All language subtitles for NOVA.S49E06.Dinosaur.Apocalypse.The.New.Evidence.1080p.WEB.h264-BAE_track3_[eng]

♪ ♪

(creatures croaking)

♪ ♪

DAVID ATTENBOROUGH:
66 million years ago,

planet Earth was very
different from today.

♪ ♪

Some of our ancestors
at the time

might have looked like this
furry creature.

♪ ♪

(animal chittering)

(dinosaur grunting)

The rulers of the land
were giant reptiles.

♪ ♪

(animal chittering,
dinosaur grunting)

(footsteps thudding)

♪ ♪

Dinosaurs.

That's one of the most
infamous, a carnivorous T. rex.

And just behind are
the bison of their time,

a common plant eater,
Edmontosaurus.

But what happened to them all?

66 million years ago,
an asteroid hit the Earth,

and scientists think that
it was this collision

that wiped out the dinosaurs.

But no one has ever found
the fossil of a dinosaur

that they know for certain
died as a result of the impact.

(dinosaur roaring)

♪ ♪

However, a truly extraordinary
dig site might change that.

Hell Creek Formation,
North Dakota.

♪ ♪

These sedimentary rocks are
rich in dinosaur remains.

(roaring)

From triceratops...

(growling)

to T. rex.

Now, in a patch of land no
bigger than two football fields,

a long-buried secret
is coming to light.

♪ ♪

Because this place might hold
evidence of one of the most

dramatic events in all the four-
and-a-half-billion-year history

of our planet.

♪ ♪

RILEY BLACK:
Everything was fine

on Tuesday in the Cretaceous,
and the next second,

the world just wasn't the same.

STEVE BRUSATTE:
Any time that an asteroid

the size of Mount Everest
smashes into the Earth,

that's not going
to be a good day.

EMILY BAMFORTH:
It's actually pretty remarkable

that anything survived.

♪ ♪

ROBERT DEPALMA:
Let me get down
here between you.

ATTENBOROUGH:
For almost ten years,
a team of scientists

has been trying to find out
exactly what happened here.

♪ ♪

DEPALMA:
You're at the edge

of your seat every moment

trying to dig this stuff up.

ATTENBOROUGH:
They call the site Tanis,

after an ancient Egyptian city,

and believe it could be a mass
graveyard of creatures

which were killed

in the asteroid strike
66 million years ago.

♪ ♪

This site might reveal
the remarkable story

not just of how
the dinosaurs lived,

but how they died.

♪ ♪

The impact really was
a worst-case scenario.

DAVID UNWIN:
It's almost beyond

what we can imagine.

ATTENBOROUGH:
If the dig team is right,

Tanis could be a
place where the remains

of a long-lost world
are frozen in time.

♪ ♪

A place that gives us,
for the first time,

an unprecedented window...

(dinosaur screeching)

into the lives of the
very last dinosaurs.

♪ ♪

And a minute-by-minute
picture of what happened

on the day the asteroid hit.

♪ ♪

"Dinosaur Apocalypse:
The New Evidence"...

Right now on "NOVA."

♪ ♪

♪ ♪

ATTENBOROUGH:
This landscape
is full of fossils

dating from the Late Cretaceous,

the period which began around
100 million years ago

and ended 66 million years ago,
when the dinosaurs vanished.

Paleontologist Robert DePalma
wants to find out more.

♪ ♪

I think anybody who has ever
liked dinosaurs in the past,

or still does, has thought
at one point or another,

well, what happened to them?

Why are they not here anymore?

♪ ♪

♪ ♪

ATTENBOROUGH:
At the end of
the Late Cretaceous,

fossil evidence tells us
Hell Creek

might have looked like this.

(creature croaking)

There were low-lying
marshy flood plains,

intercut by river channels,

and covered with horsetails,
ferns, and trees.

Back then it was warm
and wet here all year round.

(creature bellowing in distance)

♪ ♪

STEVE BRUSATTE:
If we go back to about
66 million years ago,

the Earth in some ways was
very similar to today,

and in other ways
it was an alien world.

The climate was very different,
the temperature was different.

There were no ice
caps at the poles.

ATTENBOROUGH:
Hell Creek is one
of the most famous

and well-studied areas
for digging up dinosaurs.

BRUSATTE:
Hell Creek

is really the only place
in the world,

at least right now, where we
have a really good record

of the last surviving dinosaurs.

BAMFORTH:
Hell Creek records
the very, very last

days of the dinosaurs, and it's,
it's the best information

that we have in the world
about that extinction event.

♪ ♪

ATTENBOROUGH:
This dig site lies
in the northeastern corner

of the Hell Creek Formation.

