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>> Earth, a unique planet,

restless and dynamic.

Continents shift and clash,

volcanoes erupt,

glaciers grow and recede--

Titanic forces that are

constantly at work...

Leaving a trail

of geological mysteries behind.

This episode travels back

in time to investigate

the greatest geological

mystery of all--

The Birth of the Earth.

Scientists explore how

our planet first formed from

the dust of the solar system,

how molten rock solidified

to land, how our oceans

filled with water,

and how life arrived on Earth.

These are the earliest chapters

in the incredible story

of "How the Earth Was Made."
S02x04 Birth of the Earth
Original Air Date on December 8, 2009

== Sync, corrected by elderman ==
== for www.MY-SUBS.com ==

When it comes to finding clues

to the birth of the Earth,

our planet has been good

at covering its tracks.

Billions of years of erosion,

volcanic activity,

and the shifting of continents

and oceans have destroyed

almost all the evidence

of the earliest stages

in Earth's formation.

For geologists trying to

discover how and when

the Earth first formed,

this is a major challenge.

>> As geologists began to

question the age of the Earth,

and of course they looked

for older and older rocks,

what we began to find was that

the further back you go

in Earth history, the harder it

is to find any of those rocks.

>> The search for the oldest

rocks on Earth brings

investigators to the harsh

desert landscape of northern

Arizona.

This giant hole in the ground

is meteor crater, formed

when a massive meteorite

slammed into the Earth.

>> We didn't really have

rocks from the very beginning.

Well, where could we

find something?

What about the meteorites

that have been out in space

and fall on the Earth?

>> It was here that geologists

made a vital discovery.

Meteorites are older

than any rocks on Earth.

They had found the key

that would unlock the secret

of Earth's formation.

If the oldest rocks came

from space, that is where

the investigation must begin--

in space.

Our solar system,

4 1/2 billion years ago.

At its center, the young sun.

>> The theory that emerged

was that the sun was surrounded

by a cloud of dust and gas,

and as that cloud cooled, little

grains of minerals formed.

So all these little grains

of minerals floating in this

gaseous cloud are moving around

the sun, and they start

to bump into each other.

>> But there was a problem

with this theory. Nobody could

explain how colliding

microscopic mineral grains

could ever create an object

the size of a planet.

Then in 2003, an experiment

onboard the international

space station accidentally

provided extraordinary

new evidence.

Astronaut Don Pettit

wanted to see what happened

to different substances

in the zero-gravity conditions

of space.

He did a simple experiment

by pouring some salt into

a plastic bag and shaking it.

The results were astounding.

The particles immediately

began to stick to each other,

forming little clumps,

all held together by tiny

static electric charges.

Scientists realized that

if grains of salt stuck together

in space, then so could

the mineral grains

in the solar dust cloud.

Here was real evidence

for the fundamental mechanism

that kickstarted the formation

of the Earth.

As mineral grains in the solar

dust cloud bumped into each

other and stuck together,

they grew into small pieces

of rock orbiting the sun.

Over the next few million years,

some of them collided

and grew bigger.

Many of these rocks are still

orbiting the sun today.

They have drifted for the past

4 1/2 billion years...

Unchanged from when

they first formed.

Occasionally they fall to Earth,

and we call them meteorites.

They provide scientists

with an incredible window

onto the past.

>> We brought what's called

a stony type of meteorite.

What the scientists do then

is slice across it

and look on the inside.

And to the planetary

mineralogist, you start seeing

all kinds of wonderful things.

>> This meteorite contains

minerals and metals from every

part of the solar dust cloud.

>> So what we're looking at

is the assemblage of all these

little ancient, ancient, ancient

materials that were floating

around the sun in the nebula

of dust and gas, and when they

hit each other, they gradually

aggregated into solid bodies,

which got bigger and bigger.

>> Gradually, billions of these

rocks grew as they orbited

the sun, first to the size of

boulders, then as big as houses.

And they kept on growing.

When an object reached

about half a mile across,

its own gravitational pull

became strong enough to draw

other objects towards it.

>> Some object in this huge

number of objects going around

the sun, one of them

had to be the biggest.

