Fateful Planet (2024) Season 1 Episode 2 Snowball Earth
Temperatures are about to plummet as our planet heads straight into a period known as ‘Snowball Earth’. Throughout its history, Earth has continuously fluctuated between greenhouse and icehouse. But this particular icehouse phase is the most extreme period of cold our planet has ever witnessed, with ice encasing Earth from the poles to the equator. Life, which had only recently developed on the planet, seems doomed to extinction, but somehow manages to survive.
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Temperatures are about to plummet as our planet heads straight into a period known as ‘Snowball Earth’. Throughout its history, Earth has continuously fluctuated between greenhouse and icehouse. But this particular icehouse phase is the most extreme period of cold our planet has ever witnessed, with ice encasing Earth from the poles to the equator. Life, which had only recently developed on the planet, seems doomed to extinction, but somehow manages to survive.
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TVTranscript
00:00Earth is born out of chaos and catastrophe.
00:07Despite such hostile conditions, life emerges on our planet.
00:14But it must withstand deadly disasters again and again.
00:20Planet Earth is a wild world, shaken by unimaginable impacts.
00:29Volcanic eruptions that flood the landscape.
00:34And drastic climate changes that lead to ice ages that freeze the world from pole to pole.
00:43Yet each assault creates a path for something new.
00:48Life always finds a way, despite being constantly put to the test.
00:56Without these catastrophes, life as we know it would not exist on our fateful planet.
01:11According to scientific theory, a long time ago our planet experienced an ice age of epic proportions.
01:20A period of extreme global glaciation.
01:24It is thought that the ice extended from the poles to the equator.
01:29That our entire planet was covered in ice, including the oceans and land masses.
01:36A global catastrophe known as Snowball Earth.
01:41If our planet was really struck by an all-encompassing ancient ice age,
01:46traces of this dramatic event might have survived the eons.
01:55Western Australia.
01:57In the Pilbara region, temperatures can reach more than 120 degrees Fahrenheit.
02:03Nothing much can survive here.
02:06But the dryness has helped preserve ancient sediments.
02:10Three and a half billion years in age, these Archean rocks are some of the oldest in the world.
02:17Professor Nora Knopfke and a team of international geologists have come here
02:22to search for clues that will shed light on what our planet looked like in these ancient times.
02:28And what may have created conditions for a Snowball Earth.
02:35Here we have an excellent window of really early Earth.
02:42Three and a half billion years ago, how was it?
02:45Earth was different at that time.
02:48And so this tracer formation here provides a very small glimpse
02:53into really completely strange worlds of the beginning of our planet.
02:58And that makes it so great being here.
03:02In this unique ancient landscape, the scientists are looking for fossils of the earliest microbes.
03:09Using a combination of modern techniques and decades of experience gained in the field,
03:14it's not long before Nora Knopfke spots something.
03:18That's what we call ripple marks.
03:21If we find something like that in an area like here, it's a clue which says shallow water,
03:28which was moving not too fast, but also not too slow.
03:33That means that the water probably was very clear.
03:36And that is a nice indicator for very, very early life that existed on Earth at that time.
03:45This entire landscape was once an ancient shallow sea.
03:50Warm pools of water ranging from just a few inches to a few feet in depth.
03:56Enough for the warm rays of the sun to penetrate through the gentle waves.
04:01And these conditions created the optimal environment for early life to thrive.
04:08This is gorgeous. Look at that view.
04:10So let's go measure a little bit from here upward and then we get an idea of what actually is in the rocks.
04:19What's the story they are going to tell us.
04:22Many ancient rocks are so distorted through time that the clues Nora is looking for are long gone.
04:30But here in the Pilbara, the sediments are undeformed and thus might have preserved evidence of the earliest forms of life.
04:41Look at that. Wow, look at that.
04:44Now that is spectacular.
04:47So this is really what I was looking for here.
04:50Basically colonies, assemblages of very small organisms.
04:55Microscopic small bacteria you could say.
04:59And they were living on the sea floor at that time.
05:05The colonies of bacteria clustered together and formed what are known as microbial mats.
05:12So we know that this is not geological.
05:15What we're looking at here, it's biology because we have here those round shaped lobes basically in the outline of those fragments.
05:26These bacterial mat colonies are examples of Earth's earliest life forms.
05:32Recording the evidence of the colonies, the team can build up a picture of early life here in the Pilbara.
05:40Life in these shallow pools, although primitive, is efficient.
