Original subtitles

Narrator: Mysterious bones are discovered

in one of the world's highest caves.

Dr. Leonard: The object has what looks like

two teeth embedded in it,

and we seem to be looking here at a human jaw bone.

James Ellis: So exactly how old is this jawbone

and who did it belong to?

Narrator: A strange creature is unearthed

from Siberia's frozen permafrost.

Dr. Riskin: Almost everything's intact.

You've got skin, fur, teeth,

nose, claws, even internal organs.

How is that even possible?

Narrator: An enormous iceberg breaks free from Antarctica.

Anthea Nardi: This thing is massive!

About 35 times the size of Manhattan.

Narrator: Leading to a unique discovery...

Dr. Riskin: Most life on Earth is based on a food chain

that starts with the sun. So, without any direct sunlight,

coming into this particular place,

how is any energy going into that food web?

♪♪

Narrator: These are the strangest mysteries

trapped in the coldest places.

Lost relics.

Forgotten treasures.

Dark secrets.

Locked in their icy tombs for ages.

But now, as ice melts around the world,

their stories will finally be exposed.

♪♪

♪♪

Narrator: 10,700 feet up,

where the oxygen is thin

and the climate is cold and dry,

sits The Tibetan Plateau.

James Ellis: It's the world's highest and largest plateau

and for this reason is known as 'The Roof of The World',

The Tibetan Plateau has winter temperatures

that get as low as minus 40 degrees Fahrenheit.

Dr. Leonard: Nestled on a steep rocky slope

of the Northeastern Margin of the plateau,

is a massive cavern known as the Baishiya Karst Cave.

It has been a Buddhist sanctuary for centuries

and monks still make the arduous trek here

to fast and meditate.

Narrator: In 1980, a Buddhist monk

made the journey to the cave.

And when he sat down to pray,

he noticed something strange on the ground.

James Ellis: He's not quite sure what it is.

It's not a rock - the shape is unusual,

kind of elongated and curved and the texture is porous.

But he knows he may have found something important

because the Baishiya Karst Cave

is a known archaeological hotspot.

Narrator: Owing to the archaeological significance

of the cave, scientists are summoned

to investigate the discovery.

Dr. Leonard: The object has what looks like

two teeth embedded in it.

They're broad and flat, which makes them very suitable

for grinding down food.

So these are actually molars,

and we seem to be looking at a human jaw bone.

James Ellis: They're way bigger than the teeth of modern humans,

Homo sapiens.

So exactly how old is this jawbone

and who did it belong to?

Narrator: The team embarks on a series of excavations

in the cave and what they discover

is nothing short of astounding.

Dr. Leonard: There are a staggering 2,567

unique bone fragments from all types of creatures!

There are blue sheep, yaks, snow leopards, foxes,

hyenas and larger animals like rhinoceros.

Several of these creatures are now extinct,

or haven't been present in this area for thousands years.

So how on earth did these animals wind up in this cave?

Narrator: Curious if there is a connection between the jaw bones

and the animal remains, the archaeologists decide

to continue examining the animal bones.

Dr. Agbedor: They appear to be covered in cut marks

and notches, which researchers believe were caused

by stone tools also found in both caves.

These tools include simple flakes,

scrapers and points which were likely used for cutting

or scraping hides and other tasks.

James Ellis: My guess is that if they were to be placed

under the microscope,

those bones would reveal tiny little fragments of stone

that have broken off into those little marks and notches,

meaning, that someone long ago was using

the stone tools to butcher these animals.

date back to the time of Homo habilis,

around 2.6 million years ago.

So is it possible that the jaw bone discovered by the monk

is that old?

James Ellis: Homo habilis actually means

Handyman in Latin.

They were called this because stone tools

have been found near some of their fossilised remains.

Some scientists actually believe that Homo habilis

was the first of our human ancestors

to fashion tools out of stone,

but this has never been proven to be 100% true.

Dr. Leonard: However, looking at the Baishiya Karst Cave,

there are some remains of a strangely shaped bone

with these little markings on it.

These little markings are an indicator

that it's been shaped by direct hits to it.

Maybe by a stone tool.

