Over millions of years, Uranus’s inner moons may have collided and spread out into rings. As the material in the rings diffused, they moved farther away from the planet. Eventually, that material can start to accumulate, recycling itself back into a moon.

“No other planet has as many small inner moons as Uranus, and their complex inter-relationships with the rings hint at a chaotic history that blurs the boundary between a ring system and a system of moons,” SETI Institute researcher Matthew Tiscareno said in a statement for NASA.