A Design example. Did you know that the planet Jupiter is considered our guardian planet? Just about everything that comes at us from space hits this planet instead of earth. Why? Jupiter is huge in size, and has strong gravity which pulls things to it. An example of this is what happened in 1994  that the Hubble telescope was able to observe. Comet fragments, which are like hydrogen bombs upon entering a planet's atmosphere. Collided with Jupiter instead of earth. Here are the scars left by the explosive impacts left on the surface of this planet. The dark brown spots are scars left by the comet fragment impacts on the surface of this planet. The biggest has been said to leave such a huge gash, the earth could fit inside it. Now just imagine if Jupiter was not there? And those comet fragments hit earth instead. If one can blow a hole big enough to fit earth in, imagine what it would have done to our planet if one had hit us instead. Even to collide with the moon would have killed us. So a comet, or meteor does not have to hit us directly. Just destroy the moon, and our axis tilt, which provides the season changes, would be gone. In fact our rotation tilt would no longer be controlled by the moon, and we could end up rotating like the planet below: Uranus is fully tilted on it's side (90 degree angle). One pole constantly faces the sun. There are no other planet that rotates, or orbits like this. In fact, it's rotation and orbit cannot be explained scientifically. And the scientific excuse? It just happens.