Hbaker: There's a much bigger problem: Compare the Earth & Venus. Both are approx the same size; both have approx the same total amount of nitrogen in their respective atmospheres. The pressure at the bottom of the Earth's ocean is approx the same as the pressure on the surface of Venus. So, where did all of Earth's CO2 go? Or similarly, where did all of Venus's H2O go? --WDS: Suppose Earth & Venus have the same amount of CO2 -- but Venus evidently has a lot of more that stuff in the atmosphere. Well, why? Duh. Venus is hot. It bakes all the CO2 out of its carbonate rocks. Similarly the N. Earth is cold. It doesn't. On the contrary earth rocks tend to absorb CO2. The atmospheric pressure on Venus is the same as 1km of water pressure on Earth. Mostly CO2. The N2 component of that pressure is about 3 earth atmospheres worth. I suspect Venus lost a lot of H2O hydrogen to outer space, since it all was gaseous and exposed to about twice as much sunlight to decompose it, and less gravity to hold on to the H. Also Mars & Venus have no magnetic field to protect themselves from solar wind, etc stripping off H. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)