Nova (1974–…): Season 40, Episode 6 - Earth from Space - full transcript

NARRATOR:
Our planet: Earth.

You may think you know it well.

But a startling new picture
is emerging

of a world shaped by forces

more dynamic and intertwined
than we ever imagined,

raising possibilities
that defy common sense.

How can sandstorms
in the Sahara Desert

transform the Amazon rainforest
over 5,000 miles away?

In the frigid ocean
beneath Antarctica,

how can a vast
undersea waterfall

500 times bigger
than Niagara Falls



lead to a gigantic
feeding frenzy near the equator?

And how can warm water streaming
past the coast of Africa

trigger a weather catastrophe

half a world away
in the southern United States?

Scientists have begun to find
surprising answers

to these and other
profound questions

thanks to a network
of satellites

orbiting high above the earth.

Ever watchful,

their senses extend far beyond
what our eyes can see.

EMILY SHUCKBURGH: It's really the
last bastion of human discovery.

We're discovering new things
every day.

NARRATOR: What are these hidden forces
that rule our world?

How are the oceans,
the continents, the atmosphere



and even the sun
bound together,

and how do they affect
all living things?

For the first time,
we can understand

how earth, fire, wind and water
join together

to create the dynamic
environments

that shape life
in all its forms.

WALEED ABDALATI:
Their interaction

is what has created
the environment, the diversity,

the kind of life
we see on earth today.

NARRATOR:
With astonishing images

created from a wealth of new
information from satellites,

this is our planet
as never seen before.

"Earth from Space,"
right now on NOVA.

♪ NOVA 40x11 ♪
Earth From Space
Original Air Date on February 13, 2013

== sync, corrected by elderman ==

Major funding for NOVA is
provided by the following:

NARRATOR: Since humans first ventured
into space,

some of the greatest gifts
of exploration

have been the new views
of our home.

Who can forget the iconic
"earthrise" images

of the Apollo era?

And now from the International
Space Station,

we have these spectacular
vistas.

The blue marble is finally
revealing its secrets.

It's a planet alive with
activity and constant change,

its surface transformed
by humans

yet still ruled by powerful
natural forces

that we are only beginning
to understand.

ABDALATI: It's just spectacular
when you view it from space.

It's teeming with diversity,
with beauty.

Amazing colors, you know,

the blues and the greens
and the whites.

PIERS SELLERS:
You see the world

as one huge system

all linked through
the atmosphere and the oceans,

rolling its way
around the sun.

NARRATOR: So what is it that shapes
Earth's dynamic face?

What are the essential
ingredients,

and how do they combine to
generate and sustain all life?

How do the natural forces
that surround us work together

to create an engine
powerful enough

to nourish and drive life
forward in all its diversity?

Our best hope for answers
may come from above.

Orbiting over our heads
are 120 satellites

keeping watch from space.

Most operate at altitudes

ranging from a few hundred miles
above the surface of the planet

to as high as 25,000 miles.

Each one of these
Earth-observing satellites

reveals a different piece
of the puzzle.

Each carries an array of
exquisitely sensitive detectors,

designed to reveal
what would otherwise

be hidden from our view.

The satellites are
absolutely amazing

because not only can we see
visible things from space,

but also we can see things that
aren't visible to the human eye.

So satellites are enabling us

to turn what are
invisible processes

into visible things we can see
and then understand.

NARRATOR: To see how our world works,
in this program

we have taken information
provided by satellites,

combined it with
computer models,

and rendered the results

in these scientifically
accurate graphics.

With the invisible
now revealed,

we can see Earth as
an endlessly changing system.

These images will show
in great detail

how sunlight, moisture,
land and atmosphere interact

in unexpected ways,

with seemingly local events

often triggered by forces
far away in space and time.

And with these new insights,
for the first time,

scientists can begin
to understand

the intimate relationship
between the planet

and all the living things
it supports.

ABDALATI:
It's really the thrill,

because it matters so much,

of piecing together the story
of what the earth is doing,

how it's changing,
why it's changing

and how ultimately
that affects humans.

NARRATOR:
The first piece of the puzzle

is in understanding
the massive influence the sun,

from 93 million miles away,
has on our planet.

The world's continuously bathed

in a flow of energy
from the sun.

That warms the earth.

Everything that you can see
that lives and breathes

and moves on the earth
is pushed by the sun.

NARRATOR:
Now an electronic eye in space

can measure the impact
of the sun's energy

all around the earth.

One of NASA's newest satellites,

named for a meteorologist,
polar-orbiting Suomi,

launched in 2011,
provides the view.

The spacecraft is the size
of a small school bus.

It orbits 500 miles up, circling
the planet 14 times a day.

On board, it carries
five separate sensors

that enable it to see things
invisible to human eyes.

The light that we can see

is confined to a narrow band
of electromagnetic radiation,

just a tiny portion of what
the satellite can pick up.

Electromagnetic radiation
spans a spectrum

that goes far beyond the
familiar colors of the rainbow.

ABDALATI: If you were to consider
the full spectrum to be a line

that stretched from New York
City to Los Angeles,

the piece that our eyes
could see

would be about
the size of a dime.

There is so much other
information out there

available to us,

and that's in large part
what these satellites do.

NARRATOR: One of this satellite's
key instruments is called CERES,

an acronym for Clouds and
Earth's Radiant Energy System.

It detects a broad range
of the spectrum,

including the very short and
very long wavelengths of light

in the ultraviolet and infrared
that we can't see.

This is a CERES-eye view
of the planet.

Anything that emits heat
gives off infrared radiation,

so the CERES data shows
the earth in shades of heat,

accurate to a fraction
of a degree.

It reveals how the planet
as a whole reacts to sunlight,

both absorbing and reflecting
the radiation

coming from our local star.

At the poles, the sun strikes
at an oblique angle,

and what little light there is

gets reflected back out to space
by the ice and clouds.

These are the primary reasons
why the poles remain cool.

At the equator,
it's a very different story.

Not only does the planet receive
more direct sunlight here,

the lack of ice means that

less of the sun's energy
is reflected back into space.

And at the equator,

the sun's concentrated energy
fuels a heat engine

that can trigger weather events
around the world.

Perhaps the best place to see
the impact of the sun's heat

is an area in the Atlantic

just north of the equator
and west of Africa:

the coastal waters
of the Cape Verde islands.

Here, the sea provides a living.

The local fishermen keep
a careful eye on the weather.

They know that storms
can bring a good catch.

Turbulent weather stirs up
nutrients from the deep,

attracting great shoals of fish.

It's the hottest time
of the year,

and the sun beats down
relentlessly.

By late afternoon,
the huge inflow of heat energy

has led to the buildup
of large cloud formations.

Sometimes, these formations
develop into massive storms.

It's a process that satellites
are revealing in fine detail.

Circling above the fishermen is
a NASA satellite called Aqua--

Latin for "water."

It orbits the poles.

One of its key tasks is to
monitor the complex interaction

between sunlight and water.

JEFFREY HALVERSON: Aqua satellite
is one of NASA's flagship satellites.

