Earth From Space

Earth From Space

PBS Airdate: February 13, 2013

NARRATOR: Earth: you may think you know it well, but a startling new picture is emerging of a planet with forces more dynamic and intertwined than we ever imagined.

How can sandstorms in the Sahara transform the Amazon rain forest, over 5,000 miles away? Beneath Antarctica, why does a vast undersea waterfall, 500 times bigger than Niagara Falls, lead to a gigantic feeding frenzy near the equator? And how can warm water off the coast of Africa drive devastating weather in the southern United States?

The veil is finally lifted, thanks to satellites high above the earth. Ever watchful, they sense what our eyes cannot see.

EMILY SHUCKBURGH (British Antarctic Survey): It's really the last bastion of human discovery. We're discovering new things every day.

NARRATOR: What hidden forces rule our world? How are the oceans, the continents, the atmosphere and the sun bound together with all living things? For the first time, we can see how earth, fire, wind and water merged and united to shape life in all its forms.

WALEED ABDALATI (NASA Chief Scientist): 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 satellite data: our planet, as never seen before. This is Earth from Space, right now, on NOVA.

Since humans first ventured into space, one of the greatest revelations has been the new view of our home. From the iconic "Earthrise" image of the Apollo era, to these spectacular vistas from the International Space Station, the blue marble is revealing its secrets: a planet alive with activity and constant change, its surface transformed by humans, yet still ruled by powerful natural forces that we're only beginning to understand.

WALEED 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 (NASA Goddard Space Flight Center): 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 are the essential ingredients for this vibrant system, the only one we know in the universe that sustains complex life? What intricate combination of water and earth and air can build an engine powerful enough to create and drive life forward?

Our best hope for answers may come from above, namely, 120 satellites staring down at us from space. Each one of these Earth-observing satellites reveals a different piece of the puzzle. Each carries an array of exquisitely sensitive detectors to observe what is often hidden.

EMILY SHUCKBURGH: Satellites are absolutely amazing because, not only can we see 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: With the invisible now before us, we can see Earth as a dynamic, endlessly changing system.

These images have been created using real satellite data and computer models. They reveal, in unprecedented detail, how sunlight, moisture, land and atmosphere interact in remarkable and unexpected ways. And with their help, for the first time, we can begin to understand the real relationship between the planet and all the living things it supports.

WALEED ABDALATI: It's really the thrill—mdash;because it matters so much—mdash;of piecing together the story of what the earth is doing, how it is changing, why it is changing and how, ultimately, that affects humans.

NARRATOR: The first piece of the puzzle is the massive influence the sun has on our planet.

PIER SELLERS: The world is continuously bathed in a flow of energy from the sun, and that warms the earth. Everything that you can see that lives and breathes and moves on the earth is pushed by the sun.

NARRATOR: Tracking the sun's effect on Earth is one of NASA's newest satellites, Suomi N.P.P., launched in 2011. It orbits 500 miles up, circling the planet 14 times a day. It carries five separate sensors that enable it to see effects 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 actually pick up. Electromagnetic radiation spans a spectrum that goes far beyond the familiar colors of the rainbow.

WALEED 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. It detects the ultraviolet and infrared parts of the spectrum.

This is what it actually sees.

Anything that emits heat gives off infrared radiation, so the CERES data shows the earth in shades of heat. 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, seen here in blue, what little light there is, is reflected back out to space by the ice and clouds, one reason why the poles remain cool.

At the equator, it's a very different story. Not only does it receive more sunlight, less of the sun's energy is reflected back into space. Perhaps the best place to see the effect of the sun's heat is an area of the Atlantic just north of the equator and to the west of Africa: the coastal waters of the Cape Verde islands.

Here the local fishermen are busy. Every few days, storms stir up nutrients from the deep, attracting great shoals of fish. It's the warmest time of the year, and the sun beats down. The heat triggers a process that's invisible to the fishermen but vitally important to the planet as a whole, a process that satellites are revealing in fine detail.

