present at any given time is a function of the equilibrium reached between
the creative and destructive chemical reactions and the solar radiation
reaching the upper stratosphere.

The mechanism for the production of ozone is the absorption by oxygen
molecules (O2) of relatively short-wavelength ultraviolet light. The
oxygen molecule separates into two atoms of free oxygen, which immediately
unite with other oxygen molecules on the surfaces of particles in the upper
atmosphere. It is this union which forms ozone, or O3. The heat released
by the ozone-forming process is the reason for the curious increase with
altitude of the temperature of the stratosphere (the base of which is about
36,000 feet above the earth's surface).

While the natural chemical reaction produces about 4,500 tons of ozone per
second in the stratosphere, this is offset by other natural chemical
reactions which break down the ozone. By far the most significant involves
nitric oxide (NO) which breaks ozone (O3) into molecules. This effect was
discovered only in the last few years in studies of the environmental
problems which might be encountered if large fleets of supersonic transport
aircraft operate routinely in the lower stratosphere. According to a
report by Dr. Harold S. Johnston, University of California at Berkeley--
prepared for the Department of Transportation's Climatic Impact
Assessment Program--it now appears that the NO reaction is normally
responsible for 50 to 70 percent of the destruction of ozone.

In the natural environment, there is a variety of means for the production
of NO and its transport into the stratosphere. Soil bacteria produce
nitrous oxide (N2O) which enters the lower atmosphere and slowly diffuses
into the stratosphere, where it reacts with free oxygen (O) to form two NO
molecules. Another mechanism for NO production in the lower atmosphere may