Asteroid Strikes are very devastating events that happen very rarely. A sizable crater will be blasted into the terrain and Meteorite Rock will appear there. This can damage or destroy buildings, kill monsters, and kill even end-tier armored players.
It is advised to build a high sky roof to prevent these damaging houses or marring scenic terrain, especially on a player's home world.
If there is an Asteroid Field in your current Planet-System, it seems Asteroid Strikes do happen very often. They can appear in several smaller impacts or one large impact.