The heavens. The great bowl of the
heavens, of our sky.
Just so beautiful!
I love the sky because, wherever I am
in the world, if I can find
some space, I can look up at this
big, blue, pristine space.
And I like the apparent permanence -
the fact that I can stare into
a sky that the dinosaurs stared into,
that Neanderthals stared into.
The atmosphere is essential for the
Earth to be habitable at all.
This thin layer of gas that clings to
our planet,
keeps liquid water on the Earth's surface
and shields life from the most harmful
of the sun's rays.
As far as we know, our thin blue line
is unique
in the vast void of space...
..and today, scientists are beginning
to piece
together just how our planet got its
special blue bubble.
By going back to the Earth's earliest origins,
we can now tell the almost implausible
story of our atmosphere.
How it emerged from a toxic orange hell...
..and transformed the planet from an
exposed ball of rock...
..to a beautiful, living world...
..capable of nurturing a staggering
abundance of life.
This atmosphere has been the planet's
great protector
for 2.5 billion years,
soaking up everything that our planet
has thrown at it.
It's a thin, delicate, fragile cloak
that shields
and protects all life on Earth.
Our atmosphere is a unique mix of
gasses not found anywhere
else in the solar system,
gasses that allow Earth to be a
living, breathing world.
78% of our atmosphere is nitrogen,
which can be taken up by
bacteria in the soil and plants, and
it's an integral part of DNA.
21% of our atmosphere is oxygen.
It's there for animals to breathe, but
also for many living things
to use to convert their food into energy.
Even less abundant gasses are crucial
for sustaining life.
A fraction of a percent is water
vapour, which condenses
and falls as rain,
and a tiny amount is carbon dioxide,
which might be a waste product to us
but it's absolutely
essential for plants when it
comes to photosynthesis.
It almost appears that this unique
c*ck of gasses
is here as a sort of life-support system.
So, where did this beautiful
atmosphere come from
and how did it lead to the origins of
life here?
Well, to answer that, we need to go
back to the very beginning...
..4.6 billion years ago.
Our Earth began as nothing more than
dust and gas.
A nebulous cloud containing every
element our new world would need.
Over tens of millions of years, the
cloud begins to clump together,
forming rocks.
Pulled together by gravity...
..they grow bigger and bigger...
..until, finally, a new world is formed.
Asteroids rain down on the young Earth
for hundreds of millions of years...
..its molten surface still searing
from the heat of its creation.
But something is missing.
The colour blue.
You see, the Earth has no atmosphere.
The sun and the newly formed moon sit
in a jet-black sky.
This is how the Earth could have remained...
..a lifeless ball of rock, floating in
the void of space.
This is what the surface of the Earth
may have
looked like 4 billion years ago.
Stark, brutal and yet,
in some ways, beautiful landscape.
The early Earth was little more than a
ball of cooling rock,
so where did the planet's first
atmosphere come from?
Now it might surprise you, but I've
got some clues to the answer
to that question in my pocket,
in the form of this tiny,
but extremely rare and valuable,
granular piece of rock.
This, you see, is a carbonaceous
chondrite meteorite,
and it was formed at the same time our
solar system was formed -
and I've got it in my hand!
I am holding the history of our solar system
and the Earth in my hand.
4.5 billion years ago, trillions of
tonnes of this
type of material came together to form
our planet.
These meteorites are leftovers from
the Earth's creation.
So, through chemical analysis,
scientists can discover the raw
ingredients that made our world.
These meteorites contain heavy
elements, like iron,
and the rocky constituents that formed
the planet itself.
But chondrite meteorites contain
lighter elements too.
Chemical analysis reveals that these
rocks contain carbon,
hydrogen and sulphur,
and we can still see them belching as gasses
from volcanic vents around the world today.
When combined, these elements form new
compounds like methane,
carbon dioxide and hydrogen sulphide,
which are light enough to exist as gasses
but not so light they drift off into space.
So, meteorites like this weren't just the
building blocks of our planet -
they contained the essential
ingredients for its atmosphere.
And 4.5 billion years ago,
that had begun to change everything.
The ancient Earth holds within it
everything it needs to create the
first atmosphere.
Those ingredients just have to make it
to the surface.
But deep within the young Earth,
something is stirring.
Across the globe, molten magma races
up from within...
..and these rivers of liquid fire
unleash gasses that will
transform our planet.
The world is smothered by a thick
toxic fog.
As the sun creeps above the horizon,
gas scatters the light.
Earth gets its first colour-filled sunrise.
This new world now has an atmosphere...
..but one like nothing we've ever seen.
