All language subtitles for NOVA.S49E07.Dinosaur.Apocalypse.The.Last.Day.1080p.WEB.h264-BAE_track3_[eng]

♪ ♪

♪ ♪

DAVID ATTENBOROUGH:
Dinosaurs.

Perhaps some of the most
dramatic animals

ever to have walked the Earth.

(dinosaurs lowing)

They dominated the world
for over 150 million years,

until a huge asteroid
struck the planet.

But how exactly did they die?

Paleontologists
have been searching

for the answer for decades.

♪ ♪

And now new evidence is coming
to light.

STEVE BRUSATTE:
We're out looking for clues.

And each fossil is a clue,

and that tells us something

about what the world was like
at that time.

ATTENBOROUGH:
Since 2012,

a team of paleontologists
has been investigating

a remarkable site deep in the
Badlands of North Dakota.

The team's leader,
Robert DePalma,

hopes it holds evidence of what
happened

on the very last day
of the dinosaurs.

(thunder rumbling)

Could it even contain the
remains of an animal

that bore witness
to that terrible event?

We've got all these bones
in the ground right now,

but the one thing that we would
just dream of finding

is that one dinosaur that died
on the day of the impact.

♪ ♪

BRUSATTE:
The idea that there is a
dinosaur fossil potentially

that's a direct victim of that,
that's very exciting.

MAN: Whoa!
DEPALMA:
That's skin right there.

That's actually scaly skin.
My God!

ATTENBOROUGH:
Can they find a dinosaur

that died on the day
the asteroid hit?

♪ ♪

"Dinosaur Apocalypse:
The Last Day,"

right now, on "NOVA."

♪ ♪

♪ ♪

ATTENBOROUGH:
For ten years,

paleontologist Robert DePalma
and his team

have been digging
in a small corner

of the Hell Creek Formation,

an area famous for more
than a century

of major dinosaur discoveries.

They've already found a wealth
of fossilized creatures

in a patch of land they call
Tanis.

(chuckling):
Oh, wow.

ATTENBOROUGH:
What appears to be a piece of
fossilized skin

from a triceratops;

the unhatched egg

and what looks like
a pterosaur embryo;

jawbones of a mammal

called a pediomyid;

and teeth

and footprints
of carnivorous dinosaurs

like T. rex.

DEPALMA:
There is no other dinosaur

that has teeth like this.

ATTENBOROUGH:
Many of these fossils

were found in a thick layer
of crumbly rock.

The rock here is really not
quite rocky,

and it just falls apart
in your hands.

ATTENBOROUGH:
Right above the crumbly rock
is the K-Pg boundary,

a layer of iridium-rich
debris from the asteroid impact

that hit the Earth
66 million years ago.

It marks the end of the age
of dinosaurs.

CATHY PLESKO:
If you look below this layer,

you see fossils of dinosaurs.

If you look above this layer,
no dinosaurs.

ATTENBOROUGH:
The four-foot-thick layer of
rock at Tanis

is full of ejecta spherules.

DEPALMA:
And beautiful... look at that.

♪ ♪

ATTENBOROUGH:
Tiny glass droplets created
in a major asteroid impact.

♪ ♪

Robert thinks that this
is compelling evidence

that everything in the layer was
buried while the spherules fell.

♪ ♪

If he's right,
and the spherules he's found

can be matched
to the asteroid impact,

this dig site could provide
a snapshot

of what happened on the very
last day of the dinosaurs.

BRUSATTE:
Stories like this

are eminently plausible.

Proving them is more
challenging.

EMILY BAMFORTH:
It opens up that whole debate
about, how do we link

catastrophic events to fossil
and geologic deposits?

SONIA TIKOO:
If we can

both match spherules
to the impact site,

geochemically and in terms
of radiometric ages,

that's pretty accurate...
That's a smoking gun.

After ten years of digging,

there is now enough evidence
to piece together

much of the story of Tanis

and the creatures
which lived here.

But how, exactly, did they die?

♪ ♪

The asteroid that struck
the Earth 66 million years ago

created what is today known
as the Chicxulub crater.

♪ ♪

To find out if the ejecta
spherules they've found

in North Dakota can be linked

to Chicxulub, Robert has come

to the Diamond Light
Source Synchrotron

in the U.K.

Joining him is Phil Manning of
the University of Manchester.

They've already run

initial tests in America
on over a dozen spherules

found in different areas
of the crumbly layer.

What have you found out so far?

These little glass spherules,
these globs

of molten material
from the impact site,

have a chemical signal
that ties it

with where they came from.

