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Don't Let This Happen to Your Planet -
Presented by Science@NASA
Ozone stinks.
People who breathe it gag as their lungs burn.
The EPA classifies ground-level ozone as air pollution.
Yet without it, life on Earth would be impossible.
A fragile layer of ozone
25 km above Earth's surface
is all that stands between us
and some of the harshest UV rays from the sun.
The ozone molecule O3
blocks radiation which would otherwise burn skin
and cause cancer.
On Mars, which has no ozone layer to protect it,
solar UV rays strafe the surface with deadly effect,
leaving the apparently lifeless planet
without the simplest of organic molecules
in the upper millimeters of exposed Martian soil.
To keep track of our planet's ozone layer,
NASA is about to launch the most sophisticated
space-based ozone sensor ever:
SAGE III,
slated for installation on the International Space Station in 2014.
'The ISS is in the perfect orbit for SAGE III,'
says Joe Zawodny,
Project Scientist for the instrument
at the Langley Research Center.
'It will be able to monitor ozone all around the Earth
during all seasons of the year.'
SAGE III works by using the Sun and Moon as light sources.
When either one rises or sets behind the edge of the Earth,
SAGE III analyzes the light that passes through Earth's atmosphere.
Ozone and other molecules
absorb specific wavelengths that reveal their density,
temperature and location.
'SAGE III is, essentially,
analyzing the colors of the sunset to track ozone,' says Zawodny.
'It sounds romantic,
but this is hard science.'
Researchers began to worry about ozone in the early 1970s
when University of California chemists
Sherry Rowland and Mario Molina
testified before Congress that manmade CFCs,
a key ingredient of common aerosol sprays,
could destroy ozone in the stratosphere.
In 1985,
researchers with the British Antarctic Survey announced
abnormally low ozone concentrations above Halley Bay
near the South Pole.
Our planet had an 'ozone hole,'
and it was rapidly growing.
In a remarkable display of international cooperation,
an ozone treaty was negotiated only two years later.
The Montreal Protocol regulates the production of CFCs
and other ozone-destroying chemicals.
First signed in September 1987,
it has since been ratified by every member of the United Nations.
Because of this agreement,
ozone is now on the mend.
Ozone holes still open every year above the South Pole,
but thanks to the treaty,
ozone-destroying chemicals have either leveled off or decreased.
At this rate,
the ozone layer could recover almost fully by 2050.
To insure that ozone really is recovering,
NASA has been flying ozone sensors in Earth orbit for decades.
The first of the SAGE sensors
rode to space on Earth observing satellites
in the late-1970s and early-80s.
SAGE II data helped confirm the decline of the ozone layer
and measured the effect of the Mt. Pinatubo eruption
on the stratosphere.
A SAGE sensor onboard the Russian Meteor-3M satellite
extended the ozone record into the 2000s
with higher precision than ever.
Zawodny is eager to learn
what SAGE III finds in the lower stratosphere over the tropics.
'The recovery of ozone there
is tied to changes in greenhouse gases like CO2.
Given what we know about recent increases in greenhouse emissions,
it is possible that ozone in the tropics
will never return to 1980s levels.'
SAGE III probes Arctic regions, too.
Using the Moon as a light source,
SAGE III can detect ozone during the darkness of polar winter
where other satellites have trouble seeing.
It's enough to make a hard-nosed researcher wax eloquent:
'Images of the moon and sun rising and setting are dramatic and spectacular.
The interplay between the source of light
and the environment delights the senses
and stirs the imagination.
The ability for SAGE III to turn those perceptions into something meaningful
is a great pleasure.'
In other words,
get ready for some beautiful ozone data.
For more information on SAGE III and our atmosphere,
stay tuned to science.nasa.gov