Circling above the fishermen is a satellite called Aqua. One of its key tasks is to monitor the complex interaction between sunlight and water.

JEFF HALVERSON (University of Maryland, Baltimore Campus, Meteorologist): 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, called AIRS, looks at the region of sea around Cape Verde, again, in infrared. Highlighted here, in yellow, over 1,000,000 square miles of ocean reaches a critical temperature: 80 degrees. At this temperature, the sea is evaporating fast, producing an invisible gas: water vapor.

EMILY 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 region 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 we could actually see it.

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.

JEFF 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.

JEFF HALVERSON: Molecules condense in the atmosphere and become liquid again, and when that happens, that heat is given off into the atmosphere and warms the atmosphere, and that's the heat that powers storm systems.

NARRATOR: The process produces more energy than the global production of electricity. The result is something we can see. The rising heat drives the clouds up to 10 miles high. As the clouds climb upward, the earth's rotation causes them to spin. The thunderclouds merge into a vast circle. A hurricane forms.

On August 27, 2005, a meteorological satellite is tracking a category 3 hurricane that started in the Bahamas. Its name is Hurricane Katrina. Throughout the region, there is one question on everyone's minds: "Will the hurricane hit land, or will it blow itself out?"

The answer may come from a satellite called T.R.M.M., the Tropical Rainfall Measuring Mission. T.R.M.M. is equipped with a radar and imager that can sense microwaves toward the longer range of the electromagnetic spectrum. Microwaves bounce off raindrops in the clouds, allowing scientists to build a three-dimensional model of the internal structure of a hurricane.

JEFF HALVERSON: We can actually look at microwave energy, which is generated within the clouds and coming from the ocean surface. It's almost as if the clouds are now invisible to us. We can see right through them, like taking a CT scan, to look inside those clouds.

NARRATOR: T.R.M.M. is a powerful tool. Its sensors reveal a strange phenomenon: huge, vertical columns of warm water vapor are bursting up from near the center of the hurricane. Almost like hurricanes within hurricanes, these climbing vortices deliver more of the sun's energy into the heart of the storm. These new sources of energy are dubbed "hot towers."

JEFF HALVERSON: If they occur in the right place at the right time, in the very center of the system, they can be like a giant sparkplug that gets that whole engine running at very, very high speed.

NARRATOR: The hot towers are drawing more and more water vapor off the ocean. This triggers a runaway reaction. In just 24 hours, Hurricane Katrina grows into a Category 5 monster.

The violence is testament to the power of the sun on the ocean. Ferocious winds blow for two days straight, reaching 175 miles per hour, twisting steel like paper and ripping apart homes. Over three trillion gallons of rain a day and a massive tidal surge from the Gulf of Mexico combine to submerge whole districts under water. Katrina reshapes 90,000 square miles of the southern states. Over a million people are displaced.

But even a mighty hurricane is just a tiny brushstroke in a much bigger picture of how the sun drives water around the entire planet. 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. Seven thousand miles away, in Mumbai, 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 how they are connected.

Orbiting much higher than T.R.M.M. and Aqua, at 22,000 miles up, is a chain of five meteorological spacecraft, including this one: the GOES East 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.

EMILY 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 a single process, the impact of the sun on water, produces radically different conditions in different places all across the globe.

Converted from the numerical data, these five circles depict what the satellites actually sense. They reveal the total picture of the 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.

Now, a new piece of the giant puzzle comes into play, as water vapor is driven across the land, all around the globe. Its impact varies from place to place.

In India, at the end of July, the warm water vapor is drawn onto the land and forced to higher altitudes. As the vapor cools, it 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.

As the water vapor reaches China, the monsoon fills up countless paddy fields. This process nourishes three billion people, almost half the world's population.

Meanwhile, on the other side of the world, the westward-bound water vapor must cross the high mountains of the Andes, before reaching central Chile. The altitude strips the air of its moisture, which falls as snow on the mountains, creating, on the far side, the arid desert of the Atacama.

