Saturn's rings are vanishing at 'worst-case' rate, says NASA
Tuesday, December 18, 2018, 8:31 PM - Saturn may be known as the Ringed Planet, but those iconic rings are vanishing, and the latest research shows that they are disappearing at an astounding rate.
Decades ago, when the Voyager 1 and 2 spacecraft flew past Saturn, giving us our first close-up look at this amazing planet, scientists used the data the probes sent back to discover that the wide rings surrounding it were raining down into the planet's upper atmosphere.
They found that this was due to water molecules in the icy rings becoming electrically charged, either by interaction with ultraviolet radiation from the Sun, or by meteoroid bombardment, and that the water was then being caught up in Saturn's magnetic field, and dragged down into the planet's atmosphere by gravity. Based on their findings, the scientists plotted different rates of loss of the rings, to estimate how long it would before they completely disappeared.
In this artist's impression, charged water molecules spiral around Saturn's magnetic field lines, flowing from the rings to the planet's upper atmosphere. Credit: NASA's Goddard Space Flight Center
"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," James O'Donoghue of NASA’s Goddard Space Flight Center said in a NASA press release on Tuesday. "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."
Leading up to the September 15, 2017 'Grand Finale' of NASA's Cassini spacecraft, when the mission team plunged the probe down into the planet's atmosphere, the spacecraft was sent on a trajectory to slip between the planet and its rings. Data the spacecraft beamed back showed that, while that region of space around the planet was fairly devoid of matter, it also revealed that Saturn's gravity was dragging particles from the inner edge of the ring down into the atmosphere.
Based on a new research paper, penned by O'Donoghue and six other researcher from institutions across the US and UK, the combined effect of these two mechanisms is causing ring material to rain down onto Saturn at what NASA calls the "worst-case-scenario" rate of the estimates provided by the Voyager data.
'RINGED PLANET', NO MORE?
One hundred million years is a long time by human reckoning, but on a time-scale that is fairly quick compared to the age of the solar system, Saturn is expected to dramatically change appearance.
This artist's conception shows how Saturn's appearance may change over the next hundred million years, as the innermost rings disappear first, raining down onto the planet, and then very slowly followed by material from the outer rings. Credit: NASA/Cassini/James O'Donoghue
Research has already shown that Saturn's rings are fairly young. Rather than forming along with the planet, billions of years ago, they most likely came from some process, such as a collision or a large icy moon straying too close to the planet, that happened, at most, around 100 million years ago.
"We are lucky to be around to see Saturn’s ring system, which appears to be in the middle of its lifetime," O'Donoghue added. "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!"