Birth of Planet Earth || 4k

Summary

This script narrates Earth's dramatic origins and evolution, from its birth amidst supernovae in the Milky Way to its turbulent early history shaped by Jupiter's gravitational influence. It explores the formation of the Moon through a colossal impact, Earth's near misses with extinction, and the emergence of life that ultimately led to a balanced ecosystem. The video ponders whether Earth's story is unique or one of many in a universe potentially teeming with life.

Takeaways

• 🌌 The story of Earth begins within the Milky Way galaxy, where supernovae seed the cosmos with the building blocks of planets.
• 🌞 Our Sun was born from a collapsing cloud of dust and gas, heating up and igniting at its core to become a star.
• 🪐 The formation of planets started with dust grains that grew into larger bodies, eventually forming planetesimals, including the primordial Earth.
• 📊 Traditional models of solar system formation suggested a clear division between gas giants and rocky inner planets, influenced by the young Sun's winds.
• 🌀 Newer observations have challenged this model, showing gas giants in the inner zones and a variety of planetary arrangements.
• 🔥 Jupiter played a crucial role in the early solar system, possibly growing quickly and causing a divide that prevented inner and outer solar system objects from mixing.
• 🌐 Jupiter's migration, known as the grand tack, influenced the size and composition of the inner solar system, preventing the formation of large rocky planets.
• 🌕 The Moon is believed to have formed from a massive impact between Earth and another planet, Theia, which contributed to Earth's mass and created the Moon.
• 💧 Earth's early atmosphere was likely rich in hydrogen, nitrogen, and carbon dioxide, with water vapor, which was essential for the emergence of life.
• 🌱 Life on Earth emerged around 4 billion years ago, possibly in undersea volcanic vents or hot springs, and photosynthesis played a key role in its evolution.
• 🌍 Earth's magnetic field, generated by the core-crust heat exchange, shields the planet from solar radiation, providing a protective environment for life.
• 🔄 The carbon cycle, driven by life and geological processes, helps regulate Earth's climate and maintain its habitability.

Q & A

How did the Earth's formation process begin?

The Earth's formation began within the Milky Way galaxy, where a supernova explosion seeded the cosmos with the building blocks of planets, such as carbon, silicon, and iron. A nearby cloud of stardust collapsed under its own gravity, leading to the birth of the Sun and the formation of a disk from which planets, including Earth, took shape.

What is the role of gas giants in the early solar system?

Gas giants, like Jupiter and Saturn, played a crucial role in the early solar system by stirring chaos and affecting the formation of other planets. They grew quickly by sweeping up gas pushed out by the Sun beyond a point called the ice line, which helped define the division between gaseous outer planets and rocky inner planets.

How did Jupiter influence the formation of the inner solar system?

Jupiter's rapid growth and its migration inward, known as the grand tack, disrupted the flow of matter into the inner solar system, preventing the formation of large rocky planets or Super Earths. It also cleared away cosmic debris, reducing the mass of the inner solar system and affecting the size of planets that could form there.

What is the significance of the Moon's formation in relation to Earth?

The Moon was formed from a giant impact event where a planet named Theia collided with Earth. This impact not only created the Moon but also contributed to Earth's rapid spin and slightly tilted axis, which later helped stabilize Earth's climate and provided a constant reminder of the cataclysmic event.

How did the early Earth avoid a fate similar to Venus, with a runaway greenhouse effect?

Earth avoided a runaway greenhouse effect due to its protective magnetic field, which deflects powerful solar radiation, and the presence of life that helped regulate the carbon cycle. Photosynthesis by early bacteria and later plants converted carbon dioxide into oxygen, preventing the buildup of CO2 that led to Venus's extreme heat.

What is the role of photosynthesis in the development of Earth's atmosphere?

Photosynthesis played a key role in the development of Earth's atmosphere by converting carbon dioxide into oxygen. This process not only fueled the growth and evolution of life but also helped regulate the atmospheric composition, preventing the loss of hydrogen and the buildup of carbon dioxide.

How did the early solar system's planetesimals contribute to the formation of Earth?

Planetesimals, or miniature planets, formed from the coalescence of dust, rocks, ice balls, and boulders within the solar system's disk. Over millions of years, these planetesimals collided and merged, eventually leading to the formation of the primordial Earth.

What evidence do scientists have about the early solar system from asteroids?

