New research suggests that Saturn's famous rings may have formed in surprisingly recent history. In a paper soon to be published in the Astrophysical Journal, scientists argue that the rings — and the planet's inner moons — may have been formed just 100 million years ago, some 4 billion years after the formation of Saturn itself.
There were bees 100 million years ago, guys. Bees. Most of the planets and moons in our solar system are thought to be billions of years old, so moons forming when dinosaurs (and bees!) already roamed Earth would be pretty wild.
“I think we are at a point where we can confidently say that the inner moons are not as old as the planet,” lead author Matija Cuk, principal investigator at the SETI Institute, told Ars Technica.
Unfortunately, that would kill any hope of finding life on Saturn's ocean-filled moon Enceladus: Even the earliest, most controversial evidence of life on Earth suggests it took hundreds of millions of years to evolve. Scientists have had high hopes for finding microbial life in sub-surface oceans on moons such as Enceladus. But if this particular oceanic moon is only 100 million years old, it would have to be a real whizkid to have produced even single-celled organisms.
Cuk and his colleagues used computer models to assess the way Saturn's 62 moons have changed their orbits over time. From the SETI Institute:
All of their orbits slowly grow due to tidal effects, but at different rates. This results in pairs of moons occasionally entering so-called orbital resonances. These occur when one moon’s orbital period is a simple fraction (for example, one-half or two-thirds) of another moon’s period. In these special configurations, even small moons with weak gravity can strongly affect each other’s orbits, making them more elongated and tilting them out of their original orbital plane.
The researchers found that some of the inner moons weren't as tilted as one would expect, suggesting that they hadn't been around long enough to enter many orbital resonances.
Based on their calculations, they believe that all moons that are closer to Saturn than the moon Rhea (an average of 327,487 miles) are less than 100 million years old. Because the planet's most visible rings were probably formed from the same space rubble that created those inner moons, they could be incredibly young as well.
“Our best guess is that Saturn had a similar collection of moons before, but their orbits were disturbed by a special kind of orbital resonance involving Saturn’s motion around the Sun," Cuk said in a statement. "Eventually, the orbits of neighboring moons crossed, and these objects collided. From this rubble, the present set of moons and rings formed."
Titan and Iapetus would be the only "major" moons of Saturn not implicated by the study — they're much farther out than Rhea is. Titan has been described by NASA as "one of the most Earth-like worlds we have found to date," and some scientists believe it could potentially host strange, methane-based life.