James Ellis: It also has a perfectly flat,

sharp edge to it.

So this bone has actually been used as a tool!

Well, that rules out the idea

that this is the work of Homo habilis

because they hadn't advanced to this level of toolmaking.

Dr. Leonard: Homo habilis is also known for having

smaller, delicate molars.

While those in the jawbone found in the Baishiya Karst Cave

are large and thick.

So this might not be the remains of Homo habilis at all,

but perhaps some other ancient species.

James Ellis: This makes sense because archaeologists

have only found actual remains of Homo habilis

in eastern and southern Africa and not in Asia.

So if this was the work of Homo habilis,

they'd have travelled very, very far.

Narrator: Studying the sediment layers in the cave,

the archaeologists find more evidence

of early human presence.

Dr. Leonard: The different layers of sediment reveal

even more animal bones and stone tools that are dated to

anywhere from as far back as 190,000 years ago

till only about 30,000 years ago.

James Ellis: This was a time when Neanderthals

inhabited much of Europe,

the Middle East and Asia.

So is it possible that the jawbone found

in the Baishiya Karst Cave

belonged to a Neanderthal?

Narrator: Neanderthals weren't alone in roaming the earth.

Another similar but genetically different species of humans

known as the Denisovans were contemporaneous to Neanderthals

and only recently became known to science.

Their remains were first discovered in a cave

in Siberia's Altai Mountains.

Dr. Leonard: Genetically speaking,

along with Neanderthals,

they are the closest extinct relatives of modern humans.

Narrator: Reasoning that the ancient human remains

could be either from a Denisovan or a Neanderthal,

scientists extract collagen from the molars

embedded in the jawbone.

Collagen is a protein, and the main building block

of your bones, skin and muscles.

And by comparing the structure of the collagen present

in the two molars to that we see in the teeth

of both Homo sapiens and Neanderthals,

the answer is clear.

The jawbone is Denisovan.

James Ellis: The Denisovans are fascinating

for many reasons.

But mostly because of how very little we know about them.

They were only just discovered in 2010,

and owing to a relative lack of evidence,

since then, scientists have only managed to paint

a murky picture of who they were.

Dr. Leonard: The oldest evidence we have of Denisovan presence

on this earth is 500,000 years old.

And they seem to have gone extinct

somewhere around 30,000 years ago.

But this means they were contemporaries with us,

Homo Sapiens.

James Ellis: Studies of their genes reveal

that the Denisovans had

dark skin, eyes, and hair.

Other than teeth that kind of jutted out,

they looked very much like Neanderthals.

Narrator: Despite being a more primitive form of human,

the Denisovans show signs of having been preoccupied

with beauty and memorialising the environment around them,

just like modern humans do.

James Ellis: This is an example of artwork potentially made

by the Denisovans that was found on the Tibetan Plateau.

The markings are thought to be around 160,000 years old

and consist of negative handprints,

which are created by placing a hand on a surface

and then blowing or spraying pigment around it.

Dr. Leonard: Evidence also suggests

that they may have evolved traits suited

to various environmental conditions,

something that scientists believe

they could have passed on to modern day Tibetans.

This gene variant helps modern humans adapt

to high-altitude environments

by improving oxygen efficiency.

James Ellis: One of the more captivating elements

of the discovery of the Denisovans,

is the significant genetic evidence showing their DNA

is present in modern human populations.

This is particularly true for those from East Asia to Oceania.

This indicates that Denisovans contributed

to the genetic makeup of contemporary humans.

As a result, a part of them still survives to this day,

hundreds of thousands of years later.

Narrator: While the precise reasons for Denisovans'

extinction remain unclear,

it likely resulted from a combination of factors,

including competition with other hominins

like Neanderthals and modern humans.

Deeper investigations at The Baishiya Karst Cave

and other yet to be discovered sites may help us further

understand this enigmatic branch of human history.

♪♪

Narrator: In the far reaches of the Russian Federation,

lies the massive Republic of Sakha,

also known as the Yakutia.

This remote, frigid land occupies eastern Siberia.

It takes up one fifth of the total territory of Russia.

That's about four times the size of Texas.