Its primary function is to study
the hydrologic cycle on Earth:

vapor in the atmosphere,
liquid ocean,

the temperature of that ocean
and the ice.

NARRATOR:
One of Aqua's instruments

looks down at the sea
around Cape Verde,

again in infrared,
sensing heat.

Highlighted here in yellow,

over one million
square miles of ocean

reaches a critical temperature:
80 degrees.

At this temperature,
the sea is evaporating fast,

producing an invisible gas:
water vapor.

SHUCKBURGH: By looking at the infrared,
the Aqua satellite

is able to measure the amount
of water vapor evaporating

from the surface of the ocean.

NARRATOR:
Aqua shows that this area

is producing millions of tons
of water vapor every hour.

Based on that data,
it's possible to create an image

of what the vapor
might look like

if these fishermen
could actually see it

in the air around them.

Water vapor is much lighter
than air,

and vast columns rise upward,

directly from the surface
of the sea.

The water vapor carries with it
heat, the energy of the sun.

HALVERSON: Well, water vapor is like
invisible energy.

It's like molecules
escaping the ocean,

taking heat energy with them,

and they're like little
mobile solar collectors

that are zipping
around the atmosphere.

NARRATOR: Half a mile up,
as the air cools,

the water vapor condenses
back into liquid water--

tiny droplets
that form vast clouds.

The vapor releases
the sun's energy,

the heat it received earlier.

The result is a storm.

HALVERSON: Molecules condense
in the atmosphere

and become liquid again,

and when that happens,

that heat is given off
into the atmosphere

and it warms the atmosphere,

and that's the heat
that powers storm systems.

NARRATOR: In the worst storms, the heat
captured by the water vapor

is equivalent to up to 200 times

the global production of
electricity at any given moment.

The process of evaporation
results in something

we don't need special
instruments to see.

The rising heat drives
the clouds up to ten miles high.

As the clouds rise upward,

the earth's rotation
causes them to spin.

The thunderclouds merge
into a vast vortex.

This is the birth
of a hurricane.

(loud winds blowing)

It is 2005, the busiest
hurricane season on record.

On August 27,
a meteorological satellite

is tracking
a category three hurricane

that started in the Bahamas.

Its name is Hurricane Katrina.

Throughout the region,

there is one question
on everyone's mind:

will the hurricane hit land,
or will it blow itself out?

The answer may come from
a NASA satellite called TRMM,

the Tropical Rainfall
Measuring Mission.

TRMM is equipped with a radar
and imager

that operate in the microwave
range of the spectrum.

These are higher in energy

and shorter in wavelength
than other radio waves.

The instruments
bounce microwaves

off raindrops in the clouds,

allowing scientists to build
a three-dimensional model

of the internal structure
of a hurricane.

HALVERSON: We can actually look
at microwave energy

which is generated
within the clouds

and coming from
the ocean's surface.

It's almost as if the clouds
are now invisible to us;

we can see right through them
like taking a CAT scan

to look inside those clouds.

NARRATOR: This satellite is
a powerful tool,

and now its sensors reveal
something ominous.

Huge, vertical columns
of warm water vapor

burst up from near the center
of the storm.

Almost like hurricanes
within hurricanes,

these climbing vortices deliver
added infusions of energy

into the heart of the storm,
fueling its growth even more.

These new sources of energy
are called hot towers.

HALVERSON: If they occur in the right place
at the right time,

near the very center
of the system,

they can be like
a giant spark plug

that gets that
whole engine running

at very, very high speed.

NARRATOR: The hot towers draw more and
more water vapor off the ocean.

This triggers a feedback loop

that leads to
a runaway reaction.

In just 24 hours,

Hurricane Katrina grows
into a category five monster.

(loud winds blowing)

(screaming)

NARRATOR: All this violence
is a direct result

of the power of the sun
on the ocean.

Ferocious winds blow
for two days straight,

reaching 175 miles an hour,

twisting steel like paper

and ripping apart homes
and buildings.

Over three trillion gallons
of rain a day

and a massive tidal surge
from the Gulf of Mexico

combine to inundate whole areas
of the Gulf Coast.

Katrina leaves its mark
across 90,000 square miles.

Over a million people
are displaced.

Katrina becomes the standard

by which future hurricanes
will be assessed.

But even this extreme hurricane

is just a tiny brushstroke
in a much bigger picture:

a picture of how the sun drives
water around the entire planet

with radically different effects
in different places,

all under the watchful gaze
of our eyes in space.

Take just a single day in July.

In New York, commuters swelter
in 95 degree heat.

Searing winds pump hot air
into the region from the south,

creating oppressive,
humid conditions.

7,000 miles away,
in Mumbai, India,

commuters here struggle
to cope with torrential rain.

The deluge comes so fast

that the streets
are flooded in hours.

Meanwhile, in Chile,

the desert of the Atacama
is almost totally dry.

There are places here

where rainfall
has never been recorded.

Such diverse environments,
thousands of miles apart,

appear totally unrelated.

But by pulling back
for a wider view,

we can see that they are in fact
intimately connected.

Orbiting 22,000 miles
from Earth's surface

is a chain of five
weather-tracking spacecraft,

including this one:
NASA's GOES East.

GOES is an acronym

for Geostationary Operational
Environmental Satellite.

Each moves in a fixed position
relative to the earth,

called a geostationary orbit.

They always look down
on the same parts of the planet.

The combined data
from these five satellites

gives scientists a unique
perspective on the earth.

SHUCKBURGH:
By having several of them

located at different positions
around the equator,

we're able to get a view
of the whole earth

24 hours a day.

NARRATOR: By observing the entire earth,
these satellites reveal

how energy moves
throughout the globe,

beginning with the impact
of the sun on water.

The process is the same
everywhere,

but the outcome will be very
different in different places.

Converted from
the numerical data,

these five circles
graphically depict

what the satellites
actually sense.

They reveal the total picture
of water vapor produced on earth

in a single frame.

Seen here in fast forward,
one second is equal to a day.

It shows how water vapor
produced at the equator

continuously transports the
sun's energy towards the poles.

Local landscapes and topography
affect the vapor's impact,

with results unique
to each region.

In India at the end of July,

the warm water vapor is drawn
from over the ocean

by the difference in temperature
between land and sea.

Rising to high altitude,

the vapor cools over the land
and condenses back into water.

We call the result
the Asian Monsoon.

Nearly a trillion tons of rain
falls out of the sky,

transforming parched land
into fertile plains.

The monsoon eventually moves
to the east, reaching China,

where it floods the paddies
that are ideal for growing rice.

This process helps provide food
for three billion people,

almost half the world's
population.

Meanwhile, on the other side
of the world in South America,

westbound winds
drive water vapor

across the high peaks
of the Andes.

The altitude strips the air
of its moisture,

which falls as snow
on the mountains,

creating on the far side
in central Chile

the arid desert of the Atacama.

That same July day
in the eastern United States,

hot, moist air surges north

straight from
the Gulf of Mexico.

With no natural barrier
in the way,

more than 100 million Americans,
from Memphis to New York,

swelter in the summer heat.

This graphic,

based on information
provided by satellites,

depicts the interaction between
the atmosphere and the oceans

as they connect in a global
pattern of circulation

that results in our
local weather.

