Scientists have long debated whether Saturn's rings were born with the planet or are a relatively new acquisition. Some models suggest that the ring material is debris left over from the planet's formation more than four billion years ago. But others theorise that the rings formed when objects like comets, asteroids or even moons broke apart in orbit around the massive planet.
It's hard to imagine the sixth planet from the sun without its most famous feature. Though Jupiter, Uranus and Neptune are also banded, Saturn's adornment is by far the most impressive in the solar system. The planet's rings span 273,500km across and are bright enough to be visible with a child's telescope.
And although they look solid from Earth, observations by the Voyager and Cassini spacecraft have revealed that the rings are instead made of floating bits of material, ranging in size from as small as specks to larger than the Empire State Building. They stay suspended around the planet's midsection through a careful balance of gravity, which tries to pull the material inward, and their orbital velocity, which seeks to sling them into space.
But sometimes ring particles get electrically charged by light from the sun or other cosmic phenomena. This makes them susceptible to the siren song of Saturn's magnetic field, which bends inward at the rings. The particles slide along magnetic field lines into the planet's atmosphere, where they vaporise, generating glowing, charged hydrogen and droplets of water.
O'Donoghue and his colleagues observed this phenomenon with the huge Keck telescope in Hawaii and concluded that a combination of Saturn's gravity and magnetism pulls an Olympic-size swimming pool worth of material into the planet every 30 minutes.
Combining this analysis with data collected by the departed Cassini spacecraft, which dove through the rings before plunging into Saturn last year, O'Donoghue predicts that the rings have less than 100 million years to live.