In the eastern United States, hot moist air arrives straight from the Gulf of Mexico. With no natural barrier to stop it, more than 100 million Americans, from Memphis to New York, swelter in 95 degree heat.

The satellite data show how the atmosphere and oceans connect in a global pattern of circulation that results in our local weather.

EMILY 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. An equally striking cycle involves extreme cold. To see that part of the puzzle, we have to turn the earth around 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 nothing could be further from the truth.

Antarctica's ice plays a vital part in maintaining global climate, sustaining life, even in lush, warm jungles, thousands of miles away.

WALEED 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, that spread out all over the world, that affect the world as a whole.

NARRATOR: It's a paradox that such a bleak, cold and barren place is so critical to life on our planet. On average, it's 43 degrees colder than the North Pole. Now, satellites are helping us understand why Antarctica is so cold and how it affects the rest of the world.

The ultraviolet and infrared detectors on Suomi N.P.P. supply part of the answer. They show that the poles receive little of the sun's energy, and reflect most it back out to space so they stay cold. But there's another factor that makes Antarctica colder still.

This image has been pieced together from seventeen 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.

EMILY SHUCKBURGH: 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 (NASA Scientist): 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 sensor on the Aqua satellite 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, depriving it of warmth from the rest of the planet. That is why the whole region remains exceptionally cold, all year round.

WALEED 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 using its microwave scanner, looking through the clouds, to detect the distinct signature of ice.

EMILY 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: The data from this satellite gives us an accurate picture over the Antarctic, over the course of a year. Seen here in summer, it 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 impact on life across the planet.

One of the best places to see why is off the remote area of coastline in 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.

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 a brine that drips down narrow tubes and holes in the ice as it forms. The brine is denser than regular seawater, and it sinks downwards.

As winter's icy grip tightens, the formation of ice accelerates in speed and scale. 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 two hundred billion tons of ice forms in the Weddell Sea alone, releasing tens of trillions of tons of brine into the ocean. The fate of all this dense brine is a mystery. The crucial question is, "Where does it all go?"

A satellite called Jason is providing new answers. Jason is equipped with radar that measures the height of the ocean surface. This technique also reveals the shape of the seafloor far below.

GENE CARL FELDMAN (NASA Oceanographer): We can make very accurate maps of the ocean floor, 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 it can detect minute changes in the level of the sea surface produced by the peaks and valleys of the terrain beneath. The data makes it possible to map the ocean floor.

DAVID 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 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 enables 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: a precipice over which the brine must fall.

Other data, from sensors attached to the seafloor, track the flow of the brine as it sinks.

EMILY 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 the satellite and undersea data helps scientists visualize what is happening, hidden beneath the ice. One trillion gallons of salty brine plunges down through the Weddell Sea every hour—mdash;a torrent equivalent to the volume of 500 Niagara Falls. It 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 explored, but computer modeling combined with the satellite data are helping scientists to reconstruct 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 seafloor.

DAVID 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 stirs and cools all the world's oceans. As it migrates towards the equator, it 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, at Antarctica, the seawater freezes and releases its salt again, completing the cycle.

It's this endless loop that's so critical to the whole planet.

WALEED 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 waters.

NARRATOR: A similar process happens in the Arctic. All over the world, slow-moving currents of seawater are regulating the average temperature 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 the oceans don't work alone. The currents affect the air that sits above them. Ocean connects to atmosphere once more. For instance, the Gulf Stream takes warm water from the Gulf of Mexico north to the eastern United States and Europe, generating warm air.

Half a world away, another current, called the Kuroshio, carries heat from China north to Japan. A similar process is underway all across the ocean; spreading heat around the entire globe.

WALEED ABDALATI: 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 driver of the world's ocean currents, Antarctica helps protect Earth's climate from wild swings in temperature. The circulation of currents enables life to prosper, from the equator almost to the poles. Such long-term stability allows life to flourish and complex organisms to evolve. This is how Antarctica affects life all across the world.