'Cause when an asteroid hits,

it melts the ground
that it hits,

but also, that glass has a
little bit of contamination

from the asteroid itself.

And that gives you a unique
geochemical fingerprint.

MANNING:
We can see once we've scanned
it, and looking at other sites

from around the world...

Haiti, Mexico,
and North Dakota...

We can get a baseline for
what the ejecta

should look like when
it's related

to the Chicxulub crater.

You can see each element here

and the ratios of those
elements.

And when we look at Tanis,

it's a match... I mean,

it perfectly overlays.

So I think this
is powerful evidence

supporting that Tanis
and Chicxulub

are linked.
Wow.

And what do these findings mean

for the rest of the fossils
that you're finding in Tanis?

This data is key
for the entire site,

because once you have that link

and you know what impact
affected Tanis,

then you essentially know that

every object in that site,
all the animals

and the plants and everything
buried in those sediments,

are linked to the last day
of the Cretaceous.

ANUSUYA CHINSAMY-TURAN:
This is very important

because it immediately gives
a time stamp

for the locality itself.

BAMFORTH:
The Tanis site is

like a window into a snapshot
of time.

ATTENBOROUGH:
With ejecta spherules
found everywhere throughout

the four-foot-thick deposit,

Robert and his team seem
to be able

to link their site
to a single day.

♪ ♪

And the synchrotron here
in the U.K.

reveals something even more
remarkable.

DEPALMA:
So this is showing
a beautiful synchrotron scan

of the half of one spherule.

The glass

is a good geochemical
fingerprint, but,

when we look
at the entire thing,

we see something quite
unexpected.

That's your entire spherule.

What's this?

In this, we've got
a little bit of a nugget.

There was a little particle
right there.

So we scan it, and that's a lot
of iron in there.

Over here, we've got chromium,
a big peak in chromium.

Over here, we've got
a big peak in nickel.

And the abundances of iron,

nickel, and chromium,
all together,

that matches what you expect
to see in a meteoric body.

That does not match what you
would normally have

down here.

So this
is extraterrestrial material.

If you were to sort of grind up

and stuff into a, a spherule

a piece of meteorite,

that's what
it's gonna look like.

DEPALMA:
This could be

piece of the Chicxulub asteroid.

The piece of the bullet that
killed the dinosaurs.

No.

♪ ♪

Robert's team may have found
a fragment

of the asteroid itself in
North Dakota,

physical evidence linking this
site to the Chicxulub impact.

But Tanis is almost
2,000 miles away

from where the asteroid hit.

So exactly how did the asteroid

cause the death
of the animals here?

To answer that question,

Robert is searching
in something he calls

the mass death assemblage.

DEPALMA:
Right here we've got this
intertangled mass of fish.

There's one fish here,
another sturgeon goes this way,

underneath the body of
a paddlefish.

There's another sturgeon
that goes this way,

underneath this log, and
continues out the other side.

And his head hit that log,

and has deflected downward
at a 90-degree angle.

ATTENBOROUGH:
Robert uncovered a tangled mass
of fossilized creatures and logs

surrounded by spherules
and crushed together

in what's known as a logjam.

He has a theory
that the creatures were swept

to their death in some kind of
turbulent surge of water,

and quickly entombed in
sediment,

which is why they are so
well-preserved.

But what could have caused
the wave?

♪ ♪

One hypothesis is a tsunami:

the asteroid hit at sea.

We talk about a tsunami of
completely different scale,

much higher, much larger than
we've ever seen before

in modern tsunamis.

SEAN GULICK:
So if you had 6,000 feet
of water,

at least half of that would
have left as the rim wave.

So at least 3,000 feet high
at a minimum.

ATTENBOROUGH:
The tsunami raced towards land.

TITOV:
When they reached
the coastlines,

they were still very high waves
of up to 300 feet high.

At least... probably as high
as 1,000-feet-high wave.

That's, that's very impressive
wave.

Imagine the wave
that's the size of a building

approaching the coastline.

ATTENBOROUGH:
In the Late Cretaceous,

North America was divided
by a narrow sea

that has been called
the Western Interior Seaway.

The tsunami could have
theoretically

traveled up this towards
Hell Creek.

Tsunamis generally travel

at about the speed of a
jet plane.

It's not something you could,
say, run away from.

It had plenty of energy to get
over the, the coastline.

It could easily still have been
tens of meters high

by the time it reached well into
the seaway.

(wind blowing)

ATTENBOROUGH:
Could the rapid deposition
at Tanis

have been caused by a tsunami?

