The Cassini Division, a gap in the rings of Saturn, is caused by gravitational pull from Saturn’s moon Mimas. The moon’s gravity affects the tiny particles that make up the rings, creating what looks like empty space. Other divisions in Saturn’s rings are the result of similar interactions with the planet’s moons.
The Cassini Division, at about 3,000 miles or 4,800 kilometers wide, is the largest of several gaps in the rings of Saturn. The area is not completely empty, but the scarcity of ring material makes it look like a dark, empty space.
The Cassini Division marks the division between what scientists call Saturn's A and B rings. Other divisions, created by the gravitational pull of other moons, exist farther out from the planet and are not as wide.