05:45Simple creatures that feed on carbon compounds that are accumulating in Earth's early oceans.
05:52We have very similar carpets, biological carpets in the modern nowadays all along our beaches, all along the Atlantic Ocean for instance.
06:03It's very common nowadays.
06:05And now we are here three and a half billion years old material and we see some of the earliest life that we have here on planet Earth.
06:17The microbial mats are not the only evidence of early life in the Pilbara.
06:23The entire region is filled with precious fossil traces of ancient life.
06:29These sedimentary structures, known as stromatolites, are formed by ancient bacteria and were discovered by Naufka's colleagues in the 70s.
06:39So you see this little dome there? It's now quite weathered.
06:45So this is a historical site with respect to science history.
06:50So this one was the first life form detected in those really, really old rocks.
06:59Three and a half billion years ago, life was beginning to thrive on planet Earth.
07:05But catastrophe was looming.
07:09In the ancient rocks, Nora Naufka detects a clue, indicating a dramatic shift in environmental conditions that could have spelled dire consequences for the early forms of life.
07:21It does not look like much, but indeed it tells us a lot about a very important event in Earth's history.
07:28So these red lines here essentially are rust.
07:32That's a mineral that contains a lot of iron and in order to produce that we need oxygen.
07:39In the first billion years, there was virtually no free oxygen on planet Earth.
07:45Life had evolved without it.
07:47But the ancient rust Nora has found only forms when iron comes in contact with free oxygen.
07:54The banded iron formation, as the ancient striped rock is known, is a hint that our planet was changing in a major way.
08:03Earth now had enough free oxygen to entirely transform a geological landscape to such an extent that its effects can still be seen today.
08:14The change was so drastic, something catastrophic must have happened.
08:20What impact did it have on early life and where did this oxygen come from?
08:26The answer may be found deep in the heart of Europe, Lake Allat in Germany.
08:35Many myths surround the lake because its turquoise waters frequently turn blood red.
08:41Biologists Patrick Jung and Michael Lakatos believe the strange coloration might have to do with some of the earliest forms of life on our planet.
08:53By finding them, they hope to discover how early life was affected by the oxygen
08:59and how it may have contributed to the complete glaciation of our planet.
09:04Lake Allat is surrounded by mountains and lies in a basin.
09:08This is very rare for lakes. It's also very deep.
09:12Through this constellation, we hope to find the clues in the depths.
09:18If there is ancient life down there, it might unveil what happened in the past.
09:25Using a special glass container, the biologists want to bring water from the deep
09:30to the surface.
09:35In the lower section of the lake, they suspect an anomaly.
09:40It's coming. That's the bottle. Watch out.
09:44Look at that. Oh, my God.
09:48The water in the container is all pink.
09:53To find out why, Michael and Patrick go to the lake.
09:58To find out why, Michael and Patrick are using a probe to measure the oxygen content of the water sample to determine its composition.
10:10What's the oxygen level?
10:12It's only 1.3.
10:14There's almost no oxygen left in the water.
10:18First, the pink color. Second, the smell of hydrogen sulfide.
10:22And finally, the lack of oxygen indicates that we are dealing with very, very old bacteria,
10:28so-called sulfur-purple bacteria.
10:33Within the depths of Lake Allet lies a layer that is deadly to most forms of life.
10:39It contains virtually no oxygen.
10:44Just like the deep water we recovered here, we have to imagine the oceans billions of years ago,
10:50because they were also oxygen-free.
10:53Around four billion years ago, our Earth was a completely different place.
10:59The so-called Archean Eon was hostile to most forms of life we know today.
11:05Even though water already covered most parts of the Earth, there was no free oxygen available,
11:12neither in the water nor in the atmosphere.
11:15So the question is, where did the oxygen come from?
11:22On the shore of Lake Allet, the biologists are searching for the answer.
11:31A layer of slime has accumulated at the edge that looks promising.
11:40The biologists suspect that the green slime is also an ancient microorganism known as cyanobacteria.
11:49Now look at this.
11:52Okay, these really are cyanobacteria.
11:55They form long filaments and are found in masses here on the shore.
12:02The cyanobacteria are ancient.
12:05They are almost as old as the sulfur bacteria and even evolved from them.
12:09What's special is that we can find them here, in the shore area, and not 18 meters deep,
12:14which is oxygen-free.
12:16We want to find out why, with further analysis.
12:21The scientists measure the oxygen concentration of the shoreline water sample.