To test the idea, the team
needs to look at the timing.

DEPALMA:
Oh, which fish is that?

It's a new, it's a new contact.
New one, yeah.

ATTENBOROUGH:
If a tsunami buried the fish,

it would have to have hit

while the ejecta spherules
were falling,

because spherules were found
everywhere,

including in the fishes' gills.

(typing)

So much depends on determining

when the spherules
were falling at the site.

RILEY BLACK:
Modeling the ejecta always
has error bars on it,

in that we're not there
to measure it

and we've had no equivalent
impact like this on Earth

since then.

PLESKO:
But we can look at the
computational models

that we do and say, all right,

this material is coming from

this point,
it's now moving away this fast,

with about this much mass.

And then we can tell,
with the sorts of equations

that we might use to calculate
the trajectory of a cannonball,

where it would go.

And we can observe from these
simulations

how long it takes these ejecta

to reach their final
destinations

down to the order of
a few minutes.

ATTENBOROUGH:
What the calculation shows
is surprising.

Robert and his team have found
that these ejecta spherules

landed at Tanis between
13 minutes

and two hours after the impact.

So, if a wave buried the fish,

it must also have reached
the site within two hours.

Data from recent tsunamis show

even a powerful wave would
take much longer than this

to travel almost 2,000 miles

from the impact site
to North Dakota.

♪ ♪

So, if it wasn't a tsunami,

what could have caused
a surge of water at Tanis?

♪ ♪

Stein Bondevik is an expert
in tsunamis.

(water sloshing)

BONDEVIK:
The fjords in Norway
are very special.

We have tall mountains
surrounding bodies of water.

So the water
is usually very calm.

ATTENBOROUGH:
In 2011,

something very strange happened.

The water in the fjord began
to move violently.

BONDEVIK:
The height of the water

increased by
one-and-a-half meter,

like a maelstrom

with the turbulent water.

Someone said that

the fjord was boiling.

♪ ♪

ATTENBOROUGH:
News started to roll in,
there'd been an earthquake

5,000 miles away in Japan.

♪ ♪

BONDEVIK:
A journalist from the local
newspaper called me

and he said that people
were observing waves

here in the fjords.

I got a video clip of the waves.

And I saw immediately that they
looked like a tsunami wave.

Here you can see that that
the fjord is perfectly calm.

(water rushing)

But at the beach here,

you could see that the water
is sloshing back and forth.

And no one had ever seen
anything like it.

Some people got very upset
and afraid.

♪ ♪

ATTENBOROUGH:
A magnitude 9.0 earthquake

had devastated the northeast
of Japan.

But how did that affect
a fjord so far away?

BONDEVIK:
So no one in Norway could feel
the earthquake.

but I could see
that the times matched

the arrival of the waves
here in the fjord.

♪ ♪

ATTENBOROUGH:
Eventually, Stein
and his team realized

that this might have something
to do with seismic waves,

shock waves that pass quickly

through the earth
during an earthquake.

BONDEVIK:
So it took
only 12 minutes before

the first signal of the
earthquake in Japan

reached all the way here
to, to western Norway.

♪ ♪
(birds twittering)

ATTENBOROUGH:
So it was the seismic waves that
caused the normally calm water

in the fjord to slosh
turbulently back and forth.

BONDEVIK:
Just thinking of that,
scientifically,

it's, it's fantastic.

♪ ♪

ATTENBOROUGH:
Could something similar have
happened in Tanis?

MARK RICHARDS:
Been large weather fronts
coming through...

(indistinct chatter)

ATTENBOROUGH:
Geophysicist Mark Richards

has been studying the site
for several years.

The events in Norway

support a hypothesis
that he's been working on

with Robert's team
about what could have caused

the surge of water here.

♪ ♪

RICHARDS:
A tsunami can't get here in less
than minimum 12 hours.

But seismic waves traveling

from the Yucatan impact site

to North Dakota can arrive here

fairly quickly.

♪ ♪

ATTENBOROUGH:
In the Late Cretaceous,

the Western Interior Seaway
that bisected North America

could have been connected
to Tanis

through the extensive river
system that once flowed here.

♪ ♪

RICHARDS:
If you have
a very large body of water,

like the Western
Interior Seaway,

and you can shake it
back and forth,

you can generate
a large water wave

coming up this river at Tanis.

GULICK:
So this is bigger than any
tectonic generated earthquake.

You would have shaking literally
everywhere on the planet.

ATTENBOROUGH:
So, their hypothesis suggests
seismic waves from the impact

could have caused surges
of water

in the Hell Creek river system.

