>> 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.addic7ed.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,
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 == == for www.addic7ed.com ==