Original subtitles

Back then, one of our closest ancestors might have

looked something like this little furry creature.

The rulers of the land were giant reptiles.

DINOSAURS Dinosaurs. That's one of the most infamous

carnivorous T. rex. And just behind are the bison of that

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 direct

evidence of that. In fact, no-one has ever found the fossil

of a dinosaur that died within 1,000 years of the impact.

However, a remarkable dig site promises to change that.

It's in the Hell Creek Formation in the American Midwest.

These badlands are rich in prehistoric remains.

From Triceratops... to pterosaurs. And here, one patch

of land about the size of a football pitch is yielding a

collection of astonishing fossils.

The precise location is a closely guarded secret because

this place may hold evidence... of one of the most dramatic

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

history of our planet.

All right, I'm gonna get down here between you. For ten

years, a paleontologist and his team have 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. It's

like trying to defuse a nuclear weapon while you're in a

rainstorm. He's named the site Tannis and believes it could

be a mass graveyard of creatures that were killed in the catastrophic asteroid strike.

A site that could reveal not only how the last dinosaurs

lived... but how they died. If the dig team is right, Tannis

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 100 million years

ago and ended 66 million years ago when the dinosaurs

vanished. Paleontologist Robert De Palma 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?

So many different theories are out there and nobody has a

tight answer to that question.

Judging from fossil evidence, this is what

Hell Creek looked like in the late Cretaceous.

There were low-lying marshy floodplains intercut by river

channels and covered with horsetails, ferns and trees. Back

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

Tannis lies in the north-eastern corner of the Hell Creek formation.

Instead of today's dusty prairies, there were sandy riverbanks.

Instead of rocky cliffs, there were forests.

And instead of the life we know today...

Well, Robert is hoping to find out more about what that was like.

A sandbank lying between a river and a forest

would one day become what Robert now calls Tannis.

He and his team have been digging here since 2012. So,

somewhere from between there and down here is where that

came from. What did they come from up above? What? Oh, yeah,

yeah, yeah. OK. And what they found is unexpected. Here

we've got this freshwater environment of the Hell Creek

formation and this shocking red-green colour is 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. How they got here

is a mystery. And there's more. I'm just going to go ahead

and plane down some of this rock. Sitting just above the

ammonites is something that many dinosaur hunters are

desperate to find. So, this orange layer right here is

composed 100% of impact-related debris that is enriched in

iridium. Iridium is an element that's rare in the Earth's

crust, but it's common in asteroids. The layer it's in is

called the K-P-G boundary. Your mum-um. Oh, dear. Really?

It's made up of dust and debris from a huge asteroid impact.

Look at that. That's me. Yeah, yeah, yeah, yeah, yeah.

That's what we want. OK, so it's coming from this area here,

so somewhere within that region is where these pieces are

coming from. The boundary separates the age of the dinosaurs

from the age of mammals, so the rocks here come from about

the time that the dinosaurs became extinct. No rattlesnakes.

What makes the site even more exciting is the rock layer

right beneath the boundary, where Robert found the

ammonites. The rock here is really not quite rocky, as you

would expect dinosaur bones and things to be encased. You'd

expect really, really hard rocks and jackhammers and things

like this, but it's very, very crumbly, and it just falls

apart in your hands. As well as being crumbly throughout,

this layer of rock is also around a metre thick, which,

along with other unusual features, makes Robert think that

something very strange must have happened here.

Maybe a flood or a mudflow, burying anything within it in

an instant. Oh, there's a beautiful... Look at that one.

Beautiful. This could mean that anything he finds in this

layer would have been quickly entombed, like the bodies in

the volcanic ash of Pompeii.

Robert knows from the geology that anything he finds at

Tannis will be tantalisingly close to the end of the age of

the dinosaurs and could be so well-preserved that it could

reveal new evidence that would bring this time period to

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

Robert digs at Tannis each summer. The only time the weather

allows him 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.

Paleontologists Dr David Burnham and Lauren

Gucci have been digging with Robert for years.