We're all familiar with the colours in
the early-morning sky,
but a sunrise 4 billion years ago
would have been very different.
Sunlight passing through that churning
mixture of methane
and carbon dioxide would have given
the whole planet an orange hue.
But this toxic atmosphere was very important.
It was the first time that our planet had
a protective shield from space.
But, of course, it was still a very
alien world -
would have been to us - and not just
because of that noxious
orange fog, or the searing, hot,
black, bare volcanic rocks
beneath our feet.
It was because something fundamental,
something that we take for granted
every day, was missing.
Water.
Today, 70% of the Earth's surface is
covered in water.
A planet of almost limitless blue...
..with endless rivers...
..freezing ice caps...
..and turquoise tropical paradises.
But 4.5 billion years ago...
..there wasn't a single drop of liquid water
on the ancient Earth's surface.
However, the planet wasn't totally dry.
The young atmosphere did contain water.
Asteroids and volcanic eruptions have
released a vast
ocean of water vapour.
Trillions of droplets were floating in
the sky...
..so small they soar on moving air.
Colliding and merging with each other,
they slowly grow...
..until they can no longer fight
Earth's gravity.
En masse, they are pulled downwards,
towards the ground.
But with the atmosphere still
scorchingly hot from heat
trapped by Earth's formation...
..not a single drop of rain...
..has ever made it to the surface.
And it's been the same story every day
for tens of millions of years.
The Earth is stuck - a barren desert world
totally incapable of supporting life.
Water today is on a continual journey.
It emerges from the leaves of green
plants as vapour,
rises up to the sky, where it forms clouds,
which then condense into rain,
which falls onto the ground, which
drains into the rivers,
which eventually flow into our vast oceans.
And we're very used to seeing water
appear out of our atmosphere.
What about those lovely soft layers of
mist that we see over rivers,
or the dew on your toes if you scuff
across a summer lawn,
or when it falls as rain or snow?
The only reason our planet is a water
world is because it's the
right temperature and pressure for
water to form out of the atmosphere.
4.4 billion years ago, Earth needed to
cool down.
Slowly, heat has been radiating out
into space...
..over millions and millions of years.
Until...
..a tipping point is reached.
What starts with just a few drops
becomes the greatest deluge
the solar system has ever seen.
Huge weather systems sweep across the planet
and storms which last centuries dump
oceans of water from the skies.
A key element in the equation of life
had been
well and truly unleashed.
Our planet is transformed.
As the Earth continued to cool, the
rains that fell from its thick,
dense atmosphere created a new water world.
And for the first time in its history,
it would have looked a little bit like
this.
If you gazed into the sky, you would
have seen clouds,
you would have felt the wind and the
rain on your face.
And if you listened,
you'd have heard waves carving a new coastline.
But that's where the similarities
would have ended,
because this rocky, wet world was
devoid of life.
But it was a world where life could begin.
Water was the crucial ingredient.
Not long after Earth's oceans rained
from the sky,
a shallow pool was about to play host
to the most important
moment in the history of the Earth.
So much of how life began is still a mystery.
It's not known exactly when, where or
how it happened.
But we do know that, one day on Earth,
a living thing came into existence.
The first microscopic organism.
And in that instant of pure chance,
everything changed.
The Earth became a living world.
All trace of the first life has
vanished, lost to history.
But even today,
we can get clues as to what early life
might have been like.
High in the Andes is one of the
largest geyser fields in the world.
The water in this vent is boiling at
85 degrees Centigrade
and NASA scientists have looked into
this water and found
that it contains one of the highest
concentrations of arsenic,
a serious toxin, anywhere in the world.
And these toxic conditions are similar
to those
found on the early Earth.
But amongst the poison and boiling water,
something ancient is flourishing.
Just look at all of these beautiful
colours here.
That's life - a primordial mat of
billions of thriving bacteria.
These hardy bacteria are called
extremophiles and, just
like their predecessors, they've
adapted to live in this hot water.
In fact, they've carved out a niche
where they can proliferate.
There are a great range of species
here and an enormous
number of individual organisms.
Which just goes to show that even the
simplest life is inherently
flexible, adaptable and tough.
So, perhaps it's not surprising that
that early life grabbed
an opportunity to try and live in an
environment which, for us,
is incredibly harsh and hostile,
but where they could prosper.
Today, life is prolific.
It thrives in the most unlikely of
places across the world.
But living in these extreme
environments comes
with severe limitations.
The extremophile bacteria living
around these
hot springs are essentially locked in,
defined by the very precise
requirements in terms of the
heat of the water and the nutrients in
it. And if we were to remove
them from this highly specialised
environment, they would likely die.