And as soon as it gets bigger

than the others, it's sweeping

up more objects, just like

you're driving through a cloud

of mosquitoes at night

in your car, and the front

windshield is getting hit

more often. So the bigger it is,

the faster it grows,

and the faster it grows,

the more gravity it gets,

and that pulls in more objects.

So the biggest object starts

to run away from the crowd.

It starts to grow fastest.

>> And that biggest object...

Was the fledgling Earth.

Soon the young planet had

so much gravitational pull

that it began to attract

bigger and bigger objects.

As they crashed onto its

surface, Earth's size increased

with every impact.

The bombardment was so intense

that it only took about

30 million years for the planet

to grow to almost

its present size.

The young Earth was made

of billions of pieces of rock

randomly stuck together.

But geologists know

that the modern Earth

is not like that.

Below the surface, Earth is

separated into distinct layers--

a thin crust, then a massive

dense layer of rock called

the mantle, and at the center,

an iron and nickel core.

Some extraordinary event

must have occurred

to transform the interior

of the young planet.

Geologists now believe

that soon after it formed,

the Earth completely melted.

>> Originally the Earth was

probably just a big collection

of rocks like this,

but it heated up to the point

where these rocks all melted,

and when that happened,

the denser elements sank down

through to the very core

of the Earth, and the lighter

elements floated at the top.

>> The huge gravitational pull

dragged the heavy iron

and nickel down to form the core

and separated the rest

of the planet into layers.

What caused such a huge mass

of rock and metal to heat up

in the freezing depths of space

puzzled geologists

for many years.

>> We think it's from

the incorporation of very hot

radioactive elements.

They're out there floating

in space. As the Earth accretes,

it includes some of this

ferociously hot material.

As it gets inside there,

it begins to heat up

the rocks around it.

And if you build the Earth

fast enough and you incorporate

enough of these really hot

radioactive elements, it will be

enough to melt the Earth

from the inside out.

>> Only 30 million years

after it began to form,

Earth had become a giant

round ball of boiling liquid

rock and metal orbiting the sun.

>> Imagine a totally molten

world. I mean, it had

molten magma oceans.

No dry land anywhere. No water.

Just flowing lava everywhere.

>> The temperature of the molten

Earth was now a staggering

2,000 degrees.

But at the edge of the planet,

the vacuum of space

is a constant minus 450 degrees,

almost 2,500 degrees colder.

The surface rock could not

stay molten for long.

>> It's cooling from the outside

in, so from the outside,

it begins to crust over,

and you get this little scab,

like on a wound, of cooled rock

that's still really hot

and then gradually begins

to cool from the outside in.

>> In less than a million years,

Earth's surface was covered

in a thin crust.

But volcanoes still spewed out

lava and choking gases.

Meteorites rained down

in a constant bombardment.

Earth had a long way to go

before it could support

continents, oceans, and life.

Scientists investigating the

earliest origins of the Earth

have uncovered evidence

from salt grains in space.

They reveal that the Earth

began to form when fragments

of the solar dust cloud

stuck together.

The Earth's internal layers

provide the clue that,

soon after it formed, the young

planet completely melted.

Scientists had worked out

how the Earth first formed

from a cloud of dust in space.

But they were missing

a vital piece of the puzzle.

They still did not know

the age of the Earth.

>> Billions of years

before humans evolved,

tiny mineral grains in space

clumped together to form

the molten ball that became

the Earth.

But exactly when that happened

is a question that has taxed

the minds of scholars

and scientists for centuries.

In 1650, the Irish archbishop

James Ussher added up

the ages of all the prophets

and kings in the Bible.

His calculations led him

to very precise conclusions

that Earth was created

at nightfall before Sunday,

October 23, 4004 B.C.

A century later, geologists

realized that Earth's

thick layers of sediments

and volcanic lavas must have

been laid down over millions

rather than thousands of years.

The next breakthrough came

in 1897, when physicist

Ernest Rutherford figured out

that measuring radioactive decay

could accurately date

the age of rocks.

Rock samples from around

the globe were found to be

not just millions,

but billions of years old.

But in their hunt for the age

of the Earth, scientists hit

a major obstacle.

