Original subtitles

NARRATOR: A massive crater materialises in the Arctic tundra.

- Why is there a colossal gaping hole right there? It makes no sense.

NARRATOR: The sweltering desert reveals a forbidden chasm.

- If you go in, you're never coming out.

NARRATOR: Dark openings infect the edge of a vast frozen landscape.

- That's so... weird.

NARRATOR: And satellite images expose a mystifying, icy void.

- What is it and why is it there?

NARRATOR: Everywhere we look on our planet,

there's evidence of the past.

In nature...

in buildings...

in relics.

Each holds a mystery that technology now allows us to see from above.

What new secrets are revealed?

- (sonar bleeps)

NARRATOR: The surface of our planet is full of strange terrains.

Some are in plain sight, but with unexplained holes

that delve deep into the earth,

the view from above could provide a key

to solve the mysteries that lie below.

The immense tundra of Yamal, a remote peninsula

in the Siberian Arctic, contains a deeply mysterious discovery.

- Whoa, what is that?

NARRATOR: A huge and inexplicable crater

has emerged in the permafrost.

- Why is there a colossal gaping hole right there? It makes no sense.

- Is that a hole? It's massive!

NARRATOR: This gigantic chasm in the Earth

is about 20 metres wide.

- Ho...ly...

- If I were to draw a comparison, I'd say it kinda resembles

an entryway, a portal into an abyss.

NARRATOR: Its appearance in 2014 has puzzled scientists

around the world.

What could have created this mysterious hole

in the Siberian tundra?

GEORGE: It looks like something heavy hurtled through the sky

and pounded into the Earth.

Could a meteorite have caused this?

NARRATOR: Every year, millions of rocky shards tumble

through outer space and penetrate the Earth's atmosphere.

CYLITA: Most look like shooting stars

and vaporise before reaching the Earth's surface.

But thousands survive, and they collide violently into the ground.

GEORGE: If you look at images of impact craters -

even just the ones in Russia -

they look a lot like what we have here.

NARRATOR: Almost 2,500km away, near the Russian city of Yakutsk,

could the Macha craters give us a clue?

- It's believed that about 7,000 years ago,

a small asteroid broke up in the sky

and five meteorites crashed into the Earth.

The biggest crater is 300m wide -

just imagine the explosion needed to create something that huge.

- But nothing compares to the epic Siberian Tunguska Event.

It happened in 1908, but it's still the largest impact event

in recorded history.

NARRATOR: South west of Yakutsk,

the Tunguska meteorite disintegrated above the ground

in a deafening blast.

SHEILA: Experts say it was 60m wide, and the fireball it created exploded

with a thousand times more power than the Hiroshima bomb.

TORRI: An estimated 80 million trees over an area of 2,000 square km

were flattened - that's the size of Tokyo.

Over 100 years later, many of the trees have still not grown back.

CYLITA: An impact creator isn't a bad guess.

This hole is about 20m wide and over 50m deep.

Could something that huge go completely undetected by satellites?

- A meteorite that size, you would have heard about it.

It would have been the breaking news everywhere.

- So, what is this blasted thing?

- I can tell you what it looks like.

A sinkhole - likely caused by melting ice

wreaking havoc in the permafrost.

- Permafrost is made out of soil.

It has water in it, but the water is frozen,

and the organic material in the soil

is often low growing mosses,

the sort of things you'd see in a bog.

So, you can think of it as frozen peat.

CYLITA: We know climate change is causing the permafrost to melt,

so it makes sense that the ground underneath is going to be weakened.

TORRI: Permafrost, that's expected to be frozen all-year round,

is thawing and collapsing around 200% faster

than expected in the last 20 years.

DAN: What does this mean for the Arctic landscape?

Is it giving us a final warning before all hell breaks loose?

This thawing is creating a type of terrain called thermokarst -

this irregular surface of holes and hollows

as the icy permafrost liquefies.

NARRATOR: In countries like Sweden, thermokarst melted the landscape

so severely, it created hundreds of lakes.

CYLITA: And thermokarst gullies are appearing in places like

the Taymyr Peninsula in Russia.

- What happens in thermokarst is when water freezes,

it expands, and when it melts, it contracts,

so this differential freezing and thawing

creates an uneven topography.

NARRATOR: And some things under that topography

haven't changed in millennia.

- Besides the landscape shifting, another potentially scary thing is

when permafrost thaws, it releases ancient bacteria

and viruses that have been frozen in the ice.

- Scientists have discovered microbes more than 400,000 years old

in thawed permafrost.

- Now, I'm quite certain that not very many people are

all that enthusiastic about letting ancient viruses on the loose.

- So, are we dealing with an extreme example of thermokarst in Siberia?