66 million years ago,

instead of today's
dusty prairies,

there were sandy,
silty riverbanks.

Instead of rocky cliffs,
there were forests.

♪ ♪

And instead of the
wildlife we know today...

(creatures bellowing)

Well, scientists are trying
to find out what that was like.

BAMFORTH:
One of the great things
about paleontology

is also one of its
most frustrating elements,

and that is that
you can never be sure.

Until somebody builds
a time machine

and we can go back in time
and actually observe dinosaurs

in their natural environment,

we will never know for sure

whether our inferences
are correct or not.

So it'll always be open
to a bit of interpretation

and uncertainty
because fundamentally

trying to pinpoint
something that happened

on a given day
66 million years ago

is really, really tough.

BAMFORTH:
And so a lot of paleontology

is putting forth theories

and then other paleontologists
coming forward and saying,

"No, that doesn't make sense
because here's another theory."

ATTENBOROUGH:
Every paleontologist
can only hope

their site might uncover
something new to debate.

♪ ♪

A sand bank lying between
a river and a forest

would one day become what
Robert now calls Tanis.

♪ ♪

The site had been explored
by others in the past.

(wind whipping)

But it wasn't until after
Robert and his team

started digging here in 2012...

DEPALMA:
So somewhere from between

there and down here is
where that came from,

it's coming from up above.
Hey, look at this.

What?

ATTENBOROUGH:
That anyone would know how
important this site could be...

DEPALMA:
Here we've got this

freshwater environment of the
Hell Creek formation, and this

shocking red, green colors
coming from the shells

of ammonites, a marine organism,

kind of like a coiled
snail in appearance.

So we've got this marine
organism that's been thrown up

into this freshwater environment

and they do not belong here.

ATTENBOROUGH:
How they got there is a mystery,

but even more intriguing.

DEPALMA:
I'm just gonna go ahead and
plane down some of this rock.

ATTENBOROUGH:
Sitting above the ammonite
shells is something that

holds a crucial clue about
the age of these rocks.

So this orange layer right here

is composed

100% of impact-related debris.

It is enriched in iridium.

ATTENBOROUGH:
Iridium is an
element that's rare

in the Earth's crust,

but it's common in asteroids.

The layer it's in marks
the K-Pg boundary.

The boundary is made up
of dust and debris

from a huge asteroid impact.

It's been dated to
66 million years ago,

the time when
dinosaurs disappeared.

Look at that.
That's what you need?

Yeah, yeah, yeah, yeah, yeah,
that's what we want.

Okay, so it's coming
from this area here.

So somewhere within
that region is where

these pieces are coming from.

ATTENBOROUGH:
And it has been found
all over the world.

SONIA TIKOO:
In this layer,
the concentration of iridium

is a hundred times higher
than the baseline

for the rest of
the Earth's crust.

So, perhaps the simplest
answer to that is that

it came from outer space.

SEAN GULICK:
And so we have this

wonderful marker

that is the iridium layer,

that coincides

with the extinction event.

So this is one of those few
cases where you can

really tie what is often
a fuzzy thing and kind of

bring it into focus
because you have

this moment in time represented
by that layer.

♪ ♪

ATTENBOROUGH:
Having the K-Pg
boundary here at Tanis

dates the site to around the
time dinosaurs went extinct.

No rattlesnakes.

BRUSATTE:
Once you see that layer,

once you identify it,

it really does stand out
because it is a thin layer

of rock that caps one world,

the world of dinosaurs.

And it ushers in another world,
a world where you never find

a single dinosaur bone
or tooth or footprint again.

♪ ♪

ATTENBOROUGH:
What makes this site
even more exciting is

the rock layer right
beneath the boundary,

in which Robert and his team
found the ammonites.

The rock here is
really not quite rocky,

and it just falls
apart in your hands.

ATTENBOROUGH:
This crumbly rock isn't unique,

especially in Hell Creek.

But it's rarely found
in layers like this one.

♪ ♪

Over four feet thick,
this layer contains

several geological features
which, to an expert,

signify that it was
deposited very rapidly.

As in a storm or a flood,

burying anything within
it in an instant.

(rocks tumbling, water gurgling)

ATTENBOROUGH:
Which could mean that

anything in this layer would
have been quickly entombed,

like the bodies in
the volcanic ash of Pompeii.

BAMFORTH:
Generally speaking,

the faster you get
buried after you die,

or even if the burial is what
actually kills the animal,

that's one of the best
scenarios for fossilization.

(creature grunting in distance)

ATTENBOROUGH:
Robert knows from the geology
that anything he finds

could be so well preserved
that it could reveal

new evidence that will bring
this time period

to life in a way no one
has ever done before.

