From: "Paul F. Dietz" <dietz@interaccess.com>
Newsgroups: sci.space.policy
Subject: Re: Terraforming Venus
Date: Sun, 09 Jul 2000 11:26:04 -0500

BigPilot wrote:
>
> > thing down to a fraction of that, but I'd still be surprised if it took
> less
> > than 150,000 to 250,000 years.
>
> No way. Microbes can reproduce at an astounding rate once things get going
> so you should see substantial atmospheric changes within decades.


Yes way.  Remember, photosynthesis didn't create
an O2 atmosphere on earth by itself.  It's
photosynthesis *plus burial of the reduced organic
matter*.  The latter is a slow process, since almost
all the carbon in organic matter produced by
photosynthesis gets quickly oxidized back to CO2,
producing no net addition of O2 to the atmosphere.
It is irrelevant if the microorganisms grow
rapidly if their dead remains are not sequestered
somehow.

If you look at the quantity of O2 in the
earth's atmosphere vs. the net production from
longterm burial of organic matter in sediments,
the time constant is on the order of 1 million
years.

	Paul