Original subtitles

(soft dramatic music)

Earth is born out of chaos and catastrophe.

Despite such hostile conditions,

life emerges on our planet.

But it must withstand deadly disasters again and again.

Planet Earth is a wild world

shaken by unimaginable impacts,

volcanic eruptions that flood the landscape,

and drastic climate changes that lead to ice ages

that freeze the world from pole to pole.

Yet each assault creates a path for something new.

Life always finds a way

despite being constantly put to the test.

Without these catastrophes,

life as we know it would not exist

on our "Fateful Planet."

According to scientific theory,

a long time ago,

our planet experienced an ice age of epic proportions,

a period of extreme global glaciation.

It is thought that the ice extended

from the poles to the equator,

that our entire planet was covered in ice,

including the oceans and land masses.

A global catastrophe known as Snowball Earth.

If our planet was really struck

by an all-encompassing ancient ice age,

traces of this dramatic event might have survived the eons.

Western Australia, in the Pilbara region,

temperatures can reach more than 120 degrees Fahrenheit.

Nothing much can survive here,

but the dryness has helped preserve ancient sediments.

3 1/2 billion years in age,

these Archean rocks are some of the oldest in the world.

Professor Nora Noffke and a team of international geologists

have come here to search for clues

that will shed light on what our planet looked like

in these ancient times

and what may have created conditions for a snowball Earth.

(gentle music)

Well, here we have an excellent window

of the really early Earth.

I mean, 3 1/2 billion years ago, how was it?

Earth was different at that time.

And so this formation here provides

a very small glimpse into really completely strange worlds

of the beginning of our planet,

and that makes it so great being here.

In this unique ancient landscape,

the scientists are looking for fossils

of the earliest microbes.

Using a combination of modern techniques

and decades of experience gained in the field,

it's not long before Nora Noffke spots something.

That's what we call ripple marks.

If we find something like that in an area like here,

it's a clue which says shallow water

which was moving not too fast but also not too slow,

that means that the water probably was very clear,

and that is a nice indicator for very, very early life

that existed on Earth at that time.

This entire landscape

was once an ancient shallow sea,

warm pools of water raging from just a few inches

to a few feet in depth,

enough for the warm rays of the sun

to penetrate through the gentle waves.

And these conditions created the optimal environment

for early life to thrive.

This is gorgeous, look at that view.

So let's go measure a little bit from here upward,

and then we get an idea what actually is in the rocks,

what's the story they're going to tell us.

Many ancient rocks

are so distorted through time

that the clues Nora is looking for are long gone.

But here in the Pilbara,

the sediments are undeformed

and thus might have preserved evidence

of the earliest forms of life.

Look at that.

Wow, look at that.

Now, that is spectacular.

So this is really what I was looking for here.

Basically, colonies, assemblages of very small organisms,

microscopic small, bacteria you could say,

and they were living on the seafloor at that time.

The colonies of bacteria clustered together

and formed what are known as microbial mats.

So we know that this is not geological.

What we're looking at here it's biology

because we have here those round-shaped lobes basically

in the outline of those fragments.

These bacterial mat colonies

are examples of Earth's earliest life forms.

Recording the evidence of the colonies,

the team can build up a picture

of early life here in the Pilbara.

Life in these shallow pools,

although primitive, is efficient.

Simple creatures that feed on carbon compounds

that are accumulating in Earth's early oceans.

We have very similar carpets, biological carpets,

in the modern nowadays, all along our beaches,

all along the Atlantic Ocean, for instance.

So it's very common nowadays.

And now we have here 3 1/2 billion-years-old material,

and we see some of the earliest life

that we have here on Planet Earth.

The microbial mats are not the only evidence

of early life in the Pilbara.

The entire region is filled with precious fossil traces

of ancient life.

These sedimentary structures known as stromatolites

are formed by ancient bacteria

and were discovered by Noffke's colleagues in the 70s.

So you see this little dome there,

it's now quite weathered,

so this is a historical site

with respect to science history,

so this one was the first life form detected

in those really, really old rocks.

3 1/2 billion years ago,

life was beginning to thrive on Planet Earth,

but catastrophe was looming.

In the ancient rocks,

Nora Noffke detects a clue

indicating a dramatic shift in environmental conditions

that could have spelled dire consequences

for the early forms of life.