Dr. Agbedor: Almost half of Yakutia is found

in the Arctic Circle.

It is known for having the coldest winters on the planet,

which drag on for 9 months.

The capital city of Yakutsk has broken weather records,

reaching minus 83.9 degrees Fahrenheit!

That's cold!

Dr. Cantor: Founded in 1632,

Yakutia boasts a treasure trove

of rich natural resources.

[loud explosion]

Diamond, gold and tin are mined here.

In fact, 99% of Russian diamonds come from this area.

Dr. Riskin: Besides these mineral resources,

the land often reveals something,

I think, it's even better then dimonds,

ancient artifacts and fossils.

Narrator: A local hunter is exploring the shores

of the Tirekhtyak River in the Abyssky district,

when he sees something strange poking out of the riverbank.

Dr. Leonard: About 130 feet below the permafrost,

there's a lump of fur sticking out of the mud.

It looks like it must be an animal of some kind...

But what exactly is it?

Narrator: Just off the northern coast of the Sakha Republic,

between the Laptev Sea and the East Siberian Sea,

lies Bolshoy Lyakhovsky Island.

In 2020, reindeer herders on the remote Arctic Island

made a startling discovery.

Dr. Riskin: Sticking out of the permafrost were the remains

of an ancient bear.

mummified by the frigid earth.

Almost everything was intact.

You got skin, fur, teeth, nose, claws,

body fat and even internal organs.

How is that even possible?

Dr. Agbedor: The carcass is preserved through

natural mummification, which typically occurs

in extreme environments like deserts,

glacial regions,

or very high altitudes.

The continuous freezing conditions in this area

have prevented the decomposition of organic material,

allowing for exceptional preservation over millennia.

Dr. Cantor: Soft tissues are dehydrated,

allowing the body to be preserved

in a frozen time capsule.

This method allows the preservation

of connective tissue, muscle and internal organs.

Narrator: The bear was found to be a female

just over five feet tall and around 170 pounds

and thought to be 2 to 3 years old at the time of death,

which was later revealed to be caused by a spinal injury.

Dr. Leonard: It was originally theorized

that it was an extinct cave bear

that dated back at least 22,000 years,

toward the end of the last glacial maximum.

The coldest part of the last Ice Age.

But testing revealed that it was only around 3,500 years old

and was a species of brown bear.

So could the animal discovered in the Tirekhtyak riverbank

also be a brown bear?

Dr. Riskin: Possible, but it's a lot smaller than a bear.

And it's fur is not really brown.

Not to mention it's 131 feet below ground,

which means it's a lot older than that bear

that was discovered on Bolshoi Lyakhovsky Island.

So it's not a 3,500 year old bear.

And if it is a bear at all,

it's going to be like a cave bear.

And to be honest, there's no real reason to think

this is a bear in the first place. So what could it be?

Narrator: In 2019, in the Verkhoyansk region

of the Sakha Republic,

a team of mammoth tusk hunters

were excavating the Batagaika crater,

when they came across something stunning embedded in the mud.

Dr. Leonard: Under 330 feet of permafrost

was a wonderfully preserved foal.

Unlike anything seen before.

It was just a baby, only 1 to 2 weeks old when it died.

And it stood just 39 inches at the shoulder.

It's thought that it probably drowned in mud.

Dr. Riskin: What's incredible is that this baby horse

turned out to be 42,000 years old!

And its internal organs, including the digestive system,

were in great condition.

They were even able to extract liquid blood from it.

Literally the oldest sample of liquid blood

ever found in anything.

Dr. Leonard: The foal still had its hair

and was in such good condition thanks to its icy tomb,

that you could tell that it had a darker colored

mane and tail and a paler body.

So could the animal in the riverbank have been

an ancient horse like this one?

Dr. Riskin: Maybe. But this is a furry animal.

Horses aren't furry. They have fine hair,

except for their manes and their tails.

Narrator: Researchers are called to the site

at the Tirekhtyak River,

and the animal is removed and transferred

to a facility in Yakutsk for testing.

Dr. Leonard: At first glance, it looks like a wolf or a dog,

it's hard to tell exactly.