12:29It's around 8 mg per liter, that corresponds to the surface water.
12:35Okay, let's put it in the sun and see what happens.
12:38The biologists believe that the power of the sun will affect their sample.
12:48After a short amount of time, the oxygen level increases drastically.
12:56The cyanobacteria have brought along an innovative metabolism
13:00and developed the so-called oxygen-free metabolism.
13:03The cyanobacteria have brought along an innovative metabolism
13:06and developed the so-called oxygen photosynthesis.
13:09In this process, oxygen is released as a by-product,
13:12and this oxygen has changed the earth forever.
13:17While purple bacteria depend on sulfur
13:20and could only survive in niches like the deep water layer in Lake Alet,
13:25cyanobacteria only need light, carbon dioxide and water to survive.
13:31Things that are available nearly everywhere in the Archean world.
13:39Scientists are sure that this must have paved the way
13:43for a global spread of cyanobacteria,
13:46a story that should again be written in the rocks.
13:51South Africa.
13:53In the dusty plains of Grigualand,
13:55scientists hope to decipher the events
13:58that unfolded at this early stage of Earth's history.
14:02The rocks in this billion-year-old landscape
14:05act like an archive for field geologists,
14:08like Professor Tony Prave.
14:11You know, when you say a rock to most people,
14:14they think, yeah, just a rock.
14:16When I look at a rock, it holds a story.
14:19And in many respects, that story is in some ways very poetic
14:22because it's the history of our planet,
14:25is a record of what happened on Earth at that place
14:28at that particular time in the past.
14:35Professor Prave is looking for rock formations
14:38from about 2.4 billion years,
14:41a time when our planet is supposed to have turned into a snowball.
14:47Oh, my.
14:48These features that you see in the rock,
14:51these curvy planar surfaces, these are stromatolites.
14:54These are beautiful examples of stromatolites.
14:57And these stromatolites have been generated by cyanobacteria.
15:02And it's the cyanobacteria that's part of the evidence
15:05that we want to talk about the genesis of oxygen,
15:08free oxygen, that would go into the water column
15:11and could ultimately change climate on Earth 2.4 billion years ago.
15:15One of the reasons why I'm in South Africa
15:18is to find these types of fossils,
15:21but also because these fossils represent a fundamental change
15:25in the chemistry of the oceans and in the chemistry of the atmosphere.
15:30Stromatolites provide a record of primordial microbial activity
15:35and sediment accumulation.
15:39Despite their ancient origins dating back billions of years,
15:42stromatolites can still be found in certain aquatic environments today,
15:47providing invaluable insights into early Earth's ecosystems
15:52and the evolution of life.
15:56Myriads of tiny cyanobacteria carry out photosynthesis,
16:01converting sunlight, carbon dioxide, and water into organic matter,
16:07releasing oxygen as a by-product.
16:09They form sticky biofilms, or microbial mats,
16:13which are thin layers of microorganisms that attach to surfaces
16:18such as rocks or sediment.
16:22Over time, these layers build up, creating a stratified structure.
16:29What is left are stromatolites.
16:33Professors at the University of South Africa
16:35call them stromatolites or stromatolites.
16:39Professor Prave can find them in all sizes.
16:46You know, I'm smiling to myself because I've seen stromatolites
16:50that are the size of cabbages, and I've seen larger ones
16:53that are almost the size of me.
16:55This rock that I'm on is a massive stromatolite.
16:59Cyanobacteria have formed this colossal structure.
17:042.4 billion years ago,
17:07they generated oxygen on an unimaginable scale.
17:13As a result of their extensive expansion,
17:16earlier lifeforms were placed under increasing pressure.
17:23In the Archean oceans, cyanobacteria were found
17:26to be real killers.
17:28Because life was not adapted to oxygen at that time,
17:31it wiped out almost all life.
17:34A real catastrophe was triggered here, a mass extinction.
17:39The ancestors of the sulfur-purple bacteria
17:42and other anoxic ancient forms of life
17:45are driven away to places which the oxygen could not reach.
17:49But those who cannot escape are wiped out by the deadly poison.
17:53And that was not the only harmful effect of the oxygen.
18:00The oxygen produced by the cyanobacteria
18:03first saturated the oceans and then diffused into the atmosphere,
18:07which was then changed by the accumulating oxygen.
18:10As a consequence, the earth cooled down more and more,
18:14which led to the formation of ice and snow at the poles.
18:18These glaciers then advanced to the equator,
18:20so that the earth turned into a real snowball.