CYLITA: Although what we're seeing in Siberia is very strange,

the hole itself looks quite different than thermokarst sinkholes

which are irregular in their appearance.

This Siberian hole is almost too perfect.

NARRATOR: Considering this hole in Siberia is so defined and circular,

is it possible that it's not a natural occurrence?

- Could it be man-made?

Just over 2,000 km away, in Mirny, Siberia,

is the Mir Diamond Mine.

It's more than 500m deep and has a diameter of 1,200 m.

- It's one of the largest man-made cavities on the entire planet.

Is it possible that mining is the reason

for this mammoth hole in Siberia?

GUY: A huge amount of mining happens in the Arctic. It's got lots there.

I mean, besides diamonds, it holds vast quantities of minerals.

You've got things like phosphate, bauxite, iron ore, copper,

nickel, you name it, it's in the Arctic.

DAN: But mining requires a ton of equipment and power.

I don't see any signs of that around this hole,

so mining doesn't make sense in this case.

NARRATOR: So, what is it?

To solve the mystery of the mammoth hole,

another clue might be found from above... in the numbers.

GEORGE: Reports from Russia claim that since 2014,

over 20 of these openings in Siberia have materialised

in the Yamal and Gydan Peninsula.

- What the heck could have created so many terrifying black voids

in the permafrost?

- What about a covert military operation? It's not impossible.

During the Second World War, Hitler secretly tunnelled deep

into the ground to build a huge supergun under a hill in France.

NARRATOR: If it wasn't discovered by the allies and destroyed

in a bombing raid, the supergun could have radically changed

the outcome of the war.

TORRI: And during the Soviet era,

Siberia was home to many Cold War installations.

Who's to say that Russia hasn't recently started building

secret missile silos?

- If you think about it, strategically, the far north offers

the shortest route to America for intercontinental ballistic missiles.

- The region also represents the first line of defence

against a NATO attack.

DAN: Or maybe they're related to Russian space research?

Could they be launching rockets on the sly?

- But if any of this were true, wouldn't we be seeing some concrete

and metal in these cavities? I mean,

I don't think it's possible for a launch pad to be built from,

what is essentially, dirt.

GUY: If these things are, in fact, launch pads, I'm gonna be

seriously impressed with the state of Russian engineering!

- Anything human-made means digging down into the Earth.

And if we move closer to the edge of the cavity.

we get a better look at the permafrost scattered all around it,

something just doesn't add up.

- Can the debris somehow explain how these holes emerged?

NARRATOR: In the view from above,

the pattern of the discarded permafrost

makes something very clear.

This chasm was not created from a collapse of the Earth

or by excavation.

- Although no one has seen these pits appear,

people have heard a deafening blast from quite a distance away.

- Oh, that does not sound good.

- These holes were created by a massive explosion from below!

- Around many of them, there's a very clear blanket of ejecta.

There's stuff that's been thrown out in the hole.

NARRATOR: What could be bursting out of the permafrost powerful enough

to create a pit that's 20m wide?

- An exhaust pipe from hell sounds about right.

- What else could explode from the ground out?

GEORGE: When I think of Siberia, volcanoes aren't the first thing

that pop to mind, but it is worth considering.

- Well, now that's not a bad idea, but are there volcanoes in Russia?

GEORGE: Russia's Kamchatka Peninsula

is one of the world's most concentrated areas

of geothermal activity, with about 30 active volcanoes.

CYLITA: The Kamchatka Peninsula extends into the Pacific Ocean

along the infamous Ring of Fire.

NARRATOR: But since the Kamchatka Peninsula

is 4,000km away from Yamal,

is it reasonable to think these holes are active volcanoes?

GUY: Although the craters resemble a volcano,

complete with a raised edge and ejected substances,

Siberia's not a volcanic landscape. There's no boiling lava.

There are no giant vents of blistering hot fire.

- And according to witnesses, the holes begin to fill up with water

not long after they were discovered.

They turn into what looks like small lakes in the landscape.

NARRATOR: So, what is the cause of these enormous, exploding craters?

- Could these holes be the aftermath of some kind of mud volcano?

Like a lava volcano, a mud volcano can be the result

of tectonic pressures creating a geological pathway

where materials below the ground can be pushed up.

- But is Siberia a place where geophysical forces are at work?

GEORGE: Mud volcanoes are often associated with hydrocarbon gases,

and this part of Siberia is home to Russia's vast oil and gas reserves.

- Could gas be the reason for these enormous expulsions?

CYLITA: No evidence connects nearby oil

and gas infrastructure or pipelines

to these holes, so scientists don't know exactly what is happening.

- I want to know, has anyone actually investigated

one of these holes?

CYLITA: In 2015, Scientists from Moscow's

Skolkovo Institute of Science and Technology

travelled to Siberia to take a closer look.