Rocks from the earliest

stages in Earth history

are very hard to find.

>> If you want to go back

as a geologist and try to find

evidence of those early days,

it's very hard to do

on the Earth because, of course,

we have rain eroding,

we have tectonics

and continental drift

destroying continental surfaces.

We simply can't find the rocks

that go back to that age.

>> In the early 1950's,

the American geologist

C.C. Patterson tried

a new approach using meteorites.

He knew that meteorites

must have clumped together

from the same mineral grains

in space that formed the Earth.

And that happened at the same

time as the Earth was born.

So if he could date a meteorite,

he should get the true age

of the Earth.

In 1953, Patterson came

to meteor crater in Arizona

looking for samples.

The meteorite which blasted out

this enormous crater was

about 50 yards across.

It slammed into the Earth

at a fantastic speed.

>> Objects hitting the Earth

from space may typically come in

at 10 or 15 miles per second,

hitting the ground,

penetrating into the ground,

generating enormous pressure

and shockwave and creating

a huge explosion.

>> The meteorite hit the Earth

with the force of a 2-megaton

atomic bomb. The explosion

vaporized most of the meteorite,

but individual fragments

survived.

>> This is one of the pieces

of the object that crashed into

the Earth and made this crater.

This is pure iron.

We know it's iron because,

for example, it's magnetic.

An amazing piece of something

that was floating in space.

This was the kind of place

that people could get samples

for the first radiometric dating

of meteorites.

And so Patterson came here

and got samples like this.

>> Patterson dated the samples

and was amazed by the results.

The meteorite was a staggering

4.5 billion years old...

Meaning that the Earth was also

born 4.5 billion years ago.

Patterson had solved the problem

that had defeated scientists

for centuries.

>> There's this apocryphal story

that Patterson got so excited

about the date that was coming

back from the laboratory

and so hyper about it,

he thought he was having

a heart attack, and he was

driven to the hospital,

and it turned out to be

just his excitement

over this fantastic discovery.

>> Modern radiometric dating

techniques have refined

the age of the Earth to

a remarkable degree of accuracy.

The most recent study

dates the Earth as

4,567,000,000 years old.

So scientists now knew how

and when the Earth was formed.

But nobody had figured out

what happened next.

Then in 1974,

a radical new theory emerged.

In the early solar system, there

were dozens of mini-planets

chaotically orbiting the sun.

According to the theory,

one of these was on

a collision course with Earth.

The idea was the brainchild

of Bill Hartmann, who was trying

to explain the origin

not of the Earth,

but of the moon.

>> What we came up with was that

maybe during that period

of intense impacts,

maybe a very large impact

hit the Earth and blew some

crustal outer mantle rock

off of the Earth into space

around the Earth, and the moon

formed from that material.

>> Hartmann suggested that

another planet, about the size

of Mars, crashed into the Earth.

He claimed that the moon

could have been formed

by debris from that collision.

To many scientists,

this was nothing but fantasy,

but Hartmann had evidence...

Collected from the moon itself.

>> If I fall in the...

in the plumb crater

getting this rock.

>> Footage from the Apollo XVI

mission in April 1972

shows astronaut Charles Duke

struggling to pick up

a large sample of moon rock

to bring back to Earth

for geologists to analyze.

>> That's 20 pounds of rocks.

>> At the Johnson Space Center

in Houston, this actual piece

of moon rock is still kept under

strict laboratory conditions.

>> I would say, behold the moon.

This is an actual piece

of the moon, and it's

the largest single rock

that they brought back

from the surface of the moon

when the Apollo astronauts

went there.

We can't touch it.

They don't want human beings

touching these rocks

and leaving organic material

on them.

>> Until the late 1960's,

geologists thought that the moon

formed in the same way as

the Earth, by clumps of mineral

grains sticking together

in the solar dust cloud.

They believed it had layers

like the Earth

and a heavy iron core.

But when geologists analyzed

lunar samples, they were

astonished to discover that

the moon rocks contained much

less iron than they expected.

>> One of the mysteries

has always been why isn't there

as much iron in the moon

as there is on the Earth,

if the two objects are

right close together in space?

