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00:00Six-six million years ago, planet Earth was very different from today.
00:18Some of our ancestors at the time might have looked like this furry creature.
00:31The rulers of the land were giant reptiles.
01:01Dinosaurs. That's one of the most infamous, a carnivorous T-Rex.
01:18And just behind are the bison of that time, a common plant-eater, Edmontosaurus.
01:25But what happened to them all?
01:28Sixty-six million years ago, an asteroid hit the Earth.
01:32And scientists think that it was this collision that wiped out the dinosaurs.
01:40But no one has ever found the fossil of a dinosaur that they know for certain died as a result of the impact.
01:50However, a truly extraordinary dig site might change that.
01:55Hell Creek Formation, North Dakota.
02:03These sedimentary rocks are rich in dinosaur remains.
02:07From Triceratops.
02:13To T-Rex.
02:17Now, in a patch of land no bigger than two football fields, a long-buried secret is coming to light.
02:27Because 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.
02:39Everything was fine on Tuesday in the Cretaceous.
02:45And the next second, the world just wasn't the same.
02:49Any time that an asteroid the size of Mount Everest smashes into the Earth, that's not going to be a good day.
02:55It's actually pretty remarkable that anything survived.
03:01Get down here between you.
03:03For almost ten years, a team of scientists has been trying to find out exactly what happened here.
03:13You're at the edge of your seat every moment trying to take a step up.
03:16They call this site Tannis, 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.
03:33This site might reveal the remarkable story, not just of how the dinosaurs lived, but how they died.
03:40The impact really was a worst case scenario.
03:47It's almost beyond what we can imagine.
03:51If the dig team is right, Tannis could be a place where the remains of a long lost world are frozen in time.
04:02A place that gives us, for the first time, an unprecedented window
04:06into the lives of the very last dinosaurs.
04:17And a minute-by-minute picture of what happened on the day the asteroid hit.
04:26Dinosaur Apocalypse. The New Evidence.
04:30Right now on NOVA.
04:36Dinosaur Apocalypse. This landscape is full of fossils dating from the living CAC.
04:38This landscape is full of fossils dating from the late Cretaceous,
05:06the period which began around 100 million years ago
05:10and ended 66 million years ago when the dinosaurs vanished.
05:18Paleontologist Robert de Palma wants to find out more.
05:24I think anybody who has ever liked dinosaurs in the past, or still does,
05:29has thought at one point or another, well, what happened to them?
05:32Why are they not here anymore?
05:36At the end of the late Cretaceous,
05:54fossil evidence tells us Hell Creek might have looked like this.
05:59There were low-lying marshy floodplains intercut by river channels
06:06and covered with horsetails, ferns, and trees.
06:11Back then, it was warm and wet here all year round.
06:15If we go back to about 66 million years ago,
06:25the Earth in some ways was very similar to today,
06:28and in other ways it was an alien world.
06:31The climate was very different.
06:32The temperature was different.
06:33There were no ice caps at the poles.
06:34Hell Creek is one of the most famous and well-studied areas
06:39for digging up dinosaurs.
06:42Hell Creek is really the only place in the world,
06:46at least right now,
06:47where we have a really good record of the last surviving dinosaurs.
06:51Hell Creek records the very, very last days of the dinosaurs,
06:55and it's the best information that we have in the world
06:58about that extinction event.
07:03This dig site lies in the north-eastern corner
07:07of the Hell Creek formation.
07:1066 million years ago,
07:12instead of today's dusty prairies,
07:14there were sandy, silty riverbanks.
07:17Instead of rocky cliffs,
07:19there were forests.
07:23And instead of the wildlife we know today,
07:26well, scientists are trying to find out what that was like.
07:37One of the great things about paleontology
07:40is also one of its most frustrating elements,
07:43and that is that you can never be sure.
07:46Until somebody builds a time machine
07:48and we can go back in time
07:49and actually observe dinosaurs in their natural environment,
07:53we will never know for sure
07:54whether our inferences are correct or not.
