Continuing on extra-terrestrials, somebody asked me a question the other day and my answer really shocked him!  And I thought it was something I ought to share.
He asked if there was an asteroid that was going to hit the Earth, would the extra-terrestrials stop it?
My answer was no, and he asked why.  I explained the answer is two-fold.  One, mankind has reached the state of development where they could build their OWN defensive systems against such a catastrophe, be prepared with shelters and such, to survive such a catastrophe.  It is not the extra-terrestrials' responsibility to take actions to correct a race's shortcomings and unpreparedness.
Secondly, the survival of such a natural disaster would be part of a race's natural development.
Many races have suffered such catastrophies to rebuild and become even stronger than they were before.  By interfering the extra-terrestrials would not give humankind such an opportunity.  Only if an asteroid was moved by an outside force so it would hit the Earth, would the extra-terrestrials interfere.  That would be a deliberate attack and not part of natural evolution.