It's possible that DNA analysis could tell us more.

Dr. Cantor: Although DNA testing of ancient specimens

has been possible since the mid 1980s,

it's not 100% foolproof.

One of the most pressing problems when you're trying

to analyze ancient DNA, is contamination of the samples.

There have been instances where other well-preserved specimens

have confounded scientists.

Narrator: In 2018, an 18,000 year old puppy named Dogor,

which means 'friend' in the Yakut language,

was also found in the Siberian permafrost.

Dr. Riskin: Because it was preserved so well,

researchers were able to sequence

some of the animal's DNA, using some of the rib bone.

The results showed that this was a male.

But even after two rounds of analysis,

they couldn't quite nail down

whether this was a dog or a wolf.

Narrator: A necropsy, or animal autopsy is performed

on the animal found in the riverbank.

And samples from the internal organs are tested

to determine its age.

Dr. Leonard: It's 44,000 years old! That's amazing!

But we still don't know if it's a dog or a wolf.

Dr. Agbedor: Dogs were domesticated from wolves

between about 30,000 to 14,000 years ago.

So given that this animal dates from before

the domestication process began,

I think we can safely conclude

that it's a wolf from the late Pleistocene.

Dr. Cantor: The Pleistocene epoch, also called the Ice Age,

began 2.6 million years ago,

and ended 11,700 years ago.

Wolves entered the picture millions of years

after the dinosaurs became extinct.

Dr. Riskin: Mammals started to fill the niches

that had once been occupied by these large reptiles,

and 35 million years later,

animals that would become the canids, or dogs,

evolved with these long legs and sharp claws.

Enter the wolf.

Dr. Agbedor: What makes this discovery unique

is that this is the world's first discovery

of a late Pleistocene predator of any sort.

Narrator: As the wolf's autopsy continues,

more important details are revealed.

Dr. Agbedor: Since the teeth of the wolf are well preserved,

the carcass is receiving a pre-molar tooth examination.

By looking at the wear of the teeth and the development

of the sagittal ridge where the jaw muscles are attached,

it's confirmed that this is an adult male wolf.

Dr. Cantor: It was an active and large apex predator,

meaning it was at the top of the food chain.

As early meat-eaters, these wolves stalked their prey,

into almost every available habitat

in the Northern Hemisphere.

Ancient wolves came in extra large sizes,

and they hunted large game,

such as bison, camels and horses.

Dr. Leonard: Besides humans, wolves were one of the most

widely distributed land mammals that ever lived.

The wolf's movements and actions help keep the ecosystem

in balance by hunting primarily on prey

that is weak, sick or elderly.

So this leaves the stronger and healthier animals

to survive and produce viable young.

Narrator: The necropsy also reveals

that the stomach contents are preserved in an isolated form.

Therefore, there are no contaminants.

Tests to determine the contents are ongoing,

but researchers are hopeful that they may contain some vital

clues about animal behavior during this time period.

Dr. Cantor: We want to understand what this wolf ate,

what its victims ate, and how it influenced the ecosystem

of the ice age in this part of the world.

The animal's last meal could still be in there.

Dr. Agbedor: If some of the microorganisms

that inhabit the animal's insides are still alive,

they are suspended in a hibernation like state.

Dr. Riskin: The microbiota in the gut could even

potentially still be active.

Permafrost is known to have preserved viruses

for nearly 50,000 years.

Those zombie viruses can be revived

and become infectious again under the right conditions.

Dr. Leonard: Imagine that information from

this wolf's gut could lead to the discovery of compounds

to help in the fight against cancer or heart disease...

But until we find out what's in there for certain,

that might just be wishful thinking.

Dr. Riskin: The wolf necropsy is part of an ongoing project

to study the wildlife that lived in this part of Siberia

during the last Ice Age.

But it also provides a starting point to understanding

the evolution of modern dogs from their wolf ancestors.

Instead of looking at the cousin of dogs,

a wolf that's alive today,

we're looking at the great, great grandparents of dogs,

the wolves that were alive long ago.

So that clump of fur sticking out of the ice,

might be the key to understanding a whole

heck of a lot more about humans' best friends.