18:29Some scientists believe this critical change
18:32ended up having a catastrophic impact on the planet,
18:36plunging it into a deep freeze,
18:39and quite possibly a snowball earth,
18:42wiping out nearly all life.
18:45But if this really happened, it should have left no trace.
18:49Vatnajökull Glacier in Iceland.
18:52The rugged landscape provides a glimpse
18:55of what this frozen world might have looked like.
19:00Here, geologist Professor Colin Devey
19:03wants to find out if earth really witnessed an ancient ice age.
19:10I'm looking for traces of ice.
19:13I'm looking for traces of ice.
19:16I'm looking for traces of snowball earth.
19:20And if you want to do that, then you come to a very big glacier.
19:24And this is Europe's biggest glacier, a land of snow and ice.
19:29And I'm hoping to find evidence here
19:32of processes that happen in a glacier,
19:35so that I can compare it to evidence we have from way back in time,
19:39when the earth was probably covered totally in ice.
19:42Scientists believe that snowball earth
19:45was caused by changes in the chemical composition
19:48of the earth's atmosphere.
19:51It coincided with the occurrence of the so-called great oxidation event
19:55that happened at the beginning of the Paleoproterozoic era.
19:59Prior to that point, the atmosphere on our planet
20:03was far different than it is today.
20:06If I was on the earth 2.4 billion years ago,
20:09and I really aren't that old,
20:11I would need a space suit to sit here.
20:14The atmosphere of the earth contained almost no,
20:17really no, no, no oxygen.
20:20It was made of some nitrogen, lots of methane and CO2.
20:24But then, life came along.
20:27The atmosphere went from something I couldn't possibly breathe
20:30to being full of oxygen.
20:33Then something happened to the methane, which we call oxidation.
20:36The methane molecules get attacked by the oxygen
20:38and get turned into carbon dioxide.
20:41Carbon dioxide is also a greenhouse gas, but much less potent.
20:47By producing oxygen through photosynthesis,
20:50life changed the world it was living in,
20:53in a revolutionary way.
20:56It's a milestone in the history of the earth.
20:59It changed the planet completely,
21:01changed our atmosphere completely,
21:04and made our atmosphere from a very, very nice greenhouse atmosphere
21:07to something with a lot less greenhouse potential.
21:10It was like taking a down jacket off the earth.
21:13Methane is a really good greenhouse gas,
21:15and if you take it away,
21:17even if you turn it into CO2 into large parts,
21:20you're still, you're one jacket less than you were before.
21:23As a consequence, scientists believe the earth cooled significantly,
21:27forming glaciers at the poles that grew and grew
21:30until the whole planet was covered in snow and ice.
21:33To prove this, Colin Devey is analyzing the behavior of glaciers.
21:37It's important to understand that although they look static,
21:41they are constantly moving like a very slow river.
21:45Glaciers move all the time,
21:48not as fast as water, but much faster than tectonic plates.
21:52Accumulate snow high up in the mountains,
21:55lots of snow falls up there,
21:57and it gets so deep and thick
21:59that it compresses itself down into really solid ice.
22:01But that ice moves because the next lot of snow is coming on top,
22:05so it's being constantly pushed from above.
22:09Glaciers end up reforming the landscape they travel across.
22:14The force of the ice acts like a bulldozer for everything in its way.
22:19At Vatnajökull,
22:21Devey wants to check which traces the glacier left behind.
22:25I'm in front here rather than on top of the ice
22:28because when the ice is gone, what's left are stones.
22:32And for a geologist, the stones are the things that tell the story.
22:35If you look at the rocks, you see that many of them are scratched,
22:39and that's because the ice has used them as tools
22:42to grind down the landscape.
22:44And if you get down to the bedrock,
22:47then you'll see the bedrock has been scraped really well.
22:50And has what we call in geology striations.
22:53It looks as if somebody's gone with pretty hard fingernails across it
22:57and just scratched it.
22:59And for glacial processes, the stones are absolutely characteristic
23:04because the glacier is the only thing that can pick up stones
23:09and rub them together.
23:11This process can be observed throughout the ages.
23:15If there had been glaciers in the past,
23:17this would have been recorded in the landscape.
23:20Glaciers are hugely powerful.
23:22If a glacier's been in a landscape, you can see the traces of it.
23:26When ice goes away, it leaves almost a signature
23:30on the surface of the planet.
23:32If the Earth really turned into a snowball,
23:36the glacial signature should be found in ancient rocks.
