A National Aeronautics and Space Administration (NASA) spectrometer has detected an Antarctic ozone hole three times larger than the land mass of the United States, the largest such hole ever observed.

The hole expanded to a record size of approximately 28.3 million square kilometers on September 3. The previous record was approximately 27.2 million square kilometres on September 19, 1998.

The ozone hole's size has stabilised, but the low levels in its interior continue to fall. “Although production of ozone-destroying gases has been curtailed under international agreements, concentrations of the gases in the stratosphere are only now reaching their peak. Due to their long persistence in the atmosphere, it will be many decades before the ozone hole is no longer an annual occurrence”, said Dr Michael Kurylo, manager of the Upper Atmosphere Research Program at NASA's headquarters in Washington, DC.

Ozone molecules, made up of three atoms of oxygen, comprise a thin layer of the atmosphere that absorbs harmful ultraviolet radiation from the Sun. Most atmospheric ozone is found between approximately 9.5 kilometres and 29 kilometres above the Earth's surface.

The measurements were obtained using the Total Ozone Mapping Spectrometer instrument aboard NASA's Earth Probe satellite. Data and pictures are available at <http://jwocky.gsfc.nasa.gov/TOMSmain.html>.

[From <http://www.nasa.gov>.]

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