Scientists have studied asteroids, which have remained largely unchanged since their formation almost 5 billion years ago, to understand the early solar system. By measuring isotopes, particularly of metals, they have identified two distinct asteroid populations that formed in the inner and outer solar system, indicating a division that prevented mixing.

How did the Apollo 11 mission contribute to our understanding of the Moon and Earth?

The Apollo 11 mission and subsequent Apollo missions brought back lunar rocks that were found to have much in common with Earth rocks, including similar oxygen isotopes. This suggested a common and violent history between the Moon and Earth, leading to major discoveries about their formation and relationship.

What is the significance of the carbon cycle in maintaining Earth's habitability?

The carbon cycle is crucial for maintaining Earth's habitability as it helps regulate the levels of carbon dioxide in the atmosphere. Through processes involving life, such as photosynthesis, and geological processes, carbon is cycled between the atmosphere, oceans, and land, preventing extreme climate conditions like those on Venus.

Outlines

00:00

🌌 Birth of the Solar System

The script begins with a dramatic portrayal of the early solar system's tumultuous formation. It describes the birth of worlds amidst chaos, with gas giants causing disturbances and the young Sun in a state of fury. The Earth's survival against these odds is highlighted, setting the stage for the exploration of its origins. The paragraph takes us back to the Milky Way galaxy, a vast spiral of dust and gas, and introduces a simulated view of the cosmos over 50 million years. Supernovae are depicted as the seeds of planetary creation, scattering elements like carbon and iron across space. The narrative culminates in the collapse of a stardust cloud, leading to the birth of our Sun amidst a storm of dust, gas, and ice crystals.

05:06

🪨 Formation of Planets and the Role of Jupiter

This paragraph delves into the process of planet formation, starting from dust aggregation into planetesimals and the growth of the primordial Earth. It challenges the once-held belief in a predictable pattern of planetary formation, contrasting our solar system's structure with new discoveries of gas giants in inner zones and Super Earths. The paragraph discusses the division between gaseous and rocky planets and introduces the idea that Jupiter's rapid growth and its migration, known as the grand tack, played a pivotal role in shaping the inner solar system, preventing the formation of large rocky planets and influencing the final size of Earth.

10:09

🌕 The Moon's Origins and Impact on Earth

The script narrates the Apollo 11 mission and the subsequent lunar explorations, highlighting the significance of the Moon's rocks in understanding Earth's history. It discusses the discovery that lunar and Earth rocks share common oxygen isotopes, suggesting a shared violent past. The widely accepted theory of the Moon's formation through a giant impact, known as Theia, is described, illustrating how the collision created a ring of molten rubble that coalesced into the Moon. The paragraph explains the consequences of this impact on Earth's spin and tilt, and how the Moon's presence contributed to stabilizing Earth's environment, setting the stage for life.

15:14

💥 Earth's Early Bombardment and Water Acquisition

This paragraph discusses the aftermath of the Moon's formation, describing how Earth and the Moon endured a barrage of impacts from objects thrown into the inner solar system by Jupiter and Saturn. It details the modeling of these impacts based on lunar craters and how at least four major impacts could have reshaped Earth's surface. The process of impact erosion is explained, which stripped Earth of its crust and contributed to the cooling of the planet. The paragraph also explores how these impacts may have brought water to Earth, setting the stage for a world covered in water.

20:15

🌊 The Role of Water and the Threat of Solar Flares

The script paints a picture of Earth as a water-rich planet with seas stretching to the horizon, punctuated by volcanic islands. It discusses the Moon's influence on Earth's tides and the early atmosphere's composition. The paragraph highlights the threat posed by the young Sun's powerful flares, which could deplete Earth's water through a process called impact erosion. The script also compares Earth's situation with Mars and Venus, illustrating the potential loss of water and the importance of Earth's protective magnetic field in preserving its atmosphere and water.

25:15

🌱 The Emergence and Evolution of Life

This paragraph explores the origins of life on Earth, suggesting undersea volcanic vents and hot springs as possible cradles. It describes the emergence of photosynthesis in simple bacteria as a key development, allowing life to harness solar energy. The script details the process of photosynthesis, from capturing sunlight to producing ATP, which serves as the energy currency for life. The evolution of life is traced from bacteria to plants, leading to the release of oxygen as a byproduct and the beginning of the carbon cycle.

