Re: CONCULTURE: dual planets

Barry Garcia wrote:

> This was never answered with my post about the discovery of a world
> where the sentient life is extinct. So...
>
> How big would a moon orbiting an earth sized (or slightly bigger)
> planet have to be to have a visible atmosphere? Would a moon that size
> cause problems?
>
Good question. In Le Guin's "The Dispossessed" there is just such a system--
the secondary moon/companion planet is habitable (though it's a difficult
environment), and it's where a large group of political dissidents from the
main planet set up their communal society.  But the novel is far more
concerned with politics and personalities, so the technical details get
short shrift.

IIRC some of the moons of Jupiter and/or Saturn apparently have atmospheres,
so it's not impossible.

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