mod, when our solar system was formed 4-5 billion yrs ago, they were more celestial bodies in our system, more than we have now; our infant planet was a very hot piece of rock. the encounter with one of this celestial body gave our iron core, responsible for our magnificent magnetic field, and whatever debris were left from this impact formed the moon. a major element in development of life was the water brought by comets..that my friend was the keystone in creation of life. whatever "shows" you might see on Discovery network can give you a point of view, not meaning is the good or wrong one. we cant even understand the creation of the universe, but we go and boldly assume that we can "see" what if....my 2 cents