SHUCKBURGH:
The satellite data shows that

it's all one
interconnected system,

but that in different parts
of the world,

different processes
are happening.

We can see the monsoons
and their effect.

We can see the effects
on deserts

in a different part
of the world.

And that together shows us

how water vapor is connecting
with life on earth.

NARRATOR: But this vast cycle
of sunlight, water and land

is just one pattern among many
on this planet we call home.

A cycle with even
greater consequences

for the long-term climate
involves extreme cold.

To see how that works, we have
to turn the earth upside down

and look at it from below.

Antarctica remains the earth's
last great wilderness,

a vast frozen continent
plunged in darkness

for almost six months
of each year.

In winter,
temperatures can drop

below minus 110 degrees
Fahrenheit,

and an incessant
100-mile-an-hour gale blows.

It's hard to believe
that anything life-giving

could start here
in this bleak place.

But that's exactly
what happens.

Antarctica's ice
plays a vital part

in maintaining global climate,

sustaining life even in lush,
warm jungles

thousands of miles away.

ABDALATI: Antarctica is a fundamental
element of the climate system.

And while it may sit silently
and majestically

at the edge of the planet
for very few to see,

things go on there

that spread out
all over the world,

that affect the world
as a whole.

NARRATOR: It's a paradox that such a bleak
and barren place

is so critical
to life on our planet.

On average, it's 43 degrees
colder than the North Pole.

Why should Antarctica
be so much colder,

and how does that affect
the rest of the world?

The detectors on NASA's
polar-orbiting satellite Suomi

provide part of the answer.

The instruments sense

in the infrared and ultraviolet
parts of the spectrum.

They show that the poles receive
little of the sun's energy

and reflect most of it
back out into space.

That's one reason why the poles
stay cold.

But there's another factor that
makes Antarctica colder still.

This image has been
pieced together

from 17 different satellites

that sense the infrared,
or heat.

The continental mass
of Antarctica

lies beneath this swirling
maelstrom of cloud.

A computer model of the data
shows what happens

as the warm moist air
arriving from the tropics

collides with the cold air
over the South Pole.

The result is
a massive storm system.

And just like a hurricane,

it rotates as a result
of the spin of the earth.

Only this is much larger
than a hurricane,

4,000 miles in diameter.

Where that cold air and warm air
meet high up in the atmosphere,

the air starts to rotate
around Antarctica.

The winds can be up
in the atmosphere

as much as 200 miles an hour.

NARRATOR: This circulation pattern
is called the polar jet,

a ceaseless circle
of wind and storms.

The relentless clockwise wind,
seen here in yellow,

drives the seawater below,
shown in light blue.

DAVID ADAMEC: Those strong winds are sending
a jet around in the ocean,

and it's driving
an ocean circulation

that is felt almost all the way
to the bottom of the ocean,

two and a half miles deep.

NARRATOR: The Southern Ocean
rings the continent

with no land to interrupt
a vast body of moving water.

This is the Antarctic
Circumpolar Current.

And these are
the "Screaming Sixties,"

the roughest, most dangerous
seas on the planet.

Here, storms rage almost
every day of the year,

whipping hundreds of trillions
of gallons of water

into a ceaseless frenzy.

Now the infrared instrument
on the Aqua satellite

which senses atmospheric
temperature

puts the pieces
of this puzzle together.

The winds of the polar jet

and the water
of the circumpolar current

together form an impenetrable
barrier around Antarctica,

isolating it from the rest
of the planet

and depriving it of warmth.

That is why the whole region

remains exceptionally cold
all year round.

ABDALATI: What's incredible about
what the satellites tell us

is that the movement of air

and actually the movement
of ocean current

around the perimeter
of Antarctica

isolates the continent
from the rest of the world.

NARRATOR: So why is this relentless cold
so important to the planet

way beyond Antarctica?

The answer lies in a remarkable
property of water:

what happens when it freezes.

The Aqua satellite reveals
the start of the process.

It sweeps the surface
with its microwave scanner,

looking through the clouds

to detect the distinct
signature of ice.

SHUCKBURGH: The microwave instruments
on the satellite

enable us to see through
the clouds

to the sea ice around Antarctica
throughout the year.

What's particularly incredible
about that is

we're able to take measurements
of the sea ice

in places where as scientists,
as humans, we can't even go.

NARRATOR: This satellite gives us
an accurate picture

of the extent of sea ice
around Antarctica

over the course of a year.

Seen here in summer,
Antarctica is nearly

one and a half times the size
of the United States,

covered in ice.

But in winter,
it grows even more.

Over five and a half million
square miles of ice form

around the continent.

It grows to the size
of all of Africa.

This vast ice formation
has a profound effect

on life across the planet.

How can its impact
extend so far?

One of the best places
to understand the power of ice

is the huge bay

along the northwestern coast
of Antarctica: the Weddell Sea.

Here, a constant gale blows
and cools the seawater

to freezing temperatures.

Once the upper layer of ocean

falls below 29 degrees
Fahrenheit,

a critical threshold is crossed.

The surface of the ocean
begins to freeze.

(crackling)

At a microscopic level,
tiny crystals start to grow,

knitting themselves together.

As the crystals bond,
they expel salt into the water.

The salt forms brine that drips
down long, narrow tubes

and holes in the ice
as it forms.

The brine is denser than regular
seawater and it sinks downwards.

As winter's grip tightens,

the formation of ice
speeds up and spreads.

Soon, large slicks appear
on the surface

and thicken into a solid mass.

What started as
a microscopic process

can soon be seen from space.

Each year, more than
200 billion tons of ice form

in the Weddell Sea alone,

releasing tens of trillions
of tons of dense brine

into the ocean.

The fate of all this brine
is a mystery.

The crucial question is
where does it all go?

A satellite called Jason,

jointly operated by NASA
and the French space agency,

is providing new answers.

Jason bounces radar signals
off the surface of the ocean

to measure its height.

The instrument also reveals

the shape of the sea floor
far below.

We can make very accurate maps
of submarine bathymetry.

But we don't do that directly;

we do that by measuring the
surface of the sea from space,

very, very accurately
and over time.

NARRATOR:
Jason's radar is so precise

that it can detect
minute changes

in the level of the sea surface

produced by the peaks and
valleys of the terrain below.

The data makes it possible
to map the ocean floor.

ADAMEC: You have a satellite that's
up there, 500 miles up in space,

and it's returning an accuracy

of a little less
than half an inch.

What that means is, you know,

I've stuck this instrument
in Washington, D.C., say,

and I'm looking at a crowd
of people in Boston

and I can tell you
whether or not their toes

are over the curb or not.

That's what this satellite
is doing.

NARRATOR:
The satellite data

allows scientists to make
a three-dimensional map

of the ocean floor
beneath the Weddell Sea.

It reveals a vast chasm,
two miles deep,

off Antarctica's
continental shelf.

As the brine descends
into the ocean,

it eventually falls over
this precipice.

Other sensors attached
to the sea floor

track the flow of the brine
as it sinks.