And things were pretty much the same
for early life on Earth.
It was essentially stuck, trapped in
the niches that it evolved to
survive in. And because all of the
nutrients were in the water,
the option for life on land simply
wasn't there.
Early life wasn't prolific,
widespread, or even visible.
The ancient Earth is harsh and unforgiving...
..with barren black land...
..and acidic green oceans.
But the biggest barrier to life's
flourishing is the atmosphere,
toxic and orange.
An atmosphere in constant turmoil.
Tectonic movements in the Earth's
crust drives land formation,
which in turn creates massive
atmospheric instability.
Vicious winds sweep dust high up into
the air...
..and these dust particles create more clouds.
Storms rage across the planet, laced
with poisonous gasses...
..deadly to the vast majority of life
we know today.
But whilst chaos rages above the
waves, deep underwater
our ancestors are simply existing,
seemingly trapped...
..with no means of escape...
..day after day, for nearly a billion years
where nothing appears to happen.
Today, life is no longer confined to
the water.
Oh, yes, what a view!
Both life and the atmosphere that
supports it have undergone
an astonishing transformation.
It's a male.
It's got the comb on top of its head
and its feathers are all silvery,
rippling in the wind as it glides
along the edge of this escarpment.
With a wingspan of more than 3m,
the giant Andean condor is one of the
largest birds on Earth.
Oh, goodness me! Look at that!
Absolutely sensational. Now I can see
its eye.
I'm looking into the eye of an Andean condor.
Oh!
It's ornithological nirvana!
Watching these giant birds soaring here
just reveals how their life is
completely intertwined with
that thin cloak of air that's wrapped
around our planet.
But then, when you think about it,
everything - every plant,
fungi, every bacteria, every tiny
insect, every giant reptile,
even us - are completely dependent on
this atmosphere.
So, how DID the atmosphere go from a
toxic orange haze to the
nurturing c*ck of gasses we know today?
Well, it was life itself that would
make the difference...
..thanks to a giant evolutionary leap.
The development of complex life was
far from inevitable.
When you think about it,
there are plenty of forks in the road
of evolution,
trillions of dead ends
and there is no definitive end point.
But the very fact that we exist proves
that whatever card
is thrown at life, it plays it and it survives.
And that's precisely
what was happening 3.5 billion years ago.
Life was playing its card - slowly
evolving, gently proliferating -
and it wasn't quite as stuck as we
might have thought it was.
In fact, a significant development in
a single cell was about to
change the way that life could exist.
Life was about to take a quantum leap forward.
A leap, that would change our
atmosphere forever.
It started with a mutation that
altered the fundamental
chemistry of the cells...
..giving them the ability to capture
the sun's rays...
..and store the energy as glucose,
energy the cells can then use to grow
and reproduce.
This was photosynthesis...
..an evolutionary innovation that will change
the course of Earth's history forever.
The ancestors of this cell are still
around today.
They can be found in almost every
puddle, lake,
sea or ocean across our planet.
Peering down through this microscope
is like taking a look
back at life on Earth almost 3.5
billion years ago.
You see, these rod-shaped structures
here are cyanobacteria,
and we think they're pretty similar to
those that existed
trillions of generations ago, when our
atmosphere was very different.
Now, they may not look impressive, but
I've got to tell you,
they're probably one of the most
successful organisms to ever live.
A little over 3 billion years ago,
these tiny flecks,
these microscopic organisms
just a fraction of a millimetre
across, started to build
an atmosphere which humans could live
and breathe in.
Thanks to energy from the sun, these
cells are able to steal
hydrogen from water molecules and
combine it with the carbon dioxide
dissolved in the oceans, fabricating
essential tools for life.
Individually, these revolutionary
cells,
which you can still find in water
bodies like this all across
the planet, produced a negligible,
unremarkable, nonexistent effect.
But when they combined in their trillions,
when they combined en masse, they were
about to demonstrate,
for the very first time, the awesome
power of life on Earth,
and that would have a profound,
long-lasting
physical resonance on our planet.
Life powered by photosynthesis thrived.
Cells with this new ability to harness
energy from the sun
out-competed those that couldn't.
So, they began to multiply.
One becomes two.
Two become four.
Until there are literally trillions of offspring.
Enough to fundamentally change the
chemistry of our world.
Photosynthesis was a game-changer for
life because the
ingredients that it required were so
readily available and abundant.
But the by-products of many types of
photosynthesis include a very
reactive and dangerous gas.
Now, for these revolutionary early organisms,
this was just a waste product,
something to be thrown away.
But for the likes of you and I,
and the rest of complex life on Earth,
it's absolutely essential.
