About 2 years ago, somebody wrote a very funny piece (on sci.astro?) entitled "Downsizing the Solar System" which detailed Congress's plans to drastically deuce the numbers of asteroids, planets etc in order to make space exploration cheaper. Might be worth checking Deja News.
> Whether Luna was captured or blown off of the Earth
> is still up for debate.
> Points in favor of capture include an apparently
> significantly different makeup,
As I understand it, the current idea is that Luna is compositionally similar to the Earth's *mantle* (but not the core), and this resulted from mantle material being thrown off by an impact between the proto-Earth and another (Mars-sized) proto-planet.
> and the difficulty of modeling an impact
> that could throw off so
> much mass, without ejecting it completely from
> co-orbit, or having it fall
The impact would provide the energy to throw off the mass.
> It's damn convenient that it's *just* big enough at
> this point in our
> planet's history to give us great solar eclipses.
> Seems almost too perfect.
> But of course, any alien patrons that wanted to help
> our little species out
> with figuring out the whole planet-solar
> system-galaxy thang, could have
> cut us a real break by letting the moon hang on to
> some of it's rotational
> momentum just a few tens of millions of years
> longer. A spinning moon face
> would have made it pretty obvious to our ancestors
> that we were surrounded
> by globes (and probably lived on one ourselves).
Darn! There goes one of my pet theories ;-).