Everywhere we look, life exists in both the most hospitable of environments and in the most extreme. Yet we have only ever found life on our planet. How did the stuff of stars come together to create life as we know it? What do we really mean by 'life'? And will unlocking this mystery help us find life elsewhere?
Features the research and ideas of geologist Stephen J Mojzsis, chemists Stanley Miller and Harold Urey and their student Jeffrey Bada, Jen Blank of a search for extraterrestrial intelligence project, biologist Jack Szostak, chemist John Sutherland, physicist Paul Davies and microbial geobiologist/biogeochemist Felisa Wolfe-Simon, and planetary scientist Ben Weiss. Tackles the Hadean period, shadow biospheres, a Winogradsky column, life among the toxic chemicals of Mono Lake, ALH84001 and life on Mars.
Thanks for watching. Follow for more videos.
#cosmosspacescience
#throughthewormhole
#season1
#episode5
#cosmology
#astronomy
#spacetime
#spacescience
#space
#nasa
#morganfreeman
#spacedocumentary
#howdidwegethere
#beginningoflife
Features the research and ideas of geologist Stephen J Mojzsis, chemists Stanley Miller and Harold Urey and their student Jeffrey Bada, Jen Blank of a search for extraterrestrial intelligence project, biologist Jack Szostak, chemist John Sutherland, physicist Paul Davies and microbial geobiologist/biogeochemist Felisa Wolfe-Simon, and planetary scientist Ben Weiss. Tackles the Hadean period, shadow biospheres, a Winogradsky column, life among the toxic chemicals of Mono Lake, ALH84001 and life on Mars.
Thanks for watching. Follow for more videos.
#cosmosspacescience
#throughthewormhole
#season1
#episode5
#cosmology
#astronomy
#spacetime
#spacescience
#space
#nasa
#morganfreeman
#spacedocumentary
#howdidwegethere
#beginningoflife
Category
📚
LearningTranscript
00:00Earth teems with life.
00:10But billions of years ago, our planet was just a ball of molten rock.
00:15Did the first Earthlings rise from a chemical soup bubbling in a primordial pond?
00:21Or did the seeds of life crash down from outer space?
00:26Now, at last, science may be on the cusp of solving that most enduring mystery.
00:32How did we get here?
00:40Space. Time. Life itself.
00:47The secrets of the cosmos lie through the wormhole.
00:56Life is full of mysteries.
01:03But the most compelling mystery is life itself.
01:08The ancient Greeks believed the gods shaped man from clay.
01:12The Vikings tell of two great continents.
01:15One made of fire, one of ice.
01:18When they met, sparks flew and the first living beings were born.
01:23Scientists are still trying to solve this age-old conundrum.
01:28How simple chemicals were somehow transformed into living molecules.
01:33Molecules that eventually evolved into you and me.
01:38But the answers may at long last be close at hand.
01:42And more surprising than we could have ever imagined.
01:46As a kid, I used to go around with a magnifying glass, trying to set things on fire.
01:58Was I being destructive?
02:01I don't think so.
02:03I was seeing what I could create with the power of the sun.
02:06There was something magical to me about that spark.
02:09Is this what happened on Earth billions of years ago?
02:17Did a spark turn inanimate matter into something that can grow, reproduce and evolve?
02:24Something we would define as alive?
02:27It's a puzzle that science has been struggling to piece together.
02:30We have a very good theory of life's evolution, but we have no agreed theory of life's origin.
02:37We don't know how a mix of non-living chemicals turns itself into a living thing.
02:42That's a very good question.
02:43Because no one's actually experimentally converted the non-living into living,
02:47we don't know precisely what we need.
02:50It's a question that may never find an answer.
02:53But the scientists who dare to probe our moment of creation are leading us on a fascinating journey
03:02to an unexpected destination.
03:09To solve the mystery of our genesis, we have to rewind evolution,
03:15go back to the time and the place where the first living things came to be.
