[el_zorro]

I'm going to ignore so many things in this post and just point out that there is not enough material in the asteroid belt to create another planet. All said, the asteroid belt is about 4.5% the mass of the moon, or a quarter of Pluto [0].

[0] http://www.wolframalpha.com/input/?i=mass+of+the+asteroid+be...

[doubleyou]

Thank you! What an embarrassing bout of ignorance on my part... I should have done just a little bit of research...