Proton bomb

A proton bomb was a type of bomb which only destroyed organic matter when exploded.

In 2266, when the USS Enterprise (NCC-1701) discovered an uninhabited planet which was also a duplicate of Earth, Captain James T. Kirk speculated that it may have been depopulated in a proton bomb war. However, Spock pointed out that there would still be skeletons and vehicles left behind, of which there were none.