Allen Kenitzer Wincel.A.Kenitzer.1@gsfc.nasa.gov (Phone: 301/286-2806)

April 8, 1997

RELEASE NO: 97-31P

MARCH TOMS/EARTH PROBE IMAGES (1979-97) - These false color images show March monthly average ozone levels over the North Pole. The data were taken by NASA's Total Ozone Mapping Spectrometer (TOMS) aboard the Nimbus-7 satellite, and Earth Probe. Shown here are the first four years of TOMS imaging, 1979-1982, and then, 1990, 1993, 1996, and 1997. The 1996 data are taken from the NOAA-14 Solar Backscatter Ultraviolet instrument. The color scale on the bottom of this image shows the total ozone values in Dobson units (DU). A Dobson unit is the physical thickness of the ozone layer if it were brought to the Earth surface (300 Dobson units equals 1/10th of an inch or three millimeters). The high ozone values are represented by the red and green shades while lower values are represented by the blues and purples. Ozone, a molecule made up of three atoms of oxygen comprises a thin layer in the upper atmosphere that acts as a shield against harmful ultraviolet radiation from the Sun. Studies have shown that ozone depletion is caused by complex coupled chemical reactions. Scientific data have indicated that man-made chlorofluorocarbons (CFCs) used in refrigeration, electronics and other industries are capable of altering the levels of atmospheric ozone. Scientists believe that continued buildup of CFCs could lead to additional ozone loss worldwide. Ongoing studies are essential to provide the necessary understanding of the causes of ozone depletion. To ensure that ozone data will be available through the next decade, NASA is continuing the TOMS program using U.S. and foreign launches. On Aug. 15, l991, the former Soviet Union launched a Meteor-3 satellite carrying a TOMS instrument provided by NASA. A third TOMS, Earth Probe, was launched aboard a U.S. expendable Pegasus rocket in 1996 and the Japanese Advanced Earth Observations Satellite (ADEOS) carried a fourth TOMS into orbit in August l996. A fifth TOMS is scheduled to be launched on a Russian Meteor-3M satellite in 2000. The TOMS Program is managed by NASA's Goddard Space Flight Center Greenbelt, Md., for the Office of Mission to Planet Earth, Washington, D.C.