30:16

🌿 The Carbon Cycle and Life's Role in Climate Regulation

The script delves into the intricacies of the carbon cycle, emphasizing its importance in making Earth habitable. It describes how life, particularly phytoplankton, plays a crucial role in regulating carbon dioxide levels by absorbing it and incorporating it into the food chain. The paragraph explains how carbon moves through the ecosystem, from the ocean depths to the land, and how it is stored long-term in the form of oil, limestone, or through geological processes. The script highlights the interplay between life, the Sun, and Earth's geology in maintaining a balanced climate.

35:16

🌍 Earth's Uniqueness and the Quest for Extraterrestrial Life

The final paragraph reflects on Earth's unique characteristics and the delicate balance of factors that have made it a paradise. It contemplates the rarity of such conditions, pondering whether Earth is one of many habitable worlds or a singular outcome of chance, chemistry, and energy. The script concludes by emphasizing the ongoing quest to understand our planet and the potential for life elsewhere in the universe.

Keywords

💡Solar System

The solar system refers to the collection of celestial bodies, including planets, moons, asteroids, and comets, that orbit a star. In the video, the solar system's formation is depicted as a dramatic and chaotic process involving the birth of worlds and the destruction caused by gas giants and the young Sun's activity. The script describes the early solar system as a cradle for the formation of planets, including Earth.

💡Supernovae

Supernovae are powerful explosions that occur at the end of a massive star's life cycle, releasing vast amounts of energy and matter into space. The script mentions supernovae as the events that seed the cosmos with the building blocks of planets, such as carbon, silicon, and iron, which are crucial for the formation of planetary bodies like Earth.

💡Planetesimals

Planetesimals are small celestial bodies that are precursors to planets. They form from the coalescence of dust and rocks in a protoplanetary disk. In the script, planetesimals are described as miniature planets that come together through the force of gravity, contributing to the formation of larger planetary bodies like the primordial Earth.

💡Ice Line

The ice line, also known as the frost line, is the distance from a star beyond which volatile compounds like water, methane, and ammonia can condense into solid ice grains. In the video, the ice line is the point beyond which large gas planets like Jupiter, Saturn, Uranus, and Neptune grow quickly by sweeping up gas pushed out by the Sun.

💡Grand Tack

The grand tack refers to the hypothesis that Jupiter, during its formation, migrated inward toward the Sun and then migrated back to its current position. This migration is believed to have had a significant impact on the early solar system's architecture. The script describes Jupiter's grand tack as a pivotal event that cleared away cosmic debris and influenced the size and composition of the inner planets.

💡Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons. In the script, isotopes, particularly of metals, are used by scientists to trace the origins of asteroids to two distinct populations from the inner and outer solar system, providing insights into the early solar system's composition and dynamics.

💡Anorthosite

Anorthosite is a type of rock composed almost entirely of plagioclase feldspar, typically formed from the crystallization of a magma. The script mentions anorthosite as a rock type found on the Moon, which is indicative of a molten surface history and provides clues about the Moon's formation and its connection to Earth.

💡Impact Erosion

Impact erosion is the process by which the collision of large celestial bodies with a planet can strip away its surface material, including atmosphere and water. The script describes impact erosion as a mechanism that could have potentially stripped Earth of its water, but instead, the process contributed to the planet's geological and atmospheric evolution.

💡Photosynthesis

Photosynthesis is the process by which plants, algae, and certain bacteria convert light energy into chemical energy, storing it in the form of glucose or other sugars. In the video, the emergence of photosynthesis in simple bacteria is highlighted as a key event that allowed life to flourish and evolve, changing the Earth's atmosphere by producing oxygen.

💡Carbon Cycle

The carbon cycle is the process by which carbon is exchanged between the Earth's biosphere, pedosphere, geosphere, hydrosphere, and atmosphere. The script explains the carbon cycle as a critical process that helps regulate Earth's climate by removing carbon dioxide from the atmosphere and storing it in various forms, such as plant matter and sedimentary rock.

💡Magnetic Field

A magnetic field is a region around a magnetic material or a moving electric charge within which the force of magnetism acts. The Earth's magnetic field, generated by its core, protects the planet from harmful solar radiation. In the script, the magnetic field is described as a crucial defense mechanism that helps maintain Earth's habitability by deflecting solar winds.

Highlights

Earth's survival against all odds in a chaotic early solar system.

The Milky Way as the birthplace of Earth, with its dust clouds and gas providing the raw materials for planets.

