The Day the Dinosaurs Died Page #6

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led to total destruction.

But Marcelo has found evidence

that that may not have been the story here.

Plants that the hadrosaurs used to eat.

This is Nothofagus, the southern beech.

They're all around here, aren't they?

And if you want to see it,

look at that architecture.

And I want to show you also this one.

This is from Las Chinas,

the same valley we were

looking for the hadrosaurs.

Oh, this is fantastic.

- This is what the hadrosaurs

were walking on. - Yeah.

- And if you want to compare it...

- Well, that looks incredibly similar.

Is there actually a relationship

between this fossil leaf

and this living one?

Oh, there is a direct line

from this fossil and this one that

is living today in Patagonia.

So this is fantastic evidence

that, down here in Patagonia,

some spaces did actually make it through.

66 million years ago,

this region was warm, wet

and dense with vegetation

like the southern beech.

A species of plant that survived

the fires on impact day.

And if plants survived,

maybe the dinosaurs here

could have done, too.

Life down here should have been badly hit,

but the fossil evidence,

particularly of plant life,

is telling us a different story -

that the immediate fallout from Chicxulub

in Patagonia was not as bad as predicted.

So perhaps our hadrosaurs

had a stay of execution,

maybe they made it through that first day.

But something...

Something got them in the end.

To determine exactly what did happen

in the days, weeks and months

after the asteroid struck,

the Bremen team are still

hard at work studying rock

samples from the impact crater.

Dr Philippe Claeys thinks he's found

perhaps the most important clue yet.

So, Philippe, when this

asteroid struck Earth,

it had a massive and devastating impact.

But that didn't quite seal the

fate of the dinosaurs, did it?

Probably not. Remember, the

dinosaurs were ideally adapted

to the late Cretaceous environment.

They were the ultimate

animal for the Cretaceous.

What happened here is that

we have an incredible change

in the Earth's system,

basically kills the dinosaur

everywhere on Earth -

in Africa, Antarctica, in the

forests, or in the savanna.

But what made them extinct?

You talk about a global scale, suddenly.

- What went global? What happened?

- What went global is really

the ejection of material from the crater.

- Look at what I have in my pocket

- this is gypsum. - Right, OK.

This was part of Yucatan at the

time of impact. - Yeah. - OK?

And this material here contains sulphate.

And this gypsum affects the

chemistry of the atmosphere.

It changes it drastically.

This area's meant to be

rich in this sort of stuff.

It's supposed to be full of it.

But it's not.

We can look for the remnants of it here.

In the core, it's totally absent,

which means that almost the

entire sequence of gypsum

that was present in the sedimentary target

at the time of impact

went into the atmosphere.

This is a huge discovery.

The presence of gypsum means

the plume of vaporized rock

that spread across the world

was dense with sulphates

that blocked sunlight.

The same thing happened after the

1991 eruption of Mount Pinatubo

in the Philippines.

Sulphates reduced the amount of

sunlight reaching land by 10%,

which caused a drop in global temperatures.

25 years ago, Pinatubo had an

incredible effect on the atmosphere.

It cooled it by very little,

but it had an effect.

- And it stayed for a couple of years.

- Right.

Here, we have an event which is

orders of magnitude more important.

Pinatubo is nothing compared

to the Chicxulub impact.

It is really going global,

no place is protected,

no dinosaur can escape

the consequence of the Chicxulub impact.

This is the gypsum.

- This is what killed the dinosaurs.

- Wow.

This astonishing find is the

final piece of the jigsaw...

allowing us, for the first time,

to model what finally killed the dinosaurs.

It's what happened in the

days after the impact

that made it a global extinction.

Our blue planet turned Grey.

Long after the hot skies cooled,

ash and dust in the atmosphere

almost completely blocked out the sun.

As the lights went out,

global temperatures plunged

more than ten degrees

centigrade within days.

This is where we get to the

great irony of the story.

Because in the end, it wasn't

the size of the asteroid...

the scale of the blast,

or even its global reach

that made dinosaurs extinct.

It was where the impact happened.

Had the asteroid struck

a few moments earlier,

or maybe even a couple of seconds later,

then rather than hitting

shallow coastal waters,

it might have hit deep ocean.

An impact in the nearby

Atlantic or Pacific oceans

would have meant much less vaporized rock,

including the deadly gypsum.

The cloud would have been less dense

and sunlight could have still

reached the planet's surface...

meaning what happened next

might have been avoided.

In this cold, dark world,

food ran out in the oceans within a week,

and shortly after, on land also.

With nothing to eat anywhere on the planet,

the mighty dinosaurs stood

little chance of survival.

In Patagonia, 10% of plant

species went extinct.

The southern beeches would

have shed their leaves,

shutting down for the long winter

that the asteroid set off.

The hadrosaurs were left to starve.

The demise of the dinosaurs

down here in Patagonia

was nowhere near as dramatic as

being obliterated by a blast wave,

or drowned in a tsunami,

or even being caught up in

a colossal forest fire.

But they were doomed, nonetheless.

The dinosaurs as a group were

hugely successful and diverse,

they'd been on the planet for

more than 150 million years.

But this Chicxulub event was more

than just a local phenomenon.

It changed the climate globally,

plunging the world into

a deep, deep winter.

And there was no time to adapt.

So, in some ways,

the dinosaurs that died

instantaneously were the lucky ones.

This sudden climate change may

finally solve the mystery of

what happened in New Jersey.

As the food supply in the oceans dwindled,

shallow water creatures roamed ever deeper.

But eventually, the food would run out.

And all of those animals from

different parts of the oceans died,

coming to rest in a single layer.

It's been an incredible adventure

decades in the planning.

A multi-million-pound

scientific expedition,

weeks of drilling rock samples

from deep inside a super crater,

and months of studying hundreds

of metres of rock samples.

- So, this was E4. - Yep.

- Which is 53 million to 55.

We were just jazzed about

the science, all day long.

Many people have been up for 20 hours

and they were still just

going with enthusiasm,

describing the cores, looking

at the micro-fossils.

It was a heady experience.

All that hard work has

paid off in a big way.

The team has been able to reveal

extraordinary new details,

evidence about how the dinosaurs died.

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