WALEED ABDALATI: When you put it all together, you get a story about how ocean circulation affects climate and weather, and what that means today, tomorrow and 20 years out into the future.

NARRATOR: But ocean currents are not the only players. Beneath the seafloor, forces inside the earth are a crucial source for the basic materials that sustain life. This hidden mechanism is driven by ceaseless, often violent activity.

A magnitude nine earthquake strikes Japan; an entire section of the country moves eight feet towards North America. Two and a half thousand miles to the south, in Papua, New Guinea, the volcano Rabaul erupts. It fires a vast plume of ash 10 miles up into the air. These are catastrophic, hugely destructive events, yet, despite the cost in human lives, they provide many of 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 across 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 animation of Mount St. Helens, in Washington State, shows how the crater swells over the course of three weeks, driven by the motion of molten magma beneath the earth's crust.

PIERS SELLERS: Satellites can actually see the crustal plates moving. We can see bulges and dips where the magma is moving around underneath the crust.

NARRATOR: This animation shows the expansion of Mount Etna, in Italy, as magma accumulates beneath it over nine years. When the volcano erupts, the land sinks back.

PIERS 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. The earth is continually throwing out fresh material from its interior. So how does this seismic activity affect life?

Part of the answer lies deep beneath the ocean's surface. There, 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. Here, we can see that critical interaction between molten rock and freezing water. This footage was taken with a remotely operated submarine, also called Jason.

Jason also shows what happens when the dense, cold water from the poles penetrates into cracks in the ocean floor. A magma chamber below heats the water to 750 degrees Fahrenheit. In the pressure-cooker environment inside the crust, the dense salty water actually dissolves the solid rock. Complex chemical reactions take place, producing minerals containing sulfur and iron. These form nutrients that living organisms need to survive. The seawater emerges out of hydrothermal vents. These nutrients feed a thriving ecosystem that includes shrimp and exotic creatures, like tube worms.

The leftover nutrients are carried away by the deep ocean currents. Over thousands of years, they circulate through the oceans, ultimately rising to the surface, and contributing to an amazing explosion of life.

We can see this with the Aqua satellite, which is equipped with instruments that observe the earth in many wavelengths of the electromagnetic spectrum. One is called MODIS.

PIERS SELLERS: MODIS is pretty much the crown jewel of the Aqua satellite. It's an enormous scanner; it basically covers the whole world, every day.

NARRATOR: MODIS scans the ocean in multiple wavelengths, from infrared to the visible spectrum. This allows it to detect extremely subtle changes in the temperature and color of the water.

GENE FELDMAN: 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: MODIS detects an upwelling of cold water, 150 miles off the coast of Peru, seen here in pale blue. Then, looking at another wavelength, it detects a particular shade of green. This is the color of chlorophyll, a signal of plant life. The satellite has spotted a bloom of tiny organisms, called phytoplankton. They are absorbing the rich soup of minerals that have come from the deep ocean, and with the light from the sun and carbon dioxide from the air above, they multiply by the billions.

As MODIS shows, the plankton replicate so quickly that in just 24 hours, 500 square miles of ocean have turned from blue to green.

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: The minerals from beneath the earth's crust have helped create a vast plankton bloom: over 800,000 tons of living material. 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. And up above, humans are here, too. 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.

GENE FELDMAN: Phytoplankton provide that key link between this energy out here, the raw materials that this planet holds, and the, the food engine that allows life to flourish.

NARRATOR: These vast green ribbons of plankton can cover as much as one fifth of the world's ocean surfaces, about 45 billion tons of biomass every year. They are part of a chain of life that connects to the earth, deep beneath the seafloor.

GENE FELDMAN: 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 don't live long. MODIS shows how, in just 72 hours, a bloom can rapidly weaken and fade. Any plankton that have not been eaten die and sink into the abyss. They take with them their precious minerals all the way back to the ocean floor. Here they will stay 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 to life on land.

Situated half the world away is the Sahara Desert, one of the driest and dustiest places on the earth. From these arid wastes, ancient plankton will rise once more.

