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- BET YOU PLAYED IN THE DIRT AS A KID.
MAYBE YOU MADE MUD PIES
OR DUG HOLES WITH A SPECIAL TRUCK,
AND YOU PROBABLY CAME HOME WITH DIRT ON YOUR PANTS
AND WERE SENT INSIDE TO WASH THE DIRT OFF YOUR HANDS.
BUT DO YOU KNOW HOW IMPORTANT THAT DIRT REALLY IS?
DIRT, OR SOIL, IS ACTUALLY ONE OF OUR WORLD'S
MOST USEFUL NATURAL RESOURCES.
WITHOUT SOIL, MOST PLANTS COULD NOT GROW.
PEOPLE AND ANIMALS WOULD NOT HAVE FOOD TO EAT.
THERE WOULD BE NO WOOD TO BUILD HOUSES
OR COTTON TO MAKE CLOTHES.
JUST THINK ABOUT ALL THE THINGS YOU USE EVERY DAY
THAT STARTED IN THE SOIL.
- SOIL BASICALLY TAKES, LIKE, YOU KNOW, LIKE,
THOUSANDS OR MILLIONS OF YEARS TO FORM.
SOIL IS ACTUALLY A MIXTURE OF MINERALS, AIR, WATER,
ORGANIC MATTER, WHICH MAY BE PLANT RESIDUE
OR THE ANIMAL REMAINS.
- THE DECAYED ANIMAL MATTER AND PLANTS, THAT'S CALLED HUMUS,
AND THE HUMUS IS ACTUALLY A REALLY, REALLY DARK,
ORGANICALLY RICH SOIL.
AND THEREFORE, THE PLANTS THAT ARE IN THAT HUMUS
FEED OFF OF THOSE NUTRIENTS
IN ORDER TO, YOU KNOW, SUSTAIN THEMSELVES.
- BUT THE HUMUS HAS ANOTHER IMPORTANT JOB.
IT ACTS LIKE A SPONGE,
SOAKING UP THE RAINWATER TO KEEP THE SOIL MOIST.
EVERY TIME IT RAINS OR SNOWS, THE WATER SEEPS INTO THE GROUND.
THE SOIL IS WHERE ALL THE EXTRA WATER IS STORED
SO PLANTS CAN USE IT AT A LATER TIME.
SCIENTISTS CAN ACTUALLY MEASURE HOW MUCH WATER IS IN THE SOIL.
THEY CALL THIS MEASUREMENT SOIL MOISTURE.
YOU CAN EVEN MEASURE SOIL MOISTURE IN YOUR OWN BACKYARD.
ALL YOU NEED IS A SOIL MOISTURE PROBE.
YOU PROBABLY DON'T HAVE ONE AT HOME, BUT YOUR SCHOOL MIGHT.
YOU JUST STICK THE PROBE INTO THE GROUND
AND READ WHAT THE METER SAYS.
THE HIGHER THE NUMBER,
THE MORE MOISTURE THERE IS IN THE SOIL.
NASA UNDERSTANDS HOW IMPORTANT THE SOIL IS
TO LIFE HERE ON EARTH
AND WHY IT IS IMPORTANT TO UNDERSTAND
HOW MUCH MOISTURE SOIL HOLDS.
BUT HOW DO SCIENTISTS MEASURE SOIL MOISTURE
FOR THE ENTIRE EARTH?
- SMAP IS THE SOIL MOISTURE ACTIVE PASSIVE MISSION,
AND IT IS A MISSION
THAT WILL BE MEASURING SOIL MOISTURE FROM SPACE.
- MOST OF THE TIME,
PEOPLE UNDERESTIMATE THE IMPORTANCE OF SOIL MOISTURE.
- YOU CAN THINK OF HOW IMPORTANT IT IS TO GROW CROPS FOR FOOD.
GROWING CROPS, GROWING ANY VEGETATION,
TREES, GRASSES,
DEPENDS ON HOW MUCH WATER THERE IS IN THE SOILS.
SOIL MOISTURE IS KIND OF A NICE INDICATOR OF DROUGHT,
BECAUSE DROUGHT IS BASICALLY A LACK OF WATER,
AND WHERE DO YOU SEE THAT LACK OF WATER?
YOU CAN SEE THAT LACK OF WATER IN THE SOIL.
- BY STUDYING THIS ONE VARIABLE IN THE SOIL, SOIL MOISTURE,
THERE ARE SO MANY APPLICATIONS THAT BENEFIT MANKIND.
- SMAP WILL MEASURE THE ENTIRE PLANET'S SOIL MOISTURE
EVERY THREE DAYS.
THAT'S DEFINITELY FASTER THAN USING THIS.
I KNOW THERE ARE MANY DIFFERENT KINDS OF SOIL.
DOES ALL SOIL HOLD THE SAME AMOUNT OF MOISTURE?
- DIFFERENT SOIL TEXTURES, DIFFERENT SOIL SIZES
HAVE DIFFERENT ABILITIES TO HOLD THE WATER.
YOU CAN THINK OF A TEXTURE OF A SOIL AS BEING
HOW MUCH SAND YOU HAVE VERSUS HOW MUCH CLAY YOU HAVE
VERSUS HOW MUCH SILT YOU HAVE.
THOSE RELATIVE AMOUNTS, THOSE RELATIVE PERCENTAGES
DETERMINE THE TEXTURE OF A SOIL.
THEY AFFECT HOW THE WATER DRAINS THROUGH THE SOIL
AND HOW MUCH WATER THE SOIL CAN HOLD.
- SO DIFFERENT TYPES OF SOIL HOLD DIFFERENT AMOUNTS OF WATER.
I WONDER, WHAT OTHER THINGS CAN AFFECT SOIL MOISTURE?
- SOIL MOISTURE CAN ALSO BE AFFECTED
BY THINGS LIKE FROZEN SOIL,
YOU KNOW, WHEN THE GROUND IS FROZEN.
- WHY IS THAT IMPORTANT?
BECAUSE WHEN THE GROUND IS FROZEN,
THEN A LOT OF WHAT WE CALL THE HYDROLOGICAL CYCLE
INVOLVING THE LAND, THE MOVEMENT OF WATER
BETWEEN THE LAND AND THE ATMOSPHERE,
FOR EXAMPLE, STOPS.
WHAT WE'RE GONNA BE ABLE TO DETERMINE
IS THE FREEZE/THAW CYCLE.
IT'S A SEASONAL CYCLE OF FREEZE/THAW.
EVEN THOUGH IT IS FROZEN, IT IS STILL PART OF THE SOIL.
- YOU CAN SEE THAT STUDYING SOIL MOISTURE IS VERY IMPORTANT.
IT CAN HELP PREDICT WHEN A DROUGHT MAY OCCUR
OR IF A FLOOD IS LIKELY TO HAPPEN.
IT CAN EVEN HELP FARMERS IMPROVE THEIR CROPS
OR HELP US UNDERSTAND MORE ABOUT WATER
IN THE FROZEN GROUND.
SO AS SMAP COLLECTS MEASUREMENTS ABOUT SOIL MOISTURE,
NASA WILL BE HELPING MAKE OUR WORLD
A BETTER PLACE TO LIVE.
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children: OUR WORLD!