>> The question bothered

Hartmann so much that he began

to think that conventional

theories about how the moon

formed might be wrong.

>> That lack of iron in the moon

or to put it another way,

the fact that the moon

is made out of rock that looks

like the crust and the upper

mantle material of the Earth,

that was a clue that the moon

may have formed from rocks

from the outer portion

of the Earth.

>> This was the key

to Hartmann's idea

of a collision between Earth

and another planet.

The force of the impact

completely destroyed

the other planet and flung

billions of tons of Earth's

crust and mantle out into space

and into orbit around the Earth.

Within a few thousand years,

this debris clumped together

to form the moon.

Advanced computer models

show that the collision

was a glancing blow.

The other planet did not

hit Earth head-on.

This meant that while Earth's

outer layers were ripped off,

none of its iron core

was blasted away.

>> That lack of iron would

end up explaining why

we have a moon that is

only the rocky material

without the iron material.

>> Hartmann's collision idea

is now accepted as fact.

It was his fascination

with the moon that led

to a new understanding

about a vital stage

in the formation of the Earth.

>> The moon always, to me,

is a reminder that we live

in a larger environment

than just the Earth.

It's the cosmic environment.

The inner solar system

is our environment

that we can move around in now.

>> In the quest to discover

the age of the Earth,

evidence from radiometric dating

of meteorites proves

that the Earth was formed

just over 4.5 billion years ago.

The lack of iron in rocks

brought back from the moon

is evidence that the Earth

survived a massive collision

with another planet.

But vital parts of the modern

Earth were still missing

from the newly born planet.

The investigation now needs

to figure out how the Earth

gained 2 essential components--

solid land...

And water.

>> 4.5 billion years ago,

Earth formed out of the solar

dust cloud, then survived

a devastating impact

with another planet.

The investigation now moves

200 million years forward

in time, as scientists try

to discover how the first

continents and oceans formed.

They are looking for evidence

on the northeast shores

of Hudson Bay, Canada.

This is the desolate landscape

of Porpoise Cove,

the site of an important new

scientific discovery.

And it's all down to a young

Ph.D. student's fascination

with ancient rocks.

>> I was interested in studying

the early Earth, so the idea

is to get as far as we can back

in time, to get these old rocks

and study rocks that were there

in the past.

>> Geologists already knew

that rocks in this part

of northern Canada

are extremely old.

But something about a small area

in this vast wilderness

caught O'Neil's eye.

>> The overall aspect

of the rocks really looked

different, and right away

we knew that something was

really bizarre, really unusual

about these rocks.

>> The rocks are highly altered

deformed volcanic lavas

known as amphibolites.

>> The chemistry was unusual.

The mineralogy was unusual.

And nobody had seen

rocks like that before.

>> O'Neil decided the rocks

needed further investigation.

He sent samples to be

radiometrically dated.

The results were astounding.

>> We were in the lab

in Washington, D.C.,

when we first got the first

number out of the machine.

And the first reaction is

we didn't believe it.

So what you do is you reanalyze

the rock a second time.

And then the same number

comes up, and then a third time,

and then again and again.

So you say, "ok. We'll analyze

"more of these rocks,

because I can't believe it."

And these numbers,

this signature, this really,

really old signature

keeps coming up,

keeps coming up,

and keeps coming up.

And in the end, you have to

come to the conclusion

that these rocks have been

formed nearly 4.3 billion

years ago.

>> The results were

indisputable.

The amphibolites are

4.28 billion years old,

200 million years older

than any other rocks

so far discovered.

They are the closest

anyone has come to finding

Earth's original crust.

>> These are the oldest rocks

in the world, and it's amazing

when you stand on it.

You can try to imagine yourself

almost 4.3 billion years ago,

when the Earth was so young

and just barely forming...

Walking on this landscape, and

it's a really amazing feeling.

>> These rocks are now yielding

clues about the thickness

of the early crust.

O'Neil has found unusual

minerals which can only form

in conditions of very high

temperature and pressure.

They prove that the amphibolites

were made at least 12 miles down

in the crust of the Earth.