GEORGE: They took samples of air and water

from boreholes around the crater.

What they discovered was a very unexpected clue -

unusually high levels of one single gas.

Methane.

- Are these holes in Siberia methane explosions?

I wouldn't wanna be near one,

but it sure would be something to see.

NARRATOR: Could the key to this mystery be methane?

- It's considered a super greenhouse gas,

because it's 25 times more powerful than carbon dioxide

and contributes to the warming of the planet.

TIM: There's a lot of methane in the permafrost in Arctic regions,

and that leads to a little bit of a scary situation.

GEORGE: Estimates say there is over one trillion tons of methane

stored beneath the Arctic.

It represents what some climate scientists have termed

a methane time bomb.

- The first hole appeared in 2014 after one of the hottest years

on record in Siberia, and all of them since have also appeared

during uncharacteristically warm temperatures.

SHEILA: So, is climate change somehow responsible for these holes?

TIM: If we warm the planet, the permafrost will melt,

that's going to release methane to the atmosphere,

which will enhance the greenhouse effect,

which will cause more permafrost to melt.

- So, we could enter this feedback loop

that increases global warming very rapidly.

NARRATOR: But what does the melting of the permafrost surface

have to do with these deep holes?

- The current hypothesis is that warming temperatures in the Arctic

haven't just caused the ground to thaw at the surface,

but also within these thaw chimneys known as 'taliks'.

TIM: The Earth has this normal geothermal gradient

that the deeper you go, the warmer it gets.

GEORGE: If the permafrost thaws in certain places,

the extra weight may force methane,

that's been under the Earth for millions of years,

up through this talik.

- So, essentially these taliks are creating a route

for ancient and intensely pressurised methane.

- It's like squeezing the bubbles on bubble wrap

GEORGE: Like a large pimple, the Earth bulges on the landscape

as pressure underneath grows.

Eventually, with enough pressure, the gases erupt,

tearing a cavity in the earth's surface.

NARRATOR: But that's just the latest theory.

- No one is certain simply because nothing like this

is happening anywhere else on the Earth.

These craters have shocked the entire scientific community.

NARRATOR: Researchers are now using satellite data to locate the methane

swellings before they explode.

- Documenting these explosions isn't gonna stop them from happening,

but it could help us get a better understanding of what they are.

Because one thing is for sure - any large-scale increase

in methane emissions have scientists seriously concerned.

CYLITA: What's happening will not just have consequences for Siberia

and the Arctic, it will ultimately affect all life on this planet.

NARRATOR: From exploding chimneys of permafrost

to a crater in the sweltering sands,

some of the Earth's most mysterious holes

will only reveal their secrets through the view from above.

Far from the Arctic circle, hidden deep within the scorching desert

in Al Mahara, Yemen,

a dark void exists in the ancient Barhout valley.

- Whoa. Ah... that is very, very, eerie.

- There appears to be a black hole in the middle of the desert.

GEORGE: There are striations or ridges

that almost looks like a throat, as if the desert is screaming.

- It looks like a gateway to another dimension.

I mean, look at that thing!

NARRATOR: The view from above reveals a 30m chasm

that resembles the stuff of nightmares.

Its official name is the well of Barhout...

..but it's also known as the well of hell.

- If you go in, you're never coming out.

NARRATOR: So, here's the question: Is this hole natural

or supernatural?

Frightening stories of the well have been woven deeply

into the culture for centuries.

CYLITA: Legends say it's an ancient prison for genies and dark spirits.

Many consider it bad luck to even speak about the well.

- I can almost imagine some horrible,

guttural sounds coming out of there.

- Some visitors to the well have actually claimed

that they hear strange voices and screams,

and some even complain that there's this

kind of foul odour emanating from the kind of

poisonous water in the bottom of this really shadowy pit.

- OK, but if we calm down for a second,

is it possible that this Well of Hell

is actually just an ancient well?

- Generations ago, the well-diggers of Yemen

would have used hand shovels in their search for water.

- Unlike modern wells that are dug by machines,

could the Well of Hell be one of the oldest and deepest

hand-dug wells in the world?

NARRATOR: Almost 6,000km from Yemen, in Brighton, UK,

You'll find what's known as the world's deepest hand-dug well.

- The Woodingdean Water Well was originally dug to provide water

for a workhouse - a place of work and shelter

for Victorian England's poor.

NARRATOR: The dig started in 1858 and took four years

to finish with the well being only one metre wide.

KAREN: Workers had to scale the shaft in complete darkness

on rickety ladders.

And it was so hot inside that many of the men worked naked.

- That's scary on so many levels.

GUY: At 390m deep, the Woodingdean water well

is deeper than the Empire State Building is tall.

- And quite astonishingly, only one person plunged to his death

during its construction.