07:57So it'll always be open
07:59to a bit of interpretation and uncertainty,
08:02because fundamentally,
08:04trying to pinpoint something
08:06that happened on a given day,
08:0866 million years ago,
08:09is really, really tough.
08:11And so a lot of paleontology
08:13is putting forth theories,
08:15and then other paleontologists
08:17coming forward and saying,
08:18no, that doesn't make sense
08:20because here's another theory.
08:23Every paleontologist
08:24can only hope their site
08:26might uncover something new to debate.
08:31A sandbank lying between a river and a forest
08:34would one day become
08:36what Robert now calls Tannis.
08:38The site had been explored
08:45by others in the past.
08:50But it wasn't until
08:51after Robert and his team
08:53started digging here in 2012...
08:56So somewhere from between there
08:58and down here is where that came from,
09:00wouldn't it come from up above?
09:01What?
09:02...that anyone would know
09:03how important this site could be.
09:05Here we've got this freshwater environment
09:08of the Hell Creek Formation,
09:10and this shocking red-green colour
09:14is coming from the shells of ammonites,
09:16a marine organism,
09:17kind of like a coiled snail in appearance.
09:19So we've got this marine organism
09:20that's been thrown up
09:22into this freshwater environment,
09:25and they do not belong here.
09:28How they got there is a mystery,
09:30but even more intriguing...
09:33I'm just going to go ahead
09:34and plane down some of this rock.
09:36Sitting above the ammonite shells
09:38is something that holds a crucial clue
09:41about the age of these rocks.
09:44So this orange layer right here
09:47is composed 100% of impact-related debris
09:50that is enriched in iridium.
09:52Iridium is an element
09:53that's rare in the Earth's crust,
09:56but it's common in asteroids.
09:58The layer it's in marks the KPG boundary.
10:06The boundary is made up of dust and debris
10:08from a huge asteroid impact.
10:12It's been dated to 66 million years ago,
10:15the time when dinosaurs disappeared.
10:18Look at that.
10:19That's me.
10:20Yeah, yeah, yeah, yeah, yeah.
10:21That's what we want.
10:22Okay, so it's coming from this area here.
10:23So somewhere within that region
10:24is where these pieces are coming from.
10:25And it has been found all over the world.
10:29In this layer,
10:30the concentration of iridium
10:31is 100 times higher
10:32than the baseline
10:33for the rest of the Earth's crust.
10:35So perhaps the simplest answer to that
10:38is that it came from outer space.
10:40And so we have this wonderful marker
10:43that is the iridium layer
10:45that coincides with the extinction event.
10:48So this is one of those few cases
10:49where you can really tie
10:51what is often a fuzzy thing
10:53and kind of bring it into focus
10:55because you have this moment in time
10:56represented by that layer.
11:01Having the KPG boundary here at Tannis
11:04dates the site to around the time
11:06dinosaurs went extinct.
11:10No rattlesnakes.
11:12Once you see that layer,
11:13once you identify it,
11:15it really does stand out
11:16because it is a thin layer of rock
11:19that caps one world,
11:22the world of dinosaurs.
11:24And it ushers in another world,
11:26a world where you never find
11:28a single dinosaur bone
11:30or tooth or footprint again.
11:35What makes this site even more exciting
11:37is the rock layer
11:39right beneath the boundary
11:40in which Robert and his team
11:42found the Ammonites.
11:44The rock here is really not quite rocky
11:47and it just falls apart in your hands.
11:51This crumbly rock isn't unique,
11:54especially in Hell Creek.
11:57But it's rarely found in layers like this one.
12:00Over four feet thick,
12:04this layer contains several geological features
12:07which, to an expert,
12:09signify that it was deposited very rapidly.
12:13As in a storm or a flood,
12:16burying anything within it in an instant.
12:19which could mean that anything in this lair
12:29would have been quickly entombed,
12:31like the bodies in the volcanic ash of Pompeii.
12:34generally speaking,
12:39the faster you get buried after you die,
12:41or even if the burial is what actually kills the animal,
12:45that's one of the best scenarios for fossilization.