♪♪

Narrator: In the frigid expanse of Northern Greenland's

high-arctic region is Peary Land,

a roughly 200-mile peninsula that extends

along the Arctic Ocean between Victoria Fjord

and the Greenland Sea.

Dr. Cantor: This is one of the most remote,

inhospitable places on the planet.

It's imposing mountains rise to an elevation

of over 6,000 feet, with rugged fjords

gouged into the coastline between the peaks.

Dr. Agbedor: What little vegetation there is

provides nourishment for a small number of mammal species,

like musk oxen, arctic hares, and lemmings.

Which are then hunted by the predators of that region,

so polar bears, arctic foxes, and polar wolves.

Dr. Riskin: Peary land isn't just north.

You basically can't be any farther north anywhere on Earth

unless you're in a boat.

So, as you can imagine, it's cold there.

Temperatures dip as low as minus 30 Fahrenheit.

It's too cold for any permanent human habitation.

But scientists love to come here in the summers,

because this has one of the richest fossil localities

anywhere on the planet.

Narrator: A team of scientists are on a research expedition

at the Sirius Passet Lagerst ätte,

a well-known fossil site,

[gentle tapping]

when they make a surprising discovery

while examining layers of rock

dating back to the Cambrian period.

Anthea Nardi: It's a fossil of what appears to be

a worm like species,

measuring about a foot long,

which would have been giant in the Cambrian era.

With fins down the sides of its body,

a distinct head with long antennae

and huge jaw-like structures inside its mouth.

What on earth is this thing?

Dr. Cantor: It kind of resembles Amiskwia sagittiformis,

the fossil of a symmetrical, flattened sea worm.

It too had a pair of lateral fins,

in addition to a paddle-like tail fin,

and a well-defined, rounded head.

Narrator: Amiskwia sagittiformis

was first described by paleontologist

Charles Walcott in 1911, when he discovered it

at the Burgess Shale in British Columbia, Canada.

Dr. Agbedor: The Burgess Shale is a region

of layered rock that contains fossils

from over 500 million years ago.

It was established as a valuable site for research

in the early 1900s.

However, it wasn't until the second half of the 20th century,

that its importance was fully realised.

Some of the most significant Cambrian fossil discoveries

have been made here.

Dr. Riskin: The Cambrian period is from about

half a billion years ago,

but the beginning of the Cambrian

is this extremely magical moment in Earth's history,

where we went from relatively little diversity

to this overwhelming explosion of life forms.

We get trilobites, we get these worm like things.

We get all these strange creatures that have long

since disappeared, including Amiskwia sagittiformis.

In fact, the increase in diversity at that time point

was so rapid, people literally call it

the Cambrian Explosion,

and the Burgess Shale fossils

are from exactly that moment in time.

Dr. Cantor: Burgess Shale fossils are from the middle

of the Cambrian period, making them between roughly

505 and 510 million years old.

But the Sirius Passet fossils from Peary Land,

are from the Early Cambrian period,

which makes them 10 to 15 million years older.

Dr. Agbedor: So not only is the newly discovered fossil

much older, but it's believed that Amiskwia sagittiformis

is the only known species,

of an otherwise unknown phylum.

So the Peary Land fossil can't possibly be

Amiskwia sagittiformis.

What else could it be?

Narrator: On a 512-hectare parcel of hilly land

in the Yunnan province of Central China

lies the Maotianshan shales,

an extraordinary site containing diverse

and well-preserved fossils from the Early Cambrian period.

Dr. Riskin: Fossils had been found in the region

way back in the early 20th century,

But it wasn't until 1984 that people realized

this was a special place.

That was when an animal called Misszhouia was discovered

in a near-perfect state of preservation

And it was then,

that the Maotianshan shales were recognized

as an important fossil site.

Anthea Nardi: Since then, the area has been

intensively studied by scientists

from all over the world.

And approximately 200 species of hard and soft tissue fossils

have been discovered.

Narrator: Protosagitta spinosa was first described

in the early 2000s and is believed to be a chaetognatha,

a relative of today's arrow worms.

