Moon The presence of a moon protects planets from space debris; when objects flying in from space come close enough to earth, our moon acts as a shield and/or a deflector. Here is a visual example of the moon deflecting an asteroid, thanks to www.nasa.com: The moon also stabilizes our planet so that its axis of rotation stays in the same direction.  For this reason, we have had much less climatic change than if the Earth had been alone. There is Tidal effect due to moon's gravity helps to enable tectonic movement, which makes the earth not have such a hard “shell” that the crust is on other planets  and allows for increased volcanic action which builds up atmosphere. Introduction Habitable Zone Size Moon Home Bibliography . .