[T0T0R0]

I would wonder how long a vapor state would last, before precipitating to liquid, and then freezing into it's final solid form.

I bet the time scales for those phase transitions wouldn't be incalculable, even if gross estimates.

So, if the moon were a vapor bubble suspended in a vacuum, how long would that last? And how long for the heat to radiate out of it?

Sounds like that process would be pretty uniform, and dependent mostly on composition. But the uniformity of the temperature bleed would contribute to the maintenance of a stable orbit.

[gmazza]

From fig. 1 on the second page of pdf linked by spenrose below, it looks like vapor cloud was more doughnut/torus-shaped than spherical (due to rotation) and lasted few tens of years.

[T0T0R0]

While the distribution of mass might quickly redistribute itself into a toroidal formation, internally, I think that area of effect (the fuzzy red zone in the diagram) would probably be pretty opaque to visible light. For a period of time, a gas cloud like that would probably have a really interesting appearance.

I'm imagining that, as the hot gases cool off, and condense onto floating debris, the molten/solid debris field will probably look pretty nebulous, and then settle into unstable bands. At that point, I figure the torus shape would be very apparent.

Once the hot gases were gone, I bet it probably took a while for the rest of the debris to get swept up into decaying orbits, and impact on either body (earth/moon).

If they could visualize it with a simulation, it'd probably be fun to watch, and tweak the parameters of the event.

[azernik]

That is shockingly fast.

[Retra]

Well, that's a comparatively small volume it covered in the grand scheme of things. Just think how quickly a bunch of hair and dust will clump together in the corner of an unswept room.