Earth's intense gravity may rip space rocks apart, reducing the risk of 'planet killer' asteroids 

 Earth and other terrestrial planets probably use their gravitational forces to tear apart asteroids ― but this creates more streams of smaller asteroids. 

https://cdn.mos.cms.futurecdn.net/E8DgeoWKjdyuj7XNW5jx6k.jpg

https://www.space.com/earth-gravity-asteroid-planet-killer-reduce