It does not look like much,

but indeed it tells us a lot

about a very important event in Earth history.

So these red lines here essentially are rust.

That's a mineral that contains a lot of iron.

And in order to produce that, we need oxygen.

In the first billion years,

there was virtually no free oxygen on Planet Earth.

Live had evolved without it.

But the ancient rust Nora has found

only forms when iron comes in contact with free oxygen.

The banded iron formation,

as the ancient striped rock is known,

is a hint that our planet was changing in a major way.

Earth now had enough free oxygen

to entirely transform a geological landscape

to such an extent

that its effects can still be seen today.

The change was so drastic,

something catastrophic must have happened.

What impact did it have on early life

and where did this oxygen come from?

The answer may be found deep in the heart of Europe.

Lake Alat in Germany.

Many myths surround the lake

because its turquoise waters frequently turn blood red.

Biologists Patrick Jung and Michael Lakatos

believe the strange coloration might have to do

with some of the earliest forms of life on our planet.

By finding them, they hope to discover

how early life was affected by the oxygen

and how it may have contributed

to the complete glaciation of our planet.

Lake Alat is surrounded by mountains

and lies in a basin.

This is very rare for lakes.

It's also very deep.

Through this constellation,

we hope to find the clues in the depths.

If there is ancient life down there,

it might unveil what happened in the past.

Using a special glass container,

the biologists want to bring water from the deep

to the surface.

In the lower section of the lake, they suspect an anomaly.

It's coming.

That's the bottle, watch out.

Look at that, oh my god.

The water in the container is all pink.

To find out why,

Michael and Patrick are using a probe

to measure the oxygen content of the water sample

to determine its composition.

[Patrick's Translator] What's the oxygen level?

[Michael's Translator] It's only 1.3.

[Patrick's Translator] Wow, there's almost no oxygen left

in the water.

First, the pink color.

Second, the smell of hydrogen sulfide.

And finally, the lack of oxygen indicates

that we are dealing with very, very old bacteria,

so-called sulfur purple bacteria.

Within the depths of Lake Alat

lies a layer that is deadly to most forms of life.

It contains virtually no oxygen.

Just like the deep water we recovered here,

we have to imagine the oceans billions of years ago

because they were also oxygen-free.

Around 4 billion years ago,

our Earth was a completely different place.

The so-called Archean Eon was hostile

to most forms of life we know today.

Even though water already covered most parts of the Earth,

there was no free oxygen available,

neither in the water nor in the atmosphere.

So the question is, where did the oxygen come from?

On the shore of Lake Alat,

the biologists are searching for the answer.

A layer of slime is accumulated at the edge

that looks promising.

The biologists suspect that the green slime

is also an ancient microorganism known as cyanobacteria.

[Patrick's Translator] Now look at this.

Okay, these really are cyanobacteria.

They form long filaments

and are found in masses here on the shore.

The cyanobacteria are ancient.

They're almost as old as the sulfur bacteria

and even evolved from them.

What's special is that we can find them here

in the shore area

and not 18 meters deep, which is oxygen free.

We want to find out why with further analysis.

The scientists measure the oxygen concentration

of the shoreline water sample.

[Patrick's Translator] It's around 8 milligrams per liter.

That corresponds to the surface water.

[Michael's Translator] Okay, let's put it in the sun

and see what happens.

The biologists believe

that the power of the sun will affect their sample.

After a short amount of time,

the oxygen level increases drastically.

The cyanobacteria have brought along

an innovative metabolism

and developed the so-called oxygen photosynthesis.

In this process, oxygen is released as a byproduct,

and this oxygen has changed the Earth forever.

While purple bacteria depend on sulfur

and could only survive in niches

like the deep water layer and Lake Alat,

cyanobacteria only need light,

carbon dioxide and water to survive,

things that are available nearly everywhere

in the Archean world.

Scientists are sure that this must have paved the way

for a global spread of cyanobacteria,

a story that should again be written in the rocks.

South Africa, in the dusty plains of Griqualand,

scientists hope to decipher the events

that unfolded at this early stage of Earth's history.

The rocks in this billion-year-old landscape

act like an archive for field geologists

like Professor Tony Prave.

You know, when you say a rock to most people,

they think, yeah, just a rock.

When I look at a rock, it holds a story.

And in many respects, that story is in some ways very poetic

because it's the history of our planet,

it's a record of what happened on Earth at that place

at that particular time in the past.