Dr. Cantor: Arrowworms are tiny, ocean-dwelling carnivores

found in waters all over the world

as a component of plankton.

Their arrow-shaped bodies range from transparent

to translucent or opaque.

Their size varies from about an eighth of an inch to 4 inches,

with species living in colder seas

typically larger than those found in tropical waters.

Dr. Riskin: Despite their abundance in today's oceans,

chaetognatha fossils like Protosagitta spinosa

are fairly rare.

Mostly because they're softbodied swimmers.

So to be preserved half a billion years,

they have to just happen to be buried in a mudslide

or something like that.

Narrator: Protosagitta spinosa bodies were divided

into three sections.

A short head, only 10% of the body length,

a cylindrical trunk and a slender tail.

Dr. Cantor: So the body composition is similar to that

of the newly discovered fossil in Peary Land.

And the Maotianshan shales are Early Cambrian,

just like the Sirius Passet Lagerst ätte,

meaning that they're from the same time period.

Could the Peary Land fossil be Protosagitta spinosa?

Dr. Agbedor: That's unlikely, because there are

some physical differences.

First of all, at a foot long, the new fossil

is considerably larger than Protosagitta spinosa,

which only reached about an inch and a half.

Another difference is, Protosagitta spinosa

had grasping spines on either side of their heads,

for gathering prey in their mouths,

which are absent in the Peary Land worm.

Dr. Riskin: Also, Protosagitta spinosa had small tentacles

protruding from the top of the head,

whereas this new fossil has a significant pair of antennae.

So, I think it's pretty safe to say

these are not the same animal.

Narrator: After a thorough examination of the fossil

and consultation of scientific records,

the team from Peary Land comes to an exciting conclusion.

Dr. Cantor: They've discovered a new species!

They decide to name it "Timorebestia",

which is Latin for "terror beasts".

It's an apt description,

as during the Early Cambrian period,

this would've been one of the biggest and baddest predators

lurking in the depths of the Earth's oceans.

And like Protosagitta spinosa, it's classified as a chaetnogath

- an ancient relative of today's arrowworms,

only it would've been closer to the top of the food chain.

Anthea Nardi: What's amazing is that living arrow worms

have a distinct nervous centre on their belly,

called a ventral ganglion,

entirely unique to these animals,

and remarkably, the same nerve structure was discovered

on the half-billion-year-old Timorebestia.

Narrator: Through remains in the digestive track,

the team is able to determine that Timorebestia

feasted on Isoxys, a common food source

for many other animals in the Early Cambrian Period.

Dr. Cantor: Isoxys fossils are quite prevalent

at the Sirius Passet site.

They were swimming arthropods with long protective spines,

pointing both forwards and backwards

as a defense against predators.

But it doesn't look like they did them any good

against this fearsome hunter.

Anthea Nardi: Timorebestia were probably the dominant predators

in the oceans before arthropods took off.

In all likelihood, they had a reign of about

10 to 15 million years, before they were overtaken by

other more successful groups,

such as the shrimp-like predator Anomalocaris,

which may have reached lengths of three feet or more.

Dr. Cantor: The discovery of Timorebestia shows

that prehistoric ocean ecosystems were more intricate

than previously believed, with a food chain

comprised of several levels of predators.

It also provides an undeniable evolutionary link

between today's arrow worms

and these great beasts that swam the Earth's waters,

more then half a billion years ago.

Narrator: The Sirius Passet Lagerst ätte

on the edge of the world in northern Greenland

has been giving up our planet's ancient secrets for decades now.

Who knows what further discoveries wait,

buried beneath thousands of years of ice and snow.

♪♪

Narrator: Near Antarctica's northern rim,

on the eastern side of the Weddell Sea,

sits the Brunt Ice Shelf.

1,200 square miles of frozen uninhabitable terrain

and home to some of the coldest temperatures on Earth.

James Ellis: Floating Ice shelves like the Brunt

represent one of the great unexplored

habitats of the planet.

Covering almost 580,000 square miles,

or 1.5 million square kilometers

and with only about an area the size of a tennis court

being explored so far, very little is known about them.

