WEBVTT

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- GOOD OZONE, BAD OZONE.
WHAT'S THE DIFFERENCE?

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AND WHY IS NASA INTERESTED
IN MEASURING OZONE?

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FIND OUT NEXT
ON "REAL WORLD."

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HAVE YOU EVER LIVED IN A CITY
THAT POSTED AN OZONE ALERT

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ON A REALLY HOT SUMMER DAY?

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JUST WHAT DOES THAT ALERT MEAN
AND WHAT CAUSES THE PROBLEM?

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IT ALL GOES BACK
TO BASIC CHEMISTRY.

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YOU SEE, THE OXYGEN WE BREATHE
IS ACTUALLY A MOLECULE

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MADE UP OF TWO OXYGEN ATOMS.

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SO ITS MOLECULAR FORMULA
IS O2.

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OZONE IS AN UNSTABLE
AND REACTIVE FORM OF OXYGEN

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THAT IS MADE UP
OF THREE OXYGEN ATOMS,

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SO ITS MOLECULAR FORMULA
IS O3.

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NOW, THAT DIFFERENCE
OF ONE OXYGEN ATOM

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MIGHT SEEM INSIGNIFICANT,
BUT IT'S ACTUALLY A HUGE DEAL.

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BAD OZONE,
OR GROUND-LEVEL OZONE,

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IS ACTUALLY AN AIR POLLUTION
PROBLEM THAT IS CREATED

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WHEN POLLUTANTS LIKE EXHAUST,
PAINTS, CLEANING FLUIDS,

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OR OTHER INDUSTRIAL EMISSIONS
REACT WITH SUNLIGHT,

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CREATING MORE
OF THE UNSTABLE OZONE MOLECULES.

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IN THE TROPOSPHERE,

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WHICH IS THE LOWEST LEVEL
OF EARTH'S ATMOSPHERE

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AND THE ONE WE'RE IN RIGHT NOW,

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OZONE'S NATURAL CONCENTRATION
IS ABOUT TEN PARTS PER BILLION,

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OR ABOUT 0.00001%
OF THE ATMOSPHERE.

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THAT'S REALLY SMALL.

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ACCORDING TO THE ENVIRONMENTAL
PROTECTION AGENCY,

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OZONE LEVELS GREATER THAN
80 PARTS PER BILLION

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OVER A LONG PERIOD OF TIME

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CAN CAUSE
THROAT AND LUNG IRRITATION

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OR AGGRAVATION OF ASTHMA
OR EMPHYSEMA.

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AND THAT BRINGS US BACK
TO THOSE OZONE ALERTS.

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WHEN LEVELS GET HIGH ENOUGH
TO CAUSE PROBLEMS,

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ALERTS ARE ISSUED,

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AND PEOPLE ARE ASKED
TO CHANGE THEIR REGULAR HABITS,

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THINGS LIKE DRIVE LESS,
DELAY MOWING,

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AND STAY INSIDE IF YOU HAVE
CERTAIN HEALTH CONDITIONS.

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OF COURSE, NOT ALL OZONE IS BAD.

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90% OF THE OZONE
IN OUR ATMOSPHERE

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SITS IN THE STRATOSPHERE,
THE LAYER OF OUR ATMOSPHERE

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BETWEEN ABOUT 10
AND 50 KILOMETERS ABOVE EARTH.

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STRATOSPHERIC OZONE PROTECTS
EARTH'S SURFACE

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FROM EXCESSIVE ULTRAVIOLET
RADIATION.

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NASA ASTRONAUTS ON
THE INTERNATIONAL SPACE STATION

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HAVE AN AMAZING VIEW
OF OUR FRAGILE ATMOSPHERE

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AND THE THIN LINE THAT MAKES UP
THE OZONE LAYER.

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BUT WHY IS NASA
SO INTERESTED IN OZONE?

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WELL, LET'S HEAR
FROM DR. JOE ZAWODNY,

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A SCIENTIST AT NASA'S
LANGLEY RESEARCH CENTER.

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- IN THE MID-1980s,

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WE DISCOVERED THAT THERE WAS
AN OZONE HOLE IN THE ANTARCTIC,

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AND SHORTLY THEREAFTER,

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WE DISCOVERED THAT THE GLOBAL
OZONE LAYER WAS DECREASING.

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WE DISCOVERED THE REASON
BEHIND THAT

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WAS DUE TO CHLORINE COMPOUNDS
RELEASED BY HUMANS.

