The cocktail ingredients may be common, the stirring is not.
When there is very little information to go on the best that can be done is to assume that the situation is average. In case of life on other planets that would tend to suggest that life is not very common, as the average planet with life on it, should have a very large moon, as a result of some early collision during it's formation.
Now it is possible that the only life we know about just happens to be on such a planet, but statistically it is not very likely.
And of course if we find life on Mars/Jupiter's Moons etc., we will then need to show it could not have originated on earth, to get our second reference point.
So while the cocktail ingredients may be common, the stirring is not.
Biting the hand that feeds IT