Supernovae as the seeders of the cosmos with essential elements for planet formation.

The formation of the Sun from a collapsing cloud of stardust, marking the beginning of our solar system.

Planetesimals as the building blocks of planets, formed through the coalescence of dust and ice.

The role of Jupiter in shaping our solar system, including its migration and the 'grand tack'.

The discovery of diverse solar systems, challenging the traditional model of planetary formation.

The importance of isotopes in understanding the origins of asteroids and the early solar system.

The impact of Jupiter's growth on the formation of rocky planets like Earth.

The Apollo 11 mission and its contribution to our understanding of the Moon's and Earth's shared history.

The Giant Impact Hypothesis explaining the formation of the Moon and its impact on Earth's spin and tilt.

The role of Earth's magnetic field in protecting the planet from solar radiation.

The emergence of life on Earth, possibly around undersea volcanic vents, and its early forms.

Photosynthesis as a key development for life, converting sunlight into energy and producing oxygen.

The carbon cycle's role in regulating Earth's climate and maintaining a habitable environment.

The potential loss of Earth's water due to solar flares and the role of life in mitigating this.

The uniqueness of Earth in the context of other solar systems and the search for habitable worlds.

Transcripts

(dramatic music)

- [Narrator] In the fiery beginning of

our young solar system, world's are born.

And obliterated.

(dramatic music)

Gas giants stir chaos

and a young Sun vents its rage.

(dramatic music)

How did Earth survive against all odds?

(dramatic music)

Gazing down from space we marvel

at Earth's bountiful oceans,

its continents, and life giving atmosphere.

We ask how did our planet begin?

How did it come support life?

And life to support Earth?

(intense music)

The story of Earth starts within

a giant spiral galaxy, the Milky Way.

At 100,000 light years across the galaxy is a cauldron

of swirling dust clouds and glowing gas.

(intense music)

This simulated view shows a 50 million year span,

a cosmological blink of an eye.

(intense music)

In that time millions of stars die

in powerful explosions called supernovae,

shown here as flashes of light.

(intense music)

They seed the cosmos with the stuff of planets.

Carbon, silicon, iron and more.

(intense music)

One explosion has packed enough punch to send

a nearby cloud of stardust into collapse.

(intense music)

Huge volumes of dust and gas stream into its core.

(intense music)

This cloud is about as cold the universe gets.

But the tighter it's packed the more it heats up.

(intense music)

A storm erupts at its center,

a vast raging hurricane of dust, gas and ice crystals.

(intense music)

In its eye temperatures soar,

a star ignites and our Sun is born.

(intense music)

The Sun is being fed by a slowly spinning disk.

The cradle of our solar system.

Within the disk planets take shape

in a long violent process.

It starts with dust gathering into sand-like grains.

(intense music)

They form pebble sized objects

within clouds of loose gravel.

(intense music)

Over millions of years gravity draws them

together to form rocks, ice balls and boulders.

(intense music)

These objects coalesce into miniature planets,

or planetesimals.

One such body, the primordial Earth,

is growing steadily, but it's fate hangs in the balance.

(intense music)

We once thought that planet formation

followed a predictable pattern.

Our planetary neighbors bear this out

with their nearly circular orbits.

And the neat division between gaseous outer planets.

Jupiter.

Saturn.

Uranus.

And Neptune.

And rocky inner planets.

Mercury.

Venus.

Earth.

And Mars.

This division originates soon after a star ignites.

The young Sun produces hot winds that drive

lighter hydrogen gas to the outer part of the disk.

Beyond a point called the ice line large gas planets

grow quickly by sweeping up gas pushed out by the Sun.

The dusty inner region, devoid of gas and ice,

is where rocky worlds like Earth form.

This is not necessarily how most solar systems end up.

(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)

Jupiter sized giants have been found orbiting

so close to the star that hot stellar winds

are stripping them of gas.

(intense music)

Then there's a class of large rocky

planets called Super Earths.

How did those planets get there?

Why did our own inner planet stay so small?

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.

Most are so small that they simply

burn up in our atmosphere.

(intense music)

A few larger ones survive the fall.

Scientists have been able to dig these planetary shards

by measuring molecular variations called isotopes,

in particular metals.

They appear to come from two distinct asteroid populations

that formed in the inner and the outer solar system.

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.

It would have cut off the flow of matter

into the inner solar system, staling the formation

of large rocky planets, or Super Earths.

