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0:00
(dramatic music) - [Narrator] In the fiery beginning of our young solar system, world's are born.
0:13
And obliterated. (dramatic music)
0:23
Gas giants stir chaos
0:27
and a young Sun vents its rage.
0:31
(dramatic music)
0:36
How did Earth survive against all odds? (dramatic music)
1:02
Gazing down from space we marvel at Earth's bountiful oceans,
1:09
its continents, and life giving atmosphere.
1:15
We ask how did our planet begin?
1:20
How did it come support life?
1:24
And life to support Earth? (intense music)
1:39
The story of Earth starts within a giant spiral galaxy, the Milky Way.
1:50
At 100,000 light years across the galaxy is a cauldron of swirling dust clouds and glowing gas.
1:59
(intense music)
2:11
This simulated view shows a 50 million year span, a cosmological blink of an eye.
2:19
(intense music) In that time millions of stars die in powerful explosions called supernovae, shown here as flashes of light.
2:32
(intense music)
2:42
They seed the cosmos with the stuff of planets.
2:48
Carbon, silicon, iron and more. (intense music)
3:12
One explosion has packed enough punch to send a nearby cloud of stardust into collapse.
3:20
(intense music)
3:35
Huge volumes of dust and gas stream into its core.
3:40
(intense music)
3:44
This cloud is about as cold the universe gets.
3:51
But the tighter it's packed the more it heats up.
3:56
(intense music)
4:00
A storm erupts at its center, a vast raging hurricane of dust, gas and ice crystals. (intense music)
4:14
In its eye temperatures soar,
4:19
a star ignites and our Sun is born. (intense music)
4:29
The Sun is being fed by a slowly spinning disk.
4:36
The cradle of our solar system.
4:42
Within the disk planets take shape in a long violent process.
4:51
It starts with dust gathering into sand-like grains. (intense music)
5:05
They form pebble sized objects within clouds of loose gravel. (intense music)
5:23
Over millions of years gravity draws them together to form rocks, ice balls and boulders. (intense music)
5:38
These objects coalesce into miniature planets, or planetesimals.
5:48
One such body, the primordial Earth, is growing steadily, but it's fate hangs in the balance. (intense music)
6:02
We once thought that planet formation followed a predictable pattern.
6:09
Our planetary neighbors bear this out with their nearly circular orbits.
6:15
And the neat division between gaseous outer planets. Jupiter.
6:23
Saturn.
6:28
Uranus.
6:32
And Neptune.
6:34
And rocky inner planets.
6:37
Mercury.
6:41
Venus.
6:44
Earth. And Mars.
6:49
This division originates soon after a star ignites.
6:56
The young Sun produces hot winds that drive lighter hydrogen gas to the outer part of the disk.
7:07
Beyond a point called the ice line large gas planets grow quickly by sweeping up gas pushed out by the Sun.
7:20
The dusty inner region, devoid of gas and ice, is where rocky worlds like Earth form.
7:29
This is not necessarily how most solar systems end up.
7:34
(intense music) A new generation planet finding telescopes has found that gas planets the size of our Neptune commonly patrol the inner zones. (intense music)
7:52
Jupiter sized giants have been found orbiting so close to the star that hot stellar winds are stripping them of gas.
8:01
(intense music)
8:10
Then there's a class of large rocky planets called Super Earths.
8:16
How did those planets get there?
8:20
Why did our own inner planet stay so small?
8:29
Much of what we know about the formation of our solar system comes from asteroids that haven't changed since they formed almost 5 billion years ago.
8:41
Most are so small that they simply burn up in our atmosphere.
8:46
(intense music) A few larger ones survive the fall.
8:53
Scientists have been able to dig these planetary shards by measuring molecular variations called isotopes, in particular metals.
9:04
They appear to come from two distinct asteroid populations that formed in the inner and the outer solar system.
9:14
Something must have driven a wedge between these two regions, preventing the objects from mixing. (intense music) If this great divider was the young Jupiter it had to have grown quickly.
9:33
It would have cut off the flow of matter into the inner solar system, staling the formation of large rocky planets, or Super Earths.
