(For perspective, 15.4 million billion metric tons is about 40% the mass of the Saturn moon Mimas, which is 250 miles, or 400 kilometers, wide.) Such studies cite the rings’ composition-more than 95% pure water ice-and total mass, which NASA’s Cassini mission pegged at about 15.4 million billion metric tons shortly after the probe’s epic “grand finale” at Saturn in 2017. This latter hypothesis has been gaining steam in the last few years, with multiple papers reporting that the rings could be even younger than the dinosaurs. The great Saturn ring debate is far from settled, a new study suggests.įor years, scientists have argued about the age of Saturn’s famous rings: Are they ancient, dating to the birth of the planet itself? Or did the ring system form more recently, in just the past hundred million years or so?