QUOTE (Jyril @ Jun 27 2006, 05:54 PM)
Add various disturbances and it becomes clear that no large satellite can have own moons in our Solar System.
I am not smart enough to set up a simulation to see if this is possible, but there may be a congenital (if that is the right word) reason why we don't see satellites of moons.
Upon formation, let's say a moon like Dione, could be expected to be rotating non-synchronously with the host planet. Seems I have seen figures around 8 to 10 hours. Over time, the moon will tide lock to the planet, but during the period when it is not, any satellites of the moon will be subject to tidal effects from the moon, and will be accelerated in their orbit around the satellite, just as our moon is being accelerated today by tidal effects.
The orbital evolution of such satellites should be interesting. As they 'loft' away from their host moon, the effect weakens and the satellite may be expelled ever so gently from the 'Hill sphere' of the moon.
Well the little satellite is still in orbit around the host panet, and not moving away very quickly from the original 'host' moon.
I feel such objects are quite likely to wind up in a Trojan relationship with the moon.
Objects such as Pandora and Calypso may be old satellites of moons, conveniently left for us to explore, time capsules of the materials swept up by the original host moon, and never processed thermally or tectonically.
In the case of a larger moon such as Titan, we might expect the 'spin off' process to be rather more energetic and the cast off satellite might wind up in a higher orbit around the host planet, rather than in a Trojan relationship.
Hyperion might be such a body. It's crater devestated surface recording the influx of debris coalescing into Titan, back in the time when Saturn's moon's (and their satellites) were forming.