(gentle music)

Professor Prave is looking for rock formations

from about 2.4 billion years,

a time when our planet is supposed to have turned

into a snowball.

Oh my.

These features that you see in the rock,

these curvy plainer surfaces, these are stromatolites.

These are beautiful examples of stromatolites.

And these stromatolites

have been generated by cyanobacteria.

And it's the cyanobacteria,

is part of the evidence that

we want to talk about the genesis of oxygen,

free oxygen that would go into the water column

and could ultimately change climate on Earth

2.4 billion years ago.

One of the reasons why I'm in South Africa

is to find these types of fossils,

but also because these fossils represent

a fundamental change in the chemistry of the oceans

and in the chemistry of the atmosphere.

Stromatolites provide a record

of primordial microbial activity and sediment accumulation.

Despite their ancient origins dating back billions of years,

stromatolites can still be found

in certain aquatic environments today,

providing invaluable insights into early Earth ecosystems

and the evolution of life.

Myriads of tiny cyanobacteria carry out photosynthesis,

converting sunlight, carbon dioxide, and water

into organic matter,

releasing oxygen as a byproduct.

They form sticky biofilms or microbial mats,

which are thin layers of microorganisms

that attach to surfaces such as rocks or sediment.

Over time, these layers build up,

creating a stratified structure.

What is left are stromatolites.

Professor Prave can find them in all sizes.

You know, I'm smiling to myself

because I've seen stromatolites

that are the size of cabbages

and I've seen larger ones that are almost the size of me.

This rock that I'm on is a massive stromatolite.

Cyanobacteria have formed

this colossal structure.

2.4 billion years ago,

they generated oxygen on an unimaginable scale.

As a result of their extensive expansion,

earlier life forms were placed under increasing pressure.

In the Archean oceans,

cyanobacteria were real killers.

Because life was not adapted to oxygen at that time,

it wiped out almost all life.

A real catastrophe was triggered here, a mass extinction.

The ancestors of the sulfur purple bacteria

and other anoxic ancient forms of life

are driven away to places which the oxygen could not reach.

But those who cannot escape

are wiped out by the deadly poison.

And that was not the only harmful effect of the oxygen.

The oxygen produced by the cyanobacteria

first saturated the oceans

and then diffused into the atmosphere,

which was then changed by the accumulating oxygen.

As a consequence,

the Earth cooled down more and more,

which led to the formation of ice and snow at the poles.

These glaciers then advanced to the equator

so that the Earth turned into a real snowball.

(soft ominous music)

Some scientists believe this critical change

ended up having a catastrophic impact on the planet,

plunging it into a deep freeze

and quite possibly a snowball Earth,

wiping out nearly all life.

But if this really happened, it should have left traces.

Vatnajokull Glacier in Iceland.

The rugged landscape provides a glimpse

of what this frozen world might have looked like.

Here, Geologist Professor Colin Devey wants to find out

if Earth really witnessed an ancient ice age.

I'm looking for traces of snowball Earth,

and if you want to do that,

then you come to a very big glacier.

And this is Europe's biggest glacier,

a land of snow and ice.

And I'm hoping to find evidence here

of processes that happened in the glacier

so that I can compare it to evidence we have

from way back in time

when the Earth was probably covered totally in ice.

Scientists believe that snowball Earth

was caused by changes in the chemical composition

of the Earth's atmosphere.

It coincided with the occurrence

of the so-called Great Oxidation Event

that happened at the beginning of the Paleoproterozoic era.

Prior to that point,

the atmosphere on our planet

was far different than it is today.

If I was on the Earth 2.4 billion years ago,

and I really aren't that old,

I would need a spacesuit to sit here.

The atmosphere of the Earth contained almost no,

really no, no, no oxygen.

It was made of sort of nitrogen, lots of methane, and CO2.

But then life came along.

The atmosphere went

from something I couldn't possibly breathe

to being full of oxygen.

Then something happened to the methane,

which we call oxidation.

The methane molecules get attacked by the oxygen

and get turned into carbon dioxide.

Carbon dioxide is also a greenhouse gas

but much less potent.

By producing oxygen through photosynthesis,

life changed the world it was living in

in a revolutionary way.

It's a milestone in the history of the Earth.

It changed the planet completely,

changed our atmosphere completely,

and made our atmosphere

from a very, very nice greenhouse atmosphere

to something with a lot less greenhouse potential.