23:41South Africa.
23:43The South African glaciers are the only ones
23:46The signs for primordial ice sheets
23:49are not always where you would expect to find them.
23:52In the dry, dusty plains north of the Karoo Desert,
23:56Professor Tony Prave is trying to unravel the story
24:00behind our planet's icy past.
24:03You could think of it as being in part like a detective.
24:06And that aspect is fascinating
24:08because it makes you feel a bit like Sherlock Holmes
24:11taking disparate pieces of evidence
24:13and building to make a case to come to an understanding
24:18of a particular process that happened in the past.
24:21And when we're talking about the past in this case,
24:24we're talking billions of years ago.
24:26In the 2.4 billion-year-old rocks in this region,
24:29the geologist finds banded iron formations,
24:32similar to the ones found in Australia.
24:35This is step one in our understanding
24:39of how climate could have changed 2.4 billion years ago.
24:43It's important for us then, in step two,
24:46to go to younger rocks that would be on top of these rocks
24:50to see if there is that evidence for the global cooling
24:54in these so-called snowball earthquakes.
24:59A cliff in the vicinity has caught the attention of the geologist.
25:08Now this, this is what we've been looking for.
25:10Here we have this rock unit, and it's massive.
25:13It forms this entire cliff that we saw below.
25:16And it's composed of dimictite, these pebbles that you can see,
25:20that are sitting in a mud matrix.
25:23That mud matrix and those pebbles
25:26can be formed by a couple of different processes.
25:29One is mud flows, but the other is glaciers.
25:32And the extent and size and scale of this deposit
25:35makes us really think it has to be a glacial deposit
25:38formed by the movement of ice.
25:40But the key line of evidence that I want to find
25:43would be striations.
25:46And that is what I want to see if I could find
25:49that associated with this rock.
25:54Tony Prave is scanning the rocks in the vicinity for scratches,
25:59clues that would prove the presence of former glaciers in this region.
26:04This surface shows these very fine lines, these very fine striae.
26:09Those striae are formed by ice moving over Earth's land surface.
26:14And we know then that that movement of ice
26:18was what deposited this dimictite.
26:22This proves that glaciers covered this landscape 2.4 billion years ago.
26:28But here we are in the middle of a very hot, dry South African desert.
26:34And it seems crazy to have ice and snow here.
26:38But we also know plate tectonics shifts Earth's land masses.
26:43Just think 2.4 billion years ago what the Earth may have looked like.
26:48We need to find out where this land surface was 2.4 billion years ago.
26:53To find out more, Tony Prave is meeting geologist Professor Nick Bukas
26:59from the University of Johannesburg.
27:02He is an expert on early Earth history
27:05and knows the area here like the back of his hand.
27:10Hi Nick, good to see you again.
27:12Tony, it's nice to see you.
27:14Thanks for meeting me.
27:16So today I'd like you to be able to tell us
27:19how we could find out where this land surface was 2.4 billion years ago.
27:23How we could find out where South Africa was at that time of the glaciation.
27:27Tony, I think if we look around and you look at the far distance there,
27:31we have this very thick and very extensive flat basalt succession,
27:37which is a lava succession.
27:39And if we can go and look at that,
27:41we can try and figure out the question that you ask,
27:45where the glaciation happened.
27:48And that's where we have to go.
27:50Lava from a large-scale eruption,
27:54a so-called flood basalt event,
27:57covered the ancient glacial sediments soon after they were formed.
28:04It is these volcanic rocks that the scientists now want to analyze
28:09to answer the question where these glaciers once existed.
28:13So Tony, this is it.
28:16The special thing about lava sediments
28:19is that they contain precise information
28:22about the latitude in which they were formed.
28:25The magnetic signature that's preserved in this rock
28:28is found in very small crystals that when this lava cools,
28:32those crystals align themselves to Earth's magnetic field
28:36and the orientation of Earth's magnetic field.
28:38And in this rock, the signature that has been analyzed
28:41is that the angle of Earth's magnetic field
28:44is plus or minus 10 degrees,
28:46which means that we have to be close to the equator.
28:52The lava cooled on rocks that immediately before
28:55had been covered with glaciers.
28:58And the paleomagnetic measurements show
29:01that this happened very close to, or directly at,
29:04the equator.
29:07If we have ice, as we saw in that glacial diamictite,
29:11at the hottest latitudes on the planet, the tropics,
29:15then that means we must have ice
29:18across the coldest regions of the planet.
