A gravitic mine was a type of mine which was used in the 23rd century and beyond. These mines consisted of explosive charges which were left at a fixed point in space and programmed to detonate when a starship approached it. (TOS movie: Star Trek II: The Wrath of Khan, TNG episode: "Ethics") In the Kobayashi Maru scenario, the distress call sent out from the stricken SS Kobayashi Maru stated that it has been struck by a gravitic mine and disabled. (TOS movie & novelization: Star Trek II: The Wrath of Khan)