12:47Robert knows from the geology
12:50that anything he finds could be so well-preserved
12:53that it could reveal new evidence
12:55that would bring this time period to life
12:58in a way no one has ever done before.
13:01When you think about it for a second,
13:03it's actually incredibly amazing
13:05that we have any fossils at all,
13:07much less a fossil record.
13:09So 99.9% of the animals that we have
13:17don't get preserved as fossils
13:20because you have scavengers
13:22and you have other animals
13:23that tear away the skeleton
13:25as it's being deposited.
13:26To become a fossil,
13:28you need certain conditions for fossils to form.
13:31And so a lot of the fossil record is really missing.
13:37So for fossil hunters,
13:38this site is particularly interesting.
13:42Such rapidly deposited sediments so close to the KPG boundary
13:46could be evidence that what happened to the last dinosaurs here
13:50was as swift as it was destructive.
13:54Yet the story of that devastating day begins long before.
14:00Millions of miles away and billions of years earlier.
14:08Most scientists think it all started in a ring of dust, rocks and debris
14:14known as the asteroid belt.
14:22It's usually an uneventful place.
14:30But sometimes a rock can get bumped into a new orbit.
14:38And diverted onto a collision course with planet Earth.
14:51Jupiter in particular is a big bully in our solar system.
14:55Because it's the largest planet, it has the most gravity.
14:57And it doesn't just take one orbital pass for an asteroid to be influenced.
15:02This is a slow buildup over tens of millions of years,
15:06interacting with Jupiter over and over and over in its orbit.
15:11Another thing that can change asteroid orbits is collisions within the asteroid belt.
15:16And what happens is over time, the asteroid's orbit can be nudged
15:20until it becomes a near-Earth orbiting asteroid.
15:24And it has to be pretty bad luck for both the asteroid and the Earth
15:29to be in the same place at the same time.
15:32But it does occasionally happen.
15:40Robert and his team dig at this site in North Dakota each summer,
15:44the only time the weather allows them to do so.
15:48Come on down, check out this lens over here.
15:50In order to understand how the impact affected life on Earth,
15:56you really need to get a very clear picture
15:58of what the world was like right before.
16:01That is a critical part of the story.
16:06Paleontologists Dr. David Burnham and Lauren Goerche
16:10have been digging with Robert for years.
16:16Oh, wow.
16:18See the brown?
16:20Yep.
16:21That might be a tubercle right there.
16:23And it seems today is their lucky day.
16:26Oh, my God.
16:27Look at that.
16:28Look, the scales are preserved.
16:30It's like doing a freaking dissection.
16:32Oh, my God.
16:33Biology of Tannus.
16:36Oh, the scale.
16:37Look, look, the wrinkles continue down that way.
16:40It's all nice and wet so far.
16:42The scales are getting smaller in that direction.
16:44How big are they there?
16:44I got one with the projection over here.
16:47What?
16:48Oh.
16:49Oh.
16:50Yeah, there's the protuberance right there.
16:51I've only seen that on one other specimen.
16:53Oh, my life.
16:54Yeah.
16:55This is the closest thing to getting the touch of living, breathing dinosaur.
16:58It is.
16:58They found something extraordinary, dinosaur skin, and they've uncovered it right next to another
17:06fossil.
17:07This is obviously horn, the gnarliest horn I've ever seen.
17:11It is so exceedingly rare, a piece of triceratops skin in the Hellcreek formation.
17:23The 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.
17:34Triceratops bones are relatively common finds in Hellcreek, but skin in such condition as this is very rare indeed.
17:48The 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.
17:59The presence of the horn where the skin was found supports this.
18:04The brown color contains traces of organic material, so it might even be possible from this to work out which pigments were in it.
18:15Finding and studying such well-preserved fossils as this helps paleontologists build a much more detailed picture of how these creatures lived.
18:24Combining 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.
18:47We know from bones that adult triceratops could reach 30 feet in length and 10 feet in height.
18:54Marks on the fossil also show us that this one was badly scarred.
19:11Triceratops were plant eaters.
