The basis of my claim (which was posted on math-fun a long time ago -- probably before you joined) is that the Earth's atmosphere is very far out of equilibrium with the space surrounding it. I.e., if the Earth's atmosphere basically started in gravitational equilibrium, and lost gas molecules by exceeding escape velocity over 4.5B years, we'd still look a lot more like Venus today. In fact, Venus is the counter-example, since to a first approximation, it was formed at about the same time as Earth. The atmospheric pressure at the surface of Venus is 92x that of the Earth! (That's about the same pressure as 3000' of water on the Earth.) http://en.wikipedia.org/wiki/Atmosphere_of_Venus At 01:26 PM 4/3/2014, Warren D Smith wrote:
I've been claiming for a long time that the Earth's atmosphere would have been a lot more like Venus without an event like this one that removed most of it. For the same reason, we won't be able to turn Earth back into Venus, no matter how much carbon we burn.
--interesting and important claim, if true. But it might have worked the opposite way,e.g. the collision released more gases causing the Earth atmosphere to become larger, not smaller. I have no idea; I'm just asking if this "claim" can be backed up somehow.