What gas giant, what moon(s) are split in half and.

[rrw4rusty]

Hello,

I searched and searched, even emailed my astronomer friend in the land down under but I need the answer NOW! LOL.

One of our gas giants has a moon that is split in half and when the two halfs meet they trade places.

Which gas giant?

What are the names of the two half moons?

Thanks!
Rusty

 

[granpa]

http://en.wikipedia.org/wiki/Co-orbital_moon

 

[Nabeshin]

Whatever you're asking for is quite vague, what comes to my mind is:
http://en.wikipedia.org/wiki/Iapetus_(moon)