SHUCKBURGH: What we're really
excited about is that

we're able to take that data

that shows us what the bottom
of the ocean looks like

and combine it with data
from sensors under the water.

And that enables us
to look at the dense water

and where it goes.

NARRATOR: Combining data from satellites
and undersea instruments,

scientists can reconstruct
what is happening

hidden beneath the ice.

What they learn is astounding.

One trillion gallons
of salty brine

plunge down through
the Weddell Sea every hour,

a torrent equivalent to the
volume of 500 Niagara Falls.

The brine spreads out
towards the edge

of the Antarctic
continental shelf

and then falls into the chasm
revealed by Jason.

A vast submarine waterfall
plummets downward.

The cold, dense brine

falls slowly, silently,
into the abyss,

two miles down
to the ocean floor below.

It will not resurface
for hundreds of years.

What happens to the brine next
is still being investigated.

But computer models
combined with satellite data

are helping scientists
to figure out where it goes.

This animation shows the
undersea current in action.

The purple area is the brine.

The outflow from Antarctica

drives the salty water
towards the equator,

along the sea floor.

ADAMEC: All the water in the bottom
of every ocean around the globe

has its start within six miles
of the Antarctic continent.

It creates the coldest, densest
water that's on the planet.

NARRATOR:
The cold, salty liquid

becomes part of a worldwide
circulation system,

stirring and cooling
all the world's oceans.

Leaving Antarctica,
it has embarked on a journey

that could take 1,000 years
to complete.

As it migrates
towards the equator,

the cold bottom current mixes
with fresher and warmer water

and slowly rises.

It then joins
other ocean currents

and eventually returns south,
where it cools once more.

Finally, returning
to Antarctica,

the seawater freezes
and releases its salt again,

completing the cycle.

It's an endless loop that is
critical to the whole planet.

ABDALATI: The importance of dense water
in Antarctica is that

it really forms the basis
of global ocean circulation.

The temperature
and the salt combine

to cause sinking and rising
in different parts,

which sets up
this conveyor belt,

this interaction of
all of the ocean water.

NARRATOR: In the Arctic, frigid winter
winds cause the ocean to freeze.

The North Atlantic currents
cool and sink to the bottom,

then head south again.

All over the world, slow-moving
currents of seawater like this

regulate the average
temperatures of the oceans

to within one degree.

This stability has
a profound effect on life

all across the world.

This NASA simulation shows
the surface of the entire ocean,

a web of currents
in constant motion.

But satellites show us that
the oceans don't work alone.

The currents affect the air,
the atmosphere,

that sits above them.

The ocean and atmosphere
are intimately connected.

For instance,
the Gulf Stream

takes warm water
from the Gulf of Mexico

north to the eastern
United States and Europe,

generating warm air.

On the other side
of the world,

another current
called the Kuroshio

carries heat from China
north to Japan.

ocean currents distributing heat
around the planet.

The climate we live in

is a result of ocean
circulation patterns.

The reason in the United States

that North Carolina
and South Carolina are warm

is because there is
the Gulf Stream.

And the reason there's
a Gulf Stream

really takes root in Antarctica.

NARRATOR: As a major engine driving
the world's ocean currents,

Antarctica helps protect
Earth's climate

from wild swings
in temperature.

The constant,
dependable circulation

of the oceans around the globe

and the relatively stable
temperatures it produces

have made Earth
a hospitable planet.

Long-term stability provided
time for life to flourish

and complex animals
and plants to evolve.

And this is how a process
that began with Antarctic ice

continues to sustain our world.

ABDALATI: When you put it all together,
you get a story

of how ocean circulation affects
climate and weather

and what that means today,
tomorrow

and 20 years out
into the future.

(rumbling)

NARRATOR: But ocean currents
and the atmosphere

are not the only players.

Beneath the sea floor,

forces inside the earth
are a crucial source

for the basic materials
that nurture life.

This hidden mechanism
is driven by ceaseless,

often violent activity.

Two recent examples:

A magnitude nine earthquake
strikes Japan in 2011.

An entire section
of the country

moves eight feet
towards North America.

A year earlier, 2,500 miles to
the south in Papua New Guinea,

the volcano Rabaul erupts.

It fires a vast plume of ash
high into the atmosphere.

These are catastrophic,
hugely destructive events

with an enormous cost
in human lives.

But the natural forces
behind these disasters

also provide the materials

we and other living organisms
need to survive.

And satellites help show us
how this happens.

Canada's RADARSAT is
one of several satellites

that use highly sensitive radar

to map the earth's surface
in three dimensions.

Bouncing radio waves off
the terrain below,

these satellites continually
sweep the surface of the globe.

They can measure the height
of the earth's surface every day

to an accuracy of less
than a quarter of an inch.

When the data is plotted
over time,

we can see in fine detail

how the earth's crust
is constantly moving.

This is the surface
of the crater

atop Mount St. Helens
in Washington state.

Animation reveals how it swells
over the course of three weeks,

driven by a surge of molten
magma beneath the crater.

Satellites can actually see
the crustal plates moving now.

We can see bulges and dips

where the magma is moving around
underneath the crust.

NARRATOR: This animation shows the
swelling of Mount Etna in Italy

as magma accumulates beneath it
over nine years.

When the volcano erupts,
the land sinks back.

SELLERS:
So we're getting a picture now

of what the world looks like
under the crust

and how that affects
the other dynamic processes

of the so-called solid earth.

NARRATOR: Every day, dozens of volcanoes
around the world are erupting,

while 4,000 earthquakes
shake the ground.

Our earth is dynamic,

constantly ejecting gases
and magma from its depths.

And some of this activity
has a vital impact on life.

The secret to understanding how

lies deep beneath
the ocean's surface.

Here, a crucial chemical
reaction takes place

between molten rock
and deep ocean water.

The Jason satellite's
sea surface-mapping radar

reveals a chain
of active volcanoes

a mile and a half down, at the
bottom of the Pacific Ocean.

This is where
that critical interaction

between molten rock
and freezing water takes place.

This footage was taken with
a remotely operated submarine,

also called Jason.

Lava and superheated gases

spill out of cracks
in the ocean floor,

known as hydrothermal vents.

Jason reveals what happens

when cold ocean water
penetrates into the cracks.

A magma chamber below
heats the water

to up to 750 degrees
Fahrenheit.

In the pressure-cooker
environment inside the cracks,

the dense salty water actually
dissolves the solid rock.

Complex chemical reactions
take place,

producing minerals
containing sulfur and iron.

These are nutrients that living
organisms need to survive.

The seawater, now loaded with
minerals from inside the earth,

streams out of the
hydrothermal vents.

These nutrients feed
a thriving ecosystem

that includes shrimp and exotic
creatures like tubeworms.

The deep ocean currents carry
the leftover nutrients away.

Over thousands of years, they
circulate through the oceans,

ultimately rising to the surface

and contributing to an amazing
explosion of life.

And we can see this activity
with NASA's Aqua satellite,

which is equipped
with instruments

that observe the earth

in many wavelengths
of the electromagnetic spectrum.

One tool is called MODIS.

MODIS is pretty much the crown
jewel of the Aqua satellite.