I'm talking, of course, about oxygen.
Trillions of bacteria are spread
across the ancient oceans...
..and the waste oxygen they throw away
is enough to build a new
atmosphere for our planet.
Bubbles of oxygen race upwards,
towards the surface.
But they can't escape.
The bubbles are absorbed and vanish.
Earth seems trapped, with a toxic
atmosphere of methane
and carbon dioxide.
The Earth was essentially in stasis.
You see, that toxic orange atmosphere
still enveloped
the planet.
Life was still microscopic and could
only exist in the oceans,
and there was no oxygen in the atmosphere.
To all intents and purposes, you could
say, well,
that the planet was stuck.
But that was about to change.
Because it wasn't just oxygen
dissolved in the water -
there were metals, too...
..including iron.
The iron, like oxygen, is invisible
to us when it's dissolved in water.
But we all know what happens when iron,
oxygen and water come together...
..and there's plenty of evidence of
that on this old bus.
Just look here - this lovely brown,
orange and red.
Rust.
The iron is being oxidised -
aggressively attacked
by the oxygen in the presence of
water, or water vapour.
But what's interesting is that, whilst
the iron
and whilst the oxygen are soluble in water,
the rust is not.
The newly released oxygen reacts
with the dissolved iron already present
in the oceans,
and that causes something
extraordinary to happen.
Rust pours onto the ocean floor.
The world's oceans turn red.
And if you know where to look, you can
still find evidence for this bizarre effect.
I'm armed with a rock hammer.
If I have a little tap at this stone,
there we are.
Let's have a look at what's inside.
This rock once formed part of an
ancient seafloor.
Hm, look at that.
You see that there, that red?
That's iron
laid down billions of years ago,
a volatile memory of oxygen reacting
with iron in the early seas.
A sort of geological tattoo.
I love that.
This rust was to have a profound
effect
on our Earth's young atmosphere.
For half a billion years, oxygen has
been trapped in the oceans.
But now, iron has almost been totally
flushed from the seas.
At last, the oxygen in the water has
nothing else to react with.
It can break free.
Over millions years, oxygen flooded
from the oceans...
..and our atmosphere was transformed.
When those bubbles first breached the
surface of the ocean,
you might have thought that the
atmosphere was getting
a breath of fresh air, and to some
extent it was.
But this wasn't the moment when life
suddenly flourished,
or when it developed that complete and
utter dependence that
contemporary complex life has upon oxygen.
But that's not to say that when those
bubbles first fizzed
out there that this wasn't a momentous moment.
It was.
The planet was about to be re-calibrated,
and the relationship between the ocean,
the land and the atmosphere was going
to change forever.
And as this volatile, reactive gas
flooded into the atmosphere, the
full destructive force of oxygen was
felt across the planet's surface.
Oxygen attacks the Earth.
Any rocks containing iron and
aluminium rust and crumble,
driving vast dust storms.
The world is being torn apart by its
own atmosphere...
..and this has a startling side-effect -
the entire Earth turns a vivid red.
Scientists find evidence for this red
Earth in
rock formations in landscapes all over
the world.
Direct evidence of the action of all
of those
trillions of cyanobacteria churning
out oxygen.
And before oxygen, the planet was
barren, grey and black.
You see, it's oxidation that gives us
this wonderful red hue.
But oxygen's effect on the land went further.
You see, oxygen doesn't just react
with iron -
it reacts with pretty much anything.
It attacks minerals within the Earth's crust...
..creating as many as 3,000 exotic new minerals,
all previously unknown to the solar system.
Minerals that led to an expl*si*n of
colour right across the planet.
Minerals that, to this day,
play a vital role in sustaining the
rich complexity of life we know.
Now, one of the colours unleashed by
oxygen is this rather
wonderful sea green here.
You see, when copper, the metal,
comes into contact with oxygen in the
air, it oxidises,
producing this - copper oxide.
And it turns out that this compound
was fundamentally important in the
development of more complex
life. And what's more, it retains its
biological importance today.
It's necessary for the synthesis of
neurotransmitters in our brains,
and the brains of other animals,
and also for the production of
hormones and pigments.
So, even in today's world,
life is dependent on that chemical
complexity that was unlocked
so long ago, when our atmosphere
became richer in oxygen.
Thanks to oxygen, we live in a world
of extraordinary colour
and diversity.
A myriad of minerals colours the
Earth's surface...
..and the biological world has continued
to make use of this ever-increasing
chemical complexity to transform the planet.
From the rich green carpet of plant life...
SHUTTER CLICKS
..to the fluorescent pink feathers of flamingos.
Oxygen has allowed life to flourish in
ways unimaginable
3 billion years ago.