19:19Other fossils tell us that they had sharp beaks and hundreds of teeth,
19:23which enabled them to shred hundreds of pounds of tough vegetation.
19:32Almost all adult triceratops fossils ever found were on their own.
19:39So it's possible that the adults were solitary, a pattern observed in many modern-day animals.
19:45If you look at American bison, for example, they herd through much of their youth and much of their young adulthood,
19:57but especially old males will be by themselves.
20:00So that's not to say that all the triceratops we find by themselves are these old bulls,
20:04but there might be something similar at play.
20:06So they were probably territorial, fighting rivals away.
20:13These were very large animals that probably had very large territorial ranges.
20:18There actually is fossil evidence of puncture wounds in the frills of these dinosaurs,
20:24but they were probably using their horns, just like modern caribou,
20:27where they lock their horns together to compete for mates in other territorial places.
20:34A solitary animal would perhaps mark its territory.
20:38If you weigh more than an African elephant, there's not much that can bother you.
20:54Except, perhaps, a little mammal.
20:57Robert found these jawbones in a fossilised burrow.
21:21The shape of this tiny bone and tooth means it's most likely come from what's known as the
21:27a pediomyed, an early mammal, and a type of marsupial.
21:33The team also discovered fossilised nuts and seeds in the burrow,
21:38so we have an idea of what it might have eaten.
21:43We think of...
21:45But what we often don't appreciate is that mammals and dinosaurs,
21:49their legacies go back to the same time.
21:52Some of them we think may have been opportunistic,
21:55because there's even evidence of a small mammal
21:59that actually has the remains of a baby dinosaur within its valley.
22:07The team's finds are adding to our knowledge of the complex world
22:11at the very end of the late Cretaceous.
22:13And it's not just the fossilised creatures.
22:18If you walk on damp sand, you'll leave a trace behind.
22:27A footprint.
22:29The same was true 66 million years ago.
22:33And very, very occasionally, such traces were preserved.
22:40You know, we won't foil the backside.
22:42Right, we'll just put plaster right on.
22:44Right on.
22:44The dig team has discovered a number of footprints.
22:48Yeah, let's see.
22:49Looks like a good print.
22:51Yeah.
22:51The shape gives them an idea of what might have made them.
23:06If the team is right, they were made by a winged creature
23:09that might well have liked a small mammal.
23:13For lunch.
23:21The footprints are long and narrow with four toe prints.
23:29Two are slightly longer than the others.
23:32And that suggests they were made by...
23:38a pterosaur.
23:39Pterosaurs are not dinosaurs, but flying reptiles
23:51on a different branch of the evolutionary tree.
23:58There is nothing like a flying reptile around today.
24:03Pterosaurs got two enormous sizes.
24:05A group of pterosaurs known as astarkens,
24:08which include the pterosaur known as Quetzalcoatlus.
24:11It's a pterosaur that grew up to around 40 feet.
24:14This is an animal that had a 40 foot long wingspan.
24:19Some evidence shows that some pterosaurs
24:22might have lived in large groups,
24:24much as flamingos do today.
24:29Male pterosaurs usually had crests,
24:32while females didn't.
24:34So crests may have been used in courtship displays.
24:38And we have a clue about where females laid their eggs,
24:51because evidence suggests that at least one pterosaur laid hers
24:56in the soft sandy banks of the river at Tannis.
25:15The fossil record of pterosaur eggs is really small.
25:19So far, we have a couple of eggs from northeastern China.
25:27And we also have an extraordinary trove of eggs
25:32from western China, from Xinjiang province.
25:35The only other record of eggs
25:38is a single egg that comes from Argentina.
25:42So our record is very, very small indeed.
25:46This is the fossilised egg of a pterosaur
25:48that Robert and his team found in the crumbly lair.
25:51The only one ever discovered in North America.
25:56If you look at it with the naked eye,
25:58all you see is a jumble of lines.
26:02But if you examine it with the latest technology,
26:06you can find out a wealth of information,
26:09from the chemistry of the bones
26:11to the composition of the shell.
