♪ ♪
(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.
♪ ♪