box that is shut to any attempt to peek in.
The creation of Saturn and its rings reminds me of some prose written by the revered astronomer and science communicator Carl Sagan in his book Contact. The prose is a dialogue made by his protagonist, also an astronomer, in response to the dismissal and sporadic belittling of childlike inquisition and the beauty of scientific inquiry:
“The theologians seem to have recognized a special, irrational aspect of the feeling of sacred or holy. They call it the ‘numinous’. It is believed that humans are predisposed to detect and revere the numinous, also called ‘misterium tremendum’. In the presence of misterium tremendum, people feel utterly insignificant but, if I read it right, not personally alienated. Now, if that is what religious people talk about when they use words like holy or sacred, I’m with them. I felt something like that in looking for a signal. I think the religions try to institutionalize your perception of the numinous instead of providing the means so you can perceive the numinous directly; like looking through a six-inch telescope.”