Jupiter would then play a central role in one

of the most impactful chapters in

the history of our solar system.

(intense music)

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

Each flash marks a collision.

Each ring tracks the orbit of a would be planet.

(intense music)

Giant Jupiter forms on the periphery,

its orbit shown in blue.

(intense music)

As it grows Jupiter succumbs to the

gravitational pull of the inner solar system.

It begins to spiral toward the Sun.

(intense music)

Scientists call Jupiter's big move the grand tack,

named for the term a sailboat takes into the wind.

(intense music)

Along the way Jupiter plows through clouds of cosmic debris.

(intense music)

What it doesn't swallow it flings out of the solar system.

(intense music)

The closer Jupiter draws toward the

Sun the more cosmic clutter it clears away.

(intense music)

The simulation tracks Jupiter all

the way into the orbit of present day Mars.

(intense music)

Jupiter's grand tack has further

reduced the mass of the inner solar system.

Now any planet's that form there will be relatively small.

(intense music)

In time another giant planet, Saturn,

grows large enough to pull Jupiter back out.

(intense music)

Earth, at that time, would have been an

embryo of the planet it would one day become.

(intense music)

With Jupiter's departure,

Earth and a few dozen hungry competitors

are free to scour the inner solar system for scraps.

(intense music)

Which ones will survive depends on

the luck of the cosmic draw.

(intense music)

Over the 50 million years since Jupiter departed the

inner solar system the roller derby of planets goes wild.

(intense music)

As the remaining planets tug on one another

their orbits destabilize.

Collisions between them are inevitable.

(intense music)

What's left is a handful of would be worlds,

including the planets we know today,

and at least one other.

(intense music)

Its existence was deduced in the wake of one of the most

celebrated milestones in the history of human exploration.

(dramatic music)

On July the 16th, 1969 Apollo 11 blasts off.

(dramatic music)

In 13 launches the US heavy lift launch vehicle,

the mighty Saturn 5 rocket,

never failed to safely deliver its payload.

(dramatic music)

Six times in the four years from 1969 to 1972

Apollo space craft drifted down over a pocked lunar surface.

(soft music)

12 astronauts climbed out to

experience the Moon up close.

They set up experiments.

Made measurements.

And collected rocks as they walked,

or drove across the alien terrain.

(intense music)

The world cheered as the astronauts returned to Earth.

Their exploits symbolized a spirit of optimism.

A bright ray of hope in a troubled time.

They were the first, and so far the last,

humans to travel beyond Earth and land another world.

(soft music)

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.

Back in NASA labs scientists found that rocks from the Moon

have much in common with those from Earth.

In particular they share forms of oxygen regarded

as blood types for solar system bodies.

(soft music)

The two bodies share a common and violent history.

That history is written across the lunar surface.

The Moon is pocked with large old craters,

surrounded by concentric rings.

You can see them in this image of the Mare Orientale

captured recently by NASA's lunar reconnaissance orbiter.

The rings suggest that a giant impacter

came down on a roiling, red hot liquid surface,

sending ripples outward.

(soft music)

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.

They also picked up rocks eventually nicknamed creep,

for the constituents potassium,

rare Earth elements and phosphorus.

These rocks of a type called Anorthosite

are a product of a molten surface.

What had turned the Moon into an ocean of molten rock?

And what is the connection to Earth?

The most widely accepted theory takes us back

to a time four and a half billion years ago.

(intense music)

At this time Earth may harbor volcanoes on its surface,

with a thin toxic atmosphere.

(intense music)

Our planet has sofar withstood

the on slot of planet formation.

It now awaits the test of its life.

(intense music)

Another planet, about half its size, is closing in.

This is Theia, a world have might have been.

Instead its journey ends here as it bears down on Earth.

(intense music)

Imagine the view from Earth as the ultimate

threat looms large on the horizon.

(intense music)

Theia rocks Earth to the core.

(intense music)

The impact sheers away a third of our planet

but instead of destroying Earth, Theia becomes part of it.

A computer simulation captures the first 24 hours.

Debris unleashed by the collision envelopes Earth

in a dense atmosphere of vaporized rock.

The cloud coalesces into a ring, a belt of molten rubble.

(intense music)

Much of the orbiting debris rains back to the surface,

but within a century what's left gathers into

a single wondrous body, Earth's companion, the Moon.

