Credits: NASA/JPL-Caltech/Space Science Institute

Saturn's B ring is the most opaque of the main rings, appearing almost black in this Cassini image taken from the unlit side of the ringplane. The dark bands on the lower part of Saturn are ring shadows. The B ring shadow is the darkest.

When Galileo Galilei first spotted Saturn in his telescope, he didn’t know what the shapes on either side of the planet were. He thought they might be two large moons. Today we know they’re beautiful rings.

Saturn isn’t the only planet with rings. Jupiter, Uranus, and Neptune have them too. But Saturn’s are the most visible and complex. Saturn’s rings are made mostly of pieces of water ice, with a little bit of dust and rocks. Some pieces are smaller than a grain of sand. Others are the size of a refrigerator.

Saturn’s rings aren’t the same all over. There are brighter parts, darker parts, and gaps in between them. Scientists have named the different parts of Saturn’s rings. They talk about the A ring, B ring, the Cassini Division between them, and the C ring.

Scientists have been taking a closer look at Saturn’s B ring with data from NASA’s Cassini mission. This spacecraft took off in 1997 and has been exploring Saturn, its ring system, and its many moons.

The B ring is the brightest and the most opaque (the least see-through) of Saturn’s rings. Until now, most people thought that the B ring was the densest – that it had the most ice and rock. This sounds like it makes sense based on our everyday experiences. If there’s more stuff in the ring, it’s harder to see though, and more light bounces off of it. This could explain why the B ring looks so thick and colorful.

But new information shows this isn’t the whole picture.

Scientists measured how much material was in the B ring at different spots. Where the B ring is brightest and where it’s not as bright, there’s the same amount of stuff. This is surprising. Why would they look different if they have the same amount of material? It means there is something else that determines how visible the rings are. It could be the sizes of the individual pieces in the rings. Scientists have lots of questions.

Making measurements like these can teach us more about Saturn’s rings and how they came to be and how old the different rings are.

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