♪ ♪
NARRATOR: Earth, our home.
A rocky world
enveloped by a thin blue layer
clinging to the surface.
Our atmosphere.
ROBERT HAZEN: The
atmosphere is the only thing
that stands between us and
that cold, dark void of space.
[rumbling]
NARRATOR: The story
of the air that surrounds us
is the story of Earth itself.
♪ ♪
SONIA TIKOO: It is
incredible to think that
this 4.5 billion-year-old
rock could hold clues
as to how our early
atmosphere formed.
[lightning crackling,
rain falling]
NARRATOR: Clues that
reveal colossal transformations.
MIKE WONG: It is absolutely
mind-blowing that a tiny bacteria
could affect a
planetary-scale phenomenon
like our atmosphere.
♪ ♪
NARRATOR: How did our
atmosphere make Earth a unique place,
the only home to
life as we know it?
We have never found
another planet that has
an atmosphere like ours.
PETER GIRGUIS: And understanding
how Earth got its atmosphere
is the first step in
understanding how to protect it.
NARRATOR: "Ancient
Earth: Birth of the Sky,"
right now, on "NOVA."
♪ ♪
[rumbling]
NARRATOR: In the depths of space
lies a young,
unrecognizable planet.
♪ ♪
Bombarded by asteroids,
this battered
world is our Earth.
♪ ♪
A desolate and volatile globe
overlooked by a new-born
moon that dominates the sky.
With no recognizable
atmosphere, the void of space
nearly touches the surface
of slowly cooling lava.
♪ ♪
There's little protection from
the young sun's harsh radiation.
This world looks nothing
like the Earth we know today.
Around four and a
half billion years ago,
Earth was inhospitable for life.
[rumbling]
HAZEN: There were meteors and
asteroids bombarding the surface.
It was too hot.
It was a terrible place to be.
♪ ♪
LINGAPPA: The question is,
how did our planet transform
from this barren rock,
into somewhere
capable of supporting life?
♪ ♪
WONG: This is the story of how
our planet became a living world,
and the dance, the co-evolution
between life and our atmosphere.
♪ ♪
["Never Close Enough"
by SIPHO. playing]
♪ Oh, we won't ever
hear the silence ♪
♪ Or ever see the colors ♪
[exploding]
♪ That never
lived in our minds ♪
♪ ♪
♪ Just a moment ♪
♪ Never too far out ♪
♪ Never close enough ♪
♪ ♪
NARRATOR: Today, our
planet is an oasis for life,
enveloped by a layer of
nourishing and
protective gases...
The atmosphere.
It's extremely thin, it's almost
like the skin on apple,
if you pretended the
apple was planet Earth.
TIKOO: The diameter of the earth
is about 8,000 miles across,
and the atmosphere adds
just another 60 or so
miles on top of that.
[laughing]: We
wouldn't... we wouldn't be
on planet Earth if it
weren't for the atmosphere.
And when I say we,
not just you and me
sitting here, but any life.
GIRGUIS: Everything
from fungi to bacteria,
to tiny insects,
to giant reptiles,
are entirely dependent
on this atmosphere of ours.
♪ ♪
It does many things for us,
and we can think of the
simple answer that we,
as human beings,
use the oxygen to live.
NARRATOR: Besides
oxygen, other important gases
make up the atmosphere.
LYONS: Perhaps the
single most critical aspect
of our atmosphere is the
fact that carbon dioxide
is one of the greenhouse gases
that keeps our planet habitable.
PIERREHUMBERT:
Nitrogen is an essential
component of the atmosphere,
because all life as we know it...
Amino acids, DNA,
all of the things that
are essential to us...
Rely on nitrogen.
The atmosphere protects us
from ultraviolet radiation
because it has a small amount
of a molecule called ozone.
LINGAPPA: It
controls our climate,
which makes this planet, like,
a livable temperature
for us at all.
It sort of insulates us
from the cold of space.
