Long-Lost Fifth Planet?

I've heard of this theory many times before, and always considered it somewhat probable. It makes more sense than anything else I can think of, really.

Ok, when and if man colonizes other planets and one of them is corrupt, what will man do? Destroy it, eh? What if man/celestials have done this already? Then would not it be the slightest bit possible there was a mother planet to mars, or even a cousin that was habitable just as it is believed that mars once was?

That is also entirely plausible. The article states that the destruction of the fifth planet was at about the same time as life began here on earth. Perhaps life actually began on that planet, and was seeded here by it's destruction.

Originally posted by RockerDom
Perhaps life actually began on that planet, and was seeded here by it's destruction.

If this planet's orbit was outside Mars it would have been out of "life zone" where water doesn't freeze. (or vaporising which gives another limit)

But it might be this cosmic billiard/bombardment, volcanism and effects of those caused simple chemicals to form longer and complex chemicals like amino acids and other building blocks of life. (actually comets have organic combounds)

I once had a theory that Mars big valley,Valles Marineras could have been caused by an impact of something the size of its smaller moon Deimos.I later learned about the big bulge nearby indicating plate tectonics spreading. I'm still not closed on the matter. I had heard before that the asteroid belt doesn't have enough material "now" to have been a planet. Reading this thread makes me think that we lose a lot of info over the vastness of time from events which could have changed ,dramatically the shape of the long ago solar system. I saw an asteroid impact the moon sept 29 1996,and I'm looking for a proper thread to post this info.