[doc30]

I've got a question for the up to 40% hydrogen crowd. Where did the 80% nitrogen atmosphere come from? Remember this is a rocky planet between two other rocky planets. The hydrogen planets are big, gassy, and cold.

Some people believe that it was in the form of ammonia, NH3. Also, the atmosphere of Venus contains almost the exact same quantity of nitrogen as Earth (on a mass basis). Only Venus has a heck of a lot of CO2 so the proportion of nitrogen is a lot lower. Also, only the upper atmospheres of the gas giants are cool. Jupiter is quite hot. It emits more infrared (heat energy) into space than it receives from the sun.

[AndrewC]

Some people believe that it was in the form of ammonia, NH3. Also, the atmosphere of Venus contains almost the exact same quantity of nitrogen as Earth (on a mass basis). Only Venus has a heck of a lot of CO2 so the proportion of nitrogen is a lot lower. Also, only the upper atmospheres of the gas giants are cool. Jupiter is quite hot. It emits more infrared (heat energy) into space than it receives from the sun.

I believe the premise here is hydrogen not ammonia. The reason for more carbon dioxide in the venusian atmosphere might be that life does not exist on the planet and carbon is not tied up in living or previously living things. As for Jupiter, it is cold. Mean surface temperature: -150°C

[Doctor Stochastic]

So starting with a nitrogen-carbon dioxide atmosphere, one can just remove the CO2 (dissolving in water, maybe) and have the nitrogen left over. The Earth did get her ocean rather early.