But this volatile gas had one more
gift to bestow.
As oxygen enriches the atmosphere, it
reacts with methane,
stripping it away.
And as methane levels drop, the orange
haze lifts.
Nitrogen and oxygen in the atmosphere
are left
to scatter the light.
The colour begins to change.
For the first time in Earth's history,
the sky
is an oxygen-rich, brilliant blue.
Today, this lovely thin blue line
marks our Earth as unique
in the entire known universe.
It's a spectacular demonstration of a
4 billion-year
dance between our atmosphere and life -
an atmosphere that was
created, shaped and calibrated by life itself.
Our planet went from volatile, fiery
and dead to the beautiful
living and breathing blue bubble
floating in the darkness of space.
How do scientists unravel billions of
years of our planet's history?
In this episode, we saw how meteorites -
rocks that have fallen from space -
can tell us what Earth's early
atmosphere was made from.
- This is a chondrite meteorite.
4.567 billion years old -
the oldest thing you could hold in
your hand -
and it's made of all these tiny droplets
that were part of the earliest solar
nebula, including
all the gasses that eventually would
wind up in the atmosphere.
- Meteorites are so valuable to science
that researchers go to great lengths
to track them down.
In 2020, scientists from the
University of Manchester set out
on a nine-week expedition to one of
the most remote areas of Antarctica.
- Meteorite hunters go into the depths
of Antarctica,
into the extremes of the cold, near
the South Pole, because
they can find so many meteorites in
one expedition, because the
meteorites show up so well on the
white ice...
..compared to, say, other places where
the meteorites are
very hard to spot from normal rocks.
- Studying meteorites has helped
answer some of the most
fundamental questions about our planet.
- So, the question of where the water
on Earth came from
and when it arrived is really central
to everything.
- Some water was present in the
material that formed our planet,
but that's not the whole story.
- We think that one of the other ways
that the Earth got its water
is through meteorites.
So, these meteorites would have had
water locked into their rocks,
or perhaps even on their surface, as
frozen, in outer space.
And then, the water would have been degassed
into our atmosphere as water vapour.
Later on, when the Earth cooled even further,
that atmosphere would have condensed
and the water vapour would have then
formed liquid water on our surface.
- Scientists think it's only after the
arrival of water that life
was able to get started.
- 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.
- A shallow rock pool is one of the
leading theories.
- 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.
- Through this repeated cycling of
wetting and drying,
re-flooding and evaporating, maybe
through a tide, maybe through
seasonal variation, more and more
complex molecules can form.
- And that process could have been the
precursors for things like DNA,
which is what makes up the information
in our cells today.
- But there are other theories.
- Some scientists think life began in
a deep-sea hydrothermal vent.
- Hydrothermal vents are sources of gases,
like hydrogen sulphide for example,
and provide
the kind of reactive conditions to
make the building blocks of life.
- Others think that life originated
somewhere completely else -
not on the Earth at all - and landed
here on a meteorite.
- All of these different theories have
sort of different details,
but the punch line is that life needed water
and it needed a way to harness energy.
- Although life's origins are still debated,
scientists have some idea when it happened.
- This is one of the clear-cut
examples that life was living
even 3 billion years ago.
This is a formation called a stromatolite.
What you're looking at shows a structure
created by a lot of microorganisms,
single-celled organisms.
And as they grow and they reach for
the light, they secrete various
gluey substances that glue together
bits of sand in the environment,
and that actually helps keep it from
dispersing and blowing away.
- 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.
- These fossilised structures were
created by cyanobacteria
and millions of them can still be
found along the coast
of Western Australia.
- Cyanobacteria might not seem so impressive,
but they're probably one of the most influential
and successful organisms ever to
appear on planet Earth.
- They were the organisms that
invented this ability to
break water into oxygen and hydrogen
and spit out that oxygen.
- That oxygen was able to get released
into our atmosphere.
- They completely transformed the world.
- 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.
- The evolution of our atmosphere is,
in many respects,
the story of the evolution of life on
our planet.
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.
- The story of our changing atmosphere
is not over.
It will continue to evolve both naturally
and under the influence of human activity.
- If we don't understand the history
of the atmosphere,
how can we possibly be the stewards of
the atmosphere moving forward?
- 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.
- Next time...
..the making of the modern world.
How the end of the dinosaurs...
..through cataclysm and chaos,
set the stage for a human planet...
..to take its place.
If the Earth could talk, what would it
tell us?
Well, the Open University imagine how
it might answer
some of our questions.
To experience this interactive
presentation, go to the
website on the screen and follow the
links to the Open University.
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