Are there moons with rings?

Rings, like the ones belonging to Saturn, are made of a mix of particle sizes orbiting their host; having something like that around a moon is not very likely. Rings are usually caused by material from a massive disruptive event being caught in orbit – possibly a small object being ripped apart by gravity or material from an impact. Gas and rocks of varying size form a cloud, and then a disc. The gas disappears, leaving boulders behind that collide and create a mix of different sized material. The particles are small and easily disturbed. Saturn’s rings show this nicely: shepherding moons clear gaps in the rings and cause beautiful patterns.

A ring system needs to have a stable gravitational environment, and a moon most likely can’t offer this since its planet would throw its ring system out of kilter. The moon Rhea around Saturn was briefly suspected to have rings in 2008, but this was ruled out in 2010 as they could not be directly observed. Some asteroids and even a dwarf planet that have a calmer gravitational environment around them are suspected to have rings, but again these have only been indirectly observed. Daniel Brown, associate professor in astronomy at Nottingham Trent University

“A ring system needs to have a stable gravitational environment”