BLACK:
When you think
about it for a second,

it's actually incredibly amazing

that we have any fossils at all,

much less a fossil record.

So 99.9% the animals

that we have

don't get preserved as fossils,

because you have scavengers
and you have other animals

that tear away the skeleton
as it's being deposited.

To become a fossil,
you need certain conditions

for fossils to form.

(dinosaurs grunting)

And so a lot of the fossil
record is really missing.

ATTENBOROUGH:
So, for fossil hunters,

this site is
particularly interesting.

Such rapidly deposited
sediment so close

to the K-Pg boundary
could be evidence

that what happened to
the last dinosaurs here

was as swift as
it was destructive.

Yet the story of that
devastating day

begins long before...

Millions of miles away and
billions of years earlier.

♪ ♪

Most scientists
think it all started

in a ring of dust,
rocks, and debris

known as the asteroid belt.

♪ ♪

It's usually an
uneventful place.

♪ ♪

But sometimes, a rock can
get bumped into a new orbit.

♪ ♪

And diverted onto a collision
course with planet Earth.

♪ ♪

TIKOO:
Jupiter, in particular,
is a big bully

in our solar system,

because it's the largest planet,
it has the most gravity.

And it doesn't just
take one orbital pass

for an asteroid
to be influenced.

This is a slow build-up over
tens of millions of years,

interacting with
Jupiter over and over

and over in its orbit.

Another thing that can
change asteroid orbits

is collisions within
the asteroid belt.

And what happens is, over time,

the asteroid's orbit
can be nudged until it

becomes a near-Earth
orbiting asteroid.

And it has to be pretty
bad luck for both

the asteroid and the Earth

to be in the same
place at the same time.

But it does occasionally happen.

♪ ♪

ATTENBOROUGH:
Robert and his team
dig at this site

in North Dakota each summer,

the only time the weather
allows them to do so.

Come on down, check out
this lens over here.

In order to understand
how the impact

affected life on Earth,
you really

need to get a very
clear picture of what

the world was like right before.

That is a critical
part of the story.

♪ ♪

ATTENBOROUGH:
Paleontologist
Dr. David Burnham

and Loren Gurche have been
digging with Robert for years.

♪ ♪

(chuckles)
Oh, wow.

See, see the brown?
Yeah.

That might be a
tubercle right there.

ATTENBOROUGH:
And it seems today
is their lucky day.

Oh, my God,
look at that!
Look at that!

Look, the scales are preserved.

They're, like, doing
a freaking dissection.

Oh, my God...
Biology of Tanis.

Oh, the scale... look, look

the wrinkles continue
down that way.

BURNHAM:
Mine's all nice
and wet so far.

The scales are getting
smaller in that direction.

How big are they there?

I got a, I got a one with the,

the projection over here.
What?

Oh!
Yeah.

DEPALMA:
Yeah, there's the
protuberance right there.

BURNHAM:
I've only seen that on
one other specimen

in my life.
Yeah.

This is the closest
thing to getting to touch

a living, breathing
dinosaur.
It is.

ATTENBOROUGH:
They've found
something extraordinary...

Dinosaur skin.

And they've uncovered it
right next to another fossil.

This is obviously horn.

The gnarliest horn
I've ever seen.

ATTENBOROUGH:
Which helps them piece together

the creature they're from,

a triceratops.

DEPALMA:
It is so exceedingly rare,

a piece of triceratops skin

in the Hell Creek formation.

♪ ♪

ATTENBOROUGH:
The skin that they have found

may look like an
impression in the rock,

but this is skin that
has been fossilized,

and over millions of years
has turned to stone.

♪ ♪

Triceratops bones

are relatively common
finds in Hell Creek,

but skin in such condition

as this is very rare indeed.

The size and the
patterning of the scales

together with
the age and location

of the rocks where it was found,

strongly suggests that
this is from a triceratops.

The presence of the horn where
the skin was found

supports this.

The brown color contains
traces of organic material.

So it might even
be possible from this

to work out which
pigments were in it.

Finding and studying such
well-preserved fossils as this

helps paleontologists build
a much more detailed picture

of how these creatures lived.

Combining this information
with insights

from scientists around the world
makes it possible

to speculate about what life
in the Late Cretaceous

might have been like.

♪ ♪

(dinosaur bellowing,
footsteps crunching)

We know from bones
that adult triceratops

could reach 30 feet in length

and ten feet in height.

(dinosaur grunting)
♪ ♪

Marks on the fossil
also show us that

this one was badly scared.

(dinosaur grunts)

♪ ♪

Triceratops were plant eaters.

(leaves rustling)

(dinosaur grunting)

Other fossils tell us
they had sharp beaks

and hundreds of teeth,
which enabled them to

shred hundreds of pounds
of tough vegetation.