It's an enormous scanner.

So it basically covers
the whole world every day.

NARRATOR: MODIS scans the ocean
in the infrared

and the visible portions
of the spectrum.

It can detect extremely subtle
changes in the temperature

and color of the water.

So what we have in space
is an instrument

that looks at very, very small
parts of the spectrum,

and we measure how much light
comes back

in each part of the spectrum.

NARRATOR: Looking down at the west coast
of South America,

MODIS detects an upwelling
of cold water

150 miles west of Peru.

Then it detects a particular
shade of green.

This identifies the source
as chlorophyll,

a sign of plant life.

It's clear that the satellite
has spotted a massive bloom

of tiny organisms
called phytoplankton.

Just below the surface, these
phytoplankton are absorbing

the rich soup of minerals that
have come from the deep ocean.

And with light from the Sun,

and carbon from the carbon
dioxide in the air,

they multiply by the billions.

As MODIS shows, the plankton
multiply so quickly

that in just 24 hours,
500 square miles of ocean

have turned to this
distinctive green color.

GENE FELDMAN:
They replicate very, very fast.

So you can have a plankton bloom

that doubles over the course
of a day

and can cover hundreds or
thousands of kilometers

of the ocean surface.

NARRATOR: It's the minerals from beneath
the earth's crust

that have helped fuel this
vast explosion of plankton--

over 800 thousand tons of living
material.

And that's only the beginning.

This plankton is the base of
the food chain for marine life.

The bloom triggers one of
the largest feeding frenzies

on earth.

Trillions of anchovies
and sardines

feast on the tiny organisms.

They, in turn,
attract larger predators

to one of the densest
concentrations

of marine life anywhere.

Sharks converge.

And even birds, flying above,
dive down to join the feast.

And up above, humans are here,
too, taking advantage

of one of the world's most
productive fishing grounds.

The satellite data reveals
similar upwellings

all around the world, delivering
nutrients, seen here in pink,

into the surface waters.

Each upwelling triggers
a plankton bloom.

FELDMAN: Phytoplankton provide
that key link

between this energy out here,

the raw materials
that this planet holds

and the food engine
that allows life to flourish.

NARRATOR: These vast green ribbons
of plankton

can cover as much as a fifth
of the world's ocean surfaces,

about 45 billion tons of biomass
every year.

The plankton are one link
in a chain of life

that begins deep beneath
the seafloor.

The most important plant life
on this planet

are these microscopic
little green plants

that float in the ocean.

NARRATOR:
Plankton may be key to life,

but they themselves
don't live long.

MODIS shows how,
in just 72 hours,

a bloom can rapidly weaken
and fade.

All the plankton
that have not been eaten

die and sink into the abyss.

They take their precious
minerals with them

all the way back
to the ocean floor.

Here they will remain
for millennia,

a thick carpeting of tiny
carcasses half a mile deep.

Some of the minerals may
ultimately be recycled.

Some may emerge through
hydrothermal vents again,

millions of years from now.

But some plankton,

through yet another
extraordinary chain of events,

will deliver their precious
cargo of nutrients

not just to life in the ocean,
but also to life on land.

Half a world away from the coast
of Peru, where plankton bloom,

lies the Sahara Desert
in North Africa.

The Sahara is enormous--

it makes up a tenth
of the African continent.

It's one of the driest
and dustiest places on earth.

Surprisingly, the remains
of ancient plankton are here,

hidden in this arid landscape.

It is May,
the hottest month of all.

Camel herders travel through
one of the most exposed regions

of the Sahara:
the Bodele Depression.

Six thousand years ago,

this was covered by the world's
largest freshwater lake.

The floor of the lake is covered
with the ancient remains

of plankton-- called diatomite--
laid down in a much earlier age,

when an ocean covered
the region.

With its eye on the earth
from 400 miles above,

NASA's Landsat 7 is one of the
latest generation of satellites

studying the composition of
rocks that make up our planet.

It sweeps the Bodele, producing
these high resolution pictures

in multiple wavelengths
of visible light.

The white expanse
is the diatomite

on the bed of the lake.

The size of the lake is over
a thousand kilometers long

and 600 kilometers wide.

But with a satellite image,
we can see the whole extent

of the basin on a series
of images

and visualize that on a computer
in a matter of minutes.

NARRATOR:
The satellite image analysis

shows over 24,000 square miles
of sediment,

all of it diatomite.

We can map where the diatomite
sediment is

on the floor of the lake.

NARRATOR:The diatomite from the plankton
is a rich source of phosphorous,

an element needed by all living
things to produce energy.

But for this nutrient to
re-enter the chain of life,

it must first embark
on a long journey

that can be seen from space.

The journey begins here on the
ancient lakebed in the Sahara.

The wind sweeps up a few flakes
of diatomite into the air.

The flakes fracture
into a fine powder

and are carried off by the wind.

A dust storm builds.

22,000 miles above, the European
weather satellite Meteosat 8

looks down from its
geostationary orbit.

It records a daily pulse of dust

rising off the Bodele
Depression.

Here it's visible
as a whitish dust cloud

lifting from the desert
with clockwork regularity

at noon each day.

BRISTOW: Although the individual
particles of dust are minute--

they're hundredths or
thousandths of a millimeter

in diameter-- there are such
vast clouds of this dust

that you can see it
on satellite images.

NARRATOR: The dust cloud is over
a hundred stories high

and 200 miles wide.

From here it will head west
on an epic journey.

Seen from space,
the dust is blown across Africa.

At the Atlantic coast, it's
drawn up high into the sky.

This simulation,
based on satellite data,

shows how prevailing winds carry
the dust cloud west and south

3,000 miles across the Atlantic.

As much as 7,000 tons of dust
are airborne at any one time.

The destination is set
by the winds:

South America and the Amazon.

We're taking literally thousands
of tons of this dust,

which is containing phosphate,

and exporting that
from the Bodele.

The wind is carrying it out

across the Atlantic
to fertilize the Amazon.

NARRATOR: Here in these clouds
high above the rainforest,

what was once living plankton
reaches the end of its journey.

The minerals in the dust,

which include energy-giving
phosphorous,

dissolve into water droplets

and fall to the Amazon in rain.

BRISTOW: Areas like the Amazon jungle,
although they appear very rich,

the soils are actually very
depleted, they've been leached.

And one of the things that
they're short on is phosphate.

NARRATOR:
Rain falls incessantly

throughout the Amazon's
wet season,

delivering thousands of tons of
phosphate into the forest below.

It passes into the soil
and the roots of the trees,

nourishing the rain forest.

The effect of all this
natural fertilizer

can be seen clearly from orbit.

Terra is the twin
of the Aqua satellite.

It circles the earth
every 99 minutes,

monitoring how fast vegetation
is growing.

SELLERS: We can see all the green
vegetation on earth--

wall to wall, every day--

and it tells you almost
everything you want to know

about the state of life
on earth.

NARRATOR:
With its color scanner,

Terra can see the effect of
the Sahara dust on the Amazon

at the end of the rainy season.

It observes an increase
in the distinctive green color

of chlorophyll.

