As stated this is a SPECULATIVE idea that a 5th terrestrial planet became unstable in its orbit after a few hundred million years (physically possible - chaos theory math) lurched thru the asteroid belt sending 'stroids hither and yon, bombarding the solar system and leaving behind the crater record referred to as early heavy bombardment and finally whiping into the sun. Possible, in that no laws of physics are violated but currently "unscientific" in that no falsifyable predictions have yet been made for this hypothethis.

Yah, prepare for the onslaught of TvF wackos stating that he's been "proven right" yet again.

-p (plans to stay tuned to this interesting hypothethis)