26:13And that, in turn, can tell us a lot
26:16about how these incredible creatures lived.
26:22To investigate the pterosaur egg,
26:24Robert has been given access
26:26to the diamond light source synchrotron.
26:30Situated in Oxfordshire in the UK,
26:32it's a powerful research tool that acts like a giant microscope.
26:37By accelerating electrons in this huge ring,
26:43the synchrotron creates beams of light
26:46billions of times brighter than the sun.
26:54Robert and paleobiologist Dr Victoria Edgerton
26:58now want to turn that beam onto the egg fossil
27:01to discover more about its chemical make-up.
27:07We're pretty much lined up on the skeleton,
27:08but we might have to move the stage a little bit
27:10to get to the right part.
27:12Sure.
27:13Each synchrotron scan can take several hours.
27:17Meanwhile, Robert can reveal the creature inside.
27:21Who made this wonderful thing?
27:24I got replicas of the bones from inside that egg,
27:27and I restored the remainder and put together
27:30what the skeleton would have looked like when it hatched.
27:33That's how big the creature would have been
27:35outside the egg if it had hatched.
27:36So this is the baby.
27:39How big was it going to grow?
27:41These very long neck vertebrae here are what really gave
27:45part of the story away to us, because those long bones
27:48match very, very closely with the Asdarchid pterosaurs.
27:51That is the giant pterosaurs.
27:53Oh, they were the whoppers, weren't they?
27:55I mean, what, 25 feet wingspan?
27:59Some of them.
28:00This probably had a wingspan maybe 15 feet.
28:03Well, it looks as though it could take off, really.
28:06It's easy to picture something like that just hatching out of the egg
28:09and fluttering out almost like a little bat.
28:11A lot of birds are utterly dependent on the parents bringing them food for a long time,
28:19but there are precocious birds and there are some that simply stand up after a few minutes
28:25and start foraging for food themselves.
28:27Well, pterosaurs might have taken that a stage further and they simply flew away.
28:31They've scanned the egg here and in America. Victoria has the results.
28:44So what have you learnt from the cyclophon image?
28:47What we have here is a chemical map of calcium directly within the bones of this animal.
28:53That tells us that these bones were already hardened,
28:57so it might be ready to fly not long after it hatches.
29:01Can you see any sign of the shell and what sort of shell was it?
29:05We can. What I can show you is we can see the rim of the egg in sulfur.
29:13Does that tell you whether it was a hard shell or a soft shell?
29:17We have been looking at this. We can see folding occurring and this unusual undulation.
29:24If it were a hard egg, we would expect splintered bits and broken bits just like a chicken egg.
29:31This helps to tell us that it was soft.
29:32So it was perhaps like a turtle?
29:35Absolutely.
29:36That's not the case, is it, with dinosaurs?
29:38Many dinosaurs had hard-shelled eggs.
29:41Yes.
29:41So this is a new discovery about as darky pterosaurs.
29:45Absolutely.
29:46This is something that we are confirming for the first time.
29:49Ah. Some flying pterosaurs had eggs like turtles.
29:54Yes. Much more reptilian-like than bird-like.
29:57And that can potentially tell us more about the environment in which these eggs were laid.
30:03How interesting. Yeah.
30:12Creatures that lay soft eggs tend to bury them in order to protect them.
30:19So female pterosaurs probably look for places like this to lay their eggs.
30:29Because the sandy soil here is just soft enough for the hatchling to dig itself out.
30:41Now the pterosaur just has to make sure that the hole is perfect.
30:49Now the pterosaurs is perfect.
31:05Success.
31:09But it's not over yet.
31:11Pterosaurs had two ovaries and they laid their eggs in pairs.
31:16So clearly this method, this way of reproducing for pterosaurs was incredibly successful.
31:32What it kind of says is, hey, everything's normal until the moment when the impact happens
31:39then it all goes horribly wrong basically.
31:45Here on the sandbank, sandwiched between the river and these glorious trees,
31:50It's not over yet.
31:51Life at Tannis seemed to be thriving.