Like the plankton blooms
in the ocean,

the forest is kicking
into overdrive...

watered by rain
and nourished by the minerals

borne across the Atlantic
by the dust cloud.

For every leaf that exists now,
three more will grow in a week.

It's the culmination
of a chain of events

that began far back in time
and halfway around the world.

SELLERS: Ancient sediments laid down
by other organisms

millions of years ago
get eroded, make dust,

the winds bring them
across the Atlantic,

fertilize the tropical forest
in the Amazon.

NARRATOR: The migration of Bodele dust
to the Amazon

is just one of many ways
that vital minerals spread

to living habitats
all over the world.

Every landscape has
its own story

and its own way of entering
the chain of life.

BRISTOW: The exchange of nutrients
from the land

is going on
all over the globe every day.

NARRATOR: And in certain areas,
this is what accounts

for the special productivity
of the soil.

The Great Plains of North
America are rich in minerals

eroded from the Rocky Mountains.

These are vital ingredients
for growing wheat and corn.

In Bangladesh, the Ganges delta
is rich in iron

washed down from the Himalayas
in river sediments,

ideal for growing rice.

The hidden transport of minerals
creates fertile soils

that enable plants to thrive.

These minerals are the basis
of the food chain

for all life on land,
including us.

SELLERS:
All of this reminds you

how interconnected
the earth system is...

...that no living thing lives
in isolation from processes

that may happen a long way away

in both space and time
from itself.

NARRATOR: Satellites provide a vivid
new perspective on the links

between land, sea,
air and life.

This new perspective
helps us see

how the natural forces
of our planet fit together,

and that includes the atmosphere

and something as basic
as the air we breathe.

Less than a quarter
of the air around us

is comprised of oxygen, but that
oxygen is essential to life.

It's what all animals need
to burn fuel in their bodies.

Oxygen is vital to metabolism.

It provides the energy

that allows even the most active
creatures to survive and thrive

and to master
their environments.

Scientists believe
that the abundance of oxygen

in the atmosphere was essential
for the evolution of large,

intelligent mammals like us.

The human brain alone uses about
20% of the oxygen we breathe.

But where does
all this oxygen come from?

Satellites can help us answer
that question.

NASA's Aura satellite
is one of several spacecraft

that are helping scientists
study the earth's atmosphere.

Along with ground instruments,

it can analyze the atmosphere
and pinpoint its composition.

It builds a picture
of the nitrogen,

oxygen and carbon dioxide

that together make up 99%
of the air we breathe.

This computer
visualization shows

how the earth's atmosphere
changes over 24 hours.

During the day, oxygen--
seen here in blue--

rises all over the planet.

At night, carbon dioxide--
shown in orange--

is on the rise.

And the oxygen we need
is given to us by plants.

Before plants, there was
no oxygen in the atmosphere.

So plants did all the hard work

of allowing the atmospheric
concentration

to build up over time, allowing
all other life to develop.

They made the place habitable
for us.

NARRATOR: Plants breathe in carbon dioxide
and expel oxygen.

They produce so much
that the vast Amazon rainforest

is often called the lungs
of the earth.

But the real picture
is more complex.

The verdant wilderness
of plants and animals

is one of the oldest,
most abundant living systems

on earth.

Over two million square miles
of lush rainforest

teem with half the world's
living species.

SELLERS:
The Amazon is

the largest natural preserve
of life on the continents

that's left in the world.

Thousands of miles
of almost virgin forest,

thousands of species
that have been there

for an awfully long time.

NARRATOR: So dense is the Amazon jungle
that it has a dramatic impact

on the air above it.

It starts in the trillions
of leaves far below.

We can use animation to show
what this invisible process,

known as photosynthesis,
might look like.

During the day, the leaf takes
up carbon dioxide from the air,

seen here in orange.

It converts the carbon
into sugar for energy and growth

and releases oxygen,
seen in blue.

Each one of these trees
will release

hundreds of thousands of cubic
meters of oxygen

in the course of its life.

And as for the Amazon
as a whole,

a fifth of the world's oxygen
is produced here.

But there's a surprising twist:

we will breathe
almost none of it.

Satellite data and ground
measurements reveal

that almost all the oxygen the
Amazon produces during the day

remains there and is reabsorbed
into the forest at night.

SELLERS: With the advantage
of the satellites,

we can now see that the Amazon

basically uses
all its own oxygen

and uses all its own
carbon dioxide.

It is, as far as we can tell,

almost a closed system
in itself-- almost.

NARRATOR: But the Amazon still plays
a vital part

in generating the oxygen
that we breathe.

What satellites
now make clear is

producing the oxygen that
benefits us takes an extra step.

The process begins with rain,

which falls up to 250 days
a year in the Amazon.

The soil of the rainforest

is continually washed
into the Amazon river system,

taking with it nutrients
and organic material.

An average of two million tons
of this sediment

is released every 24 hours.

The sediment flows eastward,

traveling 4,000 miles
into the Amazon delta.

Here, microscopic plankton
near the surface thrive

on the nutrients and
their population explodes.

As they spread further
out to sea,

some of these tiny organisms
act like plants,

absorbing carbon dioxide
and releasing oxygen.

Again the Aqua satellite shows
us how a giant plankton bloom

grows to cover 25,000
square miles.

This vast area translates into a
huge boom in oxygen production,

made available
to the entire planet.

FELDMAN: When plankton grow,
they release oxygen.

That oxygen ultimately finds
its way into the atmosphere.

NARRATOR:
The massive scale of this impact

is revealed when the satellite
data is visualized.

This animation shows the oxygen
produced by plankton blooms,

seen here in bright blue.

The Amazon plankton bloom
releases billions of gallons

of oxygen into the atmosphere
every day.

Within a few days
the plankton die,

leaving most of the oxygen
they produced in the air

as they sink to the bottom
of the ocean.

Similar explosions
of microscopic life

happen all over the world.

Plankton's major role
in replenishing oxygen

in the atmosphere is something
we've only fully grasped

with the help of satellites.

FELDMAN:
Satellites gave us

that very first global picture,

global assessment of what
the ocean's plants were doing.

NARRATOR: And what plankton are doing is
providing life-giving oxygen

for us.

FELDMAN: Plankton in the ocean are
responsible for over half

of the oxygen that we breathe,

and it's what most creatures on
this planet rely on to survive.

NARRATOR: Microscopic organisms
as well as rainforests

are the lungs of the earth.

So what other secrets of life
can satellites--

our eyes in space-- reveal?

It turns out that another
surprising way life is sustained

is through a violent force:
lightning.

From orbit, the whole earth
buzzes with electricity.

Astronauts are often amazed
by the intensity

of the electrical storms raging
far beneath them.

SELLERS: You can see
a thousand miles' worth

of lightning flashes left and
right as you're looking down,

and they seem to set each other
off like fireworks,

bang, bang, bang, bang, bang.

It's really quite amazing.

NARRATOR: But to understand lightning's
global impact,

we need more than just
observation.

NASA's TRMM satellite carries
a high-speed camera

that can detect individual
lightning bolts.

From this information it's
possible to build a picture

showing the distribution of
lightning all across the globe.