- I'd like to know how many souls have met their fate

in the Well of Hell, and how many people

would have been needed to dig it?

NARRATOR: The well of hell is 30m wide and 112m deep -

a space large enough to accommodate over one million people.

A hole that large would have been a nearly impossible job

for Bedouin well-diggers hundreds or maybe thousands of years ago.

GEORGE: Are we sure this is an ancient water well?

If the locals claim the water below is foul smelling and poisonous,

maybe this was not meant to be a well for drinking.

NARRATOR: If it's not a water well, what else could this hole be?

Perhaps the answer could be found within the texture

of the walls themselves?

- The walls are really strange. They don't look hand-carved.

Instead, they look almost corkscrewed.

GUY: Military enlistees that were deployed to camps in parts

of the Arabian Desert claimed that they occasionally came across

this kind of tar-like black matter containing sulphur.

Now, what could that be?

GEORGE: Hydrogen sulphide is a flammable, colourless gas

with the very familiar smell of rotten eggs.

Could this hole be an abandoned entrance to a not-so-old well

that was dug with a drilling rig?

CYLITA: It's known that the Iraq Petroleum Company once conducted

exploration in northeast Yemen.

KAREN: But oil drilling has only happened in the Middle East

within the last 100 years.

Surely the Well of Hell is older than that.

- The only way to solve the mystery of what this ominous hole

in the desert is, is to rappel down into it.

NARRATOR: Safely climbing down into an enormous cavern

is not an easy task, but the Omani cave exploration team

wants to find out what the well of hell really is.

- We really wanted to know what existed below

this large opening in the middle of the desert plain.

- Knowing the legend that claims the hole was filled with dark spirits,

the locals are probably concerned.

DAN: Entering a genie-infested hellmouth...

what could possibly go wrong?

KAREN: A king's ransom couldn't tempt me to go down in there.

It's terrifying.

- Loads of stories have been invented around this cave.

They probably wanted to create kind of a danger zone,

to prevent their children or any other person to get close to it.

NARRATOR: The team is hoping to discover what the well of hell is,

and dispel any myths of evil creatures lurking at the bottom.

- One of the most famous legends claims that the Well of Hell is

a prison for genies, also known as 'Jinn'.

In Arabian and Muslim mythology, 'Jinn' are intelligent

but rebellious spirits intent on possessing humans.

- And apparently, Jinn cannot be seen by humans,

so... good luck with that.

MOHAMMED: The entrance of the cave is almost perfectly circular

and then it goes into kind of widening geometry

as it goes down into a big, kind of, uh, pot.

CYLITA: With the sounds of falling water coming from below

and these small patches of vegetation hugging the walls,

it seems like the well contains its own tiny ecosystem.

MOHAMMED: There are at least four waterfalls actually within,

and it makes the environment just amazing and spectacular.

NARRATOR: Everything inside indicates the passage of time,

with stalagmites reaching over 9m tall,

and stunning multi-coloured cave pearls

formed over thousands of years by the dripping water.

CYLITA: The ecology inside the well is so interesting,

and just breathtaking to look at!

- It's quite amazing down there.

NARRATOR: Perhaps a hole over 6,000km away with a similar interior

could shed some light on what this hole is?

GEORGE: The Well of Barhout reminds me of an enormous cave system

in Vietnam, Hang Son Doong.

It's extremely large - a 747 could fly right through it.

NARRATOR: The Hang Son Doong cave's enormous stalagmites developed

over millions of years, and the river flowing through it

is likely responsible for its formation.

GEORGE: And it has a giant opening at the top,

so access to sunlight means vegetation can grow inside.

NARRATOR: Is it possible the well of Barhout is a much smaller version

of the Hang Son Doong?

CYLITA: Looking at the interior shape,

it doesn't look like a cave, exactly.

Could it be a sinkhole?

KAREN: It looks a lot like a sinkhole in Nevada

called the Devil's Throat.

It appeared in the early 1900's

and has collapsed further over the years.

It's now about 30m wide and 40m deep.

NARRATOR: And southeast of the Devil's Throat,

there's another sinkhole

with an equally ominous appearance from above.

GEORGE: The Black Hole Of Chile - a sinkhole that appeared

in July 2022 near the small town of Tierra Amarilla.

It collapsed to more than 50m wide and over 200m deep.

That's large enough to swallow France's Arc De Triomphe!

- So, what is this place?

GUY: After gathering photographic evidence,

collecting samples of rocks and water and vegetation,

what scientists concluded is that the Well of Hell

is in fact a sinkhole that developed millions of years ago.

NARRATOR: Although it's a desert, the view from above reveals

a landscape covered by layers of limestone beds,

which are very porous.

MOHAMMED: And when they mix with waters, they tend to dissolve.

With time, you get vertical cavities as well as horizontal cavities

connecting together and eventually they formed chambers.