31:54Whoops.
31:56Never a dull moment.
31:58But all that was about to change.
32:00Deep in space, a countdown clock is ticking.
32:15The asteroid's journey would take it through the orbit of our neighboring planet, Mars.
32:21Had the two collided, a catastrophe on Earth would have been avoided.
32:33But it didn't happen and the fate of life on Earth was sealed.
32:38New evidence is helping to build a vivid picture of late Cretaceous life here in this corner of North Dakota.
32:56And the team have found some more well-preserved footprints.
32:59So these are animals that were actually walking in the water?
33:05These guys would have been essentially on a mushy riverbank going down to drink at some point.
33:10You know, animals tend to congregate around the rivers.
33:14This footprint is about a foot long.
33:18So I think this is from a type of dinosaur that we call a duck-billed dinosaur.
33:22And they would have been very common in the Cretaceous.
33:26They ate the plants in the area and they got very large, 30 feet long.
33:32And there are more.
33:34This track, you see all the toes are very well-preserved.
33:37You even see a nail print at the tips of the toes.
33:41So the little toenails dug into the mud. I love this one.
33:47This is the team's prize footprint.
33:50It has three toes and it's longer than it is wide.
33:59So it's very likely to be a carnivorous dinosaur.
34:03It's so well-preserved that you can see the mark left by its sharp claw there.
34:09Hell Creek is well-known for one carnivore in particular, T-Rex.
34:16This footprint is too small for an adult T-Rex.
34:21But it's possible that it was made by a young one.
34:25Robert also found this.
34:37The crown of a tooth.
34:40Its shape and its serrated edge
34:43are indications that it comes from an adult T-Rex.
35:00Bite marks found on T-Rex bones show that they may have eaten each other.
35:16And a youngster would make an easy catch.
35:18But not this time.
35:37Very few footprints are preserved as fossils in Hell Creek.
35:42So if you find several in one place, as Robert has done,
35:46it's a reasonable assumption that there would have been many more nearby.
35:52When one dinosaur leaves a track, the next one that comes along obliterates that track.
35:57And eventually you end up with a ploughed field effect.
36:00If we think about the actual extent of the rock in which we're making our excavations,
36:06our excavations are tiny, tiny samples.
36:10So it's entirely possible there are more out there.
36:16And that supports the idea
36:22that dinosaurs and pterosaurs were thriving at Hell Creek shortly before the impact.
36:27And if they were thriving, they must have been reproducing.
36:38No one has ever found a T-Rex nest.
36:51But fossils from similar dinosaurs showed that they may have laid around 20 eggs in a circular nest.
36:59It's possible that, like crocodiles, they partially covered their eggs with vegetation to keep them warm.
37:18Looking after eggs must have been a tricky business when you weigh seven tons.
37:27As the team's dig continues, a vision of the prehistoric world here is emerging.
37:47It seems the sandbank was full of life.
37:51T-Rex, Triceratops, little mammals, alongside the footprints of other dinosaurs and pterosaurs,
37:59all in a very small area.
38:05See the scales?
38:05I do.
38:07Oh my God.
38:08That excites me just looking at it.
38:09In 2019, Robert finds something truly remarkable.
38:19See the cracks already forming?
38:20Yeah.
38:21Look at that.
38:22So we're gonna have to really monitor that before we glue it.
38:25Because this is getting vulnerable now.
38:28An almost complete creature.
38:31After 66 million years, finding anything intact is extremely rare.
38:38Matrix cloth, get the consultant, and to get this block out, we're freezing it.
38:42To keep the fossil in one piece as they remove it from the crumbly layer,
38:52the team decides to use a potentially tricky technique.
38:59They've covered the fossil in plaster to protect it.
39:04Freeing it means they have to flash freeze the crumbly rock surrounding it.
39:08using liquid nitrogen at around minus 300 degrees Fahrenheit.
39:22Watch the footing.
39:25Lauren, I'm worried about brittleness here.
39:27Get that hammer.
39:28Give this a couple of whacks with the hammer.
39:32Okay.