(thoughtful music)

After the impact our planet is left spinning rapidly,

on a slightly tilted axis.

(thoughtful music)

The Moon orbits much closer to Earth than it does today,

for its surface our world would have filled the sky.

(thoughtful music)

As the Moon gradually slips into a more distant orbit

its exerts a drag on Earth, that slows our planet's spin,

and steadies its tilt.

(thoughtful music)

The Moon serves as a reminder of the cataclysm

that almost spelled the end of our planet.

(thoughtful music)

But from here on it would be a welcome constant,

a source of stability,

and ultimately, beauty.

(thoughtful music)

But the violence was by no means over.

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.

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.

A recent study draws on the sizes and number of

lunar craters to model the impacts endured by Earth.

At least four impacts would have been large enough

to remake the surface of our planet

and to radically alter the course of its history.

(intense music)

Smashing into a crust rich in radioactive uranium

and potassium, they tore these elements

from the planet and sent them into space.

(intense music)

This process, called impact erosion,

left a crust that would cool more quickly

when the impacts finally died down.

Less disruptive impacts are thought to have carried

in massive amounts of water,

or released water bound to minerals deep below the surface.

(thoughtful music)

Half a billion years after the birth of the Moon,

Earth has become a world of water.

It seas span every horizon, broken only by volcanic islands.

(waves rumble)

The Moon, still in close orbit,

whips up tides that lash rocky volcanic shores.

(thoughtful music)

Earth's atmosphere is a mix of hydrogen,

nitrogen and carbon dioxide, laced with water vapor.

Land and sea are rich with chemicals,

carbon, nitrogen, oxygen, iron and more,

that came with the damn of the solar system.

(thoughtful music)

The Earth has what it needs to accomplish its ultimate feat,

to nurture life.

But there's a problem.

(thoughtful music)

Its water is slowly disappearing.

(intense music)

The young Sun, while dimmer than it is today,

is prone to powerful flares.

(intense music)

They strike the Earth's upper atmosphere.

When a solar particle hits a water molecule, H2O,

it can blast it apart.

Lightweight hydrogen wafts into space,

while heavier oxygen sinks to the surface

and binds with rocks.

(thoughtful music)

We now know what a devastating effect this can have.

Spacecraft observations show that Mars, long ago,

harbored ample stores of water.

(thoughtful music)

Its surface is etched by the meandering paths

of ancient rivers and lined with

sediments laid down on lake and ocean beds.

Mars today is a lifeless world, graced with a thin

carbon dioxide atmosphere, there is little or no water left.

(thoughtful music)

Using special sensors orbiting spacecraft have documented

the ongoing loss of water in Mars's upper atmosphere,

stripped by solar radiation.

(thoughtful music)

Scientists have observed this same process of work

on Earth's sister planet, Venus.

(intense music)

The result, Venus's atmosphere today is a witch's brew

of noxious chemicals, including thick sulfurous clouds.

(intense music)

Down at the surface Venus's atmosphere is choked

with high concentrations of carbon dioxide,

a potent greenhouse gas that traps the Sun's heat.

(intense music)

CO2 has turned Venus into a cauldron.

With surface temperatures of almost 500 degrees Celsius,

Venus is the hottest planet in the solar system.

(intense music)

This hostile environment is reinforced by active volcanoes

that dot its surface, spewing sulfur and carbon dioxide.

(intense music)

How did Earth avoid such a grim fate?

For one, our planet has a protective shield

that both Venus and Mars lack.

(intense music)

It's a magnetic field that deflects the most

powerful waves of radiation the Sun can throw at us.

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.

It's just our first line of defense.

(volcano rumbles)

Another line of defense began to simmer away across the

surface of our planet as early as 4 billion years ago.

Life.

(soft music)

Long standing theories see life's crucible

in the stirrings of undersea volcanic vents.

Heat and chemical reactions over long periods of time

produced proteins and nucleic acids, the chemistry of life.

(soft music)

More recent ideas point to hot springs and other volcanic

features that dotted the land masses of early Earth.

(soft music)

No one knows exactly how or where

life gained its first foothold.

(soft music)

What we know is that it did emerge

and that it spread thanks to a key breakthrough,

the ability to turn sunlight into energy.

(soft music)

Photosynthesis, the process that fuels plant life,

made its first appearance in

simple bacteria over 3 billion years ago.

(soft music)

Using one of the world's most powerful super computers

scientists have sought to model its chemical secrets.