NARRATOR: But the
journey to today's atmosphere
has been full of drama.
WONG: It's a long, winding road
between the initial
atmosphere that Earth had
through all of the various
different kinds of atmospheres
in the middle of its history,
and finally arriving at the
atmosphere that we have now.
♪ ♪
NARRATOR: Millions of years
after the birth of the planet,
there's still no
atmosphere as we know it.
But that is going to change.
Four and a half
billion years ago,
the Earth would have
been a very violent place.
[rumbling]
LYONS: Such that it's called
the Hadean, which comes from
the god Hades, the Greek
god of the underworld,
because it was imagined to be
a hellish kind of place.
[thundering, rumbling]
[bursting]
[magma rushing]
NARRATOR: Across the globe,
molten magma
surges up from within.
[splashing]
Rivers of fire unleash
a c*ck of gases.
[booming]
♪ ♪
Carbon dioxide,
nitrogen, and methane
explode out of
volcanoes in thick plumes.
♪ ♪
These are the building blocks
of our early atmosphere.
♪ ♪
And we can see echoes
of this young planet
still on Earth today.
♪ ♪
The volcanoes that we
have here in Iceland look
very similar to
those that we had
four and a half
billion years ago.
The early Earth was
dominated by volcanic activity,
and this lasted for
millions of years.
♪ ♪
Those volcanoes
acted as pathways
for the gases that are
trapped inside the magma
to escape into our atmosphere.
NARRATOR: But
how do scientists know
what the atmosphere
was like in the past?
Surprisingly, clues are hidden
in some of the
rocks we find today.
Throughout Earth's
history and evolution,
there's been a dynamic interplay
between the Earth's surface
and the Earth's atmosphere.
And because of this interplay,
there are chemical fingerprints
that are trapped in rocks.
The rock I'm holding in my hand
is 3.4 billion years old.
And there are tiny bubbles
trapped in this rock
that are samples
of Earth's ancient atmosphere.
So we can measure the gases
and piece together evidence
of what the atmosphere
was like in the past.
♪ ♪
NARRATOR: However,
to understand the very
earliest atmosphere,
scientists have to
go back to a time
before Earth was formed.
The planet is made up of
rock that started as debris
floating in the
early solar system.
But this debris is also falling
to Earth today as meteorites.
WILLIAMS: In my pocket here,
I've got the most
incredible rock.
This is a chondrite meteorite.
These chondrite meteorites
formed when rock
dust came together
to form small chunks
of rock like this.
They eventually
smashed together,
forming our planet Earth.
And so these are really the
building blocks of our planet.
And so it's so humbling,
because it's not only
older than all of the life
that we know on Earth,
but even the planet itself,
right back to 4.6
billion years ago.
NARRATOR: These rocks are not
just the building blocks of our planet,
but of our early
atmosphere as well.
WILLIAMS: Thanks
to these space rocks,
the ingredients for our
early atmosphere were there.
It's just that they were
locked inside the planet.
NARRATOR: Chondrite
meteorites are like time machines,
allowing scientists to
travel back billions of years
to when the atmosphere
first developed.
WILLIAMS: Experts can study
these chondrites in great detail.
They can analyze
them in the laboratory
to understand their
chemical signatures,
and that's going to tell
them about the gases
that they would
have contributed to
our early Earth's atmosphere,
such as water
vapor, carbon dioxide,
sulfur dioxide, hydrogen,
methane, and nitrogen.
HAZEN: It's remarkable
that you can learn
about the history
of the atmosphere
going back billions
and billions of years
just by studying rocks.
WONG: When I learn about
this, I feel simultaneously
like a time traveler
and a detective,
being able to piece together
the story of our ancient Earth.
LYONS: Each year, techniques
become more and more powerful
at deciphering bits of
information of what the Earth
may have been like
four and a half
billion years ago,
that even a short time ago would
have been completely a mystery.
