When the Cassini spacecraft visited Saturn, its measurements of the gas giant’s magnetic field showed that we may have been wrong about how fast the planet is spinning – it was 7 minutes slower than the last time we measured the magnetic field’s rotation with the Voyage probe.

But Cassini also gave us a deluge of images of Saturn’s rings, and buried within those pictures were clues to the giant planet’s true rotation rate.

“It turns out that Saturn’s rings are an extraordinarily …