It was like taking a down jacket off the Earth.

Methane is a really good greenhouse gas

and if you take it away,

even if you turn it into CO2 into large parts,

you're still one jacket less than you were before.

As a consequence,

scientists believe the Earth cooled significantly,

forming glaciers at the poles that grew and grew

until the whole planet was covered in snow and ice.

To prove this,

Colin Devey is analyzing the behavior of glaciers.

It's important to understand

that although they look static,

they are constantly moving like a very slow river.

Glaciers move all the time.

Not as fast as water, but much faster than tectonic plates.

Accumulates snow high up in the mountains,

lots of snow falls up there,

and it gets so deep and thick

that it compress itself down into really solid ice.

But that ice moves

because the next lot of snow is coming on top,

so it's being constantly pushed from above.

Glaciers end up reforming the landscape

they travel across.

The force of the ice acts like a bulldozer

for everything in its way.

At Vatnajokull, Devey wants to check

which traces the glacier left behind.

I'm in front here rather than on top of the ice

because when the ice is gone, what's left are stones.

And for a geologist,

the stones are the things that tell the story.

If you look at the rocks,

you see that many of them are scratched,

and that's because the ice has used them as tools

to grind down the landscape.

And if you get down to the bedrock,

then you'll see the bedrock has been scraped really badly

and has what we call in geology striations.

It looks if somebody's gone with pretty hard fingernails

across it and just scratched it.

And for glacial processes,

the stones are absolutely characteristic,

because the glacier is the only thing

that can pick up stones and rub them together.

This process can be observed

throughout the ages.

If there had been glaciers in the past,

this would've been recorded in the landscape.

Glaciers are hugely powerful.

If a glacier's been in a landscape,

you can see the traces of it.

When ice goes away, it leaves almost a signature

on the surface of the planet.

If the Earth really turned into a snowball,

the glacial signature should be found in ancient rocks.

South Africa, the signs for primordial ice sheets

are not always where you would expect to find them.

In the dry, dusty plains north of the Karoo Desert,

Professor Tony Prave is trying to unravel the story

behind our planet's icy past.

You could think of it as being in part like a detective,

and that aspect is fascinating

because it makes you feel a bit like Sherlock Holmes

taking disparate pieces of evidence

and building to make a case to come to an understanding

of a particular process that happened in the past.

And when we're talking about the past, in this case,

we're talking billions of years ago.

In the 2.4-billion-year-old rocks

in this region,

the geologist finds banded iron formations

similar to the ones found in Australia.

This is step one in our understanding

of how climate could have changed 2.4 billion years ago.

So it's important for us then in step two

to go to younger rocks that would be on top of these rocks

to see if there is that evidence for the global cooling

in the so-called snowball Earth.

A cliff in the vicinity

has caught the attention of the geologist.

Ah, now this, this is what we've been looking for.

Here we have this rock unit and it's massive,

it forms this entire cliff that we saw below.

And it's composed of diamictite,

these pebbles that you can see

that are sitting in a mud matrix.

That mud matrix and those pebbles

can be formed by a couple of different processes.

One is mud flows, but the other is glaciers.

And the extent and size and scale of this deposit

makes us really think it has to be a glacial deposit

formed by the movement of ice.

But the key line of evidence that I want to find

would be striations,

and that is what I want to see,

if I could find that associated with this rock.

Tony Prave is scanning the rocks

in the vicinity for scratches,

clues that would prove the presence

of former glaciers in this region.

This surface shows these very fine lines,

these very fine striae.

Those striae are formed

by ice moving over Earth's land surface,

and we know then that that movement of ice

was what deposited this diamictite.

This proves

that glaciers covered this landscape 2.4 billion years ago.

But here we are

in the middle of a very hot, dry, South African desert

and it seems crazy to have ice and snow here.

But we also know plate tectonics shift Earth's land masses.

Just think 2.4 billion years ago

what the Earth may have looked like.

We need to find out where this land surface was

2.4 billion years ago.

To find out more,

Tony Prave is meeting geologist Professor Nick Beukes

from the University of Johannesburg.

He is an expert on early Earth history

and knows the area here like the back of his hand.

Hi Nick, good to see you again.

Tony, yeah, it's nice to see you.

Thanks for meeting me.