[rumbling]
[steam hissing]
NARRATOR: While the
scorching Earth slowly cools,
the sky is undergoing a
dramatic transformation.
The vast sea of stars
becomes obscured.
♪ ♪
And as the young sun rises,
color bursts across Earth's sky.
These dense gases
are the beginnings
of the atmosphere as we know it.
What this fledgling atmosphere
looked like is debated.
Because it's hard to
know the precise amounts
of the various
gases it contained.
Gases like methane.
PIERREHUMBERT: If
there's enough methane,
it can reach a concentration
where it starts breaking up
under the action
of ultraviolet light
and then recombining
into longer molecules,
making these smoggy substances.
That can actually
make these hazes
which cause an orangey glow.
♪ ♪
NARRATOR: With enough methane,
thick, intermittent orange hazes
would have covered the planet.
TIKOO: There was
probably carbon dioxide.
There might have been
carbon monoxide, water vapor.
There might have been
some nitrogen or cyanide.
All in all, it was a pretty
noxious combination of stuff.
HAZEN: If you were
dropped onto early Earth
and experienced
that early atmosphere,
you'd die very quickly
because there was no oxygen.
Carbon dioxide, some
of the other molecules
that might have been
present in the atmosphere,
you just simply
couldn't live on those.
♪ ♪
NARRATOR: And the planet is
inhospitable for another reason...
The landscape has never
seen a drop of liquid water.
But Earth does have water.
[thunder crackling]
It is suspended high
above the searing surface,
pumped into the
atmosphere by volcanoes
as water vapor with
the other early gases.
♪ ♪
[woman vocalizing,
thunder crackling]
If this ocean in the sky
could reach the ground,
it would have the power to
utterly transform the planet.
[water rushing]
[roaring]
♪ ♪
Today, over 70% of our world
is covered in water.
A planet of abundant blue
with endless rivers,
freezing icebergs,
and vast oceans.
♪ ♪
GIRGUIS: Water that
we get out of our tap
has been through a long journey.
♪ ♪
DOTTIN: And the
water on our planet
gets incorporated into
various aspects of our life,
including weather,
into the food that we eat.
And because of this,
the water is recycled
over and over and over again
throughout Earth's history.
WONG: So the water that we drink
was consumed by dinosaurs
and had the first microbes
swimming around in it. [laughs]
[distant rumbling]
NARRATOR: On the early Earth,
water is stuck in
the atmosphere.
[wind howling,
thunder crackling]
But that is about to change.
♪ ♪
High up in the sky,
droplets of water,
just a fraction of a millimeter
across, are condensing.
So light and small,
they just float,
drifting in the air.
Colliding and
merging with others...
[squishing]
they slowly grow until
a tipping point is reached.
♪ ♪
Earth's gravity draws
them downwards...
but the journey is short-lived.
The planet is still hot.
[sizzling]
So any drops
nearing the ground...
[hissing]
simply evaporate.
♪ ♪ [wind whipping]
But over time,
that heat is radiating
out into space.
Earth is cooling down.
[wind whistling]
[fizzing]
♪ ♪
[thunder booming]
[rain falling]
[lightning crackling]
A deluge of rain
begins to pour
down on the surface.
[booming]
[rain pelting down]
Huge storms sweep
through the atmosphere.
[thunder rumbling]
Oceans of water are
dumped onto the land.
[rain pouring]
[thunder rumbling]
♪ ♪
[lightning striking]
The atmosphere has
unleashed a key molecule for life.
Water changes the surface
of a planet.
It evaporates,
it allows clouds to form
and rain to fall,
it erodes things,
and it also became a medium
that would
eventually harbor life.
[wildlife chittering]
Without liquid water,
we certainly would not
get life as we know it.
♪ ♪
LANE: Things that
life needs it to do
here on Earth,
to have structures like cells,
for example,
and all kinds of machinery
that operate in water,
that works really well.