RICHARDS:
Seismic waves get here
quickly enough

to cause this wall of water,
coming up the Tanis river,

inundating this area,

arriving at the same time
these spherules

are still falling
out of the air.

♪ ♪

ATTENBOROUGH:
If they're right, seismic waves
traveling through the earth,

could have caused a powerful
surge of water at Tanis...

(wave crashing)

at the same time
as spherules fell.

♪ ♪

And ultimately dumping it
on the Tanis sandbank,

burying everything
in the churned-up mud.

Debris and fine iridium dust
from the asteroid

would have gradually
covered the deposit,

forming the K-Pg boundary.

Over millions of years,
the surge of mud would become

the four-foot-deep layer
of crumbly rock.

RICHARDS:
And that's the beauty of Tanis.

What you're seeing is a deposit

that is literally recording
the last, say,

45 minutes to an hour-and-a-half

of the Cretaceous.

♪ ♪

ATTENBOROUGH:
If the extinction of the
dinosaurs was a crime,

the detective solving it would
have plenty of evidence.

They would see that the asteroid

was in the right place
at the right time.

They would see that no dinosaurs
survived after the hit.

They would have a piece
of the murder weapon,

a fragment of the asteroid.

But they would be missing one
very important thing:

a body.

♪ ♪

BLACK:
A lot of the bones that exist

from those last Cretaceous days
were basically destroyed.

BRUSATTE:
As far as we know, we've never
actually found a fossil

of a dinosaur individual,
a single skeleton, let's say,

that we can unequivocally say

was there on the day
the asteroid hit.

♪ ♪

ATTENBOROUGH:
But before the site
was timestamped

to the Chicxulub impact,
Robert's team did find

part of a triceratops
in the crumbly layer at Tanis.

So could that be the body?

A dinosaur that died
on that day?

Something that would help them

would be establishing
the cause of death,

which can be difficult

when you only have a piece
of skin and horn to go on.

This is the horn
after they've cleaned it up.

The team is particularly

interested in these lines here.

And they found that
the fractures

go right through the horn.

So rather than dying as
a result of the impact,

they wondered whether it had
been killed in a fight.

(dinosaurs growling,
horns clashing)

But when they looked at
the fractures in more detail,

they found signs of new bone
growth here.

An indication that the bone
had started to heal.

So it looked as though the
triceratops survived the event

that broke its horn.

(dinosaur grunting)

Could this triceratops
have survived

until the day of the impact?

This drooping in the skin

and the disarticulation
of some of the bones

suggested to the team that
there was decay underneath.

That means its body
had started to rot

before it was entombed

and preserved by the surge.

So, it seems that this dinosaur

didn't die as a result
of the asteroid impact.

♪ ♪
(dinosaur grunting)

Given the signs
of partial decay...

it's likely this Triceratops
wouldn't have lived

to see the last day
of the dinosaurs.

(thunder rumbling)

However, the triceratops fossil
does show

that dinosaurs were alive
shortly before the asteroid hit,

perhaps even within weeks
of the impact.

This is an extraordinary
discovery,

and one that has never been
found before.

But if it's true
that dinosaurs were here

until the final weeks
before the impact,

there could be even more still
to find in this deposit.

DEPALMA:
This is, like, looking down
onto the side of a dinosaur

that died weeks to months
before the impact.

That is such a cool thing.

We've got all these bones
in the ground right now,

but the one thing that
we would just dream of finding

is that one dinosaur that died
on the day of the impact.

ATTENBOROUGH:
And the weather
isn't helping his search.

Got...

(groans)

That therapod print is toasted.

BURNHAM:
Yeah, it was in a low corner.

Look, it's all...
it's full of mud and water.

The problem is it's wet, look.

See, if we're not careful,
we're gonna lose the print.

And that's the biggest theropod
print we've got.

I see some areas that could use
glue right now, too.

♪ ♪

ATTENBOROUGH:
The team is racing to excavate
dozens of fossils

before the rains wash them away.

♪ ♪

DEPALMA:
We are up against
the clock here.

This stuff that could be exposed
right now

is gonna get ruined by the rain.

ATTENBOROUGH:
But then, the team comes
across something

that looks very unusual.

(speaking indistinctly)

BURNHAM:
What is going on right there?

Are we sure this
isn't crocodilian?

That's not crocodilian.
No.

GURCHE:
Let me try this piece
right here.

I'll go in from the top
and then twist up,

and it separates right
on that line.

DEPALMA:
Oh... that's skin right there.