The Oh, wow. See the brown? Yep. That might be a tubercle

right there. And it seems today is their lucky day. Oh, my

God. Look at that. Look, the scales are preserved. They're

like doing a frequent dissection. Oh, my God. The biology of

Tannis. Oh, the scale. Look, the wrinkles continue down that

way. They're nice and wet so far. The scales are getting

smaller in that direction. How big are they there? I got

one with the projection over here. What? Oh, little... Yeah,

there's the protuberance right there. I've only seen that on

one other specimen in my life. This is the closest thing to

getting a touch of a living, breathing dinosaur. It is. They

found something extraordinary. It is so exceedingly rare, a

piece of triceratops skin in the Hell Creek Formation.

It 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. 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 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 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.

We know from bones that adult triceratops could reach

nine metres in length and three metres in height.

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

Triceratops were plant eaters.

Other fossils tell us that they had sharp beaks and hundreds

of teeth that enabled them to shred tough plants, such as

these cycads.

Almost all adult triceratops fossils, including Roberts,

have been found on their own. So it's possible that the

adults were solitary, like modern-day male rhinos.

So they were probably territorial, chasing rivals away.

And perhaps marking their territories.

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 the fossilised burrow at

Tannis. 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.

Robert also discovered fossilised nuts and seeds in the

burrow. So we have an idea about what it might have eaten.

Robert'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. And

that's exactly what happened here at Tannis.

You know, we won't foil the back side. Right, we'll just

plaster it on. Robert has discovered a number of footprints.

Yeah, let's see. Looks like a good print. Yeah.

Their shape gives him a clue as to what might have made them.

If he's right, they were made by a winged creature

that might well have liked a small 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.

Male pterosaurs usually had crests, while females didn't.

So crests may have been used in courtship displays.

And we have an indication of where females laid their eggs.

Because evidence suggests one pterosaur laid hers in the

soft, sandy banks of the river at Tannis.

And this is a fossilised egg of a pterosaur that Robert

found there. 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.

Robert has been given access to the Diamond Light Source

Synchrotron in Oxfordshire. It's a very powerful research

tool that acts like a giant microscope.

By accelerating electrons in this huge ring, the synchrotron

creates beams of light many times brighter than the sun.

Robert and paleobiologist Dr Victoria Edgerton now want to

turn that beam onto the egg fossil to discover more about

its chemical make-up. We're pretty much left with the egg

of a pterosaur. We're not lined up on the skeleton, but we

might have to move the stage a little bit to get to the

right part. Sure. Meanwhile, Robert can reveal the creature

inside.

And this... 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 have looked like

when it hatched. That's how big the creature would have been

outside the egg, if it had hatched. So, this is the baby.

How big was it going to grow out? 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 Asdarkid pterosaurs. That is the giant pterosaurs.

Oh, they were the whoppers, weren't they? I mean, what, 25

feet? Some of them. This probably had a wingspan maybe 15

feet, five metres. 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.

They've scanned the egg here and in America.

Victoria has the results. So, what have you learnt from

this cyclophon 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. OK. Can you see any

sign of the shell? And what sort of shell was it? We can.

What I can show you 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 helps 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 then had hard

-shelled eggs. Yes. So, this is a new discovery about those

dark-skinned pterosaurs. Absolutely. This is something that

we are confirming for the first time. Huh. Those 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 look for places like canes 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.

Grr!

Grr!

Grr! Success. But it's not over yet. Pterosaurs

had two ovaries and they laid their eggs in pairs.

Here, on the sandbank, sandwiched between the river and

these glorious trees, life at Tannis seemed to be thriving.

Whoops. Never a dull moment. But all that was about to change.

The chain of events that led to the extinction of the

dinosaurs began in the distant past, deep in space.

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 it's thought that many, many millions of

years ago, a rock was bumped into a new orbit.

And diverted on to a collision course with planet Earth.

Robert is building a vivid picture of late Cretaceous life

at Tannis. And the team have found a way to find out some

more well-preserved footprints. So these are animals that

were actually walking in the water? These guys would have

been essentially on a mushy riverbank going down to drink

at some point. Animals tend to congregate around the rivers.

This print is 30 centimetres long. So I think this is from

a type of dinosaur that we call a duck-billed dinosaur. And

they would have been very common in the Cretaceous. They

ate the plants in the area and they got very large, 30 feet

long. 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.

This is Robert'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.

Robert also found this at Tannis, the crown of a tooth. Its

shape and its serrated edge are indications that it comes

from an adult T. rex.

contarien

Bite marks found on T. rex bones show that they ate

other T -Rexes. And a youngster would make an easy catch.