It is May, the hottest month of all. Camel herders travel through one of the most exposed regions of the Sahara: the Bodele Depression, an inland lake that dried up 6,000 years ago. The sediment on the floor of the lake is composed of plankton remains, called diatomite.

With its eye on the earth, from 400 miles above, Landsat 7 is one of the latest generation of satellites studying the composition of rocks that make up the earth. It sweeps the Bodele, producing these high resolution pictures in multiple wavelengths of visible light. The pictures reveal the diatomite on the bed of the lake.

CHARLIE BRISTOW (Birkbeck, University of London): 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 analysis shows there are over 24,000 square miles of sediment, all of it diatomite.

CHARLIE BRISTOW: 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, a material that's needed by all living things to convert sugar into energy. But for this nutrient to re-enter the chain of life it must first embark for on a long journey that can be seen from space.

The journey begins here. 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. Twenty-two-thousand miles above, the satellite METEOSAT 8 looks down from its geostationary orbit. It records a daily pulse of dust rising off the Bodele Depression. Here, it's shown as a whitish dust cloud, lifting from the desert, with clockwork regularity, at noon, each day.

CHARLIE BRISTOW: Although the individual particles of dust are minute—mdash;they're hundredths or thousandths of a millimeter in diameter—mdash;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 heads west on an epic journey.

Seen from space, the dust is blown across Africa. At the west coast it's drawn up high into the sky. This simulation, based on Aqua's MODIS data, shows how prevailing winds carry the dust cloud west and south, 3,000 miles across the Atlantic. As much as 7,000 tons are airborne at any one time.

The destination is set by the winds: South America and the Amazon.

CHARLIE BRISTOW: 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.

CHARLIE 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 Amazonian wet season, delivering thousands of tons of phosphate into the forest below. It passes into the soil and the roots of trees, nourishing the rain forest. The effect of all this natural fertilizer can clearly be seen from orbit.

Terra is the twin of the Aqua satellite. It circles the earth every 99 minutes, monitoring the rate of growth of vegetation.

PIERS SELLERS: We can see all the green vegetation on Earth, wall to wall each day and it tells you almost everything you want to know about the state of life on Earth.

NARRATOR: With its own MODIS color scanner, Terra can see the effect of the Saharan 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. 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 half way around the world.

PIERS SELLERS: So 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 are spread to living habitats all over the world. Every landscape has its own story and its own way of entering the chain of life.

CHARLIE 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, vital ingredients for growing wheat and corn. In Bangladesh, the Ganges Delta is abundant 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: the basis of the food chain for all life on land, including us.

PIERS 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—mdash;in both space and time—mdash;from itself.

NARRATOR: Satellites are giving a vivid new perspective on the links between land, sea, air and life, helping us see how different parts of the puzzle fit together, including something as basic as the air we breathe.

The abundance of oxygen in air has shaped much of life around us. It's what all animals need to burn fuel in their bodies. It's oxygen that enables creatures to move their tails, wings, arms and legs. Scientists even believe that large, intelligent mammals, like us, only evolved thanks to the abundance of oxygen in the atmosphere. But where does all this oxygen come from?

The Aura satellite is one of several spacecrafts that are helping scientists study the earth's atmosphere. Along with ground instruments, it can analyze the atmosphere and pinpoint its composition, building a picture of the nitrogen, oxygen and carbon dioxide that, together, make up 99 percent 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 was given to us by plants.

PIERS SELLERS: 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 produce so much oxygen, that the vast Amazon rainforest used to be known as the lungs of the earth. But the real picture is more complex.

The verdant wilderness of plants and animals is one of the oldest and largest living systems on Earth. Over 2,000,000 square miles of lush rainforest teems with half the world's living species.

PIERS 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 and releases the gas that allows us to burn our fuel, 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 here's the surprise: 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.

PIERS 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 and of itself, almost.

NARRATOR: But there is still a way in which the Amazon does play a vital part in creating the air that we breathe. What the satellites now make clear is that it takes an extra step.