This means that more than

4 billion years ago,

Earth had a solid crust

at least 12 miles thick,

and a crust that thick suggests

there must have been continents.

And there's more. Evidence

hidden in the amphibolites

reveals that these rocks

must have originally formed

deep underwater.

>> Well, you have to understand

that when rocks form,

they can record their chemical

signature, and depending on

where the rocks are forming,

in what geological context

they will be formed,

they will carry that

specific chemical signature.

>> The chemical signature

of the amphibolites is unique.

It proves that when these rocks

formed, Earth had not only

a solid crust, but oceans.

>> The signature we see here,

it really looks like

an oceanic floor.

That means there was an ocean

and a lot of water already

at 4.28 billion years old.

So it totally changes our view

of what the Earth

was like before.

>> To the scientific world,

this idea is dynamite.

But O'Neil is not on his own.

There is more evidence

to back up his claim.

In the same ancient rock

sequence, geologists find

another unexpected rock type

called banded iron formations.

These rocks are made up

of alternating light layers

of silica and dark bands full

of a mineral called magnetite,

which, as the name suggests,

are rich in iron.

>> We usually use a magnet

to try to find these minerals.

It's a quick and easy way

to identify for sure those rocks

as banded iron formations.

>> Magnetite in banded iron

formations only forms

underwater. So these rocks

are further evidence that

there were oceans on Earth

more than 4 billion years ago.

But scientists don't know

how much of Earth's surface

was covered by water.

>> The only way to form

this magnetite is to be, like,

in an ocean. We don't know

exactly what was the ocean

at that time, but we know

for sure that we need water

to form those rocks.

>> These discoveries are forcing

geologists to rethink their

ideas of what conditions

were like on Earth

less than 300 million years

after the planet formed.

>> People often think of this

early Earth like a ball of fire

or molten rock, but this is not

the picture that we see here.

We see that, already

at 4.28 billion years old,

we probably had an ocean.

We had continent that

really, really looks like

what we know today.

So it changes totally our view

of the early Earth.

>> The investigation has now

revealed when the Earth's

continents and oceans

began to form.

Evidence from amphibolite rocks

at Porpoise Cove confirms

that the Earth had developed

a thick solid crust

4.28 billion years ago.

Banded iron formations

in the same rocks show that

there were oceans on Earth's

surface at the same time...

All of which raises

another mystery.

If oceans existed

more than 4 billion years ago,

the investigation needs

to figure out where all

the water came from.

>> After its formation

from the solar dust cloud

4.5 billion years ago,

Earth was a fiery ball

of molten rock,

but 200 million years later,

the first oceans were

already forming, and Earth today

is the blue planet,

with 70% of its surface

covered by water.

The investigation now looks

at the mystery of the origin

of Earth's water.

>> One of the important

questions I've always thought

about is, you know, where did

all of this come from,

all of this water,

all the water in the oceans

and in the atmosphere,

in our bodies, in the ground?

When you look at the Earth

from space, what really

impresses you is the water,

how beautiful this planet is.

Why does Earth have

all of this water,

and how did it get here?

>> The question has puzzled

geologists for years.

Now they believe the answer

lies in space.

New evidence showing how

our water arrived on Earth

has emerged from a meteorite

that fell in 1998 but which

has only recently been analyzed.

>> We found an astonishing

thing. This meteorite

contains grains of table salt,

just like you'd put

on your fish and chips.

>> The clue is trapped inside

the crystals of salt and

revealed under the microscope--

minute droplets of liquid water.

On the computer screen, you can

see a little fluid inclusion,

a little drop of water,

and you'll know it's water--

we know it's liquid because

you see a little bubble

moving around inside of

this little droplet of water.

>> The amazing thing about

this discovery is the age

of the water.

>> You can date this by several

different dating techniques.

The salt itself is

4.5 billion years old.

The water inside has to be

at least that old,

if not even older.

There's no question about it.

And so this water is at least

as old as the solar system.

>> Here is visible evidence

that water existed in space

when the Earth first formed.

And Zolensky is convinced

that meteorites then brought

the water to Earth.

>> And so it's looking

more and more like the water

arrived drop by drop in rocks

like this meteorite here,

landing over the course

of billions of years.

