Planet (The Krotons)

This Earth-like planet had low gravity (though not to a noticable degree) and orbited a binary star system. Its atmosphere contained high levels of both ozone and sulphur and the surface tellurium and magnesium silicate. It had humanoid life in the form of the Gonds, whom the more advanced Krotons, not native to this world, enslaved, as well as taking advantage of the minerals found on the planet. Subsequently, the the Second Doctor and his companions arrived and defeated them. (DW: The Krotons)