Dr. Riskin: The ice shelves have a crucial role

in maintaining Antarctica's ice sheets.

Together they hold back the ice from floating off the continent

and going out into the ocean under gravity.

Unfortunately, those ice shelves are melting

and they're thinning away due to global warming.

Dr. Leonard: Virtually nothing is known

about what's underneath the ice shelves.

The sheer thickness of the ice

makes scientific study almost impossible.

[drilling/buzzing]

Except for a handful of drilled holes with cameras lowered down,

these ecosystems are a complete mystery.

Narrator: The RV Polarstern, a German research ship

is on an expedition in the Eastern Weddell Sea,

when they witness a crack tear through the Brunt Ice Shelf,

creating a huge iceberg.

[slow cracking sound]

Anthea Nardi: This thing is massive!

Measuring roughly 810 square miles,

about 35 times the size of Manhattan.

To see something like that firsthand

is a once-in-a-lifetime event,

and presents a major research opportunity

because it allows the team to study an area

of seafloor that is now free of ice cover.

Narrator: Using sophisticated new imaging technology,

almost a thousand high-resolution photographs

and several long sequences of videos are recorded,

from up to half a mile under the ocean's surface.

The images leave the researchers stunned.

James Ellis: It's basically an aquarium!

There are sea stars, marine worms, sea cucumbers,

at least five different species of fish,

and even two different types of squids.

There is also a surprising abundance

of various other creatures,

most of them filter feeders like sea sponges

or organisms that attach themselves to rocks

or the ocean floor and don't move.

Nobody was expecting this!

Dr. Riskin: The reason it's surprising is that

this whole ecosystem has been in the dark for centuries.

Most life on Earth is based on a food chain

that starts with the sun!

Phytoplankton uses sunlight to make food via photosynthesis,

and then other things eat that and that supplies energy

to the whole food web. So,

without any direct sunlight coming into this particular

place, how is any energy going into that food web?

Dr. Leonard: This ecosystem had to adapt

to an alternative to sunlight.

Without any other option, these sea creatures are alive

because of an alternative energy source.

And it could be through a method called chemosynthesis.

Narrator: Chemosynthesis is the process by which

food in the form of glucose is made by bacteria

using chemicals as the energy source,

rather than sunlight.

James Ellis: In some deep sea environments,

there are areas where hydrocarbon rich gases

such as hydrogen sulfide and methane,

are released from hydrothermal vents

or cold seeps on the ocean floor.

Chemosynthetic microbes like bacteria and archaea

form the base of food webs

and use the energy released by chemical reactions

to sustain themselves

and are then consumed by animals higher up

on the food chain.

Dr. Riskin: Chemosynthesis was first observed in the 1970s

near the Galápagos Islands.

Hydrothermal vents on the ocean floor

spew hot, mineral-rich fluids

into the surrounding seawater.

And those vents support unique ecosystems,

where organisms like giant tube worms can thrive.

Dr. Leonard: Tube worms and similar organisms

have evolved in fascinating ways

to survive in their extreme environments.

They lack a mouth and a gut,

which means they cannot consume food in the traditional sense.

Instead, they formed a symbiotic relationship

with chemosynthetic bacteria.

Anthea Nardi: These environments are characterized

by extreme conditions such as high pressure, darkness,

and often high temperatures or extreme cold,

depending on the specific location.

They're usually characterized by creatures like shrimp, clams,

crabs, fish and octopus,

just to name a few.

Narrator: With no access to the sun,

the idea of these creatures surviving

because of chemosynthesis makes a lot of sense.

Anthea Nardi: There are heavy concentrations

of hydrogen sulfide and methane in Antarctica.

In fact, scientists believe that Antarctica contains

as much as a quarter of the Earth's marine methane.

So this could be a reasonable conclusion.

Dr. Riskin: There have even been studies before in Antarctica

where below an ice shelf, researchers found

chemotrophic organisms feeding on

methane and hydrogen sulfide for energy.

But those studies weren't done

anywhere near the Brunt Ice Shelf.

And the images collected by the research team

show no evidence of any vents of any kind

on the ocean floor. So,

it's unlikely that the creatures here

are thriving from chemo synthesis.