NARRATOR: Some of these underground aquifers and chambers collapse,

creating the many caves and sinkholes that can be found

in south Yemen, nothing quite as large as the well of Barhout.

KAREN: And it's incredible to think that this sinkhole

has existed in Yemen for so long

and not a single human has been inside of it.

NARRATOR: At least not any human in modern times.

- If they had, we'd see their bones

because there would be no getting out.

MOHAMMED: People were saying that this is probably

a water well dug by Jinns.

Obviously, that's not true.

It's just a beautiful structure that have formed over thousands of years.

NARRATOR: So, the mystery of the well of Barhout has been solved,

and now that we understand this sinkhole's unique interior,

it's become a new geological wonder in Yemeni history.

- So, maybe not a well from hell,

but definitely a sinkhole I don't care to visit.

NARRATOR: From ancient desert folklore

to modern secrets in the ice,

the view from above can help decipher strange openings

and their mysteries in the depths below.

Over the western edge of Greenland's ice sheet,

a dark outbreak invades the immense expanse of white.

- Oh, that's so... weird.

NARRATOR: Thousands of irregular-sized black holes

pockmark the frozen surface.

- All those spots look creepy, like some kind of disease.

- I've never seen anything like that before.

- This kind of change in the ice can't be good.

NARRATOR: Greenland's ice sheet contains

almost three million cubic kilometres of ice.

- So, the question is why is this part of the ice sheet

riddled with so many holes?

- And what the heck are they?

CYLITA: Whatever they are, it's made an enormous impact

on the Greenland landscape.

- The sheer number of vertical shafts is extraordinary.

- What could be the cause of them?

NARRATOR: If we take a larger view of Greenland from above,

we see how much access it has to ice and to water.

- What about fishing holes?

- That seems unlikely. That's just a lot of ice holes.

NARRATOR: Is it possible any kind of ice fishing would create

this many holes?

- Maybe this strange landscape is the former site

of an ice fishing competition?

NARRATOR: Could be.

Over 3,000km away, in Minnesota,

The Brainerd Jaycees Ice Fishing Extravaganza

has taken place for over 20 years.

- It boasts being the largest ice-fishing contest on Earth.

Tens of thousands of fishers create over 30,000 holes.

GEORGE: The number of holes sounds about right,

but it's not cheap to get to Greenland.

Would thousands of fishers travel there for a tournament?

- And ice fishing holes are normally about 10 inches wide.

Big enough to haul out a monster catch,

but not so big that you could fall in.

NARRATOR: If we take a closer look at the view from above,

there may be another clue.

GUY: Some of the shafts are quite wide,

they're like a kinda metre across,

but others are really very small, you know, so small

it looks like someone just got a hot poker and stabbed it into the ice.

TORRI: They're a lot smaller than I thought.

GEORGE: If we look at the edges of the openings,

there's no evidence of chopping or drilling into the ice.

- If these holes weren't made for fishing, what are they?

NARRATOR: It may be easier to uncover what these holes are

if we investigate other nearby phenomena in the ice from above.

CYLITA: Greenland is full of what are called melt water lakes.

- Those lakes can lead to the natural creation

of vertical ice caves called moulins -

a type of sinkhole formed when a melt stream on the surface

of ice develops a weakness.

DAN: The streams become rivers,

and that leads to huge holes that sink deep into the ice.

NARRATOR: Moulins can be 10m wide and, astonishingly,

hundreds of metres deep.

They form on glaciers and ice sheets all over the world.

GEORGE: By draining the melted water back into the sea,

they basically act as a natural plumbing system.

TORRI: Could these holes in the Greenland ice sheet

be miniature moulins?

KAREN: Moulins are a sight to behold,

but they don't look like the circular black shafts

in the Greenland ice sheet.

CYLITA: There's no flowing water, and although they vary in width,

they're not typically known to be more than five metres deep.

NARRATOR: Perhaps the answer lies within the bottom of the holes?

What is it that makes them so black?

DAN: Researchers investigated the Greenland holes,

and in the still water at the bottom

they found something totally unexpected -

this black, gritty sludge.

NARRATOR: Why and how could black sludge get into the bottom

of ice shafts in the Greenland ice sheet?

Is there some kind of foreign invader?

- It's a mystery wrapped up inside an enigma

inside an icy black hole.

- Glacier microbiologists were able to identify it as cryoconite

and the mysterious openings in the Greenland ice sheet

are called cryoconite holes.

- If someone says to me a moniker, like, cryoconite holes,

I'm thinking we're talking about a kind of Martian

or extraterrestrial landscape.

What exactly are they?

- Over 150 years ago, Arctic explorer Nils Nordenskiold

discovered a black windblown dust

collecting on the ice during his visit to Greenland.