(dinosaur growls)

Almost all adult
triceratops fossils

ever found were on their own.

So it's possible that
the adults were solitary,

a pattern observed in many
modern-day animals.

(dinosaur grunting)

If you look at
American bison, for example,

they herd through much
of their youth and much

of their young adulthood,
but especially old males

will be by themselves.

So that's not to say
that all the triceratops

you find by themselves
are these old bulls,

but there might be
something similar at play.

So they were
probably territorial,

fighting rivals away.

(both growling)

These were very large
animals that probably

had very large
territorial ranges.

CAMERON MUSKELLEY:
There actually is
fossil evidence of

puncture wounds in the frills
of these dinosaurs,

but they were probably
using their horns

just like modern caribou, where
they lock their horns together

to compete for mates
and other territorial places.

ATTENBOROUGH:
A solitary animal would
perhaps mark its territory.

♪ ♪

(spraying)

If you weigh more
than an African elephant,

there's not much that
can bother you.

(animal chittering,
dinosaur grunting)

Except perhaps a little mammal.

♪ ♪

(dinosaur roaring)

♪ ♪

(animals chittering, squeaking)

ATTENBOROUGH:
Robert found these jawbones

in the fossilized burrow.

The shape of this tiny
bone and tooth

means it's most likely
come from what's known as

a pediomyid, an early mammal...

and a type of marsupial.

The team also discovered

fossilized nuts and
seeds in the burrow,

so we have an idea of what
it might have eaten.

(animal bellowing in distance)

BRUSATTE:
We think of mammals oftentimes

as the new kids on the block...

But what we often
don't appreciate is that

mammals and dinosaurs,

their legacies go back
to the same time.

ANUSUYA CHINSAMY-TURAN:
Some of them, we think,

may have been opportunistic

because there's even
evidence of a small mammal

that actually has the remains of

a baby dinosaur
within its belly.

(animals grunting in distance)

ATTENBOROUGH:
The team's finds are
adding to our knowledge

of the complex world

at the very end of
the Late Cretaceous.

And it's not just
the fossilized creatures.

If you walk on damp sand,
you'll leave a trace behind.

A footprint.

The same was true
66 million years ago.

And very, very occasionally,

such traces were preserved.

GURCHE:
We wont to foil the backside.

Right.
We'll just put
the plaster right on.

ATTENBOROUGH:
The dig team has discovered

a number of footprints.

DEPALMA:
Yeah, let's see.

Looks like a good print.
Yeah.

ATTENBOROUGH:
Their shape gives them an idea

of what might have made them.

♪ ♪

If the team is right,
they were made by

a winged creature that
might well have liked

a small mammal...

for lunch.

(animal chittering,
beak thudding)

(dinosaur grunting,
animal chittering)

The footprints are long and
narrow with four toe prints.

Two are slightly longer
than the others.

And that suggests
they were made by...

A pterosaur.

♪ ♪
(pterosaur bellows)

Pterosaurs are not dinosaurs,

but flying reptiles on
a different branch

of the evolutionary tree.

♪ ♪

UNWIN:
There is nothing

like a flying reptile
around today.

Pterosaurs got to enormous
sizes.

A group of pterosaurs
known as azhdarchids,

which include the pterosaur
known as Quetzalcoatlus,

is a pterosaur that grew
up to around 40 feet.

This was an animal that had
a 40-foot-long wingspan.

♪ ♪

ATTENBOROUGH:
Some evidence shows
that some pterosaurs

might have lived
in large groups,

much as flamingos do today.

(pterosaurs bellowing)

ATTENBOROUGH:
Male pterosaurs usually had
crests,

while females didn't.

So, crests may have been
used in courtship displays.

♪ ♪
(beaks clattering)

(pterosaur bellows)

And we have a clue about where
females laid their eggs

because evidence suggests
that at least one pterosaur

laid hers in the soft, sandy
banks of the river at Tanis.

♪ ♪

♪ ♪

UNWIN:
The fossil record

of pterosaur eggs
is really small.

Um, so far we have a,
a couple of eggs

from northeastern China,

and we also have an
extraordinary trove of eggs

from western China,
from Xinjiang Province.

The only other record
of eggs is a single egg

that comes from Argentina.

So our record is very,
very small indeed.

ATTENBOROUGH:
This is the fossilized
egg of a pterosaur

that Robert and his team
found in the crumbly layer,

the only one ever
discovered in North America.

If you look at it
with the naked eye,

all you see is a
jumble of lines.

But if you examine it
with the latest technology,

you can find out a
wealth of information

from the chemistry of the bones,

to the composition of the shell.