9:45
Jupiter would then play a central role in one of the most impactful chapters in the history of our solar system.
9:53
(intense music)
10:02
Scientists have used super computers to model Jupiter's rise by simulating the interaction of dust, gas, ice and boulders in the early solar system
10:17
Each flash marks a collision.
10:21
Each ring tracks the orbit of a would be planet.
10:26
(intense music)
10:31
Giant Jupiter forms on the periphery, its orbit shown in blue. (intense music)
10:48
As it grows Jupiter succumbs to the gravitational pull of the inner solar system.
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It begins to spiral toward the Sun.
10:59
(intense music)
11:08
Scientists call Jupiter's big move the grand tack, named for the term a sailboat takes into the wind. (intense music)
11:22
Along the way Jupiter plows through clouds of cosmic debris.
11:28
(intense music) What it doesn't swallow it flings out of the solar system.
11:36
(intense music)
11:40
The closer Jupiter draws toward the Sun the more cosmic clutter it clears away. (intense music)
11:57
The simulation tracks Jupiter all the way into the orbit of present day Mars. (intense music)
12:09
Jupiter's grand tack has further reduced the mass of the inner solar system.
12:17
Now any planet's that form there will be relatively small.
12:23
(intense music)
12:27
In time another giant planet, Saturn, grows large enough to pull Jupiter back out.
12:35
(intense music)
13:04
Earth, at that time, would have been an embryo of the planet it would one day become.
13:10
(intense music)
13:18
With Jupiter's departure, Earth and a few dozen hungry competitors are free to scour the inner solar system for scraps.
13:28
(intense music)
13:32
Which ones will survive depends on the luck of the cosmic draw.
13:38
(intense music)
13:54
Over the 50 million years since Jupiter departed the inner solar system the roller derby of planets goes wild. (intense music)
14:12
As the remaining planets tug on one another their orbits destabilize.
14:19
Collisions between them are inevitable.
14:23
(intense music)
14:30
What's left is a handful of would be worlds, including the planets we know today, and at least one other.
14:39
(intense music)
14:46
Its existence was deduced in the wake of one of the most celebrated milestones in the history of human exploration.
14:55
(dramatic music)
15:08
On July the 16th, 1969 Apollo 11 blasts off.
15:14
(dramatic music)
15:38
In 13 launches the US heavy lift launch vehicle, the mighty Saturn 5 rocket, never failed to safely deliver its payload.
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(dramatic music)
15:55
Six times in the four years from 1969 to 1972
16:01
Apollo space craft drifted down over a pocked lunar surface.
16:07
(soft music)
16:13
12 astronauts climbed out to experience the Moon up close.
16:21
They set up experiments.
16:26
Made measurements.
16:28
And collected rocks as they walked,
16:33
or drove across the alien terrain.
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(intense music)
16:49
The world cheered as the astronauts returned to Earth.
16:55
Their exploits symbolized a spirit of optimism.
17:00
A bright ray of hope in a troubled time.
17:07
They were the first, and so far the last, humans to travel beyond Earth and land another world.
17:16
(soft music)
17:23
Few suspected at the time that the rocks they brought back to Earth would spur a chain of major discoveries about the Moon and Earth.
17:36
Back in NASA labs scientists found that rocks from the Moon have much in common with those from Earth.
17:45
In particular they share forms of oxygen regarded as blood types for solar system bodies.
17:53
(soft music)
17:58
The two bodies share a common and violent history.
18:08
That history is written across the lunar surface.
18:16
The Moon is pocked with large old craters, surrounded by concentric rings.
18:26
You can see them in this image of the Mare Orientale
18:31
captured recently by NASA's lunar reconnaissance orbiter.
18:37
The rings suggest that a giant impacter came down on a roiling, red hot liquid surface, sending ripples outward. (soft music)
18:53
The astronauts encountered relatively light rocks strewn about the landing sites, probably forced to the surface by heavier material as it sunk down into the magma.
19:05
They also picked up rocks eventually nicknamed creep, for the constituents potassium, rare Earth elements and phosphorus.
19:16
These rocks of a type called Anorthosite are a product of a molten surface.
19:25
What had turned the Moon into an ocean of molten rock? And what is the connection to Earth?