That's actually scaly skin.
Oh my God.

No, no, no, no, no,
look, look, look.

Look at that pattern
right there.

Have you ever seen elongated
scales like that before, Dave?

BURNHAM:
Scutellates in birds.

Just careful.

Oh, my God.
BURNHAM:
It's changing again.

It's changing again.
My God.

We're seeing it for the first
time in 66 million years.

I think we got ourselves
a dinosaur.

ATTENBOROUGH:
A dinosaur fossil.

In the same mass
death assemblage as the fish

with the spherules
in their gills.

♪ ♪

DEPALMA:
This is the most
incredible thing

that we could possibly
imagine here,

the best-case scenario.

We're excavating this
mass death layer of fish

from the surge sent up by
the impact,

and we've got dinosaur remains.

The one thing that we

would always want to find
at this site,

and here we've got it.

This is unreal.

I, I, I cannot process this in
my brain.

No, I am absolutely blown
away by this.

Just my heart is literally
pumping out of my chest

wondering what is behind there,

just a couple of centimeters
back in the outcrop.

What is waiting for us back
there?

This is amazing.

ATTENBOROUGH:
The team keeps digging.

BURNHAM:
So this could be a ribcage,

it could be laying against
ribs that are curved.

DEPALMA:
There's something here.

That's hard.

That's bone right next to
the skin.

Look, that, that's an
articular surface right there.

So this is either a hip
or a shoulder element.

♪ ♪

ATTENBOROUGH:
After hours of
painstaking work...

♪ ♪

DEPALMA:
And we can go from
the thigh of the animal.

There's the knee.

And then you've got the

little calf muscles
of the, uh, dinosaur

over there bulging out,

and you go down
to the anklebones,

and these are the toes
of the feet.

We've got nails
at the tips of the toes.

It's a beautifully
preserved leg,

all articulated,
covered with skin.

ATTENBOROUGH:
The complete leg of a dinosaur.

DEPALMA:
In my wildest dreams,

I never expected to find
a dinosaur leg in this deposit.

Yeah.

I mean, and then it's got
skin and tissue.

It does look just like
a drumstick.

It looks like
a Thanksgiving turkey

just laid out in the ground.

ATTENBOROUGH:
Robert and his team think
they've found the body

missing from the crime scene...

a dinosaur that might itself
have witnessed

the cataclysmic impact.

DEPALMA:
Dinosaur fossils

are not known from the last
years of the Cretaceous.

And it was unclear whether
they were already extinct,

or in decline,
or what was going on.

So they were just
sort of absent.

♪ ♪

And this answers that question:
were dinosaurs still there then?

Well, yes, they were there weeks
to months before the impact.

This one likely died
in that surge.

♪ ♪

ATTENBOROUGH:
But such big claims
need verification.

♪ ♪

RILEY BLACK:
Paleontologists,

we kind of fight like
tyrannosaurs.

There are lots of different
opinions.

There are lots of different
hypotheses.

And this is all because

science is a process.

Science isn't a matter of just
going out into the rock,

and we found a new dinosaur.

STEVE BRUSATTE:
So I think we always

want to be skeptical,

but I think we want to be
extra skeptical

when there are big claims.

And it all goes back to that
expression that we hear

all the time, and that's that
extraordinary claims

require extraordinary evidence.

ATTENBOROUGH:
Robert is in the process
of sharing the team's finds

with the wider scientific
community.

As part of this process,
he has brought the dinosaur leg

to London, England,

to get a second opinion

from paleontologist
Paul Barrett...

an expert in
ornithischian dinosaurs

from the Natural History Museum.

So what do you think
this might be?

When we look at the leg,

it has claws like the claws

we see in small, agile,

bipedal running dinosaurs
that are plant eaters.

We can also rule out things
like Triceratops

partly just because

it's not big and stocky.

And the proportions
of those legs

are also different from some
of the other plant eaters we see

in that they have this
rather long ankle

and shin compared with
its thigh bone.

So as we narrow
those possibilities down

what we're left with probably

is an animal called
a thescelosaur.

(dinosaur grunts)

(growls)

ATTENBOROUGH:
Thescelosaurus are thought
to have lived next to rivers.

(dinosaur grunts)

♪ ♪

They had leaf-shaped teeth

common amongst herbivores,

and claws on their short
front limbs,

which they may have used
for digging.

♪ ♪

At the front of their mouth
they had specialized,

pointed teeth that could
help them to pull roots

out of the ground.

So it's possible
they dug for food.