♪ ♪
NARRATOR: The early atmosphere
had started a transformation
that would set our planet apart
from every other
in the solar system.
♪ ♪
The young planet is only a
few hundred million years old.
The atmosphere has
made Earth a water world.
[waves crashing]
♪ ♪
And in that water, something
remarkable is happening...
♪ ♪
Arguably, the most pivotal
moment in Earth's history.
It would lead to the reshaping
of the entire atmosphere.
♪ ♪
So much of this
moment is still a mystery.
But we do know
that one day on Earth,
complex molecules come together
to form something never
seen on the planet before...
Life.
WONG: The origin of life
is one of the greatest
questions in science,
and it's fair to say that
we don't know when,
where, or how life started.
♪ ♪
[waves crashing]
NARRATOR: A shallow rock
pool is one of the leading theories.
ANDERSON: People
think that shallow pools
would have been
a potentially important site
for the origin of life,
because they can get wet and dry
over and over again.
[waves lapping]
LYONS: Through this repeated
cycling of wetting and drying,
reflooding and evaporating,
maybe through a tide,
maybe through
seasonal variation,
more and more complex
molecules can form.
ANDERSON: And that process
could've been the precursors
for things like DNA,
which is what makes up
the information
in our cells today.
NARRATOR: But there
are many other theories
about how life
could have started.
♪ ♪
LINGAPPA: Some scientists think
life began in a deep
sea hydrothermal vent.
LANE: Hydrothermal
vents are sources of gases...
Like hydrogen
sulfide, for example...
And provide the kind
of reactive conditions
between hydrogen and CO2 to
make the building blocks of life.
♪ ♪
LINGAPPA: Others think that
life originated somewhere
completely else,
not on the Earth at all,
and landed here on a meteorite.
[crashing, booming]
All of these different theories
have sort of different details,
but the punchline is
that life needed water,
and it needed a way
to harness energy.
♪ ♪
NARRATOR: Scientists
have some idea
what early life might
have looked like.
The very first lifeform
that existed was probably
a little bit of genetic material
enclosed in a bubble
of fatty material.
♪ ♪
NARRATOR: And while simple,
some of these early organisms
would have a powerful
effect on the atmosphere.
We think that one of
the earliest organisms
were organisms
that produce methane
as part of the way they
eat, and breathe, and live.
♪ ♪
NARRATOR: They take in
carbon dioxide and hydrogen,
producing water and
methane as waste products.
LYONS: So it is
reasonable to estimate
that a vast portion of
the early atmosphere
contains large
amounts of methane.
♪ ♪
NARRATOR: This increased methane
could have made the
orange hazes thicker.
The evolution of our
atmosphere is, in many respects,
the story of the evolution
of life on our planet.
[wind howling]
Life can change a
planet fundamentally.
But it's always this cause
and effect kind of dance
between the
environment changing life
and life changing
the environment.
♪ ♪
NARRATOR: And it's the story
of life that reveals how we got from
this orange hazy atmosphere
to the blue, oxygen-rich
one we know today.
♪ ♪
This young world is not
one we could survive in.
Earth's early oceans
are blue-green,
full of dissolved iron,
and they've absorbed large
amounts of carbon dioxide,
making them acidic.
[waves crashing]
ANDERSON: Early
life would have been
adapted specifically to
living in high temperatures
or fairly acidic conditions.
ROTHSCHILD: The ultraviolet
radiation was incredibly harsh
because there
was no ozone layer.
Furthermore, there was no
oxygen in the atmosphere;
it was a very
different composition.
NARRATOR: And some
organisms today offer clues
to how life survived in
this early environment.
♪ ♪
High in the Andes is one of
the largest geyser
fields in the world.
♪ ♪
LINGAPPA: This environment
is extreme for a lot of reasons.
First of all, the
water that's coming
out of this pool
is boilingly hot.
And the altitude means
that this environment is subject
to a lot of ultraviolet
radiation from the sun.