So today I'd like you to be able to tell us

how we could find out where South Africa was

at that time of the glaciation.

Tony, I think if we look around

and you look at the far distance there,

we have this very thick and very extensive flat basalt.

I see, I see, okay.

Which is a lava succession.

And if we can go and look at that,

then we can try and figure out the question that you asked,

where the glaciation happened.

And that's where we have to go.

Lava from a large-scale eruption,

a so-called flood basalt event,

covered the ancient glacial sediments

soon after they were formed.

It is these volcanic rocks

that the scientists now want to analyze

to answer the question where these glaciers once existed.

(drill whirring)

So Tony, this is it.

The special thing about lava sediments

is that they contain precise information

about the latitude in which they were formed.

The magnetic signature that's preserved in this rock

is found in very small crystals that when this lava cools,

those crystals align themselves to Earth's magnetic field

and the orientation of Earth's magnetic field.

And in this rock, the signature that has been analyzed

is that the angle of Earth's magnetic field

is plus or minus 10 degrees,

which means that we have to be close to the equator.

The lava cooled on rocks

that immediately before had been covered with glaciers.

And the palaeomagnetic measurements show

that this happened very close to or directly at the equator.

If we have ice, as we saw in that glacial diamictite,

at the hottest latitudes on the planet, the tropics,

then that means we must have ice

across the coldest regions of the planet, ice everywhere.

And this then is confirmation

that the glaciation was global in scale

and hence a snowball Earth.

(gentle music)

Earth had cooled to such an extent

that the glaciers that formed at the poles

extended even further

until they reached the equator

and the whole planet was covered in snow and ice.

It had become a snowball Earth.

Some scientists believe such a dramatic change

could not have been caused by an increase

in oxygen levels alone.

If so, what else could have contributed

to the global freeze?

(gentle music continues)

Switzerland, the Jungfraujoch region is home

to some of the highest peaks in Europe.

The world up here is frozen all year round.

For Patrick Jung and Michael Lakatos,

this is the perfect environment

to uncover the secrets surrounding snowball Earth.

We traveled here to find out

how an entire planet could turn into snow and ice.

(inspirational music)

As temperatures continued to drop,

a tipping point had been reached.

Ice sheets formed and enveloped the Earth

as the world had never experienced before.

The big question is, how this icehouse effect came about?

The scientists are sure

that there must have been some kind of mechanism

besides chemical changes in the atmosphere

that drove the global glaciation.

The eternal ice and snow

could be clues to what happened back then,

because different surfaces of the Earth

reflect light in different ways.

This could be a key to what happened at that time.

Patrick and Michael have a theory.

As our planet became wider and wider,

it was less and less able to store solar energy,

which eventually intensified the cooling of our planet.

The scientists have brought along

special measuring instruments

to prove their idea.

This is the so-called albedometer.

Up here, the global radiation from above is measured,

which radiates onto the Earth.

And down here, the reflected radiation is measured.

In other words,

the amount of radiation that the snow reflects back up.

From the measurement of the so-called albedo,

the researchers hope to draw conclusions

about the icy events in the early days of our planet.

The albedo describes the amount of sunlight

that is reflected by a certain surface.

So the greater the albedo, the more light is reflected.

(gentle music continues)

Alright, I'll see what it says.

Our albedo measurement here has shown

that about 90% of the incoming light is reflected.

This is the highest value we can find on Earth.

A high reflectivity

not only means that light is reflected back into space.

In addition, the much-needed thermo energy is lost.

For comparison, the researchers now want to measure

the albedo of a dark surface.

We have measured an extremely low albedo

of about 20% on this dark rock.

That means the dark surface absorbs

about 80% of the solar radiation

and thus heats up strongly.

This is roughly how we have to imagine

the function of the oceans 2.4 billion years ago.

They covered about 2/3 of the planet

and they had a much lower albedo than this rock does now.

This means that they could store much more heat

and thus heat the planet.

2.4 billion years ago,

right before the global glaciation,

Earth looked very different from ours today.

But the temperatures were comparable.

The dark oceans acted as heat reservoirs.

Normally, the Earth keeps itself warm

by absorbing an enormous amount of heat energy

from the dark surfaces

and slowly releasing it over a long period of time.

But while ice and snow have spread further

across the planet,

more heat energy has been radiated back.

This amount of heat was lost,

and thus the Earth finally cooled down.

