Originally posted by bnasty
If earth we to become inhabitable [at least due to time] the sun would probably be so big, due to it becoming a Red Giant, Mercury and Venus would have been swallowed. Earth would be a crusty Mercury-like planet, and we may be living on Mars 
But I'm sure this won't be in the near future
Yeah thats about 4 billion years from now, I highly doubt were still gonna be around for that one, we'll go extinct long before that.
Like moot said I don't think life on Mars got much passed the goo stage, it just wasn't habitable for very long. What happen to Mars is unknown but something caused it's core it cool which means it lost it's magnetic field and its atmosphere was stripped away by cosmic rays.
Now when you think about it, it would be very very long odds that were it in the universe, there are more stars in the universe then grains of sand on all the beach's of Earth, thats alot of chances for another Earth to have happen, and if we do ever find some kind of life in our solar system that will show life is common, not rare, to have happen more then once in a single solar system.