NARRATOR: These are conditions
most animals would find toxic.
But amongst the
boiling water and steam,
life is flourishing.
LINGAPPA: So the
colors that we see
in these mats around this pool
are billions of
thriving bacteria
that have sort of
carved out a niche
in this extreme environment.
It's incredible to
find so much life,
not just surviving, but
thriving in these conditions.
NARRATOR: Organisms like
these are called extremophiles.
They can survive in
environments most complex life
would struggle to live in.
LANE: We call them extremophiles
because we didn't really
think that life could exist
in such extreme conditions.
ROTHSCHILD: In fact,
we know of organisms
that can live up
to 122 centigrade.
So this is well over the
boiling temperature of water,
and, conversely, we know of ones
that can live well
below freezing.
Bacteria could
survive in outer space
quite comfortably as well.
These are behaviors that
we consider to be extreme
because we would die in them.
NARRATOR: Today,
life on Earth is prolific,
thriving in the most
unlikely of places.
From under ice sheets,
to acid-filled pools,
and the dark, high-pressure
depths of the oceans.
And researching these
modern extremophiles
can hint at what was happening
in the early atmosphere.
LINGAPPA: There's
been extremophiles
as long as there's
been life on Earth.
Studying today's extremophiles
expands our understanding
of what life can do
and what life can look like,
including trying to understand
the earliest life and our
most ancient ancestors.
GIRGUIS: Life originated
on an earth without oxygen.
So looking at the
microbes that live
in areas without oxygen
helps us understand
how they evolved
to do well in those
environments.
[water fizzing]
NARRATOR: But evolving to
live in one very specialized habitat
can have its drawbacks.
At this period of
time in Earth's history,
life would have been
limited in its energy sources.
LINGAPPA: If you're dependent
on something that's being
released from a vent in order
to generate energy to
be alive, you're going to be
extremely limited in
how fast you can grow.
NARRATOR: Because the
energy sources early life used
to survive in the oceans
were comparatively rare,
organisms struggled
to proliferate.
PIERREHUMBERT: They
had to take various chemicals
that were produced by geology
and then combine
them to release energy.
WONG: But there's about to be
a grand innovation
by life that will open up
a nearly limitless
source of energy.
NARRATOR: An innovation
that would also change
the course of the
evolution of the atmosphere.
♪ ♪
Today, life can be found
in puddles, lakes, and
oceans across the planet.
[waves crashing]
LINGAPPA: Our world today
is absolutely teeming with life.
Just a single drop of
water from the ocean
would contain tens
of thousands of cells,
and among them, you would find
organisms called cyanobacteria.
NARRATOR: There are over
and they come in
all shapes and sizes.
From long filaments
to geometric shapes.
LYONS: Cyanobacteria evolved,
as best as we understand,
around three billion years ago.
They are astounding, in that
they have the ability to adapt
to environmental change,
and to change the environment
because they can be so abundant.
NARRATOR: Cyanobacteria
sometimes changed
their local environments
by creating structures,
which they used
as habitats to live in.
This is one of the clear-cut
examples that life was living
even three billion years ago.
This is a formation
called a stromatolite.
It's really inspiring that you
can pick up a rock like this
and read the history
of what was happening
billions of years ago.
That's an amazing book to read.
♪ ♪
LINGAPPA: Cyanobacteria
are some of the most
successful organisms
ever to live on our planet.
They completely
transformed the world.
NARRATOR: This
transformation was due
to a revolutionary process
that changed the fundamental
composition of the atmosphere.
Around three billion years ago,
Cyanobacteria are
developing a unique way
to produce energy.
They capture sunlight
and use it to combine hydrogen
from nearby water molecules...
with the carbon dioxide
dissolved in the oceans.
With this, they make
carbohydrates...
And a very reactive
waste product...
Oxygen.
LINGAPPA: So this
vial contains a culture
of cyanobacteria that I grew.