♪ ♪

(biting flesh)

But how did the thescelosaur

that Robert's team found die?

Could it have killed
by another dinosaur?

BARRETT:
It's a possibility.

This is a relatively agile
animal.

And that turn of speed would've
been its primary defense

against the large predators
living alongside it.

(insects chirping,
dinosaur grunting)

DAVID MARTILL:
Whenever we're excavating
a dinosaur,

one of the things
that we're always keen to know

is how did the animal die?

It's not always easy to do that.

BRUSATTE:
So maybe we can find

evidence for things like broken
bones that didn't heal back up.

Sometimes we can even see things
like bone tumors and gout.

CHINSAMY-TURAN:
There are some wonderful fossils

where you can find bite marks
on them.

You can even find a,
a predator tooth buried

within the bones.

EMILY BAMFORTH:
In science,
we don't prove things.

We just disprove some things.

Generally speaking, unless

a cause of death leaves
a signature on the skeleton,

it's hard to tell.

ATTENBOROUGH:
CT scans Robert and the team
have taken of the dinosaur leg

allow a closer look at what the
animal might have gone through

before it died.

It doesn't seem to me
like there is any evidence

that this animal was predated.

None of the obvious tooth marks
or left over bits

of carnivore teeth

to suggest it's been eaten.

So we can see that
the bones look okay.

So this was an animal
that was probably living

and healthy at the time
that this happened to it.

ATTENBOROUGH (voiceover):
Could this be a dinosaur that
was swept up in the surge?

BRUSATTE:
The idea that there is
a dinosaur fossil,

potentially, that's a direct
victim of that,

that's very exciting.

I think ultimately it comes down
to a couple of things.

You know, are there injuries
on that fossil that show

that this dinosaur
was bobbing about,

heaving about in the water?

So are there things like breaks
on the bone or other things

that have not healed?

This is actually
a shoulder bone.

And this bone in the living
animal would actually be

way over here.

And similarly this
little bone here

would have been from about

a third of the way along
the tail, maybe halfway down.

So somehow these two bones

have been telescoped together.
Yeah.

So maybe this animal has been
tumbled around.

Could this be a victim
of the meteor strike?

I think it's entirely possible.

We've ruled out a lot of
other possible

causes of death for this animal.

So it could well be that this
was an animal that was there

being tumbled around in its
death throes in that river

as a result of the
asteroid impact.

Paleontologists do depend a lot
on tragedy.

Every little disaster

is the material we need to
actually develop our subject.

Tragic for the
individual concerned,

but we're just really happy
that it happened.

♪ ♪

ATTENBOROUGH:
After years of work
at this site,

Robert and his team
have uncovered

unprecedented detail about
the animals living there.

And he thinks that many of them
were alive on that fateful day

when the asteroid devastated
our planet.

But how exactly did they die?

The team's finds give us new
clues to answer that question.

♪ ♪

One of the most important days
in Earth's history

probably started much like
any other late spring morning.

♪ ♪

We think it was late spring
because paleobotanists

have found key evidence
about the season

from fossilized flowers.

The Tanis finds
are consistent with this,

including the fossils of
young fish that died at the size

they reach at that time of year.

♪ ♪

Perhaps this day, that would end
with so much death,

began with something different.

♪ ♪

A new life.

Robert only found
one pterosaur egg,

so it's possible that it had
a brother or sister

that hatched before the impact.

(pterosaur squawks)

To see the world
for one final day.

(pterosaur squawks)

♪ ♪

(insects chirping,
creature bellowing in distance)

No one can be certain of the
exact timings of the day

when the asteroid collided
with our planet.

But it's estimated that within
just 40 minutes of the impact,

the consequences
for the creatures of Tanis

would have been profound.

♪ ♪

Based on the team's finds,

and the latest evidence
from other scientists,

this is how the catastrophe
might have unfolded.

The asteroid is around
seven miles across...

bigger than Mount Everest...

and traveling at close
to 45,000 miles an hour.

♪ ♪

The impact causes an explosion
with over a billion times

the power of the first
atomic bomb.

GULICK::
It comes in so fast

that it wouldn't even have been
visible passing through

the atmosphere.

Right, it would have just come
in and hit in a moment.

ATTENBOROUGH:
At Tanis,
almost 2,000 miles away,

there might have been
an initial flash of light,

yet it is completely silent.

But at the impact site...

♪ ♪

...the asteroid vaporizes.

More than three trillion tons
of rock are ejected into space

in a blast of superheated
violence.

♪ ♪
(rocks crashing, wind whipping)

Winds higher than
600 miles a hour.