39:33Move over five centimeters.
39:34Good.
39:34It's cracked loose.
39:40Yep.
39:40Okay, it's loose.
39:41So we have to get this out in one piece.
39:44One, two, three.
39:49Yee-haw!
39:51Total success.
39:52Total success.
39:56This is a technique used in archaeology for digging up human remains.
40:00We've got enough time to work with the fossil and not damage it.
40:04And I couldn't be happier.
40:08And the creature Robert and his team have found,
40:12a turtle.
40:13This is the fossil, now it's been cleaned up.
40:21It's lying on its side.
40:23Here's the outline of its shell.
40:27The shape of the shell and the scarred edges here
40:31tell us that this was a binid turtle.
40:33This binid turtle would have looked very similar to modern kuto turtles
40:43and lived in the same sort of freshwater environments.
40:52The late Cretaceous period is kind of the heyday of turtles
40:57in at least northern North America.
40:59There were at least 16 species that were known from Saskatchewan.
41:05And compare that to today, we only have three.
41:08So back then, it was a much better time to be a turtle.
41:15The turtle fossil Robert found is almost complete.
41:18So we can tell a lot about the way it died.
41:21This is the underside.
41:23And this brown material up here is fossilised wood.
41:29It's the end of a stick that passes right through its body
41:33and comes out just here.
41:36So the evidence points towards this turtle having been impaled.
41:41Another well-preserved creature amongst those found in the thick rock there.
41:46When I look at the animals and plants preserved in the sediments of Tannis
41:55and the footprints beneath it, I see a picture of a vibrant ecosystem,
42:00many different dinosaurs and a thriving, thriving place.
42:04Robert and his team have found so many fossils, it looks as if even at the very end of the late Cretaceous,
42:15this area could have been flourishing.
42:20Full of dinosaurs and reptiles that had dominated the planet for more than 150 million years.
42:27It's impossible to know how much longer the dinosaur's reign would have continued.
42:41Because what happened next would bring this to an end.
42:57The asteroid hit the sea in an area that is now the Yucatan Peninsula in Mexico.
43:18It's called the Chicxulub asteroid after the town nearest to the centre of its crater.
43:27What happened next?
43:29Anything living within 900 miles of the hit is destroyed by the blast.
43:40But what effect does the impact have on Tannis nearly 2,000 miles away?
43:48Is it possible to link the creatures Robert and the team have found so far with the day of the impact?
43:55When we date rocks from the Cretaceous, we can say the end Cretaceous was 66 million years ago,
44:01plus or minus a few tens of thousands of years. That is a huge achievement of modern science.
44:06However, when it comes to the asteroid, that asteroid hit the earth one day.
44:13And really it hit the earth at one instant. And so to date fossils in the rock and to try to tie them to
44:19one instant in geological time that happened 66 million years ago is just outside of the scope
44:26of the chemical methods that we have to date rocks. So other evidence is needed to make a plausible
44:33scenario or a plausible story if somebody were to find a fossil and wanted to argue that that fossil
44:39came from the very end of the Cretaceous killed by the asteroid.
44:45To tie the site to the day the asteroid hit is a challenge. But Robert and his team are
44:52following a compelling trail of clues. The first of which lies in the jumble of fossils known as a mass
45:00death assemblage. We've got some wood and pressed up against this and all intertangled we've got the
45:07carcasses of fish. Okay. That's a beautifully preserved tail. So that fish is going to be absolutely gorgeous.
45:18Some of the evidence he's found so far has been inside the fishes themselves.
45:23In more ways than one it literally is an operation of a Cretaceous fish so we're performing surgery on
45:31this thing. Robert wants to look inside the fishes skull. And very carefully we want to separate this
45:41from the rest of the fish. Okay. There we go. Opening up the fish.
45:53Got a nice ant that made a home in there. And beautiful. Look at that. Okay. Here we have the
46:00gill bars of the fish. Those are the bars that hold the filaments of the gills. Between the gill bars
46:06all of these clusters of round objects. Tiny round balls of clay. But what are they?
