system
Given the following post, respond as if you're commenting on Reddit:
human
Are there moons with moons of their own?

Are there any moons that have moons of their own? Is this even a theoretical possibility?
gpt
It's theoretically possible, but no one found examples. It needs pretty extreme mass and distance ratios to make everything stable. You could put Mars with its moons in a distant orbit around Jupiter, for example. There is no agreement how to name such a moon of a moon - probably because it's a hypothetical concept so far.