29:21Ice everywhere.
29:23And this then is confirmation that the glaciation
29:26was global in scale and hence a snowball Earth.
29:34Earth had cooled to such an extent
29:37that the glaciers that formed at the poles extended even further
29:41until they reached the equator
29:43and the whole planet was covered in snow and ice.
29:47It had become a snowball Earth.
29:53Some scientists believe such a dramatic change
29:56could not have been caused by an increase in oxygen levels alone.
30:00If so, what else could have contributed
30:04to the global freeze?
30:12Switzerland, the Jungfrau region,
30:15is home to some of the highest peaks in Europe.
30:19The world up here is frozen all year round.
30:23For Patrick Jung and Michael Raketos,
30:26this is the perfect environment to uncover the secrets
30:30surrounding snowball Earth.
30:33We traveled here to find out
30:36how an entire planet could turn into snow and ice.
30:47As temperatures continued to drop,
30:50a tipping point had been reached.
30:52Ice sheets formed and enveloped the Earth
30:55as the world had never experienced before.
30:58The big question is how this icehouse effect came about.
31:02The scientists are sure
31:04that there must have been some kind of mechanism
31:07besides chemical changes in the atmosphere
31:10that drove the global glaciation.
31:14The eternal ice and snow could be clues to what happened back then
31:18because different surfaces of the Earth reflect light in different ways.
31:22This could be a key to what happened at that time.
31:28Patrick and Michael have a theory.
31:30As our planet became whiter and whiter,
31:33it was less and less able to store solar energy,
31:37which eventually intensified the cooling of our planet.
31:42The scientists have brought along special measuring instruments
31:46to prove their idea.
31:49This is the so-called albedo meter.
31:52Up here, the global radiation from above is measured,
31:56which radiates onto the Earth.
31:57And down here, the reflected radiation is measured.
32:01In other words, the amount of radiation that the snow reflects back up.
32:07From the measurement of the so-called albedo,
32:10the researchers hope to draw conclusions
32:13about the icy events in the early days of our planet.
32:18The albedo describes the amount of sunlight
32:21that is reflected by a certain surface.
32:24So the greater the albedo, the more light is reflected.
32:27All right, I'll see what it says.
32:31Our albedo measurement here has shown
32:34that about 90% of the incoming light is reflected.
32:37This is the highest value we can find on Earth.
32:42A high reflectivity not only means
32:45that light is reflected back into space.
32:48In addition, it also means
32:51that light is reflected back into the atmosphere.
32:53This means that light is reflected back into space.
32:56In addition, the much-needed thermal energy is lost.
33:02For comparison, the researchers now want
33:05to measure the albedo of a dark surface.
33:12We have measured an extremely low albedo
33:15of about 20% on this dark rock.
33:18That means the dark surface absorbs about 80% of the solar radiation
33:23and heats up strongly.
33:26This is roughly how we have to imagine
33:29the function of the oceans 2.4 billion years ago.
33:32They covered about two-thirds of the planet
33:35and they had a much lower albedo than this rock does now.
33:38This means that they could store much more heat
33:41and thus heat the planet.
33:462.4 billion years ago,
33:49right before the global glaciation,
33:51the oceans looked very different from ours today.
33:54But the temperatures were comparable.
33:57The dark oceans acted as heat reservoirs.
34:03Normally, the Earth keeps itself warm
34:06by absorbing an enormous amount of heat energy
34:09from the dark surfaces and slowly releasing it
34:12over a long period of time.
34:15But while ice and snow have spread further across the planet,
34:18more heat energy has been radiated back.
34:21And thus, the Earth finally cooled down.
34:25By massively decreasing the amount of strong greenhouse gases,
34:30the oxygen production of cyanobacteria
34:33had changed the chemical composition of Earth's atmosphere fundamentally.
34:38The resulting cooling led to the glaciation of the poles
34:42from which ice sheets moved further towards the equator,
34:45bit by bit.
34:47And, at a certain point,
34:48it was the nature of the ice itself
34:51that ensured that there was no turning back.
34:56The highly reflective ice layers set an unstoppable cycle in motion.
35:01More and more sunlight was reflected.
35:04There was less heat.
35:06The ice sheets grew.
35:08This process was unstoppable.
35:10And in the end, Earth went into a true catastrophe
35:13for the very first time and was enveloped in a snowball.
35:162.4 billion years ago,
35:19our planet found itself in a deadly trap.