By massively decreasing

the amount of strong greenhouse gases,

the oxygen production of cyanobacteria

had changed the chemical composition

of Earth's atmosphere fundamentally.

The resulting cooling led to the glaciation of the poles

from which ice sheets moved further towards the equator

bit by bit.

And, at a certain point, it was the nature of the ice itself

that ensured that there was no turning back.

The highly reflective ice layers

set an unstoppable cycle in motion.

More and more sunlight was reflected.

There was less heat.

The ice sheets grew.

This process was unstoppable, and in the end,

Earth went into a true catastrophe for the very first time

and was enveloped in a snowball.

2.4 billion years ago,

our planet found itself in a deadly trap.

With most of the sun's energy

now being reflected back into space,

how could Earth ever free itself

from the snowball's icy grip?

(gentle music)

White as far as the eyes can see.

The world is locked in snow and ice for millions of years.

Iceland's snow-covered landscape provides a glimpse

of what the snowball Earth might have looked like.

Scientists aren't sure

how our planet could have broken free from its icy bonds,

but Professor Colin Devey has an idea.

In the ice of Europe's biggest glacier,

he is hoping to find the answer.

(gentle music continues)

(water whooshing)

So I'm here at the toe of a tongue

from Vatnajokull Glacier.

And as you can see, the ice is gray.

There's lots of water.

This glacier is melting.

The reason it's gray is it's ash,

it's volcanic ash lying on the ice.

So we've got ash on ice, it's melting.

Is that the end of a snowball Earth?

Could volcanic corruptions have melted the ice?

Like the rest of the Earth,

the primordial volcanoes were buried

under masses of ice and snow,

so an eruption would've had to take place under ice.

Volcanoes can definitely erupt under ice.

We know it from Iceland.

Grimsvotn up there erupted in 1996

under 800 meters of glacier,

and it managed to melt all that ice

into a huge lake full of water

which then raced down the side of Iceland,

devastating all the coast here,

washing away roads and bridges

and power lines and all sorts of stuff.

But after that, the volcano was in the open air.

So it managed to free itself of that much ice,

that's no problem for a volcano.

The power of volcanoes is immense

and the heat of the magma can easily melt snow and ice.

But are there really enough volcanoes on our planet

to put an end to a snowball Earth?

(gentle music continues)

I mean, it would be possible to melt the snowball

if you had vulcanism all over the planet

at the same time everywhere.

But then I'd see the rocks, and I don't,

there isn't vulcanism all over the planet at that time.

There's always volcanoes going off on this planet,

but not more than at any other time.

So no vulcanism,

just the heat of the magma coming out

could not have melted a snowball Earth.

At some spots,

the volcanoes may have melted little parts,

but the snowball Earth remained frozen

despite the magma flows.

In fact, as I said,

it's unlikely that that's how you end a snowball Earth.

But volcanoes are not just producing molten rock as magma.

They produce other things

that may help us to get out of a snowball Earth.

Professor Devey is heading for a volcano

in the southwest of Iceland

that has recently erupted.

Here, he wants to see what it spews out apart from lava.

(soft ominous music)

Yeah, that's really what fresh lava looks like.

It's a really good place to examine fresh lava.

This is probably one of the youngest lavas

on our planet at the moment.

This is the youngest one on Iceland.

It's still warm, actually,

in several places here where I'm standing.

And this is probably a really good place to find out

how snowball Earth ended.

With a special instrument,

Professor Devey wants to analyze the vapors

that rise from the hot rocks.

This is a gas flux meter.

It sucks air out of this pot here

and measures the gases inside this box,

particularly CO2 is what I'm looking at at the moment.

Up in the air like this, we're about 400 PPM CO2,

that's what the air has on this planet at the moment.

And we go down onto here

and we're now at 405, 6, 7, 800, 900.

It's going up and up and up.

Okay, we're at 1,500 PPM.

That's four times the normal CO2 concentration

of the atmosphere,

so there's a lot of CO2 coming out of the ground here.

A subglacial eruption of many volcanoes

during the snowball Earth period

would've significantly increased the greenhouse gas level

in the atmosphere.

It's very difficult to get an icy Earth to melt again.

So probably the only way to get out of it,

or at least one of the few ways to get out of it,

is to make the atmosphere into a greenhouse,

to actually warm the planet

by increasing carbon dioxide in the atmosphere.