46:13After a large asteroid impact a mix of vaporized and molten rock is propelled into the stratosphere. Some
46:25of it into space. There much of it cools solidifying into tiny glass droplets.
46:34Some of it is high enough velocity that it can actually leave the earth's gravitational field. So
46:40it's almost certain that some of the material ejected from Chicxulub would have ended up on the moon.
46:47Which is kind of an exciting thing to think about.
46:52But most of the droplets known as ejectospherules
46:57would have been pulled back to earth by gravity.
47:00Then over millions of years pressure and chemical reactions in the ground would turn most of them
47:09to clay. They'd look something like this. So finding spherules in the gills of a fish,
47:18as Robert has done at Tannis, suggests the fish sucked them in while the spherules were still fawning.
47:25So these creatures could have died at the time of an asteroid impact.
47:34Those have to have come from the impact events. You can't make spherules
47:38in other ways. They're a vapor plume condensate feature.
47:43That shows that these were fish that were alive before the impact. Those spherules arrived in the
47:48next 20 minutes to perhaps hour. Those fish swallowed them and surely died soon afterwards. So that's
47:54absolutely amazing discovery. The fact that there are spherules in the gills of the fish at the Tannis site
48:00really brings them as close as really you can possibly get to impact.
48:06These ejectospherules could be evidence of what Robert suspects, that creatures here died on the day
48:14of the asteroid strike.
48:18Once the team begins to look for ejectospherules, they find more and more and realize the thick
48:25crumbly layer of rock at Tannis is full of them.
48:30I mean this stuff is go- oh my god look at that one. These things are just gorgeous.
48:37Ejectospherules like this give us a fingerprint of where they came from.
48:41If these spherules were connected to the Chicxulub impact, then the whole crumbly layer could be full
48:48of evidence of what happened on the day the asteroid hit.
48:51That's a good one. Oh is that a droplet right there?
48:56But to do the best analysis, they need to find a spherule that hasn't turned to clay.
49:03Oh my god, that's a beautiful droplet. Okay.
49:07The small pieces of orange material that Robert and Lauren are digging up may be able to help.
49:15They're amber.
49:19If there was anything flying through the air at that time, this is where it's going to get caught.
49:22The amber they're collecting was once sticky resin oozing out of a late Cretaceous tree trunk.
49:31It's a way for the tree to protect itself like a scab forming on a cut.
49:36Anything covered by the resin would be frozen in an amber time capsule.
49:51A well-preserved spherule can be analyzed to see if it came from the asteroid impact.
50:06Lauren has found something trapped in there.
50:08So during this batch, we were incredibly lucky that we came across two completely unaltered spherules.
50:17Could this spherule be the evidence to link the site directly with the texture lobe impact?
50:25There are several lines of evidence that geologists would need in order to
50:31definitively say that this ejecta and this ejecta are from the same event.
50:35The shape of the spherules, the size of the spherules, the color of those spherules,
50:41can be similar for material coming from different sources. Only the geochemical signature would tell
50:49you exactly what the origin of the parent material was.
50:53The ability to use trace minerals as a way to diagnose the provenance, the place from which the
51:01rocks or the particles within the rocks originally came, is a whole field of geology. And it's a pretty
51:08mature science at this point. If it's a match, tennis could be something incredibly rare.
51:16If we can match spherules to the impact site geochemically and in terms of radiometric ages,
51:23that's pretty accurate. That's a smoking gun.
51:27Does the site Robert and his team have found record the very last day of the Cretaceous,
51:33full of fossilized creatures that were alive at the moment the asteroid hit?
51:39The potential for the tannis site is huge.
51:44And might Robert's team find something extraordinary?
51:47That's bone right next to the skin.
51:50A dinosaur that died as a direct result of the asteroid impact.
51:57The day that the asteroid hit would definitely be hell on earth.
51:59No matter where it is, you're in for a bunch of chaos.
52:162.
52:18A
52:272.
52:29A
52:301.
52:30A
52:322.
52:34A
52:352.
52:38A
52:402.
52:40A
52:422.
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