Astonishingly, 40 strikes occur
every second.

That's more than three million
strikes a day.

So how is all this lightning
created?

And what is the effect
of all this energy

streaking through
the earth's atmosphere?

Each day, the combined force
of sunlight and water vapor

creates 40,000 thunderclouds.

The rising columns of moist air
generate powerful updrafts

that turn water vapor
into ice particles

inside the clouds.

As ice and water droplets smash
into each other at great speed,

vast charges of static
electricity build up.

An average thundercloud contains
enough energy

to power a city the size
of Denver for ten hours.

Eventually the charge builds
to a point

where air molecules
are torn apart

and a lightning bolt is born.

A bolt is no thicker
than a human thumb,

yet it's five times
the temperature

of the surface of the sun.

As it burns through
the atmosphere,

the electricity breaks apart
the molecules of nitrogen

contained in the air.

ADAMEC:
A lightning stroke,

it actually splits the nitrogen

into single nitrogen molecules.

Nitrogen doesn't like that.

It's desperately looking
for something

to connect back to with and it
often does it with oxygen.

NARRATOR: When oxygen bonds
with nitrogen,

it creates a vital nutrient
called nitrate.

Satellites show the extent
of nitrate--

simulated here in yellow--

produced by the more than three
million lightning bolts

that strike every day.

This creates about 13,000 tons
of nitrate.

It dissolves in water droplets
in the clouds

and falls to the ground in rain.

Most people are familiar
with nitrates

because they're fertilizers.

So when it rains
in a thunderstorm,

in a way you're getting a free
fertilizing,

because the water will have
nitrates in it.

NARRATOR: Nitrate is absorbed
through the roots of plants

and enters the food chain.

When we eat these plants, the
nitrates become available to us.

And so this vital nutrient
enters the cells

of every living organism
on earth,

where it is critical for
building the structure of plants

and helps make proteins and DNA
in our bodies as well.

It is essential for the survival
of all living things.

But nitrate production
is not the only way

in which lightning
promotes life on earth.

In the Canadian Yukon,

a massive wildfire devastates
over ten square miles of forest

in less than a week.

Such blazes often start with
a random bolt of electricity

from the sky.

In distant Siberia, over 1,500
square miles of forest

burn to the ground,
sparked by a lightning bolt.

These flames may seem
purely destructive,

but thanks in part
to satellites,

we see that they can
also be life-giving.

The Terra satellite can detect
the location of every fire

on earth by looking at its heat
signature in infrared.

SELLERS: Terra basically gives us a map
of all the fires

in all the forests and
grasslands of the world

every day.

NARRATOR: This sped-up visualization
of Terra's data

shows a year's worth of fire
all around the world.

The vast swaths of orange are
actually thousands of tiny dots.

Each one represents
a half square mile of land

where a fire has burned,

over 19 million square miles
in total.

The Terra data also reveal
fire's role in renewing life.

SELLERS:
The observations have shown us

how important fire is
as an element of change.

NARRATOR: The benefits of change
can be witnessed

in the forests
of northern Canada.

This is a vibrant forest,

but it has its share of dead
and diseased trees.

Locked inside them are
ingredients that are essential

for new life: elements like
carbon, sulfur and phosphorous.

Yet in a cold environment
like this,

trees take decades to decompose

and return these elements
back to the soil.

Fire can shorten the cycle
to a matter of hours.

The pine tree
is highly flammable.

It's full of sap and resins
that burn easily.

The oxygen in the atmosphere
fuels the flames.

ADAMEC:
When you're looking at fire,

you're looking at
a rapid oxidation.

That's what fire is.

NARRATOR:
Within a matter of hours,

what may have started as a spark
from a single lightning bolt

turns acres of forest to flames.

The nutrients these trees
have stored for so long

end up in the ash.

Fires also consume
the dead animals

whose bodies litter the forest,

returning the nutrients they
contain back to the soil.

The smoke climbs into the sky,

and the ultimate impact
of this nutrient-rich ash

can eventually be seen
from space.

With its infrared sensor,

Terra can pick out the heat
given off by the leaves

of healthy new vegetation
that grows after fire.

A pulse of new growth
follows every blaze.

Huge areas of forest get burned
down quite regularly

and they're followed almost
immediately by rapid regrowths.

NARRATOR:
In forests all over the world,

the data from Aqua and Terra
show that within months,

large areas devastated
by fire are rejuvenated.

From a global perspective,

wildfires are essential
to the cycle of life.

Fire's like a great blender
for all the materials

in the earth system, so when you
get dead living material,

particularly in the forests,

fire will rip through there
and decompose that stuff

very quickly into its basic
minerals and compounds

that new life can use
almost immediately.

NARRATOR: Fire is such an intrinsic part
of nature

that many plants have evolved
to make active use of it.

The pine tree drops its seeds in
the ashen aftermath of a blaze

to make the most
of the nutrients

that have been released.

Wildfires are essential
to maintaining the health

of many of the world's
ecosystems.

It's a mechanism by which

habitats that are no longer
productive regenerate.

We can now follow this process
over decades.

SELLERS: When you look 30 years
of satellite data,

you see this continuous, dynamic
rearrangement of the biosphere.

The nutrients that that tree
has pulled up from the soil

are being dropped back down
again on the soil

to feed the next generation.

The effect of all this is
to allow the biosphere

to turn over far more quickly
and efficiently.

NARRATOR: By looking at the world
from orbit,

we see our home planet anew.

We discover countless hidden
connections, all linked to life.

The circulation of weather
and ocean currents

affects the ebb and flow of ice
at the poles.

Originating
in the earth's crust,

erupting magma interacts
with cold ocean water,

producing nutrients that rise
to the surface

and nourish aquatic life.

Eventually, airborne in dust,

nutrients travel
around the planet,

finally enabling tiny plankton
to fill the air with oxygen.

That allows complex animals
like us to survive.

Oxygen also allows fire to burn,

which, in turn, accelerates
the pace of death and rebirth

in the forest.

Above all, life's major driver

is the energy we receive
from the sun.

As the earth rotates
over 24 hours,

the planet responds to the
incredible power of the sun,

our local star.

Each day more than
a million terawatts--

over 7,000 times our global
energy consumption--

strike earth.

This triggers a wave of activity
around the globe.

At dawn, plants on land
and plankton at sea

begin to photosynthesize
and grow.

At the same time,

sunlight drives wind and weather
around the globe.

We are also a part
of this cycle,

as our bodies respond

to the daily inflow of energy
from above.

Our skin cells use sunlight
to create essential vitamins.

Even the flight paths of planes
reveal our intimate relationship

with the rhythms
of day and night.

Aircraft travel west in
the morning to extend the day

and east in the evening
to reduce the night.

But while the sun nurtures
all life on earth,

it also has the power
to destroy.

And with the help of a very
different kind of satellite,

we are coming to understand just
how great a threat it can pose.

Orbiting 22,000 miles
above the earth

is the Solar Dynamics
Observatory.

This satellite looks not at
the earth, but away from it.

Its task is to observe the
radiation released by the sun--

what scientists call
space weather.

