Ellen Phiddian
Cosmos science journalist
It’s a favourite adage of science bores (myself included): sharks are older than the rings of Saturn.
But, according to a study in Nature Geoscience, it might not be true. Saturn’s rings could be a lot older than previously thought.
Astronomers used to think that both Saturn and its rings formed more than 4 billion years ago. But the current prevailing theory is that they’re 100-400 million years old, based on their cleanliness. (For comparison, sharks are 450 million years old.)
It was thought that the icy rocks the rings are composed of would darken over time, after collisions with micrometeoroids. In 2004, the Cassini mission revealed bright, clean rings, implying they’re youthful.
This new research proposes an alternative reason for the rings’ polished presence.
The researchers used computer simulations to model micrometeoroids crashing into the icy ring particles.
They found that the collisions vaporised the micrometeoroids, which then turned into charged particles which were either sucked into Saturn proper, or escaped the planet and zoomed into deep space.
This means that very little of the micrometeoroids deposit themselves on the ring particles, so they could stay looking bright and clean for many millions more years.
In their paper, the researchers say their results “suggest that Saturn’s rings could be as old as the age of the Solar System, even though they look clean and young based on today’s low non-icy content”.
This would make the rings 4.6 billion years old.
So, the ancient ring theory is back in play.
And for those of us scrambling to find a new fun fact to deploy at all the encroaching summer parties: there’s still the Southern Cross, which has multiple stars younger than 20 million years. Not only is the Southern Cross younger than sharks – it’s younger than mammals, birds, and flowering plants.
For those of you in the Northern hemisphere, the North Star might suffice.