- GOOD OZONE, BAD OZONE. WHAT'S THE DIFFERENCE?
AND WHY IS NASA INTERESTED IN MEASURING OZONE?
FIND OUT NEXT ON "REAL WORLD."
HAVE YOU EVER LIVED IN A CITY THAT POSTED AN OZONE ALERT
ON A REALLY HOT SUMMER DAY?
JUST WHAT DOES THAT ALERT MEAN AND WHAT CAUSES THE PROBLEM?
IT ALL GOES BACK TO BASIC CHEMISTRY.
YOU SEE, THE OXYGEN WE BREATHE IS ACTUALLY A MOLECULE
MADE UP OF TWO OXYGEN ATOMS.
SO ITS MOLECULAR FORMULA IS O2.
OZONE IS AN UNSTABLE AND REACTIVE FORM OF OXYGEN
THAT IS MADE UP OF THREE OXYGEN ATOMS,
SO ITS MOLECULAR FORMULA IS O3.
NOW, THAT DIFFERENCE OF ONE OXYGEN ATOM
MIGHT SEEM INSIGNIFICANT, BUT IT'S ACTUALLY A HUGE DEAL.
BAD OZONE, OR GROUND-LEVEL OZONE,
IS ACTUALLY AN AIR POLLUTION PROBLEM THAT IS CREATED
WHEN POLLUTANTS LIKE EXHAUST, PAINTS, CLEANING FLUIDS,
OR OTHER INDUSTRIAL EMISSIONS REACT WITH SUNLIGHT,
CREATING MORE OF THE UNSTABLE OZONE MOLECULES.
IN THE TROPOSPHERE,
WHICH IS THE LOWEST LEVEL OF EARTH'S ATMOSPHERE
AND THE ONE WE'RE IN RIGHT NOW,
OZONE'S NATURAL CONCENTRATION IS ABOUT TEN PARTS PER BILLION,
OR ABOUT 0.00001% OF THE ATMOSPHERE.
THAT'S REALLY SMALL.
ACCORDING TO THE ENVIRONMENTAL PROTECTION AGENCY,
OZONE LEVELS GREATER THAN 80 PARTS PER BILLION
OVER A LONG PERIOD OF TIME
CAN CAUSE THROAT AND LUNG IRRITATION
OR AGGRAVATION OF ASTHMA OR EMPHYSEMA.
AND THAT BRINGS US BACK TO THOSE OZONE ALERTS.
WHEN LEVELS GET HIGH ENOUGH TO CAUSE PROBLEMS,
ALERTS ARE ISSUED,
AND PEOPLE ARE ASKED TO CHANGE THEIR REGULAR HABITS,
THINGS LIKE DRIVE LESS, DELAY MOWING,
AND STAY INSIDE IF YOU HAVE CERTAIN HEALTH CONDITIONS.
OF COURSE, NOT ALL OZONE IS BAD.
90% OF THE OZONE IN OUR ATMOSPHERE
SITS IN THE STRATOSPHERE, THE LAYER OF OUR ATMOSPHERE
BETWEEN ABOUT 10 AND 50 KILOMETERS ABOVE EARTH.
STRATOSPHERIC OZONE PROTECTS EARTH'S SURFACE
FROM EXCESSIVE ULTRAVIOLET RADIATION.
NASA ASTRONAUTS ON THE INTERNATIONAL SPACE STATION
HAVE AN AMAZING VIEW OF OUR FRAGILE ATMOSPHERE
AND THE THIN LINE THAT MAKES UP THE OZONE LAYER.
BUT WHY IS NASA SO INTERESTED IN OZONE?
WELL, LET'S HEAR FROM DR. JOE ZAWODNY,
A SCIENTIST AT NASA'S LANGLEY RESEARCH CENTER.
- IN THE MID-1980s,
WE DISCOVERED THAT THERE WAS AN OZONE HOLE IN THE ANTARCTIC,
AND SHORTLY THEREAFTER,
WE DISCOVERED THAT THE GLOBAL OZONE LAYER WAS DECREASING.
WE DISCOVERED THE REASON BEHIND THAT
WAS DUE TO CHLORINE COMPOUNDS RELEASED BY HUMANS.
