David E. Steitz

Headquarters, Washington, DC

(Phone: 202/358-1730)

Lynn Chandler

Goddard Space Flight Center, Greenbelt, MD

(Phone: 301/614-5562)

RELEASE: 00-137

A NASA spectrometer has detected an Antarctic ozone “hole” (what
scientists call an “ozone depletion area”) that is three times
larger than the entire land mass of the United States – the
largest such area ever observed.

The “hole” expanded to a record size of approximately 11 million
square miles (28.3 million square kilometers) on Sept. 3, 2000.
The previous record was approximately 10.5 million square miles
(27.2 million square km) on Sept. 19, 1998.

The ozone hole’s size currently has stabilized, but the low levels
in its interior continue to fall. The lowest readings in the ozone
hole are typically observed in late September or early October
each year.

“These observations reinforce concerns about the frailty of
Earth’s ozone layer. 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 J. Kurylo, manager
of the Upper Atmosphere Research Program, NASA Headquarters,
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 six miles (9.5 km) and 18 miles (29 km) above the
Earth’s surface.

Scientists continuing to investigate this enormous hole are
somewhat surprised by its size. The reasons behind the dimensions
involve both early-spring conditions, and an extremely intense
Antarctic vortex. The Antarctic vortex is an upper-altitude
stratospheric air current that sweeps around the Antarctic
continent, confining the Antarctic ozone hole.

“Variations in the size of the ozone hole and of ozone depletion
accompanying it from one year to the next are not unexpected,”
said Dr. Jack Kaye, Office of Earth Sciences Research Director,
NASA Headquarters. “At this point we can only wait to see how the
ozone hole will evolve in the coming few months and see how the
year’s hole compares in all respects to those of previous years.”

“Discoveries like these demonstrate the value of our long-term
commitment to providing key observations to the scientific
community,” said Dr. Ghassem Asrar, Associate Administrator for
NASA’s Office of Earth Sciences at Headquarters. “We will soon
launch QuickTOMS and Aura, two spacecraft that will continue to
gather these important data.”

The measurements released today were obtained using the Total
Ozone Mapping Spectrometer (TOMS) instrument aboard NASA’s Earth
Probe (TOMS-EP) satellite. NASA instruments have been measuring
Antarctic ozone levels since the early 1970s. Since the discovery
of the ozone “hole” in 1985, TOMS has been a key instrument for
monitoring ozone levels over the Earth.

TOMS ozone data and pictures are available on the Internet at:


TOMS-EP and other ozone-measurement programs are important parts
of a global environmental effort of NASA’s Earth Science
enterprise, a long-term research program designed to study Earth’s
land, oceans, atmosphere, ice and life as a total integrated