And that, in turn,

can tell us a lot about

how these incredible creatures
lived.

To investigate
the pterosaur egg,

Robert has been given access

to the Diamond Light
Source synchrotron.

Situated in Oxfordshire,
in the U.K.,

it's a powerful research tool

that acts like
a giant microscope.

♪ ♪

ATTENBOROUGH:
By accelerating electrons
in this huge ring,

the synchrotron
creates beams of light

billions of times
brighter than the sun.

♪ ♪

Robert and paleobiologist
Dr. Victoria Egerton

now want to turn that beam
onto the egg fossil

to discover more about
its chemical makeup.

♪ ♪

We're pretty much lined
up on the skeleton,

but we might have to
move the stage a little bit

to get to the
right part.
Sure.

ATTENBOROUGH:
Each synchrotron scan

can take several hours.

Meanwhile, Robert can
reveal the creature inside.

Who made this wonderful thing?

DEPALMA:
I got replicas of the bones
from inside that egg

and I restored the remainder

and put together
what the skeleton

would've looked
like when it hatched.

That's how big the
creature would've been

outside the egg,
if it had hatched.

So this is the baby.

How big was it gonna grow?

These very long
neck vertebrae here

are what really gave part
of the story away to us,

because those long bones

match very, very closely with
the azhdarchoid pterosaurs.

That is the giant pterosaurs.

Oh, they were the
whoppers, weren't they?

I mean, what,
25 feet wingspan?
Some of them.

This probably had a wingspan,

maybe 15 feet?

Well, it looks as though

it could take off, really.

It's easy to picture
something like that

just hatching out of
the egg and fluttering

out almost like a little bat.

DAVID MARTILL:
A lot of birds are

utterly dependent on the parents

bringing them food
for a long time.

But there are precocious birds,

and there are some
that simply stand up

after a few minutes

and start foraging
for food themselves.

Well, pterosaurs might have
taken that a stage further,

and they simply flew away.

♪ ♪

ATTENBOROUGH:
They've scanned the egg

here and in America...

Victoria has the results.

♪ ♪

So what have you learned
from the synchrotron image?

What we have here
is a chemical map

of calcium directly within
the bones of this animal.

That tells us that these
bones were already hardened.

So it might be ready to fly

not long after it hatches.

Can you see any
sign of the shell

and what sort
of shell was it?
We can.

What I can show you...

Ah.

We can see the rim of the egg

in sulphur.

Does that tell you
whether it was

a hard shell or a soft shell?

We have been looking at this.

We can see folding occurring

and this unusual undulation.

If it were a hard egg,
we would expect

splintered bits and broken bits,

just like a chicken egg.

This helped to tell us
that it was soft.

So it was perhaps like a turtle?

Absolutely.

That's not the case,
is it, with dinosaurs?

Many dinosaurs laid
hard-shelled eggs.
Yes.

So this is a new discovery about

azhdarchoid pterosaurs?

Absolutely.

This is something that
we are confirming

for the first time.
Huh.

Some flying pterosaurs
had eggs like turtles.

Yes.

Much more reptilian-like
than bird-like.

And that can potentially
tell us more about

the environment in which
these eggs were laid.

How interesting, yeah.

♪ ♪

Creatures that lay soft eggs

tend to bury them
in order to protect them.

♪ ♪

(pterosaur bellowing)

So female pterosaurs
probably looked

for places like this
to lay their eggs.

Because the sandy soil here

is just soft enough

for the hatchling
to dig itself out.

♪ ♪

Now, the pterosaur
just has to make sure

that the hole...

is perfect.

(animal chittering)

♪ ♪

(pterosaur bellows)

♪ ♪

(pterosaur grunting)

♪ ♪

(pterosaur grunts)

ATTENBOROUGH:
Success.

But it's not over yet.

Pterosaurs had two ovaries
(pterosaur grunts)

and they laid their
eggs in pairs.

(pterosaur bellows)

♪ ♪

UNWIN:
So clearly,

this method,
this way of reproducing

for pterosaurs was
incredibly successful.

What it kind of says is,

"Hey, everything's normal"

until the moment
when the impact happens

and it all goes
horribly wrong, basically.

♪ ♪

ATTENBOROUGH:
Here on the sand bank,

sandwiched between the river
and these glorious trees,

life at Tanis seemed to be
thriving.

(gasps)
Whoops.

Never a dull moment.

But all that was
about to change.

♪ ♪

Deep in space,
a countdown clock is ticking.

♪ ♪

The asteroid's journey
would take it through

the orbit of our
neighboring planet, Mars.

♪ ♪

Had the two collided,
a catastrophe on Earth

would have been avoided.