03:19Our solar system, more than four billion years ago.
03:26It was a very different place from the solar system we know.
03:31The sun was a young star, cooler than it is today.
03:35Earth was much hotter, having just solidified from a molten ball of hot rock.
03:42Comets and large meteorites were whirling all around it.
03:45Fiery impacts were frequent, and often devastating.
03:51It's a period of Earth's geological history called the Hadean, the Age of Hell.
04:02Geologist Steven Moisesch, from the University of Colorado,
04:07is traveling back in time to the Hadean, trying to discover evidence of life there.
04:12It's interesting to visualize what you might see standing on the surface of the Hadean Earth,
04:19some four billion years ago.
04:21The moon would fill the sky, because it was much closer to the Earth at that time.
04:26But the sky itself would appear different.
04:29So rather than a beautiful sky blue, it must have been red,
04:33and blasted by meteors and comets.
04:42The oceans would also have looked different in the Hadean.
04:46They would not be blue and clear, but dark green, filled with iron minerals.
04:52To us, it would appear as an alien planet, incapable of sustaining life.
04:57But Steven is convinced it could have harbored primitive life,
05:02just like today's most extreme environments,
05:05where microscopic organisms find a way to survive.
05:10We know, looking at our planet today, whether in the driest desert,
05:16the coldest glacier, the deepest ocean, the tallest mountain, life exists.
05:21Why should we expect otherwise, for the earliest Earth?
05:26Paleontologists look for evidence of ancient life forms frozen in rocks.
05:31There are fossils of sea creatures and plants going back half a billion years.
05:36But the more primitive microscopic life that existed before that
05:40is much harder to detect.
05:42And finding rocks that date back to the Hadean is next to impossible.
05:46Almost all of early Earth is now gone, buried under lava flows and oceans.
05:55But a few rare outdrops of four billion year old rock do remain.
06:01Steven tracked one down in a remote region in the heart of Greenland.
06:07The traditional wisdom was that there could not be a record
06:11of the first half billion years of Earth history.
06:14Instead, what we have found by careful searches is that not only is there a record from this time period,
06:22but the record reveals to us an eminently habitable world.
06:27The rocks Steven found in Greenland came from an ocean that formed 3.8 billion years ago.
06:35They were peppered with a series of black dots.
06:38They were lumps of ancient carbon.
06:40And there was something very unusual about them.
06:44Carbon comes in two forms.
06:47Normal carbon, called carbon-12,
06:50and a much rarer form called carbon-13, or heavy carbon.
06:55Normal geological deposits of carbon contain a precise ratio of carbon-12 to carbon-13.
07:02But not these lumps.
07:03Life does something interesting.
07:06It discriminates against carbon-13.
07:11So the biological matter is profoundly enriched in carbon-12.
07:17In the world's oldest known sedimentary rocks, it's very clear there's a carbon isotope signature of early life.
07:27Stephen can't tell what the primitive life form that left this tell-tale signature was like.
07:41But it must have been able to survive in a brutal environment.
07:46A planet constantly pummeled by giant space rocks.
07:49A world where most geologists believe the deluge of impacts would have melted huge parts of Earth.
07:58Boiled its oceans dry and sterilized the entire planet.
08:03Yet, Stephen Moisesh is sure that somewhere on this hellish Earth, there was life.
08:19Stephen has developed a computer simulation to prove our planet could have remained hospitable to life,
08:25even during the intense bombing campaign it endured in the Hadean four billion years ago.
08:30Each of these episodes here is an individual asteroid or comet coming into the Earth at the time of the late heavy bombardment.
08:45We find that impact melt pools here, basically lava lakes, some of which are the size of the continent of Africa.
08:54But this blue region here, which represents cold temperatures, are areas where liquid water is still stable.
09:03Even in the intense bombardment epoch of the early solar system, the Earth would have remained a habitable place.
09:10Microbes deep down in the Earth, or deep in the ocean, like those that today gather around volcanic vents, would have the best chance of surviving these devastating blows.