35:22With most of the sun's energy now being reflected back into space,
35:27how could Earth ever free itself from the snowball's icy grip?
35:36White.
35:38As far as the eyes can see.
35:40The world is locked in snow and ice for millions of years.
35:45Iceland's snow-covered landscape provides a glimpse
35:49of what the snowball Earth might have looked like.
35:54Scientists aren't sure how our planet
35:57could have broken free from its icy bonds.
36:00But Professor Colin Devey has an idea.
36:04In the ice of Europe's biggest glacier,
36:06he is hoping to find the answer.
36:15So, I'm here at the toe of a tongue from Vatnajökull glacier.
36:22And as you can see, the ice is grey.
36:26There's lots of water.
36:29This glacier is melting.
36:32The reason it's grey is that the ice is melting.
36:34The reason it's grey is it's ash.
36:37It's volcanic ash lying on the ice.
36:40So we've got ash on ice.
36:43It's melting.
36:45Is that the end of a snowball Earth?
36:51Could volcanic eruptions have melted the ice?
36:56Like the rest of the Earth,
36:59the primordial volcanoes were buried under masses of ice and snow.
37:04So an eruption would have had to take place under ice.
37:11Volcanoes can definitely erupt under ice.
37:14We know it from Iceland.
37:16Krimsvötn up there erupted in 1996
37:19under 800 metres of glacier.
37:22And it managed to melt all that ice
37:25into a huge lake full of water,
37:28which then raced down the side of Iceland,
37:31devastating all the coast here,
37:32washing away roads and bridges and power lines and all sorts of stuff.
37:36But after that, the volcano was in the open air.
37:41So it managed to free itself of that much ice.
37:44That's no problem for a volcano.
37:49The power of volcanoes is immense.
37:53And the heat of the magma can easily melt snow and ice.
37:58But are there really enough volcanoes on our planet
38:02to put an end to a snowball Earth?
38:11I mean, it would be possible to melt the snowball
38:14if you had volcanism all over the planet at the same time, everywhere.
38:18But then I'd see the rocks, and I don't.
38:21There isn't volcanism all over the planet at that time.
38:25Somewhere, there's always volcanoes going off on this planet,
38:28but not more than at any other time.
38:30So no, volcanism, just the heat of the magma coming out,
38:35could not have melted a snowball Earth.
38:40At some spots, the volcanoes may have melted little parts,
38:45but the snowball Earth remained frozen,
38:48despite the magma flows.
38:51In fact, as I said,
38:54it's unlikely that that's how you end a snowball Earth.
38:57But volcanoes are not just producing molten rock as magma.
39:02They produce other things
39:05that may help us to get out of the snowball Earth.
39:09Professor Devi is heading for a volcano in the southwest of Iceland
39:14that has recently erupted.
39:17Here, he wants to see what it spews out, apart from lava.
39:27Yeah, that's really what fresh lava looks like.
39:31It's a really good place.
39:34To examine the fresh lava,
39:37this is probably one of the youngest lavas on our planet at the moment.
39:41This is the youngest one on Iceland.
39:44It's still warm, actually, in several places here where I'm standing.
39:48And this is probably a really good place
39:51to find out how snowball Earth ended.
39:53With a special instrument,
39:56Professor Devi wants to analyze the vapors
39:59that rise from the hot rocks.
40:02This is a gas flux meter.
40:05It sucks air out of this pot here
40:08and measures the gases inside this box,
40:11particularly CO2, is what I'm looking at at the moment.
40:15Up in the air like this, we're at about 400 ppm CO2.
40:19That's what the air has on this planet at the moment.
40:21And we go down onto here,
40:24and we're now at 400, 500, 600, 700, 800, 900.
40:28It's going up and up and up.
40:31OK, we're at 1,500 ppm.
40:34That's four times the normal CO2 concentration of the atmosphere.
40:38So there's a lot of CO2 coming out of the ground here.
40:42A subglacial eruption of many volcanoes
40:45during the snowball Earth period
40:47would have significantly increased
40:50the greenhouse gas level in the atmosphere.
40:53It's very difficult to get an icy Earth to melt again.
40:57So probably the only way to get out of it,
41:00or at least one of the few ways to get out of it,
41:03is to make the atmosphere into a greenhouse,
41:06to actually warm the planet
41:09by increasing carbon dioxide in the atmosphere.
41:12The volcanoes can do it,
41:14but once the Earth ended, increased carbon dioxide in the atmosphere,
41:18a greenhouse climate, the ice melts.
