I know it's not a bright question, but I'd like to know the answer as well. I've read that the high atmosphere of Jupiter contains molecules of Hydrogen ([tex]H_2[/tex]). It is well known that (under Earth atmosphere at least), this gas is highly explosive. I just wonder why the atmosphere of Jupiter doesn't explode at least partially. I'm guessing that the concentration of gas on the atmosphere is just way too low to start a fire reaction, but it's only a guess. If it appears to be true, I'd like to know the concentration required to start a fire reaction between Hydrogen molecules. (I know it produces water...in case I'm not specific enough of the gas I'm talking about).