The volcanoes can do it,

and so that's probably how snowball Earth ended.

Increased carbon dioxide in the atmosphere,

a greenhouse climate, the ice melts.

The volcanoes have freed the Earth

from the snowball,

not by their magma melting the ice,

but by the greenhouse gases they release.

Through them, our atmosphere is transformed

so that heat can accumulate and thaw the snowball.

But as the ice melts, one question remains.

How could any life survive

after millions of years in such a deep freeze?

The eternal ice on the highest peaks of the Alps

forms an environment that is comparable to our Earth

2.4 billion years ago

when it was firmly in the grip of snow and ice.

Patrick Jung and Michael Lakatos

therefore want to search for clues right here,

on the roof of Europe.

They wanna find out how life was able to survive

in the deep freeze of the snowball Earth.

Look at this landscape.

We came to the Aletsch Glacier

to find out if we could find life

in this hostile environment

completely covered by ice and snow

as far as the eye can see.

The scientists are led by a mountain guide,

as dangerous crevices plunge into the depths

beneath the snow cover.

With the help of a drone,

the two biologists scan the area for any signs of life.

(dramatic music)

[Patrick's Translator] Turn a little more to the left,

Michael. Okay.

[Patrick's Translator] That could be something.

[Michael's Translator] Oh yeah, you're right.

[Patrick's Translator] This black formation looks good.

That's where we should go.

To really be able to say

whether we can find organisms on the rock face,

Michael will climb up and take a sample,

because that's the only way we can clarify.

The climb is risky.

The rock face is steep.

But without the sample,

the scientists can't evaluate their discovery.

[Patrick's Translator] Further to the right.

Yeah, right there.

You think you can reach it?

(dramatic music continues)

(hammer thudding)

(gentle music continues)

[Michael's Translator] I've got something.

[Patrick's Translator] Oh, cool. Wow.

[Michael's Translator] You can see

the entire structure here.

[Patrick's Translator] And it's nice and black

on the surface.

Okay, let me rub some of that off.

Oh yeah, look.

There's some brown color on here.

Could be organic. It definitely gives us

a good indication,

but I think we should take a closer look.

Using a magnifying glass,

the biologists inspect the rock sample closer.

[Patrick's Translator] Well, Michael,

I'm pretty sure about that.

I can see it quite clearly

by the color and the shape of the growth.

These are actually cyanobacteria.

The same ancient bacteria

that caused the global ice age

are clinging to the rock face.

To determine if they are alive,

the researchers take another measurement.

[Patrick's Translator] With this device,

we can measure photosynthesis.

If it shows something,

it would be a clear indication that we have found life.

[Michael's Translator] Let me switch this

so we can see something.

[Patrick's Translator] Yes, it's everywhere.

Here where it lights up red, those are signals.

That looks alive, it's a lot.

Life amidst a world of snow and ice.

During the snowball Earth phase,

many life forms actually perished.

Those that survived have retreated to certain regions

like these cyanobacteria stains.

Ancient microbial life

has found a way to survive in this hostile environment.

Cyanobacteria and life in general

have a very hard time developing and growing

in a world without water.

Here on the other hand,

the cyanobacteria grow on these black formations.

These rocks remain free of ice and snow

for a very long time,

simply because they are too steep.

But ice regularly melts off the overhang.

This water forms a drainage channel

and cyanobacteria can thrive in it.

That's exactly how it must have been 2.4 billion years ago.

The cyanobacteria survived in ice-free niches

like the one we found here today.

By this strategy,

life was able to outlast the snowball Earth phases.

Two more times in Earth's history

almost the entire planet was to freeze over.

Each time, many species died out.

But some of them survived on the edge of the ice world.

Scientists believe that even during

the snowball Earth phases

there were small areas on Earth

that were not completely covered with ice.

These niches may have provided safe havens for early life

with oxygen and liquid water.

Tiny oases where life could survive the global ice ages.

(dramatic music continues)

After the last global glaciation 580 million years ago,

the time had come for life to flourish

on an unprecedented level.

It now began to evolve into evermore complex forms.

Snowball Earth and all the catastrophes that followed

were the kind of apocalyptic events

that life on Earth has always benefited from.

Without these catastrophes,

we literally would not be here today.

(soft dramatic music)

(soft dramatic music continues)

(music fades out)