NARRATOR: Nils gave the sediment a fancy name - cryoconite.

In Latin, 'cryo' means ice and 'conite' means dust'.

- It is believed that cryoconite is carried to the ice by wind,

but how can dust collect right here and nowhere else?

NARRATOR: The location to the coast is likely the key,

and the direction of global air patterns.

Cryoconite can also be found in other Arctic

and Antarctic coastal areas.

In Greenland, it inhabits an area called the 'dark zone'.

- This, to me, is starting to sound a bit like a horror movie.

What on Earth is a dark zone?

CYLITA: A dark zone is exactly what it sounds like.

It's the darker areas on the ice sheet.

Over the years, the cryoconite increases and so does the dark zone.

TORRI: But what exactly does cryoconite and dark zones

have to do with these deep holes in the ice?

KAREN: If cryoconite is a black, airborne pollutant,

where would it have come from to end up in Greenland's ice sheet?

NARRATOR: Perhaps the answer can be found 140 years in the past

and over 12,000km away,

when a massive eruption poisoned the skies.

GUY: Volcanoes are a possibility.

I mean, look back to 1883 when you have particulates

from the Krakatau volcanic eruption in Indonesia.

They were seen 13 days later on the other side of the world.

Krakatau created red sunset glows

as far away as New York for the next three years.

NARRATOR: For Greenland, the source of the pollutant

could lie around 1,200km away.

CYLITA: The closest volcanic landscape from Greenland

is in Iceland who've had their fair share of eruptions over the years.

KAREN: In 1783, volcano Laki erupted for over a year

and caused an immense ash cloud.

GUY: So much of the agriculture and livestock in Iceland

and all across Europe were poisoned

from the volcanic ash that rained down for months.

NARRATOR: And more recently, another Icelandic volcano

had a more debilitating effect on the skies.

TORRI: In 2014, many flights in and out of Europe were cancelled

because of the enormous eruption and subsequent black ash clouds

from Iceland's volcano Bardarbunga.

GEORGE: But forest fires, factories and ejected fuel are

probably closer in proximity than the volcanoes of Iceland.

Is it possible that soot has created the Cryoconite holes

in the Greenland ice sheet?

CYLITA: With a population under 60,000,

and a huge fishing industry in comparison,

the biggest polluter in Greenland isn't from cars.

NARRATOR: Scientists believe the leading cause of pollution

in Greenland's cryoconite holes

comes from black carbon emitted by ships.

- For Greenland, it's an important but very sobering discovery.

NARRATOR: But it's not just pollution that's been found inside

the cryoconite holes in Greenland.

They also discovered something that was completely unexpected...

life.

- What kind of living organism can actually exist in

thousands of these holes right at the edge of the Greenland ice sheet?

NARRATOR: After careful studies, scientists were able to identify

a bloom of glacial algae called zygnematophycea.

- OK, but how in the world did they get there?

NARRATOR: It turns out, dust, water and carbon from ships

are the perfect ingredients to spawn algae.

DAN: The researchers also found Cyanobacteria

and tardigrades in the cryoconite holes.

Tardigrades are also called 'water bears'.

They're super cute, and they're also survivors.

They can live at the bottom of the ocean,

on top of mountains,

they can even survive in the vacuum of space.

And if you take all of the Earth's ice,

it's estimated that there are

a hundred million billion trillion micro-organisms

living in the top two metres of it.

- What I want to know is, how far down into the ice

can these microorganisms live?

NARRATOR: In 2018, a group of international scientists

explored some moulins north of Greenland's dark zone.

They wanted to go deeper than anyone else had ever travelled

inside a glacier.

- Because of the flowing water and potential structural insecurities,

instead of going down there themselves, they sent down a drone

with a bright spotlight, and were able to investigate the entire area.

- I'm afraid to ask, but what did they find down there?

DAN: At the bottom, they found an immense ecosystem

of microorganisms living hundreds of metres beneath the ice.

NARRATOR: Cousins to Greenland's microorganisms,

they're known as extremophiles because they can survive and thrive

in the most inhospitable regions of the Earth.

- We're talking the coldest and darkest places on glaciers

to deep underwater thermal vents

to searing hot lava from volcanoes.

- The discovery of these life forms is truly a scientific marvel.

DAN: But as impressive as they are,

the problem with all those microorganisms

living in the Greenland ice

is that they are at least partly responsible for melting it.

GEORGE: When dark sediment builds up on the ice,

it decreases the 'albedo' or reflectivity of the ice,

and increases the absorption of heat from the sun

which causes the ice to melt.

As the ice melts, the black matter, or cryoconite,

sinks down into the surface.

NARRATOR: It's this process that causes the holes in the ice sheet.

These dark microorganisms can melt the ice surface

by more than 10cm in just a few hours.