♪ ♪

But it didn't happen

and the fate of life
on Earth was sealed.

♪ ♪

New evidence is helping
to build a vivid picture

of Late Cretaceous life,

here in this corner
of North Dakota.

And the team have
found some more

well-preserved footprints.

♪ ♪

BURNHAM:
So these are animals
that were actually

walking in the water?

DEPALMA:
These guys would've
been essentially on

a mushy riverbank
going down to drink

at some point, you know,

animals tend to
congregate around the rivers.

ATTENBOROUGH:
This footprint is
about a foot long.

So I think this is from
a type of dinosaur that

we call a duck-billed dinosaur.

And they would've been very
common in the Cretaceous.

They ate the plants in the area

and they got very large,
30 feet long.

ATTENBOROUGH:
And there are more.

This track, you see all the
toes are very well preserved.

You even see a nail print
at the tips of the toes.

So the little toenails
dug into the mud.

I love this one.

ATTENBOROUGH:
This is the team's
prize footprint.

It has three toes,

and it's longer than it is wide.

So it's very likely to be

a carnivorous dinosaur.

It's so well preserved

that you can see
the mark left by

its sharp claw there.

Hell Creek is well known

for one carnivore in particular,

T. rex.

This footprint is too small
for an adult T. rex,

but it's possible that it
was made by a young one.

♪ ♪

(dinosaur growls)

(growls)

Robert also found this,

the crown of a tooth.

Its shape and its serrated edge

are indications that it
comes from an adult T. rex.

(animal chittering)

(dinosaur growls)

♪ ♪

♪ ♪

ATTENBOROUGH:
Bite marks found on T. rex bones

how that they may
have eaten each other.

And a youngster would
make an easy catch.

♪ ♪

(roars, snaps jaw)

♪ ♪

ATTENBOROUGH:
But not this time.

♪ ♪

Very few footprints
are preserved

as fossils in Hell Creek.

So if you find several in
one place, as Robert has done,

it's a reasonable
assumption that

there would've been
many more nearby.

MARTILL:
When one dinosaur
leaves a track,

the next one that comes along
obliterates that track.

And eventually you end up with
a ploughed field effect.

If we think about
the actual extent

of the rock in which
we're making our excavations,

our excavations are tiny,
tiny samples.

So it's entirely possible
there are more out there.

♪ ♪

ATTENBOROUGH:
And that supports the idea...

(dinosaur squawks)
♪ ♪

...that dinosaurs and
pterosaurs were thriving

at Hell Creek shortly
before the impact.

(dinosaurs growl, squawk)

And if they were thriving...

(pterosaur bellows)

ATTENBOROUGH:
They must have
been reproducing.

♪ ♪

(snorts, growls)

ATTENBOROUGH:
No one has ever
found a T. rex's nest,

but fossils from similar
dinosaurs showed that

they may have
laid around 20 eggs

in a circular nest.

♪ ♪

ATTENBOROUGH:
It's possible
that like crocodiles,

they partially covered
their eggs with vegetation

to keep them warm.

(dinosaur snorts)

ATTENBOROUGH:
Looking after eggs must've
been a tricky business

when you weigh seven tons.

♪ ♪

(dinosaur grunts)

♪ ♪

ATTENBOROUGH:
As the team's dig continues,

a vision of the prehistoric
world here is emerging.

It seems the sand
bank was full of life.

T. rex, triceratops,

little mammals alongside

the footprints of other

dinosaurs and pterosaurs,

all in a very small area.

♪ ♪

(blows)
You see the scales?

GURCHE:
I do, oh, my God.

That excites me
just looking at it.
(chuckles)

ATTENBOROUGH:
In 2019,

Robert finds something
truly remarkable.

♪ ♪

DEPALMA:
See the cracks
already forming?

Look at that.

So we're gonna have to really
monitor that before we glue it.

'Cause this is getting
vulnerable now.

♪ ♪

ATTENBOROUGH:
An almost complete creature.

After 66 million years,

finding anything intact
is extremely rare.

(speaking indistinctly)
Get the consolidant,

and to get this block out,
we're freezing it.

ATTENBOROUGH:
To keep the fossil in one piece

as they remove it from
the crumbly layer,

the team decides to use a
potentially tricky technique.

They've covered the fossil
in plaster to protect it.

Steady.

ATTENBOROUGH:
Freeing it means they
have to flash freeze

the crumbly rock
surrounding it...

...using liquid nitrogen,

at around minus-300 degrees
Fahrenheit.

DEPALMA:
Watch your footing.

Loren, I'm worried
about brittleness here.

Get that hammer.

Give this a couple
whacks with the hammer.

(hammer tapping)

Okay... move over
five centimeters.

