Wasn't there some fear back in the '50s (on up to the '70s, as I recall it mentioned on The Bionic Woman of all things) that a Cobalt bomb could destroy the atmostphere of the earth? Would be interesting to see some discussion of that here. A brief search on Google turns up nothing. (now that I spelled it right (habit from correcting people who spell COBOL cobolt!) I found several references: Leo Szilard called the cobalt bomb a "doomsday" device since it was capable of wiping out life on earth.)-justfred
See wikipedia's hydrogen bomb or nuclear weapon - "Another variant uses Cobalt in the shell, and the neutrons convert the Cobalt into Cobalt 60, a powerful long-term emitter of Gamma rays. The primary purpose of this weapon is to create extremely radioactive fallout to permanently deny a region to an advancing army, a sort of wind-deployed mine-field. It was actually tested by the British in Central Australia, in areas that remain uninhabitable to this day." The fears over destroying the atmosphere were applied to the first atomic tests.