You have lots of material

coming in every day

and smacking into the Earth

and depositing a little bit

of water, a few drops at a time.

>> The scale of the meteorite

bombardment needed to fill

the oceans with water is

almost impossible to comprehend.

But scientists believe

that over billions of years,

there were easily enough

meteorites crashing into

the Earth to account for

all the water on the planet.

>> Gradually those rocks

were sweating water,

building up first shallow seas

here and there.

They'd grow to be giant oceans.

So you go from this to this.

>> Once Earth had land masses

and water, the stage was set

for the development of life,

the next phase in the evolution

of the Earth.

Life is an essential element

in Earth's geology.

Without life, sedimentary rocks

like chalk and limestone

would not exist.

Without life, there would be

no coal, oil, or gas.

Life has shaped the Earth

in profound ways.

But finding the origin of life

has challenged scientists

for hundreds of years.

Now there's a new explanation.

It comes from evidence found

at Allende in the desert

landscape of northern Mexico.

At about 1 a.m.

On February 8, 1969,

night suddenly turned into day.

>> A large fireball was seen

traveling from the south

northwards over northern Mexico.

And this big flash

and this fireball was caused

by a really large meteorite.

It was probably about the size

of a car. And it entered the top

of the Earth's atmosphere

at about 36,000 miles an hour.

>> As it plunged through

the atmosphere, the meteorite

broke up into thousands

of fragments.

>> There was no crater left

by the Allende meteorite.

So it fell as a shower

of stones, the largest of which

was reported to be about

the size of a beach ball.

The stones are found in--

we call it a strewn field,

and I's an area about 30 miles

by 5 miles wide.

And we are here, right in

the middle of that strewn field.

>> Because the meteorite

fragmented into so many pieces,

geologists had to search

a huge area to find samples.

>> Now I actually have a smaller

one of the stones here.

You can see it's about

the size of a plum.

It's one of the most primitive

type of meteorites.

This means that since it formed

at the very earliest stages of

solar system formation, really

not much has happened to it.

>> When they analyzed samples

from Allende, geologists made

a groundbreaking discovery.

The meteorite contained

tiny amounts of chemicals

called amino acids.

>> Amino acids are terribly

important constituents

of things like proteins,

and amino acids really are

sort of like the chemical

building blocks for life.

So to find these amino acids,

these molecules within

the meteorite was a really

exciting discovery.

>> Every living thing on Earth,

plant or animal, contains

amino acids, and life could not

exist without them.

Until they were found

in the Allende meteorite,

scientists believed that

amino acids were first made

by chemical reactions

on the surface of the Earth.

>> People thought that maybe

life had started on Earth

in these sorts of warm pools,

maybe, you know,

a few hundred million years

after Earth actually formed,

or possibly through lightning

causing chemical reactions

in the early atmosphere.

There was a few theories

as to how life may have started

on Earth prior to the discovery

of amino acids in meteorites.

>> Since Allende, amino acids

have been found in hundreds

of other meteorites.

Their discovery has

revolutionized ideas about

the origin of life on Earth.

Scientists now believe

that the building blocks of life

originally came from space.

Meteorites containing amino

acids have bombarded Earth

ever since the planet formed,

and it was these amino acids

which were the starting point

for all life.

Hunting for the origin

of Earth's water and life,

the investigation has revealed

that the water on Earth

arrived here inside meteorites,

and meteorites also brought

amino acids,he building blocks

of life, to Earth from space.

Scientists now need one more

piece of the puzzle to explain

the final stage in Earth's

journey from particles

in the solar dust cloud

to a planet where life itself

builds Earth's geological

features.

>> 4.5 billion years ago,

Earth formed out of

the solar dust cloud.

200 million years later,

the first continents and oceans

were developing.

Meteorites brought water

and amino acids,

the building blocks of life,

to the surface of the planet.

The investigation now moves

forward to the period

3.5 billion years ago.

New forms of life were about

to emerge, which by their very

existence, would create

new kinds of rocks.

But life as we know it

needs oxygen, and 3.5 billion

years ago, there was

no oxygen on Earth.

