An explosion of media coverage linking the rings to the age of dinosaurs helped to quickly solidify the new findings in the public’s eye. If you enter the search phrase “how old are Saturn’s rings,” Google returns the answer “100.1 million years.”Aurélien Crida, a planetary scientist at the Côte d’Azur Observatory, was incredulous at this definitive declaration. “I was a bit pissed off by how it was assessed, that the rings are young, and it’s over,” he said.He and other skeptics have pointed out that there are a lot of potential problems with the argument, from the physics of the ring pollution to the origins of the rings themselves. “The rings look young, but that doesn’t mean the rings are really young,” said Ryuki Hyodo, a planetary scientist at the Japanese Aerospace Exploration Agency. “There are still some processes that we are not considering.”
In response to the hypothesis, Crida co-authored a commentary for Nature Astronomy, published in September, that presented a litany of uncertainties. The dinosaurian age of the rings is an eye-catching claim, said Crida, but it circumvents an uncomfortable reality: Too many uncertainties exist to permit any firm estimate of the age of the rings. Despite Cassini’s heroics, “we’re not really far ahead of where we were almost 40 years ago,” back when the Voyager probes first took a good look at Saturn, said Luke Dones, a planetary scientist at the Southwest Research Institute in Boulder, Colorado.Proponents of the younger age stand by their work. “Every new exciting result gets challenged,” said Burkhard Militzer, a planetary scientist at the University of California, Berkeley and a co-author of the Science paper. “It’s the natural way to proceed.”
The debate is about more than the narrow question of the rings’ age. The age of Saturn’s rings will influence how we understand many of Saturn’s moons, including the potentially life-supporting world Enceladus, with its frozen ocean. And it will also push us closer to answering the ultimate question about Saturn’s rings, one that humans have wondered about since Galileo first marveled at them over 400 years ago: Where did they come from in the first place?
Photograph: NASA/JPL-Caltech/ASIThe photos Cassini sent back during its 13 years at Saturn are so stunning, they can make this already beautiful planet seem like something out of fairy tales.Photograph: NASA/JPL-Caltech/ASIOn September 15, 2017, before Cassini set a death course into Saturn, it took one last photo of Titan.
Age From a ScaleWe know the age of the Earth because we can use the decay of radioactive matter in rocks to work out how old they are. Planetary geologists have done the same for rocks from the moon and Mars.
Saturn’s rings, predominantly composed of ice fragments with trace amounts of rocky matter, don’t lend themselves to this kind of analysis, said Matthew Hedman, a planetary scientist at the University of Idaho. That means age estimates have to be based on circumstantial evidence.