Astronomers have produced the best measure yet of the planet’s signature bands.
Saturn has confounded scientists since Galileo, who found that the planet was “not alone,” as he put it. “I do not know what to say in a case so surprising, so unlooked-for, and so novel,” he wrote. He didn’t realize it then, but he had seen the planet’s rings, a cosmic garland of icy material.
From Earth, the rings look solid, but up close, they are translucent bands made of countless particles, mostly ice, some rock. Some are no larger than a grain of sugar, others as enormous as mountains. Around and around they go, held in place by a delicate balance between Saturn’s gravity and their orbiting speed, which pulls them out toward space.
Scientists got their best look at the planet nearly 400 years after Galileo’s discovery, using a NASA spacecraft called Cassini. Cassini spent 13 years looping around Saturn until, in September 2017, it ran out of fuel and engineers deliberately plunged it into the planet, destroying it. More than a year later, scientists are still sorting through the data from its final moments, hoping to extract answers to the many questions that remain about Saturn.