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 have been many more nearby.

And that supports the idea that dinosaurs and pterosaurs

were thriving at Tannis shortly before the impact.

And if they were thriving...

they must have been reproducing.

Fossils from dinosaurs similar to T-Rex show they

may have laid around 20 eggs in a circular nest.

It's possible that, like crocodiles, they

partly covered their eggs to keep them warm.

For one T-Rex, a misfortune

and one T-Rex, a disaster was looming. But for all dinosaurs, a disaster was looming.

It was approaching.

Its 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 was not to be. And Earth's fate was sealed.

As Robert's dig continues, his vision of what happened at

Tannis is finally starting to come together. It seems the

sandbank was full of life. T-Rex, Triceratops, little

mammals, alongside the footprints of other dinosaurs and

pterosaurs, all in a very small area. See the scales? I do.

Oh, my God. That excites me, just looking at it. Then Robert

finds something truly remarkable.

See the cracks already forming? Look at that. So we're going

to have to really monitor that before we glue it. Because

this is getting vulnerable now. An almost complete creature.

To get this block out, we're freezing it.

Robert is about to attempt something tricky.

Steady. Let's go. To get the fossil out in one piece,

they're trying to freeze it using liquid nitrogen at almost

200 degrees below zero.

Watch the footing. Lorne, I'm worried about brittleness

here. Sure. Get that hammer. Give this a couple of whacks

with the hammer. OK. Move over five centimetres. Good.

It's cracked loose. Yep. OK, it's loose. So we have to

get this out in one piece. One, two, three. Yee-haw! Total

success. Total success. 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.

And the creature Robert 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 scorched edges here tell us that this was a bayonet turtle.

Robert's bayonet turtle looks very similar to modern

cooter turtles and lived in the same sort of freshwater

environment.

For a turtle, tennis would have been ideal.

It would have been warm, shallow water...

...plenty to eat...

...and lots of safe places in which to warm up in the late Cotacean sunshine.

The turtle fossil Robert found is almost complete. 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.

A violent end to one of the many creatures found in the

crumbly rock layer at Tannis. When I look at the animals and

plants preserved in the sediments of Tannis and the

footprints beneath it, I see a picture of a vibrant

ecosystem, many different dinosaurs, and a thriving, thriving place.

After ten years of digging, there is now enough evidence to

piece together much of the story of Tannis and the creatures

which lived here.

Robert has found so many fossils, it looks as if even at

the very end of the late Cotaceus, Tannis was bursting with

life. Full of the giant reptiles that had dominated

the planet for more than 150 million years.

It's impossible to know how much longer their reign would have continued.

Because all this was about to end.

The asteroid hit...

...in what is now the Yucatan Peninsula in Mexico.

It's called the Chicxulub asteroid after the

town nearest to the centre of its crater.

Any living thing within 900 miles of the impact... ..was destroyed by the blast.

But what effect did the impact have on Tannis nearly 2,000 miles away?

To find out, Robert is looking for clues that might

link Tannis to the actual day the asteroid hit.

We've got some wood and pressed up against this, and all

intertangled, we've got the carcasses of fish. OK. That's a

beautifully preserved tail, so that fish is going to be

absolutely fine. Absolutely gorgeous. So part of the detail

work that we're doing right now is going in and checking out

all the individual elements in this mass death layer. Some

of the evidence he's found so far has been hidden inside the fish themselves.

In more ways than one, it literally is an operation of a

Cretaceous fish, so we're performing surgery on this thing.

Robert needs to open this fish's skull. And very carefully,

we want to separate this from the rest of the fish. OK.

There we go. Opening up the fish. Got a nice ant that made a

home in there. And beautiful. Look at that. OK, here we have

the gill bars of the fish. Those are the bars that hold the

filaments of the gills. And between the gill bars, all of

these clusters of round objects, those are the

ejectospherules. Ejectospherules are tiny balls that were

once molten rock. They could be evidence of what Robert

suspects, that creatures here died on the day of the

asteroid strike. Those ejectospherules last saw the light of

day when they were flying through the air 66 billion years

ago.

After a large asteroid impact, a mix of vaporised

and molten rock is propelled into space.

There it cools, solidifying into tiny glass droplets. Some

carry on deeper into space. But what is the result? Most are

pulled back to Earth by gravity.