DAN: Using satellites and drones,

scientists are collecting data from this microbes to discover

their impact on the ice and the global climate.

GEORGE: These newly discovered life forms in Greenland and elsewhere

will, without a doubt, continue to survive and thrive.

- We can only hope that the rest of the natural world will as well.

NARRATOR: Whether you're searching in holes with microscopic secrets

or gazing at satellite forms, the view from above can uncover

the truth in the shadowy spaces below.

Like in the ice-packed frozen deserts of Antarctica.

- This place feels like it's frozen in time.

NARRATOR: In 2017...

An enormous, dark shape appeared where there was once... nothing.

- Well, that's unexpected in a place like Antarctica.

TORRI: I can't really tell what it is,

but it doesn't look like it belongs with anything else there.

NARRATOR: This inexplicable void was discovered by a spectroradiometer,

NASA's terra satellite, while studying the Antarctic from above.

- Nothing, nothing, nothing, and then, all of a sudden, wham.

This strange-shaped... shape.

- So, the question is: what is it and why is it there?

GEORGE: My first thought,

it might be something we're already familiar with...

algae.

NARRATOR: Could algae from over 15,000km away

in Greenland's dark zone give us a hint at what we're looking at?

CYLITA: Greenland's dark zones consist of algae,

bacteria, and black carbon soot from passing ships.

Could this shape in Antarctica be from a similar combination?

DAN: Antarctica's algae blooms come in a rainbow of colours,

but they don't all come from pollution.

In fact, scientists say a lot of Antarctica's algae feed off

the nitrates found in seal poop and penguin poop.

GEORGE: Knowing this, is it possible that the excrement

of Antarctic wildlife created a dark bloom of microalgae?

- You know, I feel like that area is much too large

for a faeces-fuelled algae bloom.

NARRATOR: Researchers estimate this unknown form to be

about 9,500 square-kilometres, larger than Puerto Rico.

TORRI: So, what is this enormous, mystifying shape?

To me, it looks like a lake of some sort, but it's a very dark lake.

- Could it be a lake full of decomposing slime or tar?

- It happens. The Black Sea has a depth of over 150m

and is the world's largest body of water

that contains hydrogen sulphide.

TIM: The Black Sea has very poor circulation.

It's only connected to the rest of the world's oceans

by a little tiny strait by the Bosphorus.

So, the water doesn't circulate with the rest of the oceans.

NARRATOR: This means the salty sea water in the deep layers

and the fresh river water on top don't mix.

CYLITA: So, without water flow, living things can't thrive, right?

Dead organic materials will sink to the bottom layer

and they'll produce hydrogen sulphide as they're broken down,

eventually becoming covered with this kind of black sludge.

NARRATOR: Could that be what's happening in Antarctica?

Is this a dark lake being impacted

by high levels of hydrogen sulphide?

TIM: The waters in Antarctica tend to be more oxygenated,

less likely to accumulate these black organic sediments

that would produce hydrogen sulphide.

- There's plenty of pristine freshwater there.

It's estimated 70% of the world's freshwater reserves

are all locked up in Antarctica's ice.

NARRATOR: So, if it's not hydrogen sulphide,

what could be making it so black?

- Could it just be black ice? It can make a lake look incredibly dark.

DAN: Black ice isn't just something you drive across

when you're wiping out in your car.

It's also found in bodies of water.

GEORGE: Known as congelation ice, it has no oxygen,

which means there are no bubbles to give it a white appearance.

TIM: Perfectly clear ice may look black because

the light passes right through it, it's not bounced back to our eyes.

DAN: So, could it be that we're looking at a lake

with thousand-year-old, highly compressed, airless, black ice?

Cool.

CYLITA: Black ice has this very glossy surface.

And it's hard to tell, but in this image from NASA,

the lake doesn't really appear to have that quality.

NARRATOR: Perhaps another view from above can give us a clue.

A few weeks after the first image was taken,

NASA's spectroradiometer registered a different unexplained shape

at the same exact spot.

- Well, now, that defies explanation.

- How is this possible? A body of water can't just morph like that.

NARRATOR: And not long after,

another image makes something else very evident.

The black shape is getting larger.

- Very strange things are happening in Antarctica.

- So, now we have two mysteries:

what is this thing, and why is it ballooning out?

- Considering its growth, maybe what we thought was a lake of water

is actually a lake of oil.

CYLITA: On the opposite end of the planet, countries are racing

to gain access to oil reserves.

The Arctic Circle contains about 13%

of all the unexploited oil in the world.

NARRATOR: But the production of oil has always been prickly.

- The infamous Exxon Valdez spill in 1989

lost nearly 37,000 tons of crude oil

in Alaska's southern coast, killing over 30,000 birds.

