Fail Safe (S05E17)

When an asteroid is detected on a collision course with Earth, SG-1 is dispatched to deal with the impending calamity. Flying out on a salvaged cargo ship, the team eventually touches down on the asteroid, prepared to deposit a nuclear payload that will neutralize the threat. However, a cursory scan of the rock reveals a high concentration of naquada. Carter informs her teammates that if they trigger the nuclear device, the naquada will augment the force of the explosion, effectively destroying all life on Earth. Clearly this was no freak occurrence but an insidious Goa'uld plot. With time ticking down toward Fail Safe, SG-1 must find a way to avert a global catastrophe. (Metro-Goldwyn-Mayer (MGM))