09:23What these bombardments do is favor organisms that can find a sanctuary to ride out the raining storm of space debris until the epoch of bombardment is over and the whole world is left for them to colonize.
09:43And we think that happened on the Earth about 3.8 billion years ago, when the bombardment ceased.
09:59Stephen's discovery may have pinpointed a time and place for the origin of life.
10:04But it tells us nothing about how life actually started.
10:08To do that, scientists must recreate early Earth in their labs and try to catch a glimpse of that first magical spark.
10:17Planet Earth, four and a half billion years ago.
10:31If we stepped on its surface, molten lava would incinerate us immediately.
10:37One breath of its atmosphere would kill us.
10:42How could life have formed in this bubbling, poisonous hell?
10:51In 1953, two intrepid chemists tried to answer this question.
10:57Stanley Miller and Harold Urey designed an experiment to simulate our planet soon after its birth.
11:04The results would turn out to be so groundbreaking that the apparatus had been preserved at the Scripps Institution in San Diego.
11:11By their former student, Dr. Jeffrey Bata.
11:17At first glance, it looks like just an assortment of flasks and tubes.
11:21But this was carefully designed to, first of all, have a flask that would represent an evaporating ocean.
11:29And that was connected to a flask that represented the atmosphere.
11:32And in this atmosphere, you see these electrodes and you can apply an electric discharge to these electrodes to simulate atmospheric lightning.
11:43And the products would condense out of the atmosphere via this condenser, run into this tube and then back into the water flask.
11:52Perhaps inspired by the book of Genesis, Miller and Urey left their experiment on the origin of life running for seven days.
12:02Then, as now, the flask representing the ocean slowly started to turn dark brown, filling with a seemingly toxic sludge.
12:12It is a tricky experiment. If you're not careful, you can blow it up.
12:16And moreover, this solution is highly toxic. It contains large amounts of hydrogen cyanide.
12:22You'd never want to try and drink this thing or you'd be dead in a second.
12:25But this brown goo also contains something remarkable. Among the toxic chemicals are amino acids.
12:38Amino acids are the basic building blocks of proteins. And living things are built from proteins.
12:46They make up bones, hair and skin.
12:49It was a major breakthrough. Up to this time, people had tried to make organic compounds simulating an early atmosphere, but they'd always failed.
13:00But it was only a baby step toward life.
13:05In all these samples saved from Miller and Urey's experiments, Jeffrey Bata has never been able to detect amino acids joined together to make proteins.
13:16What you're making is simple molecules, what we call monomers. Life as we know it is made up of polymers, complex molecules that are made up of monomers.
13:29And the challenge still remains how we can assemble these simple molecules into complex molecules that have a biological function.
13:37That crucial step towards life may not come from a bubbling flask in a lab.
13:47Jen Blank is sure of that because she believes life needed something else to get started on Earth.
13:54And it came from the sky at 20,000 miles per hour.
14:00We know that in the early history of the solar system, comets were slamming into the planets and maybe this would have been a vehicle for delivering prebiotic materials to the early Earth.
14:12Comets. Mountain-sized lumps of ice and dust circling the sun.
14:18In 1999, NASA sent a spacecraft called Stardust to snag a piece of a comet and bring it back to Earth.
14:30When scientists analyzed the material, they discovered that it contained amino acids, the building blocks of protein, the very tissue of life.
14:41One of the big outstanding questions was whether or not organic compounds coming in on a comet and slamming into the Earth could survive the harsh conditions of that delivery experience.
14:52And so we set out to test this in the laboratory.
14:55Jen Blank works at SETI, the search for extraterrestrial intelligence.
15:00But she's not interested in ET so much as alien molecules.
15:05So she's developed a computer simulation to see what happens to them on impact.
15:09Comets that hit Earth head-on are not very promising.
15:14The collision almost completely incinerates them.