19:34
The most widely accepted theory takes us back to a time four and a half billion years ago.
19:44
(intense music)
19:50
At this time Earth may harbor volcanoes on its surface, with a thin toxic atmosphere. (intense music)
20:02
Our planet has sofar withstood the on slot of planet formation.
20:10
It now awaits the test of its life. (intense music)
20:21
Another planet, about half its size, is closing in.
20:28
This is Theia, a world have might have been.
20:34
Instead its journey ends here as it bears down on Earth. (intense music)
20:59
Imagine the view from Earth as the ultimate threat looms large on the horizon.
21:05
(intense music)
21:11
Theia rocks Earth to the core.
21:14
(intense music)
21:37
The impact sheers away a third of our planet
21:42
but instead of destroying Earth, Theia becomes part of it.
21:48
A computer simulation captures the first 24 hours. Debris unleashed by the collision envelopes Earth in a dense atmosphere of vaporized rock.
22:03
The cloud coalesces into a ring, a belt of molten rubble.
22:09
(intense music)
22:22
Much of the orbiting debris rains back to the surface,
22:29
but within a century what's left gathers into a single wondrous body, Earth's companion, the Moon.
22:40
(thoughtful music)
23:14
After the impact our planet is left spinning rapidly, on a slightly tilted axis.
23:21
(thoughtful music)
23:33
The Moon orbits much closer to Earth than it does today, for its surface our world would have filled the sky.
23:42
(thoughtful music)
23:46
As the Moon gradually slips into a more distant orbit its exerts a drag on Earth, that slows our planet's spin,
23:56
and steadies its tilt.
23:59
(thoughtful music)
24:05
The Moon serves as a reminder of the cataclysm that almost spelled the end of our planet.
24:12
(thoughtful music)
24:18
But from here on it would be a welcome constant, a source of stability,
24:26
and ultimately, beauty.
24:30
(thoughtful music)
24:45
But the violence was by no means over.
24:52
Unlike Earth, where erosion and geological events have erased all traces of the distant past, the Moon holds a record of the battering that followed.
25:07
The myriad craters that line the lunar surface tell of time up to 4 billion years ago, when Jupiter and Saturn hurled a barrage of objects toward the inner solar system.
25:23
A recent study draws on the sizes and number of lunar craters to model the impacts endured by Earth.
25:36
At least four impacts would have been large enough to remake the surface of our planet
25:43
and to radically alter the course of its history.
25:47
(intense music) Smashing into a crust rich in radioactive uranium and potassium, they tore these elements from the planet and sent them into space.
25:59
(intense music)
26:05
This process, called impact erosion, left a crust that would cool more quickly when the impacts finally died down.
26:15
Less disruptive impacts are thought to have carried in massive amounts of water, or released water bound to minerals deep below the surface.
26:26
(thoughtful music)
26:32
Half a billion years after the birth of the Moon, Earth has become a world of water.
26:41
It seas span every horizon, broken only by volcanic islands. (waves rumble)
27:02
The Moon, still in close orbit, whips up tides that lash rocky volcanic shores.
27:10
(thoughtful music)
27:23
Earth's atmosphere is a mix of hydrogen, nitrogen and carbon dioxide, laced with water vapor.
27:34
Land and sea are rich with chemicals, carbon, nitrogen, oxygen, iron and more, that came with the damn of the solar system.
27:45
(thoughtful music) The Earth has what it needs to accomplish its ultimate feat, to nurture life.
27:57
But there's a problem.
28:00
(thoughtful music)
28:04
Its water is slowly disappearing.
28:14
(intense music) The young Sun, while dimmer than it is today, is prone to powerful flares. (intense music)
28:30
They strike the Earth's upper atmosphere.
28:37
When a solar particle hits a water molecule, H2O, it can blast it apart.
28:45
Lightweight hydrogen wafts into space, while heavier oxygen sinks to the surface and binds with rocks.
28:54
(thoughtful music)
28:58
We now know what a devastating effect this can have.
29:05
Spacecraft observations show that Mars, long ago, harbored ample stores of water.