Good.

It's cracked loose.

Yep.
Okay, it's loose.

So we have to get
this out in one piece.

One...

two...

three.

Yee-haw!

Total success.
Total success.

DEPALMA (voiceover):
This is a technique
used in archaeology

for digging up human remains.

We've got enough time
to work with the fossil

and not damage it.

And I couldn't be happier.

♪ ♪

ATTENBOROUGH:
And the creature Robert
and his team have found?

A turtle.

♪ ♪

This is the fossil
now it's been cleaned up.

It's lying on its side.

Here's the outline of its shell.

The shape of the shell
and the sculpt edges here

tell us that this will
was a baenid turtle.

♪ ♪

This baenid turtle would
have looked very similar

to modern Cooter turtles

and lived in the same sort
of freshwater environments.

(water splashes)

♪ ♪

BAMFORTH:
The Late Cretaceous period is

kind of the heyday of turtles,

in at least northern
North America.

There were at least 16 species

that were known
from Saskatchewan.

And compare that to today,
we only have three.

So back then, it was a much
better time to be a turtle.

♪ ♪

ATTENBOROUGH:
The turtle fossil Robert
found is almost complete,

so we can tell a lot
about the way it died.

This is the underside,

and this brown material up here

is fossilized wood.

It's the end of a stick
that passes right through

its body and comes
out just here.

So the evidence points
towards this turtle

having been impaled.

Another well-preserved creature

amongst those found in
the thick rock layer.

♪ ♪

DEPALMA:
When I look at the animals
and plants preserved

in the sediments of Tanis
and the footprints beneath it,

I see a picture
of a vibrant ecosystem,

many different dinosaurs,
and a thriving, thriving place.

♪ ♪

ATTENBOROUGH:
Robert and his team have
found so many fossils,

it looks as if even
at the very end of

the Late Cretaceous, this area
could have been flourishing.

(all bellowing)

ATTENBOROUGH:
Full of dinosaurs and reptiles

that had dominated the planet

for more than 150 million years.

♪ ♪

It's impossible to know how much
longer the dinosaurs' reign

would have continued...

(pterosaur bellows)

Because what happened next

would bring this to an end.

♪ ♪

♪ ♪

The asteroid hit the sea
in an area that is now

the Yucatan Peninsula in Mexico.

♪ ♪

It's called the
Chicxulub asteroid

after the town nearest
to the center of its crater.

♪ ♪

Anything living within 900 miles

of the hit is destroyed
by the blast.

(rumbling)

But what effect does the
impact have on Tanis,

nearly 2,000 miles away?

Is it possible to link the
creatures Robert and the team

have found so far

with the day of the impact?

BRUSATTE:
When we date rocks
from the Cretaceous,

we can say the end Cretaceous
was 66 million years ago,

plus or minus a few
tens of thousands of years.

That is a huge achievement
of modern science.

However, when it comes
to the asteroid,

that asteroid hit
the Earth one day.

(chuckles)

And really it hit
the Earth at one instant.

And so to date fossils
in the rock and to try

to tie them to one instant
in geological time

that happened
66 million years ago,

it's just outside of the
scope of the chemical methods

that we have to date rocks,
so other evidence is needed

to make a plausible scenario
or a plausible story

if somebody were to find
a fossil and wanted to argue

that that fossil came from
the very end of the Cretaceous,

killed by the asteroid.

♪ ♪

ATTENBOROUGH:
To tie the site to the day

the asteroid hit is a challenge.

But Robert and his
team are following

a compelling trail of clues,

the first of which lies
in a jumble of fossils

known as a mass death
assemblage.

DEPALMA:
We've got some wood,

and pressed up against this

and all intertangled

we've got the carcasses of fish.

That's a beautifully
preserved tail,

so that fish is gonna
be absolutely gorgeous.

♪ ♪

ATTENBOROUGH:
Some of the evidence
he's found so far

has been inside
the fishes themselves.

♪ ♪

DEPALMA:
In more ways than one,
it literally is an

operation of a Cretaceous fish,

so we're performing
surgery on this thing.

ATTENBOROUGH:
Robert wants to look
inside this fish's skull.

DEPALMA:
And very carefully we
want to separate this

from the rest of the fish.

Okay...

♪ ♪

Here we go.

Opening up the fish.

Got a nice ant that
made a home in there.

And beautiful, look at that.

Okay, here we have

the gill bars of the fish.

Those are the bars that hold
the filaments of the gills.

Between the gill bars,

all of these clusters
of round objects.

ATTENBOROUGH:
Tiny round balls of clay.

But, what are they?