At the time, the atmosphere

was deadly poisonous.

Volcanic eruptions filled

the air with a choking mixture

of sulfur, methane,

carbon dioxide,

and sulfuric acid.

But primitive life forms

did exist.

The fossilized remains

of strange coral-like structures

have been found in rocks

more than 3 billion years old

in many parts of the world.

They are called stromatolites,

and they are a clue

as to how the atmosphere

filled with oxygen.

Living stromatolites

are incredibly rare.

One of the few places on Earth

where they can be found

is in another part

of the northern Mexican desert.

This is the high valley

of Cuatro Cienegas.

>> You might think that this is

just any old desert,

but it's not.

This is a very special place.

Because of a particular way

the chemistry is in this valley,

it's unlike any other place

on the planet.

>> The pool is like

a time-capsule laboratory.

By examining the modern

stromatolites, scientists

can work out how they were made

more than 3 billion years ago.

>> What's interesting

about Cuatro Cienegas is that

this is almost like a proxy

to right before the world

had a lot of oxygen in it,

and the place was dominated,

our Earth was dominated

by microbial life.

>> Siefert has discovered

that the stromatolites

are made by billions of microbes

called cyanobacteria.

>> These right here

are the stromatolites that

are here at Cuatro Cienegas.

I have a piece of it here.

And if you can see

this blue-green rim right here,

this is millions and millions

of cyanobacteria.

>> These bacteria were to change

the course of Earth history

because of one unique feature--

they produce oxygen.

>> Here at this pond,

we can actually see them

doing their job. We can

see them making that oxygen.

So when I get in the water

and I actually go up

to up to one of these

cyanobacterial mats...

If I look very closely,

all of the community

is making oxygen,

and as that oxygen collects

in that mat, it produces

a little air bubble, and you

can watch that air bubble

just transfer to the top,

and that's actually when oxygen

is being released

to the atmosphere.

>> 3.5 billion years ago,

oxygen was deadly poisonous

to other early life forms

which used sulfur

to obtain energy.

>> Cyanobacteria developed

a little molecular machine that

could actually take sunlight

and take water, and they made

a byproduct that was oxygen.

Well, on this planet back then,

none of the life

was used to oxygen.

And it's at that point

in life's history,

when they began making

excess oxygen that got

into the atmosphere,

our whole world changed

in the way it worked.

>> Over geological time,

there were enough cyanobacteria

to produce trillions of tons

of oxygen, creating

the atmosphere we breathe today.

And they were responsible

for changing the way

all life evolved.

>> From an evolutionary

standpoint on planet Earth,

we are where we are

because of cyanobacteria

and the fact that they managed

to fill our atmosphere

full of oxygen, because

unless we'd had that gas,

we wouldn't have the complex

organisms that we have

on the planet. You and I

wouldn't be here today.

>> Once the atmosphere

began filling with oxygen,

the stage was set

for the evolution of all

plant and animal life.

The impact on Earth's geology

was profound.

Over hundreds of millions

of years, decaying plant matter

from tropical forests built up

compressed layers, which

eventually formed all the coal,

oil, and gas deposits

on the planet.

Sedimentary rocks,

like limestone and chalk,

are made largely from

the skeletons of marine animals

which accumulated at the bottom

of shallow seas.

Without life, Earth's geology

would be very different.

The investigation into the birth

of the Earth has uncovered

evidence revealing the secrets

of Earth's development.

Experiments on salt crystals

in space reveal that the Earth

began to form when mineral

grains in the solar dust cloud

stuck together.

Evidence from meteorites

proves that Earth first formed

4.567 billion years ago.

The oldest rocks in the world

are evidence that continents

and oceans were forming

4.28 billion years ago,

much earlier than

previously thought.

Liquid water in meteorites

proves that water was brought

to Earth during billions of

years of meteorite bombardment.

3.5 billion years ago,

a billion years after it first

began to grow out of

the solar dust cloud,

Earth had continents, oceans,

primitive life forms,

and oxygen.

The birth of the Earth

was complete, a new canvas

on which billions of years

of geological processes

could mold the planet

we inhabit today.

== Sync, corrected by elderman ==
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