29:13
(thoughtful music) Its surface is etched by the meandering paths of ancient rivers and lined with sediments laid down on lake and ocean beds.
29:30
Mars today is a lifeless world, graced with a thin carbon dioxide atmosphere, there is little or no water left. (thoughtful music)
29:45
Using special sensors orbiting spacecraft have documented the ongoing loss of water in Mars's upper atmosphere, stripped by solar radiation. (thoughtful music)
30:07
Scientists have observed this same process of work on Earth's sister planet, Venus.
30:16
(intense music)
30:28
The result, Venus's atmosphere today is a witch's brew of noxious chemicals, including thick sulfurous clouds.
30:39
(intense music)
30:46
Down at the surface Venus's atmosphere is choked with high concentrations of carbon dioxide,
30:55
a potent greenhouse gas that traps the Sun's heat.
31:00
(intense music) CO2 has turned Venus into a cauldron.
31:10
With surface temperatures of almost 500 degrees Celsius, Venus is the hottest planet in the solar system.
31:20
(intense music)
31:34
This hostile environment is reinforced by active volcanoes that dot its surface, spewing sulfur and carbon dioxide.
31:44
(intense music)
32:10
How did Earth avoid such a grim fate?
32:17
For one, our planet has a protective shield that both Venus and Mars lack.
32:24
(intense music)
32:34
It's a magnetic field that deflects the most powerful waves of radiation the Sun can throw at us.
32:43
Generated by the exchange of heat between Earth's core and its crust, this magnetic field is a legacy of rapid surface cooling early in the planet's history.
32:57
It's just our first line of defense.
33:03
(volcano rumbles)
33:08
Another line of defense began to simmer away across the surface of our planet as early as 4 billion years ago.
33:19
Life.
33:23
(soft music)
33:33
Long standing theories see life's crucible in the stirrings of undersea volcanic vents.
33:45
Heat and chemical reactions over long periods of time produced proteins and nucleic acids, the chemistry of life.
33:56
(soft music)
34:06
More recent ideas point to hot springs and other volcanic features that dotted the land masses of early Earth.
34:15
(soft music)
34:29
No one knows exactly how or where life gained its first foothold. (soft music)
34:41
What we know is that it did emerge and that it spread thanks to a key breakthrough,
34:50
the ability to turn sunlight into energy.
34:55
(soft music)
35:06
Photosynthesis, the process that fuels plant life, made its first appearance in simple bacteria over 3 billion years ago. (soft music)
35:25
Using one of the world's most powerful super computers scientists have sought to model its chemical secrets.
35:33
(soft music)
35:48
Step one is to capture sunlight.
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Passing through a transparent membrane to the center of the bacteria we encounter a cluster of spherical pods.
36:03
Each one is equipped with special sensors designed to harvest solar energy.
36:11
When a photon hits it excites rings of chlorophyll molecules. (soft music)
36:25
This energy is transferred across a family of proteins, the machines of life.
36:31
(soft music)
36:38
Down the line electrons and protons carry the energy through a chain of chemical reactions.
36:45
(soft music)
36:50
The energy driving these reactions came from the Sun.
36:56
The cell must now convert it into action.
37:04
It's the energy stored in protons that gets things moving.
37:10
(soft music)
37:13
Streaming into watery spaces within the cell they flow toward a towering molecular structure.
37:24
As they enter their electrical charges turn a protein like a crank.
37:32
This turning motion initiates a chemical reaction, one that is essential to all life on Earth.
37:41
Two molecules join to form a third called ATP, shown in in blue.
37:50
It is the universal energy currency in every cell that has ever lived.
38:01
Like a biological battery ATP stores energy captured from the Sun, repackaged in a stable form that the cell can now use to break down food,
38:15
to power locomotion, to fuel reproduction, to live.
38:22
(soft music)
38:28
ATP made it possible for microorganisms to flourish and evolve. (soft music)
38:43
As bacteria gave rise to plants, a more advanced form of photosynthesis released a byproduct.
38:52
Oxygen.
38:55
(soft music)
39:00
This new supply of free oxygen surpassed the amount absorbed by the land and the oceans.
