Original subtitles

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.

Major funding for NOVA is provided by the following:

Supporting NOVA and promoting public understanding of science.

And the Corporation for Public Broadcasting,

and by:

And Millicent Bell, through:

Major funding for "Earth from Space" is provided by:

Furthering the values that contribute to a healthy planet.

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 ace 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 fr 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 whin 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.

It's a global process,

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 sedime 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 ev 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 thousds 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.

Major funding for NOVA is provided by:

Supporting NOVA and promoting public understanding of science.

And the Corporation for Public Broadcasting,

and by:

And Millicent Bell, through:

Major funding for "Earth from Space" is provided by:

Furthering the values that contribute to a healthy planet.

This NOVA program is available on DVD and Blu-ray.

To order, visit shoppbs.org or call 1-800-PLAY-PBS.

NOVA is also available for download on iTunes.

Captioned by Media Access Group at WGBH access.wgbh.org

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