With its extensive system of rings, Saturn is among the most beautiful planets in the Solar System. Sadly, it’s beauty may be fleeting, according to new research. Saturn’s rings are dissolving faster than scientists expected, according to the study, and they could be gone in 100 million to 300 million years—a cosmological blink of the eye.
Saturn’s rings are primarily composed of water ice, but new research published in the journal Icarus shows that the rings are being assaulted by the planet’s gravity and magnetic field, triggering a phenomenon known as “ring rain.” Scientists first documented ring rain back in 2013, but new research, led by James O’Donoghue from NASA’s Goddard Space Flight Centre in Greenbelt, Maryland, shows the effect is happening much quicker than expected, and by consequence, so is the rate at which Saturn’s rings are decaying.
Scientists aren’t completely certain if Saturn was born with its beautiful halo, or if it acquired its ring system later in life. If it’s the former, the rings formed about 4.4 billion years ago, but if it’s the latter, they only formed about 100 million years ago, likely the consequence of colliding moons in orbit around Saturn, according to research published in 2016. If the recent-formation scenario is true, that means Saturn had no rings when giant sauropod dinosaurs roamed the Earth during the Jurassic. But dinosaurs didn’t have telescopes, so it didn’t really matter. Thankfully, humans have telescopes at a time when Saturn does have its glorious rings, so I suppose we’re fortunate for that.
Artist’s impression of how Saturn may look in the next hundred million years. The innermost rings disappear as they rain onto the planet, very slowly followed by the outer rings. GIF: NASA/Cassini/James O’Donoghue
“We are lucky to be around to see Saturn’s ring system, which appears to be in the middle of its lifetime,” said O’Donoghue in a statement. “However, if rings are temporary, perhaps we just missed out on seeing giant ring systems of Jupiter, Uranus, and Neptune, which have only thin ringlets today.”
Anyhoo, when the Voyager probes visited Saturn several decades ago, they detected the gas giant’s electrically charged upper atmosphere, or ionosphere, along with density variations in its rings, and three dark and narrow bands encircling the planet’s northern latitudes. Back in 1986, NASA scientists linked these narrow, dark bands to the shape of Saturn’s substantial magnetic field. These seemingly unrelated observations led to the theory that the electrically charged particles from Saturn’s rings were flowing down along magnetic field lines—a process that resulted in water being dumped from its rings onto its ionosphere, creating the narrow bands seen in the Voyager images.
From Earth, Saturn’s rings look peaceful, but chunks of water ice—ranging in size from microscopic dust grains to giant boulders—are caught in a giant game of tug-of-war. The rings are in a delicate balancing act, stuck between Saturn’s gravitational pull and the orbital tugs drawing them outward into space. This balance gets perturbed when ice particles are charged by the Sun’s ultraviolet light, causing the particles to plummet down toward the planet along its magnetic field lines, with gravity providing an added boost.
This process, in which the water interacts with the planet’s ionosphere, can actually be detected from Earth. For the new study, O’Donoghue used the Keck Telescope at Mauna Kea, Hawaii, to detect and measure these liquid-on-ionosphere chemical interactions. His team compared the light in the planet’s northern and southern latitudes to determine the amount of rain falling from the rings, among other observations.
Incredibly, the researchers estimate that 4,400 pounds of water (10,000 kg) are pouring out from Saturn’s rings each second. At that rate of loss, the rings should be gone in about 292 million years.
O’Donoghue says this amount of ring rain could fill an Olympic-sized swimming pool in just half and hour. Other evidence collected by the Cassini probe, however, suggests an even earlier expiry date. The Cassini-spacecraft measured ring-material falling into Saturn’s equator at a rate that suggests “the rings have less than 100 million years to live,” said O’Donoghue in the statement, adding: “This is relatively short, compared to Saturn’s age of over 4 billion years.”
This latest study, I have to say, is really bumming me out. It’s sad to think of Saturn without its rings, even if it is millions of years from now. Our Solar System will be considerably less spectacular than it is today when this finally happens. But who knows—maybe another planet will gain its own ring system in that time. [Icarus]
Image: NASA/JPL-Caltech/Space Science Institute