We have this wonderful
new satellite

that is up in space, looking
at the sun 24 hours a day

and is providing unprecedented
images of the sun

and where space weather is born.

NARRATOR: These striking images
are produced

by the SDO's ultraviolet sensor,

detecting light frequencies
beyond the blue end

of the visible spectrum.

The sun emits constant light,

heat and other forms
of radiation,

along with occasional dangerous
bursts of charged particles.

GILBERT:
Most people don't realize

that the earth is exposed
to charged particles

that are constantly coming away
from the sun

at about a million miles
an hour.

NARRATOR: Sometimes a massive pulse
of those charged particles

erupts from the sun's surface.

It's called
a coronal mass ejection

and it contains billions of tons
of charged particles

superheated to tens of millions
of degrees

and blasted out at millions
of miles per hour.

It has the potential to wreak
havoc on our planet.

This supercomputer visualization
shows what happens

when a coronal mass ejection
occurs.

The explosion is equivalent
to 14 million Hiroshima bombs.

It sends a cloud of charged
particles millions of miles wide

racing towards earth.

Without some kind of protection,

these enormous blasts would
strip away the atmosphere,

destroy our fragile ecosystems
and scorch the earth.

Over time, repeated coronal mass
ejections would even cause

the oceans to dry up,

leaving behind a planet
as barren and bleak as Mars.

Fortunately the earth has
an invisible shield,

a magnetic field that satellites
are now enabling us

to better understand.

Orbiting between 40,000 and
120,000 miles above the earth,

NASA has a network of satellites
called THEMIS.

Each is equipped with highly
sensitive instruments

that can detect the strength
of magnetic fields.

GILBERT:
THEMIS is a series

of probes that are aligned along
the earth's magnetosphere

and they detect variations
in the magnetic fields.

NARRATOR: This computer model,
using THEMIS data,

shows how an invisible
magnetic force field

called the magnetosphere
protects the earth.

It's generated by the rotation
of the earth's core.

GILBERT: THEMIS allows us to build
a overall picture

of the structure
of the magnetosphere

and how it operates.

NARRATOR: THEMIS reveals how
the magnetic field

is constantly blasted
by the sun.

The wave of charged particles
called the solar wind

distorts the magnetosphere into
a gigantic teardrop shape,

120,000 miles across.

As wave after wave
of solar particles

strike the outer magnetosphere,
most are deflected.

But when a coronal mass ejection
arrives,

it tears open the magnetosphere,

allowing a vast number
of charged particles

to breach the magnetic field's
first layer.

The particles are free to rush
in towards the planet.

But the earth has a second line
of defense.

Inner magnetic fields steer
the radiation

down towards the poles.

GILBERT: This process is extremely
energetic.

Particles get accelerated
and then they travel down

along the magnetic field lines
towards the polar regions.

NARRATOR:
The radiation streams downward,

encircling both
the North and South poles,

and triggers something we can
see with our own eyes,

one of nature's true wonders:

the Northern and Southern
lights, or the aurora.

As the radiation strikes
the upper atmosphere

at extreme speed, it excites
the air molecules.

This makes them glow.

The oxygen in the air radiates
red and green.

The nitrogen, red and blue.

These charged particles
that originated from the sun

get trapped and then
interact directly

with the earth's atmosphere,
causing these beautiful colors.

So when we're looking
at the aurora,

basically we're looking
at the fact

that the sun and the earth
are intimately connected.

NARRATOR:
The aurora is a vivid reminder

of how potentially lethal energy
from the sun is dissipated

in the upper atmosphere.

The earth's magnetic field has
shielded the planet

from the sun's deadly radiation
for billions of years,

enabling life to take hold
and flourish.

Satellites are revealing
one final piece

of this incredible puzzle--
the role that humanity plays.

Our human footprint
has grown so large

that we have become a major
global force in our own right.

Our impact is the consequence
of a system

that has created
and sustained life

for three and a half billion
years.

Our success as a species
has resulted

in rapid population growth.

And today our presence
can be seen

across 80% of the landmass.

Now we, in turn, are affecting
the many natural cycles

that govern our planet.

Looking for signs of pollution,

the environmental satellite
Aura's infrared sensor reveals

the atmosphere's chemical
fingerprint

and shows us how we are
affecting the entire globe.

We already manufacture more
than twice the nitrate produced

by lightning, much of it used
for fertilizer and explosives.

Our factories release
more sulfur

than all the earth's volcanoes.

Our industry and transportation
produce more carbon dioxide

than the Amazon rainforest
captures.

Our cities generate dust,

trigger electrical storms
and affect rainfall.

And these are just a few
of our impacts

on earth's natural cycles.

Our earth is changing.

We're on a path to somewhere

and our ability to understand
that path is crucial

to success in the future.

And satellites help us answer

some of the most fundamental
questions

needed to understand
how our planet behaves.

NARRATOR:
But there is one key difference

between the impact
of nature and our own.

Unlike volcanoes,
the motion of ocean currents,

or the oxygen produced by
forests and plankton blooms,

we make conscious decisions
about what we do.

And here satellites
are crucial once more.

The information they provide
can help us meet

the challenges of the future.

SELLERS: The real power of satellite
observations

is they represent
objective truth.

They tell us about what
the world actually is doing,

not what we would like it
to be doing,

not what we might fear it
to be doing,

but what it's actually doing.

And it's that that allows us
to see change,

real change, for what it is.

NARRATOR: Satellites are telling us that
the oceans are slowly warming.

In the past 30 years,

the average temperature
of the ocean's surface has risen

by half a degree.

Models suggest this extra heat

could be increasing the
intensity of hurricanes

and violent storms
all around the world.

Satellite data shows
that in Antarctica,

ice shelves that took many
thousands of years to form

are collapsing year after year.

And in the Arctic, sea ice is
diminishing at an alarming rate.

Many factors play a part
in these dramatic changes,

but most scientists agree

that human activity through
our release of greenhouse gases

is the main driving force.

All around the globe, satellites
are recording change,

but there is a problem.

Just as we are able to capture
and measure these changes,

many of the current fleet
of satellites

are coming to the end
of their lives.

Satellites need fuel
to stay in their orbits.

When their time is up,

they must either use the last of
their fuel to boost themselves

far away from the earth

or descend and burn up
on reentry.

It's predicted that the number

of NASA's earth-observing
satellite systems will go

from 20 down to fewer than ten
within the next decade.

The constant stream
of information

from these vital instruments
in space will fade.

If we fail to replace
these satellites,

we could lose our ability to
track the web of connections

that is fundamental to life.

ADAMEC: The complex interactions would
be absolutely invisible to us

without a larger view
of the earth.

It's the consistency and the
amount of data that they provide

that allows us to understand
the processes that are going on

in the earth that are important
to maintaining life

as we know it.

NARRATOR:
Little more than half a century

after the birth
of satellite technology,

we are still only beginning
to realize its possibilities.

Our planet harbors mysteries
beneath its white clouds,

blue oceans
and verdant landscapes.

And they can only be solved
with the help

of these eyes in the sky looking
down at earth from space.

== sync, corrected by elderman ==

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