The process begins with rain. The soil of the rainforest is continually washed into the Amazon river system, taking with it nutrients and organic material. An average of 2,000,000 tons of this sediment is released every 24 hours. The sediment flows eastwards 4,000 miles into the Amazon delta. Here, microscopic plankton near the ocean surface thrive on the nutrients, and their population explodes. As they grow, some of these tiny organisms act like plants, absorbing carbon dioxide and releasing oxygen.

Aqua's MODIS instrument shows how a giant plankton bloom grows to cover 25,000 square miles. This vast area translates into a huge leap in oxygen production.

GENE 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 analyzed.

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 the oxygen in the atmosphere is something we would not know without satellites.

GENE FELDMAN: Satellites gave us that very first global picture, global assessment of what the oceans' plants were doing.

NARRATOR: And what the oceans' plants are doing is providing life-giving oxygen for us.

GENE 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, not rainforests, are the real 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.

PIERS 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. The satellite T.R.M.M. carries a high-speed camera that can detect individual lightning bolts. From this data, it's possible to build a picture showing the distribution of lightning all across the globe. Astonishingly, 40 strikes occur every second.

What is the effect of all this energy coursing through the earth's atmosphere? It sparks a special chemical reaction, as lightning burns through the air.

Each day, 40,000 thunderclouds are created by the combined force of sunlight and water vapor. The rising columns of moist air create powerful updrafts that turn water vapor into ice particles inside the thunderclouds. 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 five 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 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.

DAVID ADAMEC: The lightning stroke actually splits the nitrogen into single nitrogen molecules. Well nitrogen doesn't like that. It's desperately looking for something to connect back to and it often does it with oxygen.

NARRATOR: When oxygen bonds with the nitrogen, it creates a vital nutrient called nitrate. Simulated here, in yellow, the satellites show the extent of nitrate produced by the 3,000,000 lightning bolts that strike every day. About 13,000 tons of it is created. It dissolves into droplets in the clouds and falls to the ground, in rain.

DAVID ADAMEC: 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 providing energy for us. 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 10 square miles of forest, in less than a week. Wildfires like these often start with a random bolt of electricity from the sky. Half a world away, in Siberia, over 1,500 square miles of forest burn to the ground.

These flames may seem purely destructive but, thanks, in part, to satellites, we can see that they can also be life-giving.

The Terra satellite can detect the location of every fire on Earth, by looking at the heat signature in infrared.

PIERS 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 produced from Terra's data shows a year's worth of fire, all around the world. The vast swathes 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.

But Terra's data also reveals how fire is one way in which life recycles itself.

PIERS SELLERS: The observations have shown us how important fire is as an element of change.

NARRATOR: An ideal place to see this in action is the forests of northern Canada. Locked inside the millions of dead and diseased trees here are ingredients that are essential for new life: elements like carbon, sulfur and phosphorous. But in a cold environment, trees take centuries 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.

DAVID 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 ultimate effect of this nutrient-rich ash can eventually be seen from space.

With a special sensor in the infrared, MODIS can pick out the foliage of healthy new vegetation that grows after fire. A pulse of new growth follows every blaze.

PIERS SELLERS: Huge areas of forest get burned down quite regularly, and they're followed, almost immediately, by rapid re-growths.

NARRATOR: The data from Aqua and Terra show that, within months, large areas that were devastated by fire are rejuvenated. From a global perspective, wildfires are essential to the cycle of life.

PIERS SELLERS: 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 so important 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. Thanks to wildfires, the health of many of the world's habitats is maintained; ecosystems that are no longer productive regenerate.

PIERS SELLERS: When you look at 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 it from orbit, we see the world 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. At the bottom of the ocean, the cold deep water reacts with erupting magma, producing nutrients that rise to the surface. The journey of nutrients around the planet ultimately enables tiny plankton to fill the air with oxygen, and that allows complex animals, like us, to survive. Oxygen also generates fire, which, in turn, accelerates the pace of the endless cycle of life. But the major driver of life is the energy we receive from the sun.