TORRI: More recently in 2020, satellite images reported

an oil leak in Russia's Arctic Circle.

Melting permafrost caused a fuel tank holding 21,000 tons

of diesel oil to collapse, leading to 135 square mile oil spill.

In the satellite image, there are no signs of oil production, so...

could we assume that the black shape is oil seeping up from underground?

CYLITA: Unlike the Arctic where there is a lot of oil drilling,

Antarctica has no known oil reserves.

GEORGE: In fact, scientists believe

that if there's any oil in Antarctica, it lies offshore.

But so far, none of it has been exploited.

- This large shape has me totally baffled. What is it?

NARRATOR: If we zoom in closer on the view from above,

new evidence appears inside.

- What is that? Is that a ridge?

- Oh, it's a hole. Right, cos this is an episode about holes.

SHELIA: What's a hole doing in Antarctica?

One that's increasing in size?

- What about a sinkhole? Are there sinkholes in Antarctica?

- They're not common, but they happen.

In 2019, at the top of East Antarctica's Amery Ice Shelf,

a massive 750 million cubic metre lake vanished.

750 million cubic metres -

that's so big I've got nothing to compare it to!

- Technically, it's called a hydrofracture.

This crack opens up and the lake just drains like a bathtub.

NARRATOR: Within just three days, it left an 80-metre-deep depression

spanning 11 square kilometres.

Could this be what's causing the mysterious hole?

- Is it possible the weight of the water

shattered the ice shelf beneath it,

allowing it to drain away in a Niagara Falls-style rush?

- It's possible. A year before the hole appeared,

researchers discovered something incredible...

a series of ancient lakes that are thousands of feet beneath the ice.

- The team believes that around 15 million years ago,

water got trapped beneath the ice sheet

in what they dubbed a 'ghost lake'.

These lakes have never seen sunlight.

GEORGE: The largest of the ancient lakes had been named Lake Vostok.

It's just under 500 square kilometres - the size of Cyprus -

and a thousand metres deep.

NARRATOR: Lake Vostok is so large, you can see its outline from space,

but for at least 15 million years,

it's been covered by more than 3.5km of ice.

- Wow. So, could the hole be some kind of exit point

into one of these ancient ghost lakes?

NARRATOR: That could make sense, except for one very important clue:

the hole is off the coast of Antarctica,

which means it's a hole in sea ice.

GEORGE: In the winter, a thick layer of frozen sea water covers it,

and usually stays frozen until summer.

TORRI: So, why did this hole appear in the Antarctic sea ice

in the wintertime?

NARRATOR: When researchers investigated the history of it,

they found that it's not the only time a hole has appeared.

GEORGE: Just after the first satellites were launched,

similar holes were spotted in 1974,

1975 and 1976 -

before they broke up during the austral summer -

when the ice merged with the ocean.

The phenomenon is known as a polynya,

a Russian word that roughly means "hole in the ice".

TIM: Polynyas happen up against the shoreline quite frequently,

but to have an opening in the sea ice that far offshore

and to have one that big was very unusual.

GEORGE: So, the big question for scientists was:

why would there be a huge hole in the Antarctic sea ice in the winter?

Why doesn't that spot freeze?

NARRATOR: That spot is prone to thawing

because about 1,700 m below the surface

is a submerged mountain-like feature known as Maud Rise.

When ocean currents interact with it, deeper and warmer water

is pushed up to the surface, causing the sea ice to melt.

- And looking back at the time frames of the holes

from almost 50 years ago,

they corresponded with extreme cyclone winds.

NARRATOR: Before the 2017 polynya,

we know gusts of warm and cold air collided,

causing cyclonic winds and waves in the Weddell sea.

- The best hypothesis is that somehow warm, moist air

from higher latitudes makes it into the Antarctic,

which is not common.

TIM: So, if you get a cyclonic storm over the sea ice,

that may push the ice outwards,

you know, a little bit like tossing pizza dough and it spreads.

NARRATOR: The combination of cyclone winds and warm ocean currents

forced upwards create the polynyas.

CYLITA: The ice pack was pushed in every direction,

away from the centre of the storm,

dragging floating sea ice in opposite paths

around the cyclone's centre creating this opening.

DAN: Warmer climates mean more cyclones,

and more cyclones mean more polynyas.

This is what climate change looks like from above.

- You know, I've gotten over saying disturbing things about climate.

I used to moderate my language about it, but we're past that.

Scientists need to tell everybody how bad it really is.

NARRATOR: Because if humans continue to ignore the catastrophic changes

in Earth's climate, we're all on borrowed time.

From exploding permafrost, to a mythical sinkhole,

to a rash of pollution, and a huge breach in the ice,

the view from above gives us a unique perspective

on some of Earth's mysteries hiding just below the surface.

Subtitles by Sky Access Services