♪ ♪

A colossal earthquake.

Followed by a ring
of massive tsunamis.

♪ ♪

All the while the creatures
at Tanis

go about their business...

(pterosaurs grunting)

...just like any other day.

♪ ♪

(animals chittering)

(dinosaur makes guttural sound)

(snorts)

(thunder rumbling)

(pterosaur squawks)

The evidence suggests that baby
pterosaurs may have emerged

from eggs ready to fend
for themselves.

And that includes...

♪ ♪

Flying?

Well, almost.

(pterosaur chittering)

♪ ♪

Elsewhere, as the reverberations
of the impact

race out across North America...

(low-pitched rumbling)

...dinosaurs and creatures
of all shapes and sizes

are obliterated by the blast...

Incinerated in a firestorm
unlike anything seen since.

TIKOO:
If I were a dinosaur

standing on the coast
of North America,

I would just see a flash
and a fireball coming at me

and then I would be fried.

All you feel is an
awfully sharp,

stabbing pain in your ears,

then you explode.

♪ ♪

ATTENBOROUGH:
At Tanis, for a few more
precious minutes,

life continues.

But the clock is ticking.

♪ ♪

(creature chittering)

(dinosaurs growling,
horns clashing)

♪ ♪

The blast from the impact
never reaches Tanis,

but seismic shockwaves do.

(creatures chittering)

(rumbling)

♪ ♪

They are far more powerful than
any earthquake ever recorded.

PLESKO:
If you were standing on
the Gulf Coast of Texas,

that magnitude 12 earthquake
would have been strong enough

to actually jam your femurs
up into your body cavity

ATTENBOROUGH:
While the earthquake
that reached Tanis

was likely less destructive,

the effects would have been felt
by all that lived there.

(loud rumbling)

Seismic waves are now
slowly shaking

the whole region, causing water

to slosh and churn.

♪ ♪

At Tanis, these strange currents
in the river may be some of

the first signs
of what is coming.

♪ ♪

(thunder rolls)

Next, it begins to rain.

(pattering)

Ejecta spherules are falling
back to earth.

♪ ♪

As the spherules plummet,

friction heats them
until they're red hot.

♪ ♪

They soon transfer their heat
to the atmosphere...

which grows hotter
by the second.

♪ ♪

(sizzling)

As the searing heat builds,

the creatures of Tanis
are fighting for their lives.

♪ ♪

(dinosaur bellowing)

♪ ♪

And then, as seismic waves
rock the whole region...

♪ ♪

...a violent surge
wave 30 feet high

rushes up the Tanis River.

♪ ♪

♪ ♪

Surviving the turbulence
of the surge is a challenge

even for the best swimmers.

♪ ♪

Then, the slow but powerful
rocking of the river system

draws the water back.

♪ ♪

♪ ♪

A large, robust animal
like a T. rex

might have survived the surge.

♪ ♪
(pattering)

As might a hard-shelled reptile.

But there is much more to come.

As billions of tons

of superheated spherules
continue to fall,

the atmosphere gets
even hotter...

...igniting dead leaves

and sparking wildfires.

♪ ♪

Earthquakes...

Fire...

Devastation.

(dinosaur grunts)

Little would survive for long,

on land...

(bellowing)

Or in the air...

♪ ♪

(pterosaur groans)

BLACK:
The air around the planet
was effectively set to broil.

This was something that
you couldn't escape

if you were out on the surface.

♪ ♪

ATTENBOROUGH:
Those that live underground
may have had a better chance.

(creature chittering)

♪ ♪

As the slow rocking of the
river system continues to move

the water to and fro,
another powerful surge

hits the riverbank.

♪ ♪

(loud crashing)

For most, there is no escaping
the destruction.

♪ ♪

For many of the creatures here,

their stories end underwater.

♪ ♪

No one knows if
the giant tsunami caused by

the impact ever reaches
this far north,

but life here has already
changed forever.

The mud the two waves leave
behind will gradually turn into

the thick layer of crumbly rock

entombing the creatures
which died here.

(wind whipping)

Until 66 million years later,

when they are finally unearthed.

CLAYTOR:
We have a general idea

of what horrors were unleashed
on the landscape

by the asteroid impact.

But I think these sites may give
us the ability to actually

put them in sequence
and understand exactly

what these organisms
went through.

Even though there is a lot
of debate,

and there is a lot of
controversy,

every new thing that we find,

every new hypothesis
that's put forward,

whether it's accepted
or rejected,

gets us a little bit closer
to doing that mental time travel

and imagining ourselves back
in that Cretaceous world.