And these are
cyanobacteria of today,
but they are descended
from the organisms
that first evolved the ability
to do oxygen-producing
photosynthesis.
LANE: There are these
moments in the history of life
that seem to have
only happened once.
Oxygen-producing
photosynthesis is one of them.
Was it a freak accident?
We just don't know.
Suddenly, the oceans
became the fuel.
It allowed life to scale
up at least tenfold.
NARRATOR: Lifeforms
can now make energy
using one of the most
abundant raw materials
on the planet's surface: water.
This kind of photosynthesis
now enables organisms
to get energy from
virtually anywhere,
allowing them to spread
throughout the oceans.
One cyanobacteria
cell becomes two;
two become four.
Multiplying again and again...
until there are trillions.
And we can still find evidence
of them everywhere we look,
including in the
harshest environments.
LINGAPPA: If you
look really closely
in the mats in this pool,
you can see in some
of these greener areas
little bubbles that
are literally the oxygen
being produced by them
doing photosynthesis right now.
Cyanobacteria demonstrate
the power of life on Earth
like nothing else does.
Over two billion years ago,
the ancestors of these
extraordinary microbes
unlocked this
spectacular ability.
LANE: Cyanobacteria
were the first,
and the only, organisms
that ever evolved
oxygen-producing photosynthesis.
As soon as they
cracked the problem
of how to use water as a fuel,
the oceans became
the fuel, and they could
live almost anywhere.
These are seaweeds
from the ocean...
Ooh, right off the West
Coast of Scotland...
And oxygen-producing
photosynthesis
was such a brilliant innovation,
that some organisms at that time
actually swallowed
the cyanobacteria,
and that's how we
got algae like this.
And then the algae
ultimately gave rise
to the plants, as well.
[thunder rumbling]
NARRATOR: While life was
spreading through the oceans,
above the waves,
the atmosphere
was also undergoing
a dramatic transformation.
♪ ♪
Over millions of years,
tectonic movements in the earth
are forging the first
large-scale landmass.
And this directly affects
the dynamics of the atmosphere.
♪ ♪
[wind howling]
Air warmed by the new land
drives novel weather
patterns across the globe.
[wind blowing]
[thunder rumbling]
Winds sweep dust
high up into the air,
where tiny particles
seed vast pillars of clouds.
♪ ♪
Something resembling our
modern-day weather system
is, at last, taking shape.
HAZEN: The appearance
of large continental masses
had a huge impact
on the atmosphere.
We would have seen
high-pressure systems,
low-pressure systems,
prevailing winds, rains,
very much like the modern world.
♪ ♪
NARRATOR:
Meanwhile, in the oceans,
trillions of cyanobacteria
are photosynthesizing
and producing oxygen.
The first time it
has ever been made
in significant amounts on Earth.
Oxygen bubbles race upwards.
♪ ♪
But most vanish before
they can reach the surface.
[waves crashing]
Earth's early atmosphere
seems destined
to stay as thick orange hazes.
So what is making
the oxygen disappear?
The answer lies in a
unique property oxygen has.
Oxygen is an extremely
reactive element.
DOTTIN: What's
unique about oxygen
is that it has a chemical makeup
that allows it to bond with
so many different elements;
almost all of the
elements that exist.
NARRATOR: And this
incredible reactive power
is the reason many
scientists think
oxygen struggled
to escape the water.
♪ ♪
Around three billion years ago,
Earth's oceans were packed
full of dissolved metals.
Metals like iron.
This key that we see here
is rusty,
and in order to form rust
we need three ingredients.
The first is iron, which is
what this key is made of,
the second is water,
or water vapor in the air,
and the third crucial ingredient
is oxygen.
NARRATOR: And in
Earth's early oceans,
oxygen began to react more and
more with iron and other metals,
as cyanobacteria
spread across the oceans.
♪ ♪
Below the surface...
it's raining.