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CHLORINE WAS SEEN TO PEAK
AND THEN STARTED TO DECREASE

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IN THE LATE 1990s.

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AND WE'VE SEEN GLOBAL DECREASE
IN OZONE FLATTEN OUT.

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IT NOW HAS A SLIGHT
INCREASING TREND.

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- IN ORDER TO UNDERSTAND
HOW OZONE MIGHT BE CHANGING,

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IT NEEDS TO BE MEASURED.

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THE MOST COMMON UNIT
FOR MEASURING OZONE

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IS CALLED THE DOBSON UNIT.

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ONE DOBSON UNIT IS THE NUMBER
OF MOLECULES OF OZONE

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THAT WOULD BE REQUIRED TO CREATE
A LAYER OF PURE OZONE

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0.01 MILLIMETERS THICK.

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OF COURSE, OZONE ISN'T
ALL PACKED INTO A SINGLE LAYER

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IN THE EARTH'S ATMOSPHERE.

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IT'S DISPERSED THROUGHOUT IT.

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SINCE NASA DOESN'T HAVE A WAY

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TO ACTUALLY SCOOP UP
ALL THE ATMOSPHERE

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AND SQUEEZE THE OZONE
INTO LAYERS,

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JUST HOW DO WE MEASURE SOMETHING
THAT MAKES UP LESS THAN 0.00006%

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OF OUR ATMOSPHERE?

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FOR OVER 30 YEARS, NASA HAS USED

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THE STRATOSPHERIC AEROSOL
AND GAS EXPERIMENT, OR SAGE,

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FAMILY OF INSTRUMENTS

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TO INCREASE OUR UNDERSTANDING
OF THE ATMOSPHERE

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AND OUR KNOWLEDGE ABOUT OZONE.

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AND THE LATEST GENERATION,
SAGE III,

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IS CATCHING A RIDE ON THE
INTERNATIONAL SPACE STATION,

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BRINGING A WHOLE NEW PERSPECTIVE
TO THE PROBLEM.

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- SO, SAGE III MEASURES OZONE
THREE DIFFERENT WAYS.

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WE USE A TECHNIQUE CALLED
SOLAR OCCULTATION,

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WHERE WE LOOK AT THE SUN
DIRECTLY WITH THE INSTRUMENT

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AND THEN LOOK THROUGH
THE ATMOSPHERE

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AS THE SUN SETS OR RISES,

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AND WE CAN ALSO DO
THE SAME THING USING THE MOON.

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THE MOON'S
A MILLION TIMES DIMMER,

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SO IT'S A LITTLE BIT
MORE DIFFICULT.

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AND THE THIRD WAY IS,

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WE CAN JUST LOOK
AT SCATTERED SUNLIGHT,

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LOOK AT THE ATMOSPHERE

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AND JUST LOOK AT THE BLUE SKY,
IF YOU WILL.

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AND MOLECULES LIKE OZONE

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HAVE UNIQUE ABSORPTION FEATURES
IN THEM

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THAT ARE EASILY DETECTABLE.

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SO WHEN YOU SEE OZONE VARY,

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OR IF YOU'RE MEASURING
SURFACE TEMPERATURE,

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IF YOU WANT TO KNOW
WHY YOU SEE THE VARIABILITY

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IN THE RECORD THAT YOU DO,

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YOU NEED TO KNOW WHAT ELSE
IS GOING ON,

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SO, WHAT THE AEROSOLS
WERE DOING,

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WHAT SOME OF THE IMPORTANT
CHEMICAL SPECIES

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THAT CONTROL OZONE,
WHAT THEY WERE DOING,

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AND ONLY BY UNDERSTANDING
THAT VARIABILITY

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CAN YOU GET
AT THE UNDERLYING VARIABILITY

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THAT YOU MAY NOT
FULLY UNDERSTAND.

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- THE MEASUREMENTS COLLECTED
FROM SAGE III

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WILL PROVIDE VALUABLE
INFORMATION

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TO THE GLOBAL
SCIENTIFIC COMMUNITY,

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HELPING US ANSWER QUESTIONS
LIKE:

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AND NASA SCIENTISTS
WILL SEARCH FOR THOSE ANSWERS

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BY USING THE DATA COLLECTED
FROM SAGE III

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TO TELL THE STORY.

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SEE YOU NEXT TIME
ON "REAL WORLD."