After a major asteroid hit, trillions of ejectospherules

would fall from the sky. 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.

Once Robert begins to look for ejectospherules, he finds

more and more and realises 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. Ejectospherules like this give us

a fingerprint of where they came from. 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? To see if that's the case, Robert needs

to find a spherule that hasn't turned to clay. Oh, my God,

that's a beautiful droplet. OK. The small pieces of orange

material that Robert and Lauren are digging up may be able

to help. There, amber. If there was anything flying through

the air at that time, this is where it's going to get

caught.

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.

If they find a spherule preserved in amber, it could be

analysed to see if it comes from the Chicxulub asteroid

impact. The spherule is a very important part of the

asteroid's history. So, during this batch, we were

incredibly lucky that we came across two completely

unaltered spherules. This spherule could be something

amazing. Evidence preserved well enough to analyse for chemical clues.

If so, it could link tennis directly with the

Chicxulub impact and the last day of the dinosaurs.

It's a very important part of the asteroid's history. To

investigate, Robert is joined at the Diamond Light Source by

Professor of Natural History, Phil Manning, of the

University of Manchester. They've already run initial tests

on the spherules in America. 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. Because 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. We can see

once we've scanned it and looking at spherules from other

sites in North Dakota, we can get a baseline for what the

ejector 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 tennis, it's a match. I

mean, it perfectly overlays. So I think this is powerful

evidence supporting that tennis and Chicxulub are linked.

And what do these findings mean for the rest of the fossils

that you're finding in tennis? This data is key for the

entire site because once you have that link and you know

what impact affected tennis, 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. And the synchrotron here

in the UK reveals something even more remarkable.

So this is showing a beautiful synchrotron scan of a half

of one spherule. The glass is a good geochemical fingerprint

and we've got calcium, some iron, we've got strontium. 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 is 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 would 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 spherule, a piece of meteorite,

that's what it's going to look like. This could be a piece

of the Cheechaloobe asteroid. The piece of the bullet that

killed the dinosaurs? No.

Robert could have found a fragment of the asteroid itself

in Tannis. Physical evidence linking this site to the

Cheechaloobe impact. But Tannis is almost 2,000 miles away

from where the asteroid hit. So exactly how did it cause the

creature's deaths?

To answer that question, Robert is searching in the mass death layer.

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.

Robert uncovered a tangled mass of fossilised creatures and

logs surrounded by spherules and crushed together in what's

known as a log jam. 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're

so well-preserved. But what could have caused the wave?

One theory is a tsunami.

The asteroid hit at sea. Recent studies show

it may have caused the wave almost a mile high.

The height of the wave would have gradually reduced as it

spread across the oceans. In the late Cretaceous, North

America was divided by a narrow sea that's been called the

Western Interior Seaway. The tsunami could have travelled up

this towards Tannis.

But the wave was so high that it was almost impossible But

there's a big question about the tsunami idea. The timing.

Oh, which fish is that? It's a new contact. If a tsunami

killed the fish, it would have to have hit while ejector

spherules were falling. Because spherules were found in the

fish's gills. So, how long after impact did the spherules

arrive at Tannis? Pretend this ball of foil is a piece of

ejector coming out of the crater. It would then go on an arc

path, ballistic trajectory, out of the crater and to

wherever it lands, in this case, Tannis. If we know the

distance between myself and the landing site and if we know

the size of that ball, we can accurately calculate how long

it would take to get there.

The result is surprising. Robert and his team calculated

that these ejector spherules landed at Tannis between 13

minutes and two hours after the impact.

If a wave killed the fish, it must also have reached Tannis within two hours.

Data from recent tsunamis show even a small amount of damage

but a powerful one would take much longer than that to

travel almost 2,000 miles from the impact site to Tannis.

So, if it wasn't a tsunami, what could have caused a surge

of water at Tannis?

Professor Stein Bondovic is an expert in tsunamis.

The fjords in Norway are very special. We have tall

mountains surrounding bodies of water, so the water is

usually very calm. In 2011, something very strange happened.

The water in the field began to move violently. The height

of the water increased by one and a half metres, like a

maelstrom with turbulent water. Someone said that the fjord

was boiling. News started to roll in. There'd

been an earthquake 5,000 miles away in Japan.

