When we think about the planets, we tend to think of them as static and unchanging. While the planets unquestionably evolved into their current states, most of that evolution appears to have happened hundreds of millions to billions of years in the past. Mars has been a cold, frozen rock for billions of years. Early Venus might have supported life, but the runaway greenhouse effect that superheated its atmosphere and left it a barren hellscape happened billions of years ago as well. It’s easy to think of Jupiter, Uranus, Saturn, and Neptune as eternal, unchanging sentinels. But if NASA scientists are right, Saturn’s most striking feature — its unique system of rings — might persist for just a geological eyeblink.
As the video explains, NASA research has found that Saturn’s rings are “raining” inward towards the planet at an unsustainable rate. This was first estimated by Voyager I and II when those probes made flybys of the planet, but additional observations by Cassini have confirmed the mass loss is running at the upper end of the rate first measured decades ago.
“We estimate that this ‘ring rain’ drains an amount of water products that could fill an Olympic-sized swimming pool from Saturn’s rings in half an hour,” said James O’Donoghue of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “From this alone, the entire ring system will be gone in 300 million years, but add to this the Cassini-spacecraft measured ring-material detected falling into Saturn’s equator, and the rings have less than 100 million years to live. This is relatively short, compared to Saturn’s age of over 4 billion years.”
The “rain” isn’t just caused by Saturn’s gravity, but by the interplay between the planet’s magnetic field and the rings themselves. When the tiny particles within the rings become electrically charged, they’re pulled downwards towards the planet below. The particles interact chemically with Saturn’s ionosphere and, when energized by sunlight, glow in infrared light. By measuring the strength of this glow, NASA scientists were able to determine exactly how much “rain” is falling into the gas giant.
While Saturn’s rings receive substantial contributions of material from moons like Enceladus, the material ejected by the moon isn’t nearly enough to offset the losses from the rings. If the loss continues at the present rate, Saturn’s ring system will be gone completely within a relatively short period of time. This raises the question of whether the faint ring systems of Jupiter, Uranus, and Neptune were once much larger themselves before fading to the relatively faint traces of today.
The team’s next goal is to observe how the emissions change over Saturn’s 29.4-year orbit around the Sun. The rings receive different amounts of solar energy depending on Saturn’s position. Since the ultraviolet energy received from our star is responsible for charging ice grains and making them more susceptible to Saturn’s magnetic field in the first place, it’s possible that it “rains” more or less at different points in the Saturnian year.
Top image credit: NASA/JPL-Caltech
- Cassini Detected ‘Ring Rain’ During Plunge into Saturn
- Cassini Probe Detected Building Blocks of Life on Saturn’s Moon Enceladus
- How Cassini Changed Our Understanding of Saturn and the Solar System