Saturn’s rings are one of the treasures of the solar system, but they seem to be fleeting and not meant to be around for long.
According to the new study, the age of the rings is 400-100 million years, which is a very short period compared to the age of the solar system. And that means we’re just lucky, because we’re living in an age when the giant planet has fascinating rings. The researchers also found that these rings may disappear in the next 100 million years.
The rings were first noticed in 1610 by Galileo Galilei, who could not distinguish them well with his primitive telescope, and described them as two small planets located here and there in Saturn’s sphere, which were in physical contact with it.
In 1659, the Dutch astronomer Christian Huygens published the work Systema Saturnium, in which he described them as a system of thin, flat rings that did not touch the planet.
Huygens also showed the appearance as seen from Earth changing as the two planets moved around the Sun, sometimes disappearing altogether. The reason for this is the geometry of the view, due to which the rings are periodically visible from the Earth.
Anyone can see the rings with good binoculars or an amateur telescope. It is visible against the background of pale yellow Saturn. It is composed entirely of billions of water ice particles that reflect sunlight and shine.
Among these icy materials is also dark, dusty matter. In space science, “dust” generally refers to fine grains of rock, metal, or carbon-rich materials that are darker than ice. Collectively they are also called micrometeoroids. The solar system is littered with such grains.
Sometimes, they can also be seen in the night sky as they enter the atmosphere and burn up (called a shooting star). The planets’ gravitational fields have the effect of magnifying or focusing this dust, causing it to fall to Earth.
Over time, as a result of this fall, mass is added to the planet and its chemical composition changes. Saturn is a massive gas giant planet. Its radius is about 60,000 kilometers, almost 9.5 times that of Earth, and its mass is 95 times that of our planet. As a result, it has a very large “gravitational” wall (gravitational field around a space body) that is quite effective in directing dust grains towards Saturn.
The rings are about 2,000 kilometers above the upper layer of Saturn’s atmosphere and extend up to 80,000 kilometers in width, occupying a very large space. Falling dust collides with icy particles in the rings. Over time, the dust gradually darkens the rings and adds mass.
In 1997, the Cassini-Huygens robotic spacecraft was launched into the Saturn system. It reached Saturn in 2004 and entered the orbit of the planet, where it remained until the end of the mission in 2017. One of the instruments on board was the Space Dust Analyzer (CDA).
Using CDA data, the authors of the new study compared the amount of dust currently present in the space around Saturn to the estimated mass of dark dusty material in the rings. It turned out that the rings are not more than 400 million years old, and may even be 100 million years old. It may seem like a long time, but this time is not even a tenth of the age of the solar system, 4.5 billion years.
This also means that the rings did not form when Saturn or the other planets formed. From a cosmological point of view, they are a new addition to the solar system. For 90 percent of its existence, Saturn didn’t have them.
All this raises another mystery: how did the rings form, given that all the planets and moons of the solar system formed much earlier? The total mass of the rings should be about half the mass of one of Saturn’s small, icy moons; Many of Saturn’s moons have surface impact marks from space bodies.
especially the small moon Mimas nicknamed the Death Star; On its surface is a 130 km wide impact crater called Herschel.
It is the largest impact crater in the solar system. Mimas is only 400 kilometers wide, so an impact would not require much energy to destroy the moon. Like Saturn’s rings, Mimas is made of water ice, so it is possible that the rings were formed by one such cataclysmic impact.
A rain of rings
The future of Saturn’s rings is a bit uncertain. The ice particles are hit by dust grains at very high speeds, which causes the ice and dust particles to detach from their parent particles.
Ultraviolet light from the sun electrically charges these particles through the photoelectric effect. Like Earth, Saturn has a magnetic field, and once charged, these tiny fragments of ice are ejected from the ring system and become trapped in the planet’s magnetic field.
The giant planet’s gravity pulls them down into Saturn’s atmosphere. The ring shower was first observed in the 1980s by Voyager 1 and Voyager 2 when they flew past Saturn.
In a study conducted in 2018, the amount of dust determined by the science tool CDA was used; These data were collected by Cassini during its flyby between Saturn and its rings. His goal was to find out how much dust the rings lose over time. As this study shows, every half hour, an Olympic swimming pool’s worth of material is dumped from the rings into Saturn’s atmosphere.
Based on this flow rate, the researchers estimated that, based on the current mass, the rings would likely disappear within 100 million years. These beautiful rings have had a turbulent past, and unless they find some way to fill them, Saturn will eventually pass.
The study was published in Science Advances.
Adapted from The Conversation.