(soft music)

Step one is to capture sunlight.

Passing through a transparent membrane to the center

of the bacteria we encounter a cluster of spherical pods.

Each one is equipped with special sensors

designed to harvest solar energy.

When a photon hits it excites

rings of chlorophyll molecules.

(soft music)

This energy is transferred across a family of proteins,

the machines of life.

(soft music)

Down the line electrons and protons carry

the energy through a chain of chemical reactions.

(soft music)

The energy driving these reactions came from the Sun.

The cell must now convert it into action.

It's the energy stored in protons that gets things moving.

(soft music)

Streaming into watery spaces within the cell

they flow toward a towering molecular structure.

As they enter their electrical charges

turn a protein like a crank.

This turning motion initiates a chemical reaction,

one that is essential to all life on Earth.

Two molecules join to form a third called ATP,

shown in in blue.

It is the universal energy currency

in every cell that has ever lived.

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,

to power locomotion, to fuel reproduction, to live.

(soft music)

ATP made it possible for microorganisms

to flourish and evolve.

(soft music)

As bacteria gave rise to plants,

a more advanced form of photosynthesis released a byproduct.

Oxygen.

(soft music)

This new supply of free oxygen surpassed the

amount absorbed by the land and the oceans.

In the atmosphere it bound with hydrogen,

preventing its escape into space while

forming a new molecule of water.

(soft music)

This process would gradually stem the

loss of Earth's oceans, though not completely.

A recent study concluded that our planet has still

lost up to 25% of its original stores of water.

(soft music)

Across the surface of our planet water began to work

in tandem with life, the Sun and geology

to power a remarkable planetary engine.

The climate.

(soft music)

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)

These factors moderate global temperatures,

sending warm tropical winds toward the poles

and cold polar air toward the equator.

(soft music)

Tides and currents mix cold water

from the deep with the warm surface.

Solar energy is trapped in the atmosphere by water vapor,

along with carbon dioxide,

the greenhouse gas that ruined Venus.

What keeps CO2 in check is the

special ingredient that sets Earth apart, life.

(soft music)

The oceans are chalk full of it.

(soft music)

Microscopic phytoplankton take in CO2

driven into the ocean by waves

or drawn up from the deep by currents.

(soft music)

They send the carbon atoms on a journey up the food chain.

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.

Moving up in scale Copepods are tiny bug like crustaceans,

and the single largest source of protein in the sea.

Octopus larvae are part of a vast zoo of creatures,

smaller than the tip of your finger.

(soft music)

They get eaten by small fish

and they in turn by larger creatures.

(soft music)

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.

The larger the body, the greater the mass of carbon.

(soft music)

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.

(intense music)

The key to this carbon cycle is

Earth's ability to store it long term.

(intense music)

A NASA satellite is tuned to read chlorophyll,

a chemical tracer for plant growth.

In sync with the seasons plants take in vast amounts of

carbon dioxide while releasing the oxygen we breathe.

On land carbon finds its way into the ground

when plants and animals die and decay.

The Earth too gets into the act.

(intense music)

Exposed rocks take in CO2 when it rains,

erosion sends it into the oceans.

(intense music)

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.

(intense music)

In time carbon rich sediments can turn to oil,

or to rock, like limestone.

Carbon can return to the environment if rocks

become exposed or if the Earth begins to erupt.

(intense music)

Every year over 100 million tons of carbon dioxide

are spewed into the oceans and atmosphere by volcanoes.

(soft music)

Acting on time scales of a day to millions of years

the carbon cycle has helped to make our planet habitable.

Its success depends on life itself.

(soft music)

Earth today, endowed with ocean, atmosphere and land.

With light and warmth.

With life that's bountiful and in balance.

(soft music)

As we study the intricacies of what makes our planet tick

we marvel at what it took to achieve all that.

(intense music)

The aftershocks of supernova.

(intense music)

The violence of Jupiter.

(intense music)

A chance collision.

(intense music)

And the gift of a moon.

(intense music)

Of water and life.

(intense music)

The more we're able to reconstruct our planet's past

the more singular it seems.

That is until we realize how many

other solar systems are out there.

(intense music)

We ask, is Earth just one of countless

habitable worlds in a galaxy bursting with life?

Or is it a wondrous twist of fate?

A remarkable convergence of chemistry, energy and chance?

Our planet became a paradise,

but is it the only one?

(intense music)