41:21The volcanoes have freed the Earth from the snowball,
41:25not by their magma melting the ice,
41:28but by the greenhouse gases they release.
41:32Through them, our atmosphere is transformed
41:36so that heat can accumulate and thaw the snowball.
41:40But as the ice melts, one question remains.
41:44How could any life survive after millions of years
41:48in such a deep freeze?
41:51The eternal ice on the highest peaks of the Alps
41:55forms an environment that is comparable to our Earth
41:592.4 billion years ago,
42:02when it was firmly in the grip of snow and ice.
42:05Patrick Jung and Michael Lakatos
42:08therefore want to search for clues right here,
42:11on the roof of Europe.
42:14How could life was able to survive
42:17in the deep freeze of the snowball Earth?
42:23Look at this landscape.
42:28We came to the Aletsch glacier to find out
42:31if we could find life in this hostile environment
42:34completely covered by ice and snow as far as the eye can see.
42:40The scientists are led by a mountain guide.
42:42As dangerous crevices plunge
42:45into the depths beneath the snow cover.
42:50With the help of a drone,
42:53the two biologists scan the area for any signs of life.
43:08Turn a little more to the left, Michael.
43:11Okay.
43:13That could be something.
43:15Oh yeah, you're right.
43:17This black formation looks good.
43:19That's where we should go.
43:23To really be able to say whether we can find organisms
43:26on the rock face, Michael will climb up and take a sample,
43:29because that's the only way we can clarify.
43:35The climb is risky.
43:38The rock face is steep.
43:40But without the sample,
43:42the scientists can't evaluate their discovery.
43:46Further to the right. Yeah, right there.
43:52You think you can reach it?
44:11I've got something.
44:19Oh, cool. Wow.
44:22You can see the entire structure here.
44:25And it's nice and black on the surface.
44:28Okay, let me rub some of that off.
44:31Oh yeah, look.
44:33There's some brown color on here.
44:35Could be organic.
44:37It definitely gives us a good indication.
44:38But I think we should take a closer look.
44:43Using a magnifying glass,
44:45the biologists inspect the rock sample closer.
44:50Well, Michael, I'm pretty sure about that.
44:53I can see it quite clearly by the color and the shape of the growth.
44:56These are actually cyanobacteria.
45:02The same ancient bacteria that caused the global ice age
45:06are clinging to the rock face.
45:09To determine if they are alive,
45:11the researchers take another measurement.
45:19With this device, we can measure photosynthesis.
45:22If it shows something,
45:24it would be a clear indication that we have found life.
45:27Let me switch this so we can see something.
45:32Yes, it's everywhere.
45:35Here, where it lights up red, those are signals.
45:38That looks alive. It's a lot.
45:42Life amidst a world of snow and ice.
45:49During the snowball earth phase,
45:51many life forms actually perished.
45:53Those that survived have retreated to certain regions
45:56like these cyanobacteria stains.
46:02Ancient microbial life has found a way to survive
46:06in this hostile environment.
46:09Cyanobacteria and life in general
46:12have a very hard time developing and growing
46:14in a world without water.
46:16Here, on the other hand,
46:18the cyanobacteria grow on these black formations.
46:21These rocks remain free of ice and snow for a very long time,
46:24simply because they are too steep.
46:27But ice regularly melts off the overhang.
46:30This water forms a drainage channel
46:33and cyanobacteria can thrive in it.
46:35That's exactly how it must have been 2.4 billion years ago.
46:40The cyanobacteria survived in ice-free niches,
46:43like the one we found here today.
46:49By this strategy,
46:51life was able to outlast the snowball earth phases.
46:55Two more times in earth's history,
46:58almost the entire planet was to freeze over.
47:01Each time, many species died out.
47:06But some of them survived on the edge of the ice world.
47:12Scientists believe that even during the snowball earth phases,
47:16there were small areas on earth
47:19that were not completely covered with ice.
47:23These niches may have provided safe havens
47:26for early life with oxygen and liquid water.
47:31Tiny oases where life could survive
47:33the global ice ages.
47:40After the last global glaciation,
47:43580 million years ago,
47:45the time had come for life to flourish
47:48on an unprecedented level.
47:52It now began to evolve into ever more complex forms.
47:59Snowball earth and all the catastrophes that followed
48:03were the kind of apocalyptic events
48:06that life on earth has always benefited from.
48:12Without these catastrophes,
48:15we literally would not be here today.