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. I saw immediately that they looked

like a tsunami wave. So, later in the afternoon, you can see

that the fjord is perfectly calm. 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.

A magnitude 9 earthquake had devastated the north-east of Japan around Fukushima.

But how did that affect a fjord so far away? So, no-one in

Norway could feel the earthquake. But I could see that the

time matched the arrival of the waves here in the fjord.

Eventually, Stein and his team realised that this might have

something to do with seismic waves, shock waves that pass

quickly through the earth during an earthquake. So, it took

only 12 minutes before the first signal of the earthquake in

Japan reached all the way here to western Norway. So, it was

the seismic waves that caused the earthquake. The waves that

caused the normally calm water in the fjord to slosh

turbulently back and forth. Just thinking of that,

scientifically, it's fantastic.

Could something similar have happened in Tannis? The large

weather currents can be through the orange waves. Trying to

find out is geophysicist, Professor Mark Richards, who's

been studying the site at Tannis for several years. He's

working with Robert to discover what could have caused a surge of water here.

A tsunami can't get here in less than a minimum of 12 hours.

But seismic waves travelling from the Yucatan impact site to

North Dakota can arrive here fairly quickly.

In the late Cretaceous, the western interior seaway that

divided North America could have been connected to Tannis

through a sea wave. It's a system of rivers.

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 Tannis.

So, seismic waves from the impact could have caused surges

of water in the Tannis River system. Seismic waves get here

quickly enough, coming up the Tannis River, inundating this

area, arriving at the same time these spherules are still

falling out of the air.

The mystery of the wave and the thick layer of crumbly rock

has been solved. Seismic waves travelling through the earth

could have caused powerful surges of water at Tannis.

Possibly carrying mud and marine creatures like

ammonites from the western interior seaway.

Dumping them on the Tannis sandbank and burying

everything at the same time as spherules fell.

Over millions of years, the mud would turn into the layer of

crumbly rock. And that's the beauty of Tannis. 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.

If the extinction of the dinosaurs was a crime, the

detectives 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.

No-one has ever found the fossil of a dinosaur that was

killed by the effects of the asteroid impact. But Robert did

find part of a triceratops in the crumbly layer at Tannis.

So could that be the remains of a dinosaur that died on that

day? I'm still dubious about the horn. I kind of want to

keep the horn in the jacket. I think if you took it off, at

least take this section and see what's going on under here.

To find out, the team needs to establish cause of death,

which can be difficult when you only have a piece of skin

and a horn to go on. This is the horn after they'd 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.

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.

Could this triceratops have survived until the day of the

impact? The team found evidence, including sagging in the

skin, which suggested 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. Perhaps in

the months before the impact, the broken horn put

the triceratops at a disadvantage over its rivals.

And that might have led to starvation.

ROCK MUSIC PLAYS Robert has still not found direct evidence

of a dinosaur that was killed by the asteroid. We've got all

these bones on 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.

And the weather isn't helping his search.

Oh.

That theropod's print is toasted. Yeah, it was in a low

corner. It's full of mud and water. The problem is it's wet.

Look, see, if we're not careful, we're going to lose the

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

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

The team is racing to excavate the footprints, along with

dozens of fish fossils tangled together in a log jam before

storms wash them away. We're up against the clock here. The

stuff that could be exposed right now is going to get ruined

by the rain.

But then Robert comes across something that looks very

unusual. That's my god. What is going on right there? Are we

sure this isn't a crocodilian? That's not a crocodilian. No.

I'm going to try this piece right here. I'll go in from the

top and then twist up and it separates on, right on that

line. Oh. That's skin right there. That's actually scaly

skin. No, no, no, no, no. Look, look, look. Look at that

pattern right there. Have you ever seen elongated scales

like that before, Dave? Scudalates and birds. Just careful.

Oh, my god. That's changing again. Oh, my god. We're seeing

it for the first time in 66 million years. I think we've got ourselves a dinosaur.

A dinosaur fossil. And unlike the triceratops, this is

located in the log jam, the mass death layer, surrounded by

the fish with spherules in their gills.

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 cannot process this in my brain. 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 centimetres back in the outcrop. What is waiting for us back there?

The team keeps digging. The scales get big again over on

this side. So this could be a rib cage. It could be laying

against ribs that are curved. There's something here. That's

hard. That's bone right next to the skin. But that's an

articular surface right there. So this is either a hip or a shoulder element.

