All language subtitles for NOVA - S49E06 - Dinosaur Apocalypse - The New Evidence_track4_[eng]

DAVID ATTENBOROUGH:
Sixty-six million years ago,

planet Earth was very
different from today.

Some of our ancestors at the time might
have looked like this furry creature.

The rulers of the land
were giant reptiles.

[SOFT GROWL]

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.

Sixty-six 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.

However, a truly extraordinary
dig-site might change that.

Hell Creek Formation.
North Dakota.

These sedimentary rocks
are rich in dinosaur remains.

From triceratops...

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.

Everything was fine on Tuesday
in the Cretaceous,

and the next second,
the world just wasn't the same.

Any time that an asteroid
the size of Mount Everest

smashes into the Earth,
that's not going to be a good day.

It's actually pretty remarkable
that anything survived.

Right, 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.

You're at the edge of your seat every
moment trying to dig this stuff up.

ATTENBOROUGH:
They call this 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.

It's almost beyond what we can imagine.

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...

into the lives of the very last dinosaurs.

And a minute-by-minute picture
of what happened

on the day the asteroid hit.

This landscape is full of fossils

dating from the Late Cretaceous,

the period which began around
a hundred million years ago

and ended 66 million years ago
when the dinosaurs vanished.

Palaeontologist, 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.

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.

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.

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.

Hell Creek records the very,
very last days of the dinosaurs,

and it's the best information that we have
in the world about that extinction event.

ATTENBOROUGH: This dig site
lies in the north-eastern corner

of the Hell Creek Formation.

Sixty six 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...

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

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.

But it wasn't until after Robert and his
team started digging here in 2012...

So somewhere from between there and down here is
where that came from, it's come from up above.

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

Here we've got this freshwater
environment of the Hell Creek formation,

and, this shocking red, green colours
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...

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

that 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.

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.

In this layer, the concentration of iridium
is 100 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.

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.

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 is 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.

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 fossilisation.

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.

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% of 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.

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.

DR 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.

DePALMA: 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: Palaeontologist
Dr David Burnham

and Lauren Gurche have been
digging with Robert for years.

Oh, wow.

-See, see the brown.
-Yep.

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.

Like doing a freaking dissection.

-Oh, my God.
-Biology of Tanis.

DePALMA: Oh, the scale, look,
look the wrinkles continue down that way.

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, there's the protuberance
right there.

I've only seen that on one other
specimen in life.

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.

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 fossilised,

and over millions of years,
has turned to stone.

ATTENBOROUGH: 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 colour 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 palaeontologists 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.

We know from bones that adult Triceratops

could reach 30 feet in length
and 10 feet in height.

[LOW GROWL]

Marks on the fossil also show us
that this one was badly scarred.

Triceratops were plant eaters.

Other fossils tell us they had
sharp beaks and hundreds of teeth,

which enabled them to shred hundreds
of pounds of tough vegetation.

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.

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.

ATTENBOROUGH: So they were probably
territorial, fighting rivals away.

These were very large animals that
probably had very large territorial ranges.

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.

If you weigh more than
an African elephant,

there's not much that can bother you.

Except perhaps a little mammal.

Robert found these jawbones
in a fossilised 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 fossilised
nuts and seeds in the burrow,

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

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.

PROF 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.

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 fossilised 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 won't foil the backside.
We'll just put the plaster right on.

ATTENBOROUGH: The dig team
has discovered a number of footprints.

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
small a mammal...

for lunch.

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.

Pterosaurs are not dinosaurs,
but flying reptiles

on a different branch
of the evolutionary tree.

There is nothing like
a flying reptile around today.

Pterosaurs got to enormous sizes.

MUSKELLEY: 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 is 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.

Male Pterosaurs usually had crests,

while females didn't.

So, crests may have been used
in courtship displays.

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.

The fossil record of
pterosaur eggs is really small.

So far we have a couple of eggs
from north-eastern 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
fossilised egg of a pterosaur

that Robert and his team found in Tanis.

The only one ever discovered
in North America.

If you look at it with a 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.

ATTENBOROUGH: To
investigate the pterosaur egg,

Robert has been given access to the
Diamond Light Source Synchrotron.

Situated in Oxfordshire, in the UK,

it's a powerful research tool
that acts like a giant microscope.

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?

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.

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!

Is 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
affirming for the first time.

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.

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 Pterosaurs just has
to make sure that the hole...

is perfect.

Success...

but it's not over yet.

Pterosaurs had two ovaries,

and they laid their eggs in pairs.

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.

Here on the sand bank, sandwiched between
the river and these glorious trees,

life at Tanis seemed to be thriving.

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 neighbouring 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.

So these are animals that were
actually walking in the water?

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.

[LOW RUMBLE]

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.

ATTENBOROUGH: Bite
marks found on T-rex bones

show that they may have eaten each other.

And a youngster would make an easy catch.

But not this time.

Very few footprint 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.

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 support the idea...

that dinosaurs and Pterosaurs were thriving
at Hell Creek shortly before the impact.

And if they were thriving...

they must have been reproducing.

No-one has ever found a T-rex nest,

but fossils from similar dinosaurs showed
they may have laid around 20 eggs

in a circular nest.

It's possible that like crocodiles
they partially covered their eggs

with vegetation to keep them warm.

[SNEEZES]

Looking after eggs must've been a tricky
business when you weigh seven tons.

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.

-You see the scales.
-I do. Oh, my God.

That excites me just looking at it.

ATTENBOROUGH: In 2019,
Robert finds something truly remarkable.

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.

Matrix saw, get the consolidate 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.

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.

Lauren, I'm worried
about brittleness here.

-Get that hammer.
-GURCHE: Yeah.

DePALMA: Give this a couple
of whacks with the hammer.

Okay. Move over
five centimetres. Good.

It's cracked loose.

-Yep.
-GURCHE: Okay. It's loose.

DePALMA: So we have
to get this out in one piece.

One.

Two. Three.

Yeeha!

-Total success.
-GURCHE: Total success.

DePALMA: 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.

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 fossilised 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.

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...

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 centre of its crater.

Anything living within 900 miles
of the hit is destroyed by the blast.

But what effect does the impact have
on Tanis nearly 2000 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
in modern science.

However, when it comes to the asteroid,

that asteroid hit the Earth one day,

and really hit the Earth that 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 hidden inside
the fishes themselves.

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.

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?

After a large asteroid impact,
a mix of vaporised 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 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 falling.

So, these creatures could have died
at the time of an asteroid impact.

Those have to have come
from the impact event.

You can't make spherules in other ways,

they are a vapour 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 they're 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 realise the thick crumbly
layer of rock at Tanis is full of them.

I mean, this stuff is,
oh my God, look at that one.

These things are just gorgeous.

DePALMA: 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.

Anything covered by the resin would
be frozen in an amber time capsule.

A well-preserved spherule can be analysed
to see if it came from the asteroid impact.

Loren has found something
trapped in there.

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.

PROF MAURASSE: The shape of the spherules,
the size of the spherules,

the colour of those spherules, can be similar
for material coming from different sources.

Only the geochemical signature
would tell you exactly what the origin

of the apparent material was.

PROF 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

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.

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 record
the very last day of the Cretaceous?

Full of fossilised creatures that were
alive at the moment the asteroid hit.

The potential for the Tanis site is huge.

And might Robert's team find
something extraordinary?

That's bone right next to that skin.

A dinosaur that died as a direct
result of the asteroid impact.

The day that the asteroid hit
would definitely be hell on Earth.

No matter where it is,
you're in for a bunch of chaos.