Raving Loonie wrote:
Summary - (Aug 9, 2005) Our planet gained its nice, oxygen-rich
atmosphere about 2.4 billion years ago thanks to early bacteria. One
question that has puzzled researchers, however, is why it took at least
300 million years for oxygen to build up to large levels, even though
the bacteria had been working madly to produce it. Researchers from the
University of Washington have developed a model that shows how volcanic
gasses could have sucked up this available oxygen. Not only that, but a
large layer of iron from meteorite strikes would have used it for
rusting. Not until those sinks were filled could oxygen build up.


See http://tinyurl.com/a7ero for more

Maybe I'm stupid but I have a real big problem with what is discussed
herein. ...


Why?

Today we have become a major sink for oxygen with all our rampant
burning of fissile fuels. Today all anyone worries about is how to get
the fuel. But I predict that someday the headlines will voice concerns
about the decreasing percentage of oxygen in the atmosphere.

They used to say that oxygen was 21% of the air. Now they're kind of
hedging and saying it's a little over 20%. Makes you wonder!


Nitrogen. It makes up most of our atmosphere. Why ?



RL


Nitrogen comes from volcanic out gassings. It has also been found to
be common in the atmospheres of some other planets and moons.

Double-A