CHLORINE WAS SEEN TO PEAK AND THEN STARTED TO DECREASE
IN THE LATE 1990s.
AND WE'VE SEEN GLOBAL DECREASE IN OZONE FLATTEN OUT.
IT NOW HAS A SLIGHT INCREASING TREND.
- IN ORDER TO UNDERSTAND HOW OZONE MIGHT BE CHANGING,
IT NEEDS TO BE MEASURED.
THE MOST COMMON UNIT FOR MEASURING OZONE
IS CALLED THE DOBSON UNIT.
ONE DOBSON UNIT IS THE NUMBER OF MOLECULES OF OZONE
THAT WOULD BE REQUIRED TO CREATE A LAYER OF PURE OZONE
0.01 MILLIMETERS THICK.
OF COURSE, OZONE ISN'T ALL PACKED INTO A SINGLE LAYER
IN THE EARTH'S ATMOSPHERE.
IT'S DISPERSED THROUGHOUT IT.
SINCE NASA DOESN'T HAVE A WAY
TO ACTUALLY SCOOP UP ALL THE ATMOSPHERE
AND SQUEEZE THE OZONE INTO LAYERS,
JUST HOW DO WE MEASURE SOMETHING THAT MAKES UP LESS THAN 0.00006%
OF OUR ATMOSPHERE?
FOR OVER 30 YEARS, NASA HAS USED
THE STRATOSPHERIC AEROSOL AND GAS EXPERIMENT, OR SAGE,
FAMILY OF INSTRUMENTS
TO INCREASE OUR UNDERSTANDING OF THE ATMOSPHERE
AND OUR KNOWLEDGE ABOUT OZONE.
AND THE LATEST GENERATION, SAGE III,
IS CATCHING A RIDE ON THE INTERNATIONAL SPACE STATION,
BRINGING A WHOLE NEW PERSPECTIVE TO THE PROBLEM.
- SO, SAGE III MEASURES OZONE THREE DIFFERENT WAYS.
WE USE A TECHNIQUE CALLED SOLAR OCCULTATION,
WHERE WE LOOK AT THE SUN DIRECTLY WITH THE INSTRUMENT
AND THEN LOOK THROUGH THE ATMOSPHERE
AS THE SUN SETS OR RISES,
AND WE CAN ALSO DO THE SAME THING USING THE MOON.
THE MOON'S A MILLION TIMES DIMMER,
SO IT'S A LITTLE BIT MORE DIFFICULT.
AND THE THIRD WAY IS,
WE CAN JUST LOOK AT SCATTERED SUNLIGHT,
LOOK AT THE ATMOSPHERE
AND JUST LOOK AT THE BLUE SKY, IF YOU WILL.
AND MOLECULES LIKE OZONE
HAVE UNIQUE ABSORPTION FEATURES IN THEM
THAT ARE EASILY DETECTABLE.
SO WHEN YOU SEE OZONE VARY,
OR IF YOU'RE MEASURING SURFACE TEMPERATURE,
IF YOU WANT TO KNOW WHY YOU SEE THE VARIABILITY
IN THE RECORD THAT YOU DO,
YOU NEED TO KNOW WHAT ELSE IS GOING ON,
SO, WHAT THE AEROSOLS WERE DOING,
WHAT SOME OF THE IMPORTANT CHEMICAL SPECIES
THAT CONTROL OZONE, WHAT THEY WERE DOING,
AND ONLY BY UNDERSTANDING THAT VARIABILITY
CAN YOU GET AT THE UNDERLYING VARIABILITY
THAT YOU MAY NOT FULLY UNDERSTAND.
- THE MEASUREMENTS COLLECTED FROM SAGE III
WILL PROVIDE VALUABLE INFORMATION
TO THE GLOBAL SCIENTIFIC COMMUNITY,
HELPING US ANSWER QUESTIONS LIKE:
AND NASA SCIENTISTS WILL SEARCH FOR THOSE ANSWERS
BY USING THE DATA COLLECTED FROM SAGE III
TO TELL THE STORY.
SEE YOU NEXT TIME ON "REAL WORLD."