As the earth rotates over twenty-four hours, the planet responds to the incredible power of our local star. Each day, more than a million terawatts, over 7,000-times the power that humanity produces, strikes Earth. It triggers a wave of activity that never ceases: at dawn, plants and plankton begin to photosynthesize and grow; at the same time, sunlight drives wind and weather around the globe.

We are also part of this cycle, and 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 is vital to all life on Earth, it also has the power to wipe it all out. And with the help of a very different kind of satellite, we are understanding just how great a threat it poses.

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."

HOLLY GILBERT (NASA Solar Physicist): We have this wonderful new satellite that is 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 pictures are produced by the S.D.O.'s ultraviolet sensor. The sun constantly emits radiation, along with dangerous bursts of charged particles.

HOLLY 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: Occasionally a coronal mass ejection erupts from the sun's surface: a massive pulse containing billions of tons of charged particles, superheated to tens of millions of degrees, thrown out at millions of miles per hour. This radiation has the potential to wreak havoc on the planet.

This supercomputer visualization shows what happens when a coronal mass ejection occurs. The explosion is equivalent to 14,000,000 Hiroshima bombs. It sends a cloud of charged particles, millions of miles wide, racing towards Earth.

Charged particles from the sun constantly bombard Earth. Without some kind of protection, they could strip away the atmosphere, destroy our fragile ecosystems and scorch the planet. Over time, even the oceans would dry up, leaving behind a planet as barren and bleak as Mars.

Fortunately, the earth has an invisible shield, a defense system that satellites are now enabling us to better understand.

Orbiting between 40,- and 120,000 miles above the earth, is a network of satellites called THEMIS. Each is equipped with highly sensitive instruments that can detect the strength of magnetic fields.

HOLLY 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 the earth is protected by an invisible magnetic force field called the "magnetosphere." It's generated by the rotation of the earth's core.

HOLLY GILBERT: THEMIS allows us to build an overall picture of the structure of the magnetosphere and how it operates.

NARRATOR: THEMIS reveals the magnetic field as it's 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 strikes the outer magnetosphere, most are deflected. But when a coronal mass ejection arrives, it tears open the magnetosphere, allowing an enormous 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.

HOLLY 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 downwards, 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, blue and red.

HOLLY GILBERT: 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: Energy that would otherwise destroy life on Earth is dissipated by the upper atmosphere. In this way, the earth has shielded itself from the sun's deadly radiation for billions of years, enabling life to take hold and flourish.

Satellites are revealing one final piece to this incredible puzzle. That is the role humanity plays. Our human footprint has grown so large that we have become a major force on the planet in our own right, a direct 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 percent of the landmass. Now we, in turn, are affecting the different natural cycles that govern our planet.

Aura's infrared sensor reveals the chemical fingerprint of the atmosphere and shows us how we are affecting the entire globe. We already manufacture more nitrate than lightning; our factories release more sulfur than all the world's volcanoes; our industry and transportation produce more CO2 than the Amazon rainforest captures; our cities generate dust, trigger electrical storms and affect rainfall. In this way, we've impacted many of the earth's cycles.

WALEED ABDALATI: 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 volcanism, the motion of ocean currents, or the oxygen produced by forests and plankton blooms, we make conscious decisions over what we do. And here, satellites are crucial once more. The information they provide can help us meet the challenges of the future.

PIERS 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 zero-point-five degrees. 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 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 in order to maintain their orbits. When their time is up, they must either use the last of their fuel to boost them far away from the earth or descend and burn up on re-entry. It's predicted that the number of NASA's earth-observing satellites will go from 20 spacecraft down to just eight, within the next decade.

The constant stream of data from these vital instruments in space will fade. Soon we may lose our ability to track the web of connections that is fundamental to life.

DAVID 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 still harbors mysteries beneath its white clouds, blue oceans and green lands, and they can only be solved with the help of these eyes in the sky, looking down at Earth, from space.