In 1985, it was discovered that over half of the ozone in the Antarctic stratosphere was disappearing each spring with the arrival of the polar sun. This "Ozone Hole" appeared to grow and shrink seasonally, but roughly continued to grow deeper and wider at its maximum each year. The scientific community immediately set out to attempt an explanation as to why this was occurring. years of study have let the world's scientists to draw the conclusion that the culprit is chlorine, used by industries in compounds known as chlorofluorocarbons or CFCs. Many types of household cleaners, refrigerants and aerosol cons contain CFCs. And, it has been estimated that over 500,000 tones of chlorine is released into the atmosphere annually. Scientists discovered that these CFCs are so stable that their natural breakdown is almost impossible, except at higher elevations where sunlight can break them down. This process is a long one, and could take a century to be fully brought to bear. Worse, it has been calculated that one molecule of chlorine can break down and destroy thousands of ozone molecules.

Scientists have surmised that the chlorine molecules are stored in clouds during the long polar winter, and attack ozone when the sun returns through a series of complex chemical reactions occurring at very low temperatures. Levels of ozone are roughly restored in the summer when ozone rich air from surrounding areas mixes with the ozone depleted Antarctic air.

Using data collected from weather satellites, the determination was made that in a thirty year period, some 1.5 to 3% of the ozone layer surrounding the Earth was lost. It is too early however to state definitively that this effect was due to chlorine instead of natural causes.

The Ozone Hole is another story unfolding in Antarctica. And the outcome affect us all.

Weather satellites play an important role in the detection of ozone loss. Among the most important experiments is the TOMS Satellite (Total Ozone Mapping Satellite) carried in the NIMBUS satellite system. All gases absorb light differently, unique unto themselves. It is possible to compare a control set of laboratory monitored gaseous spectrograph readings with readings returned from the satellite system above. By making comparisons as to the absorption of light, we can theorize what gases are or are not present and in what volumes. Antarctica is home to several bases supplied with equipment capable of monitoring this process. Weather balloons also are used to sample the atmosphere and return readings to the base. Ozone levels are measured in "Dobson Units", 300 DUs being about normal in mid-latitudes.

International agreements to restrict the use of CFCs began in 1987 with the Montreal Protocol. The agreement has been modified as the scientific understanding of the Ozone Hole changed. At first, the agreement called for a reduction in the use of CFCs by50% by the year 2000, now it has been modified to include controlling the production of halocarbons and after 1995, the signatories have agreed that they will not produce any CFCs except for essential uses. Hopes are that these controls will allow a normal ozone layer to return by 2050...although studies continue. The ozone depletion over Antarctica is apparently increasing, with record losses almost an annual occurrence. The United nations has proclaimed September 16th each year as the "International Day for the Preservation of the Ozone Layer".

Launched in October of 1978, the Nimbus 7 Satellite is the last in a series of weather satellites launched by NASA. The satellite orbits 590 miles above us. Among the various types of weather data recording instruments aboard are instruments used for recording the levels of ozone in the atmosphere. After these years in orbit, the systems have finally failed, and the satellite no longer transmits useful data. Replacement satellites are still years off. The satellite mapped the total globe once every 6 days or 83 orbits.

Specifically, the mission objectives were the study and observation of atmospheric gases as they relate to air and water pollution, observation of ocean temperature, color and ice conditions--notably in coastal areas, and generally to test and improve the equipment of the day to define its parameters and possible improvement. The Goddard Space Flight Center receives and interprets the data which the satellite collects and transmits. After examining the data, it is made available to any project collaborators, and then to any interested parties in the form of archival documents and films.

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