Jupitar killed Earth's sister Theia

 

It suggests that a Mars-sized protoplanet, often called Theia, collided with the early Earth, ejecting debris into space that later coalesced to form the Moon. 

Jupiter didn't directly "kill" Theia, but its gravitational influence in the early solar system could have played a role in the dynamics of such collisions. This hypothesis is one of the leading explanations for the formation of the Moon, supported by various lines of evidence such as isotopic similarities between the Earth and Moon rocks.