After hours of painstaking work...

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

dinosaur over there bulging out, and you go down to the

ankle bones. 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. The complete leg of

a dinosaur. In my wildest dreams, I never expected to find a

dinosaur leg in this deposit. 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. And

this weird scale pattern on the thigh of the animal, which

we've never seen in a dinosaur before. Well, Thesiosaurus

don't have any form of defence, so they have to have

camouflage or something. That's a good point. So this could

have been some sort of camouflage marking. Robert thinks he

has found the body in question. A dinosaur that might itself

have witnessed the cataclysmic impact.

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, this one likely died in that search.

For such big claims, Robert needs verification.

He's brought the dinosaur leg to London to get a second

opinion. And then here are the pads of the toes. You can see

all those beautiful scales lined up. From Professor 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 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 thesilosaur.

Thesilosaurs lived next to rivers where there was plenty

of rich vegetation to feed on. They had leaf-shaped teeth

common amongst herbivores and claws on their

short front limbs. Excellent for digging.

They were also known as the thesilosaurs.

But how did Robert's thesilosaur die? Could it have been

killed by another dinosaur? It's a possibility. This is a

relatively agile animal. And that turn of speed would have

been its primary defence against the large predators living

alongside it. So,

to escape a hungry T. rex, a thesilosaurs'

first line of defence would have been to run.

But it may have had another defensive trick.

Living next to rivers, it's possible thesilosaurs were able to swim.

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

animal was predated. None of the obvious tooth marks or

leftover bits of carnivore teeth to suggest it's been

eaten. So, how do you think it died? It didn't have any

particularly nasty diseases when it died. As we can see,

the bones look OK. So, this is an animal that was probably

living and healthy at the time that this happened to it.

Could this be a victim of the meteor strike? I think it's

entirely possible. 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 maybe a third of the way along the tail, maybe

halfway down. So, somehow, these two bones have been

telescoped together. So, maybe this animal has been tumbled

around. We've ruled out a lot of other possible causes of

death for this animal. So, it could well be that this is an

animal that was there, being tumbled around in its death

throes in that river as a result of the asteroid impact.

Well, it is exactly analogous to those human bodies found

in Pompeii. It's very similar in terms of that quick

entombment. Yes. And it's almost as evocative. That's

absolutely true. You've got literally the blink of an eye at

the end of the Cretaceous snapped up into

history, and there it is ready to be dug up. Wow.

After years of investigation, Robert has found out a great

deal about the creatures which lived at Tannis. And he knows

that many of them were alive on that fateful day when the

asteroid devastated our planet. But how exactly did they

die? Robert's findings show that Tannis was a very dangerous

place to be. These kinds of findings now allow us to tell

the story of that day and finally answer that question.

One of the most important days in Earth's history

probably started much like any other late spring morning.

We know the season because Robert found fossils of young

fish that died at the size they reach at that time of year.

This agrees with evidence already found by other scientists.

Perhaps this day that would end with so much

death began with something different. A new life.

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 Tannis would have been profound. The

asteroid collided with our planet Based on Robert'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 travelling at close to 45,000 miles an hour.

The impact causes an explosion bigger than a billion Hiroshima atomic bombs.

At Tannis, almost 2,000 miles away, it's completely silent.

But at the impact site,

the asteroid vaporises. More than three trillion tonnes

of rock are ejected into space in a blast of superheated

violence.

Winds higher than 600 miles an hour. A colossal

earthquake, followed by a ring of massive tsunamis.

All the while, the creatures at Tannis go about their business.

Just like any other day.

The evidence suggests that baby pterosaurs emerged from

the egg, ready to fend for themselves. And that includes...

flying? Well, almost.

Elsewhere, as the devastation spreads out across North

America towards Tannis, dinosaurs and creatures of all

shapes and sizes are obliterated by the blast.

The Tannis is the largest planet in the world.

At Tannis, for a few more precious minutes, life

carries on as usual. But the clock is ticking.

The blast from the impact never reaches Tannis. But seismic shockwaves do.

They are far more powerful than any earthquake ever recorded.

The Thessalosaur might head for a place of safety.

But seismic waves are now slowly shaking the

whole region, causing water to slosh and churn.

At Tannis, the Tannis is the largest planet in the world.