♪ ♪

(fire crackling)

ATTENBOROUGH:
Robert's finds have helped us
understand,

in remarkable detail,
what might have happened

at Tanis in the minutes after
the asteroid impact.

But what about
the rest of the world?

♪ ♪

Fires rage, destroying many
of the world's forests.

♪ ♪

As the horrific day
draws to a close,

many of the world's dinosaurs

are likely already dead.

Research shows that the angle
at which the asteroid hit,

and the sulfur-rich rocks
at the impact site,

amplified the devastation.

♪ ♪

Without sunlight, most plants
died, and food became scarce.

(thunder rumbling)

As the weeks and months passed,

any dinosaur left alive
would have died of hunger.

♪ ♪

In the oceans, it was the same.

Nearly all of the world's
plankton died,

leading to the starvation
of most marine creatures.

It's thought that

the impact winter that followed
caused a global temperature drop

of at least 48 degrees
Fahrenheit.

After this huge change
in climate,

the fossil record tells us that
three-quarters of all species,

including the dinosaurs,
were wiped out.

(crackling)

PLESKO:
The location of the
Chicxulub impact

really was a worst-case
scenario.

If the asteroid actually
had come in, you know,

30 seconds earlier,

30 seconds later,

it would have actually hit
the Atlantic Ocean

or the Pacific Ocean

and not the sediment-rich,
sulfur-rich

target of the Yucatan Peninsula.

Forests collapsed.

The plant eaters didn't have
any food to eat; they died.

The meat eaters didn't have any
plant eaters to eat; they died.

Ecosystems collapsed
like houses of cards.

BLACK:
This unintentional accident

that just was set in motion long
before dinosaurs even existed.

And it just happened to be
the one case of bad luck,

the one worst day
in the history of the planet.

ATTENBOROUGH:
Studies suggest that the planet
was in semi-darkness

for around a decade as dust
and soot slowly fell to Earth.

But then came something
wonderful...

♪ ♪

A new beginning.

Once the dust cleared from
the atmosphere,

and the sunlight returned,

plant life was gradually
restored,

led by ferns,
the spores of which

had lain dormant
deep underground.

♪ ♪

And the world began to turn
green once more.

But what about the animals?

♪ ♪

One of the reasons
some mammals survived

the Great Extinction
were burrows.

During the impact winter,

a burrow would have provided
warmth,

protection, and a place
to store food.

♪ ♪

(sniffing)

Mammals which were able
to thrive in the aftermath

were resourceful omnivores.

And the insects which survived

could have been one source
of food.

Their size would have been
another advantage.

(chittering)

When catastrophe strikes
and food is scarce,

the largest tend to die out,

whilst the smallest
often survive.

(creature chittering)

And they weren't alone.

♪ ♪

The turtle found at the dig site
may have been unlucky,

but many others survived.

As did crocodiles, snakes,

and many fish species.

BRUSATTE:
Life has found a way,

and life is now thriving again,

and it is those ecosystems
formed in the recovery

from the asteroid
that are the foundations

of our ecosystems today.

It's kind of amazing that
we're able to put our finger

on this one line in the rock.

And as much as we miss
the dinosaurs,

say if this hadn't happened,

we wouldn't be here.

ATTENBOROUGH:
And as for the dinosaurs...

did the impact
really kill them all?

Well, this beautiful fossilized
feather isn't from a bird,

but from a predatory dinosaur.

So, we have to be careful
when we say that dinosaurs

are extinct.

Because what we call birds
originally evolved

from the smallest feathered
dinosaurs.

So, to be correct,

we should say all non-avian
dinosaurs are extinct.

♪ ♪

The finds from Robert
and his team have given us

a more detailed picture...

(insects chirping)

...about what might have
happened

on the day that destroyed

the largest beasts ever to walk
the Earth.

♪ ♪

Dinosaurs were perhaps
some of nature's

most extraordinary creatures,

dominating the planet
for over 150 million years

before they became extinct.

(dinosaurs grunting)

But extinction comes
in different forms,

and many of the amazing
creatures and plants alive today

are also threatened.

It's possible that humanity
is having as big an impact

on the world as the asteroid

that ended the age
of the dinosaurs.

As human beings,
we are unique in our ability

to learn from the distant past.

The question is:

will we use that ability wisely
and do our very best

to protect the millions
of species

for whom, alongside us,
this planet is home?

♪ ♪

(water spraying)

(waves crashing)

♪ ♪

♪ ♪

♪ ♪