As oxygen and iron interact,
rust particles
form in the water,
and sink down to the seabed...
trapping the oxygen and iron
to form solid rock at
the bottom of the ocean.
Vast swaths of
the water turn red.
LYONS: There were many,
many ingredients in the ocean
at that time that would
readily react with oxygen.
HAZEN: So there was no
way for atmospheric oxygen
to build up to any
significant level.
[seagulls calling]
NARRATOR: A
record of the reactions
that happened long
ago can be seen
in formations today.
This is a sedimentary rock,
meaning it's made up
of many different layers
that were all deposited
on the sea floor
over millions of years.
NARRATOR: And
this sample is evidence
of how iron can react
to form solid rock.
This particular sedimentary rock
is a banded iron formation,
and we can see red color
in the rock here,
and that red is evidence
of iron oxidation or rust.
NARRATOR: As these
reactions continued,
the metals in the ocean water
started to diminish,
locked away in the seafloor.
LINGAPPA: Eventually,
the oceans would have
been depleted of the things
that would readily react
with the oxygen that
was being released.
NARRATOR: But cyanobacteria
continued to produce oxygen.
♪ ♪
For up to half a billion years,
this oxygen has been trapped
in the oceans.
But now, increasing
amounts are free to escape.
[water bubbling]
♪ ♪
Over just a few million years,
oxygen floods into
the atmosphere.
[bubbling intensifies]
♪ ♪
The very composition of the
atmosphere itself is changing.
♪ ♪
This is known as the
Great Oxidation Event.
DOTTIN: The Great
Oxidation Event
was one of the most significant
periods in Earth's history.
♪ ♪
It was a period of time
over which oxygen built up
in the atmosphere.
LINGAPPA: Not only did it
completely change
the environment,
it also completely
changed the possibilities
available for life.
ROTHSCHILD: It is almost
impossible to
overstate how important
the production of
oxygen on the Earth was
to the history of planet Earth.
All of a sudden, new
chemical possibilities arose
all over the surface of Earth,
and amazing
changes were to follow.
NARRATOR: Oxygen is
used by organisms today
to release energy
from the food they eat,
so their bodies can use it.
And since oxygen is so reactive,
this energy release is immense.
ROTHSCHILD: If you use oxygen,
you are 19 times more efficient
than an organism that
doesn't use oxygen.
♪ ♪
NARRATOR: Because
of its reactive power,
one of the first consequences
of oxygen in the atmosphere
is on the rocks themselves.
Now, depending
on your perspective,
oxygen can be a creative
or a destructive force.
♪ ♪
NARRATOR: As it spreads
through the atmosphere,
oxygen begins
to react vigorously
with the surface of the Earth.
Rocks with metals
like iron react
with the oxygen and crumble.
All the elements are in place
for vast dust storms to form.
The young world is being
ripped up by its own atmosphere.
Earth's surface
is changing color
as new minerals are created.
TIKOO: We had the
formation of all these minerals
that did not exist prior
to the Great Oxidation Event.
Copper minerals like these,
blue and green minerals,
yellow and orange,
uranium minerals,
minerals of molybdenum,
minerals of nickel,
minerals of cobalt,
color of the rainbow,
all in new minerals
form because of the
Great Oxidation Event.
NARRATOR: It
isn't just minerals.
Oxygen also makes
key nutrients vital for life
far more available
by reacting with a number
of elements to form acids.
Things like sulfuric acid
and nitric acid,
and acid has this property
that when it rains out onto
the surface of the earth,
it can dissolve rocks,
cause weathering
and runoff of
nutrients and minerals
into lakes and oceans.
HAZEN: Those nutrients flowed
into the ocean, there were
new opportunities for life.
It really was a game changer.
LYONS: And as oxygen began
to increase in the atmosphere,
the relatively minor elements
that are essential for
all the processes of life
became more abundant.
In many cases, those are metals.
♪ ♪
LINGAPPA: Life on Earth evolved
because of the conditions
that the Earth provided.
