The Earth has been in the path of meteor strikes for a long time and the extinction of several species before humans inhabited the world was caused by these rock formations that come from different parts of the universe. The biggest problem with them is that they can destroy all life on our planet and a large meteor could even make the entire world disappear into millions of pieces.
The order has always been there to make sure that no meteor ever comes too close to Earth. The closest call was when we had to take out a meteor that was the size of the state of Texas. This meteor was large enough to destroy all life forms and make the planet inhabitable for centuries. We could have easily left the planet and evacuated every member of the order out of it, but we chose to destroy the threat.