Smaller Is Not Always Safer
Even smaller rogue objects can cause devastation. A Pluto sized object colliding with Earth would wipe out nearly all life. Even a smaller asteroid, similar in size to the one that ended the dinosaurs, could destroy civilization. A near miss by a Mercury sized body could still unleash massive quakes and tidal waves.
If an Earth sized object came close, the two planets could engage in a terrifying dance of destruction. Gravity could distort both worlds, pulling at oceans and land masses. Debris could end up in orbit, forming temporary rings. Eventually, the two bodies could crash into each other.