But, in turn, life has
completely remodeled
the planet, and the
world that we know today
is, in so many ways,
been created by life.
[flamingos squawking]
♪ ♪
NARRATOR: This co-evolution
of earth and the atmosphere
is apparent everywhere we look.
[waves crashing]
ANDERSON: These
particular cliffs were formed
when dinosaurs walked the earth.
But the beautiful
red that you can see
in these bands here is formed
from the iron in these cliffs
combined with water and
oxygen to create iron oxides.
So we see an example of oxygen
changing the very landscape.
NARRATOR: Oxygen transformed
our oceans, reshaped our land,
and became a vital
ingredient for life today.
But this volatile gas
was to have one more
dramatic impact on the world.
♪ ♪
Across the globe,
oxygen levels are rising,
slowly enriching the air,
reacting with the methane
to form carbon
dioxide and water.
[waves crashing]
Over millions of years,
the orange hazes
are fading away.
Sunlight is scattered by
the nitrogen and oxygen,
producing Earth's
first oxygen-rich
blue skies.
♪ ♪
In the upper atmosphere,
ultraviolet light from the sun
causes the oxygen to form
a new protective molecule...
ozone.
HAZEN: Ozone is made
of three oxygen
atoms bonded together,
and they absorb ultraviolet
radiation really well.
So, if you put a
little bit of ozone
in the atmosphere,
it's like sunblock.
NARRATOR: The level of
oxygen in the atmosphere
will fluctuate over the
next two billion years,
but eventually, reach
the 21% we have today.
♪ ♪
But the story of our
atmosphere is not over.
It will continue to evolve,
both naturally, and under
the influence of human activity.
ROTHSCHILD: If
we don't understand
the history of the atmosphere,
how can we possibly
be the stewards
of the atmosphere
moving forward?
PARAI: Because our
atmosphere is totally unique,
there's nothing
like it that we found
on any other planetary body.
WONG: Our atmospheric
composition may actually be
the thing that is screaming
out to the cosmos,
a signal to the
universe that we're here,
that life exists on our world.
DOTTIN: But then,
in many ways, we're
going back in time,
where we're putting all of
the chemicals that are toxic
to life into the atmosphere.
WONG: Over the past
couple hundreds of years,
humanity has made a difference
in the chemical composition
of our atmosphere,
most predominantly
through the release of
carbon dioxide, and this causes
myriad effects on our world.
HAZEN: The
atmosphere isn't fragile.
But we are.
We can make changes
to the atmosphere
that will make Earth
a very unpleasant place to live.
And so we need
to look to ourselves
when we think about
changes to the atmosphere.
LINGAPPA: We have immense power
over our planet.
Our atmosphere is precious.
And, if we change it too much,
the whole world
will pay the price.
[magma rushing]
GIRGUIS: But by understanding
the huge and complex steps
it took to develop our
atmosphere, hopefully,
we can develop approaches
to take care of it for
generations to come.
♪ ♪
ANNOUNCER: On
"NOVA: Ancient Earth"...
People thought it was
an outrageous idea.
The planet completely
encased in ice.
CECILIA SANDERS: Some of
the deepest, most intense cold
Earth has ever experienced.
JAZ MILLAR: Life survived events
that scientists previously
thought were unsurvivable.
SUSANNAH PORTER:
But, for life to flourish again,
we would need some
kind of drastic change.
[expl*si*n roars]
ANNOUNCER: "Frozen," on "NOVA."
Next time.
SINGER: ♪ Wish I
could go back in time ♪
♪ ♪
♪ ♪
♪ ♪
♪ ♪
♪ ♪
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50x11 - Ancient Earth: Birth of the Sky
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Nova often includes interviews with scientists doing research in the subject areas covered and occasionally includes footage of a particular discovery.
Nova often includes interviews with scientists doing research in the subject areas covered and occasionally includes footage of a particular discovery.