Strange currents in the river give a hint of what is still

to come.

Next, it begins to rain. Ejectors ferules are falling back to Earth.

As the ferules begin their fall, friction heats them until they're red hot.

Then the heat transfers to the air. Temperatures rise with every second.

As the heat builds, the creatures of Tannis are fighting for their lives.

And then, as seismic waves continue to slowly rock the whole region...

a violent surge wave, 10 metres from Earth, rises high, rushes up the Tannis River.

Surviving the turbulence of the surge is a challenge even for the best swimmers.

Then, the powerful rocking of the river system

slowly begins to draw the water back the way it came.

Swimming may have saved the Thessalosaur in the past, but not this time.

A large, robust animal like a T-Rex might have survived the surge.

As might a hard-shelled reptile. But there is much more to

come as billions of tonnes of superheated ferules continue

to fall, the atmosphere gets even hotter,

igniting dead leaves and sparking wildfires.

Earthquakes. Fire. Devastation.

Little would survive for long... on land...

or in the air.

As the air reaches the temperature of an industrial oven,

those that live deep underground may have a better chance.

As the slow sloshing of the river system continues...

another powerful surge hits.

TANIS There is no escaping the destruction.

For many of the creatures of Tannis, Their stories end under water.

In less than two hours, the world has changed forever.

The mud the surge waves leave behind will gradually turn

into the thick layer of crumbly rock entombing the creatures

which died here.

Until 66 million years later, when they're finally unearthed.

Robert's finds have helped us understand in remarkable

detail what happened at Tannis in the minutes after the

asteroid impact. But what about the rest of the world?

The impact triggered catastrophic events such as earthquakes

all over the planet. And as ferials continued to fall,

wildfires may have sprung up around the globe.

As that horrific day drew to a close, many of the world's dinosaurs were already dead.

Research shows that the angle at which the asteroid hit

and the sulfur-rich rocks at the impact site amplified the

devastation. Billions of tons of sulfur were

ejected into the atmosphere, blocking the sunlight.

Without light, most plants died and food became scarce. 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 disappeared, leading to the starvation of most

marine creatures. It's thought that the nuclear winter that

followed caused a global temperature drop of at least 25

degrees centigrade. The fossil record tells us that this

huge change in climate marked the disappearance of three

-quarters of all species, including the dinosaurs. 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?

Back at Tannis, Robert has unearthed something that could

have helped save some of the creatures from the devastating

fires. We saw a little thing poking out, so we kind of

followed it back. And I'm so glad that we did, because what

we have here is a fossil burrow from an animal 66 million

years ago. The only animals that would have been around back

then that would likely build a burrow like this would be the

small mammals, roughly ferret-sized, and also some reptiles.

If it is from a mammal, this is sort of a window into the

lifestyle of some of our oldest ancestors out here. This guy

would have burrowed sideways right into the riverbank. We

actually have some scratch marks on there from the interior

when they were digging it, going back, and he would have

lived back here and sought shelter from the dinosaurs,

because they just did not want to get eaten.

Burrows are part of the reason that mammals survived the

great extinction. During the nuclear winter, a burrow would

have provided warmth, protection, and a place to store food.

Mammals that survived were resourceful omnivores, and

insects would have been a plentiful source of food.

And they had another advantage. Their size.

If conditions are right, many animal species get larger

as they evolve over millions of years. Take T. rex as an

example. This is a cast of the lower jaw of a predecessor

called Gorgosaurus, which lived 72 million years ago.

Whereas this is the cast of the lower jaw of a T. rex, which

lived five million years later. Look at the difference in

size. But the bigger the creature, the more energy they

need to stay alive. So when catastrophe strikes and food is

scarce, the largest tend to die out, whilst the smallest often survive.

That's one of the reasons why many of the smaller mammals

lived through the great darkness. And they weren't alone.

Robert's fossil turtle may have been unlucky, but many others survived.

As did crocodiles, snakes, and many fish species. And as for

the dinosaurs, did the impact really kill them all? Well,

this beautiful fossilised 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.

Robert's finds have given us a better idea than ever before

about what happened on the day that led to the extinction of

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.

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. Now we must use that ability

wisely, and do our very best to protect the millions

of species for whom, alongside us, this planet is home.

NASA Jet Propulsion Laboratory, California Institute of Technology