39:09
In the atmosphere it bound with hydrogen, preventing its escape into space while forming a new molecule of water. (soft music)
39:25
This process would gradually stem the loss of Earth's oceans, though not completely.
39:34
A recent study concluded that our planet has still lost up to 25% of its original stores of water.
39:42
(soft music)
39:47
Across the surface of our planet water began to work in tandem with life, the Sun and geology
39:58
to power a remarkable planetary engine.
40:05
The climate.
40:08
(soft music)
40:18
The climate is driven in part by the unevenness of solar heating due to the cycles of day and night, and the seasons. (soft music)
40:33
These factors moderate global temperatures, sending warm tropical winds toward the poles and cold polar air toward the equator.
40:43
(soft music)
40:47
Tides and currents mix cold water from the deep with the warm surface.
40:56
Solar energy is trapped in the atmosphere by water vapor, along with carbon dioxide, the greenhouse gas that ruined Venus.
41:07
What keeps CO2 in check is the special ingredient that sets Earth apart, life.
41:17
(soft music) The oceans are chalk full of it.
41:25
(soft music)
41:29
Microscopic phytoplankton take in CO2 driven into the ocean by waves or drawn up from the deep by currents.
41:39
(soft music) They send the carbon atoms on a journey up the food chain.
41:48
Phytoplankton get eaten by zooplankton, like these Radiolarians, a creature that dates back to a time over 500 million years ago, when life exploded across Earth's oceans.
42:07
Moving up in scale Copepods are tiny bug like crustaceans, and the single largest source of protein in the sea.
42:21
Octopus larvae are part of a vast zoo of creatures, smaller than the tip of your finger.
42:29
(soft music)
42:36
They get eaten by small fish and they in turn by larger creatures.
42:43
(soft music)
42:49
At each step in the food chain the carbon that began as part of a diffused gas in the air is passed onto larger and larger animals.
42:59
The larger the body, the greater the mass of carbon.
43:04
(soft music)
43:18
From whales down to tiny phytoplankton, marine life is part of a global system of removing CO2 from the atmosphere then gradually releasing it back.
43:30
(intense music) The key to this carbon cycle is Earth's ability to store it long term. (intense music)
43:46
A NASA satellite is tuned to read chlorophyll, a chemical tracer for plant growth.
43:55
In sync with the seasons plants take in vast amounts of carbon dioxide while releasing the oxygen we breathe.
44:06
On land carbon finds its way into the ground when plants and animals die and decay.
44:16
The Earth too gets into the act.
44:20
(intense music)
44:24
Exposed rocks take in CO2 when it rains, erosion sends it into the oceans.
44:31
(intense music)
44:35
If it becomes part of the marine food chain carbon rich matter can sink all the way to the sea bottom in the form of waste.
44:45
(intense music) In time carbon rich sediments can turn to oil, or to rock, like limestone.
44:57
Carbon can return to the environment if rocks become exposed or if the Earth begins to erupt. (intense music)
45:13
Every year over 100 million tons of carbon dioxide are spewed into the oceans and atmosphere by volcanoes.
45:23
(soft music)
45:33
Acting on time scales of a day to millions of years the carbon cycle has helped to make our planet habitable.
45:43
Its success depends on life itself.
45:48
(soft music)
45:53
Earth today, endowed with ocean, atmosphere and land.
46:01
With light and warmth.
46:05
With life that's bountiful and in balance. (soft music)
46:17
As we study the intricacies of what makes our planet tick
46:22
we marvel at what it took to achieve all that.
46:28
(intense music)
46:39
The aftershocks of supernova. (intense music)
46:50
The violence of Jupiter. (intense music)
46:57
A chance collision.
47:00
(intense music)
47:12
And the gift of a moon. (intense music)
47:19
Of water and life. (intense music)
47:30
The more we're able to reconstruct our planet's past the more singular it seems.
47:39
That is until we realize how many other solar systems are out there.
47:45
(intense music) We ask, is Earth just one of countless habitable worlds in a galaxy bursting with life?
47:58
Or is it a wondrous twist of fate?
48:03
A remarkable convergence of chemistry, energy and chance?
48:18
Our planet became a paradise,
48:25
but is it the only one?
48:28
(intense music)
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