♪ ♪

ATTENBOROUGH:
After a large asteroid impact,

a mix of vaporized and
molten rock is propelled

into the stratosphere,
some of it into space.

There, much of it cools,

solidifying into
tiny glass droplets.

Some of it is
high enough velocity,

they can actually leave the
Earth's gravitational field.

So it's almost certain

that some of the material
ejected from Chicxulub

would have ended up on, on
the moon,

which is kind of

an exciting thing
to think about.

♪ ♪

ATTENBOROUGH:
But most of the droplets,
known as ejecta spherules,

would have been pulled back
to Earth by gravity.

Then, over millions of years,

pressure and chemical
reactions in the ground

would turn most of them to clay.

They'd look something like this.

So, finding spherules
in the gills of a fish,

as Robert has done at Tanis,

suggests the fish sucked them in

while the spherules
were still forming.

So these creatures
could have died

at the time of
an asteroid impact.

(pattering)

GULICK:
Those have to have come

from the impact event.

You can't make
spherules in other ways;

they're a vapor plume
condensate feature.

That shows that these were fish

that were alive
before the impact.

Those spherules
arrived in the next

20 minutes to perhaps hour.

Those fish swallowed them
and surely died soon afterwards.

So that's an absolutely
amazing discovery.

The fact that there's spherules
in the gills of the fish

at the Tanis site really
brings them as close

as really you can possibly get

to impact.

ATTENBOROUGH:
These ejecta spherules

could be evidence of
what Robert suspects...

that creatures here died on
the day of the asteroid strike.

Once the team begins
to look for ejecta spherules,

they find more and more,

and realize the thick
crumbly layer of rock

at Tanis is full of them.

DEPALMA:
I mean, this stuff is...

oh my God, look at that one.

These things are just gorgeous.

(voiceover):
Ejecta spherules like this

give us a fingerprint

of where they came from.

ATTENBOROUGH:
If these spherules were
connected

to the Chicxulub impact,
then the whole

crumbly layer could
be full of evidence

of what happened on
the day the asteroid hit.

That's a good one.

Oh, is that a droplet
right there?

ATTENBOROUGH:
But to do the best analysis,

they need to find a spherule
that hasn't turned to clay.

DEPALMA:
Oh, my God,
that's a beautiful droplet.

Okay.

ATTENBOROUGH:
The small pieces
of orange material

that Robert and Loren are
digging up may be able to help.

They're amber.

♪ ♪

DEPALMA:
If there was anything flying
through the air at that time,

this is where it's
gonna get caught.

ATTENBOROUGH:
The amber they're collecting
was once sticky resin

oozing out of a
Late Cretaceous tree trunk.

♪ ♪

It's a way for the tree
to protect itself,

like a scab forming on a cut.

♪ ♪

(thunder crashes)

(spherules pattering)

♪ ♪

Anything covered by the resin
would be frozen

in an amber time capsule.

♪ ♪

ATTENBOROUGH:
A well-preserved spherule

can be analyzed
to see if it came

from the asteroid impact.

Loren has found something
trapped in there.

GURCHE:
So during this batch,

we were incredibly lucky
that we came across two

completely unaltered spherules.

♪ ♪

ATTENBOROUGH:
Could this spherule be
the evidence to link

the site directly with
the Chicxulub impact?

There are several lines
of evidence that

geologists would need in order

to definitively say

that this ejecta and this ejecta
are from the same event.

FLORENTIN MAURASSE:
The shape of the spherules,

the size of the spherules,

the color of the spherules,

can be similar for material
coming from different sources.

Only the geochemical signature
would tell you exactly

what the origin of the
parent material was.

GULICK:
The ability to use

trace minerals as a way
to diagnose the provenance,

the place from which the rocks,

or the particles within
the rocks, originally came,

it is a whole field of geology.

And it's a pretty mature
science at this point.

ATTENBOROUGH:
If it's a match, Tanis could be

something incredibly rare.

TIKOO:
If we can match

spherules to the impact site

geochemically and in
terms of radiometric ages,

that's pretty accurate.

That's a smoking gun.

ATTENBOROUGH:
Does the site Robert
and his team have found

record the very last
day of the Cretaceous,

full of fossilized
creatures that were alive

at the moment the asteroid hit?

The potential for
the Tanis site is, is huge.

♪ ♪

ATTENBOROUGH:
And might Robert's team find

something extraordinary?

That's bone right
next to that skin.

ATTENBOROUGH:
A dinosaur that died

as a direct result
of the asteroid impact.

♪ ♪

The day that the asteroid hit

would definitely be
hell on Earth.

TIKOO:
No matter where it is,

you're in for a bunch of chaos.

♪ ♪

♪ ♪

♪ ♪

♪ ♪

♪ ♪