Fail Safe

An amateur astronomer discovers a rogue asteroid on a collision course with Earth. SG-1 and a couple of engineers repair the cargoship that crashed on Revanna and head for earth. Just before they reach the asteroid, there is a problem with one of the engines. They start heading for the asteroid, but manage to stop at the last moment. Teal'c and O'Neill place a naqahdah enhanced nuclear weapon. Carter discovers that the core of the asteroid is composed of naqahdah, so exploding the nuke would destroy Earth. They manage to use the ship's hyperspace engines to transfer the asteroid to the other side of earth. The episode ends with them being saved by the Tok'ra.