But the energy has to be coming from somewhere.

So if it's not coming from below,

maybe it's coming from above.

Could it be Marine snow?

Narrator: Marine snow refers to organic particles,

waste, and dead organisms

that rain down from the surface waters

to the deep sea and can provide food

for bottom-dwelling creatures.

♪♪

Dr. Leonard: Marine snow starts its journey

in the sunlit surface waters of the ocean.

Here it primarily consists of organic material

produced by phytoplankton,

which are microscopic algae and part of the plankton family

that form the base of the marine food web

and are crucial for producing organic carbon compounds.

Anthea Nardi: Marine snow is responsible

for the vertical transport

of material and energy within the oceans.

This movement is crucial for maintaining productivity

in surface waters and supporting biodiversity

in deeper regions much like this.

James Ellis: Filter feeders like marine microbes,

certain sea stars and marine worms

feed on the remains of these organisms

where animals like the vampire squid

have specialized filaments covered with sticky pads

to help trap marine snow particles as they drift by.

The snow can also be important to small growing animals

such as eel larva.

Overall, marine snow supports a diverse range of organisms.

Dr. Riskin: It's possible that the sea sponges

and other filter-feeding animals under the ice shelf

are getting hold of these snow particles,

pulling the nutrients out of them,

and feeding al that back to the ecosystem,

so the other creatures can thrive.

But how could the Marine snow get to the sealife

when they're trapped under a massive ice shelf?

Would it come in from the sides?

It's tens of miles away!

Dr. Leonard: Currents could carry the nutrients

from far-off regions.

As part of the Southern Ocean, The Weddell Sea connects

to a variety of ecosystems that could have the elements needed,

to sustain life under a thick layer of ice.

Narrator: Studying the sea currents around

Antarctica's Northern rim and the Weddell Sea,

could explain how the marine snow makes its way under the ice

and to our hidden little oasis.

James Ellis: The ocean currents around the northern rim

of Antarctica are influenced by several key factors,

including the strongest ocean current in the world,

The Antarctic Circumpolar Current,

which plays a crucial role

in redistributing heat, carbon,

and nutrients around Antarctica.

Dr. Leonard: The Weddell Sea also has a large

clockwise circular ocean current system

known as the Weddell Gyre,

that influences ocean circulation.

It interacts with the Antarctic Circumpolar Current

and local currents,

affecting the movement of water and nutrients in the area.

Dr. Riskin: Another important part of the currents in the area

are that the actual glaciers and ice shelves are melting

and adding fresh water into the ocean.

And that freshwater input has a huge influence on local currents

and ocean circulation patterns.

Anthea Nardi: These various currents could be bringing in

the nutrients these underwater creatures need to thrive,

but because this is such a new discovery,

more research to track the nutrients in the water

and where they might come from, is still needed,

especially since these are such massive currents.

[loud rumble]

Narrator: Icebergs calving off glaciers

because of global warming

have become a growing concern in Antarctica,

but there may be a silver lining.

Some recent studies have proposed that melting icebergs

can actually add key chemicals

that stimulate the growth of phytoplankton

in the surrounding ocean,

almost fertilizing the waters.

Dr. Riskin: Phytoplankton are microscopic organisms

that play a huge role in marine food chains.

They perform photosynthesis

to convert the sun's rays into energy.

And when they do that, they take in carbon dioxide

and they give off oxygen.

James Ellis: In theory, as the iceberg melted away

from the Brunt Ice Shelf,

it could have been feeding the creatures underneath,

helping them sustain life.

It also could be a combination of several icebergs melting

over the years, feeding everything under the surface.

Anthea Nardi: While we can measure the effect

melting icebergs have on a region,

there is, unfortunately, no way to study underneath the iceberg

before it breaks off.

So it's impossible to say

whether or not the melting ice is responsible

for providing the necessary nutrients

to sustain the sea life discovered

under the Brunt Ice Shelf.

Narrator: Exactly how these creatures survive

without sunlight remains a mystery,

one that requires further study.

For now, the answer lies deep under the frigid waters

of the Weddell Sea waiting to be found.

♪♪