15:17In this movie, the blue colors are cold and as you go toward the red it gets hotter and hotter.
15:23And so we expect the normal impact to have the most extreme conditions.
15:30You can see there's no blue color so it's essentially the materials all volatilized or vaporized.
15:35But when a comet makes a glancing blow, it doesn't incinerate, it melts and dumps massive amounts of water and amino acids on our primeval planet.
15:48This time we're coming in at a 15 degree angle from the horizontal.
15:51Watch the blue, which would correspond to the liquid water.
15:53So you can see it's really, a lot of the water is going away but you still are retaining somewhere on the order of 20% that's being delivered as liquid water.
16:03But these simulations only track the temperature of the comet as it crashes to Earth.
16:09To see what happens to the amino acids, Jen needs to get her hands on some serious firepower.
16:14Here's where you might want to have a picture of a gun or something.
16:21This is the Shockwave lab at Caltech.
16:25Its pride and joy?
16:27A 65 foot long gun capable of firing projectiles at over 16,000 miles per hour.
16:35And this is Jen's bullet.
16:38Let's imagine this is a comet.
16:43It's a metal canister with a liquid fill volume that contains water and dissolved amino acids.
16:48And in our experiment we want to test the response of this to a collision with an Earth.
16:54This is actually a two-stage gun and at the far end we use gunpowder to compress gas.
16:59The gunpowder is ignited and the compressed air slammed into the projectile and sends it traveling down the barrel of the gun at velocities of around 2,000 to 3,000 miles per hour.
17:09This corresponds to an oblique angle impact between a comet and a rocky Earth.
17:14To simulate this glancing interplanetary blow, Jennifer dials down the gun from its maximum muzzle speed and prays her canister and its payload will survive.
17:24Temperatures in these impacts would be essentially thousands of degrees centigrade.
17:31So these are really extreme conditions.
17:32Pen-papным一個 Ich simple my time would.
17:56300 volts spreading.
17:58smell that that's the gunpowder the gunpowder smell the capsule is sent into this larger tank
18:12which is called the recovery tank it weighs about two tons and so it really muffles the collision
18:17and really at the end of experiment if all things would go well it looks much the same as when we
18:22first started now jen breaks open the bullet capsule to retrieve its smashed contents and
18:29discover what happened to this cometary soup of organic chemicals and here's an example with two
18:37different amino acids in it glycine which is the simplest amino acid and proline which is another
18:41one and here's the initial solution you can see just two here's an analysis of the solution afterwards
18:47most high abundance byproducts turned out to be all combinations of the first two amino acids
18:53so we're actually very excited because the reactions that were occurring were actually
18:56forming larger biologically relevant molecules
19:02gin's high-powered experiments suggest comets may have bludgeoned early earth one step closer
19:08to life they helped amino acids join together perhaps even forming primitive proteins we're
19:16actually harnessing the power of the impact to build larger biologically relevant molecules and so
19:22this could have been a dominant source of the building blocks that led to the origin of life
19:31we used to think our planet was a hellhole four billion years ago where any spark of life would have
19:38been instantly incinerated now we know the chemicals of life are inside comets raining down on our planet
19:46and they didn't crash and burn they thrived but other ingredients of life are still missing
19:53at the top of the wanted list is dna the molecule that carries our genetic identity now at last one
20:00man may have cracked the code to the origins of dna itself
20:04it's taken four billion years for life to evolve into organisms as complex as you and me
20:19we're at the tip of a tall branch of the tree of life down in the deepest roots are microbes whose bodies are
20:28just a single cell but each microbes biology is just like ours no matter how different it looks
20:37its identity resides in a strand of dna every living organism we know belongs somewhere on this tree
20:47but why did the tree of life grow in the first place to solve that mystery we have to find the seed
21:00scientists don't know much about this seed but they are sure about one thing
21:04every living organism on earth shares one common feature a tough outer layer that separates it from
21:13the world outside every cell has a membrane the first seeds of life must have had one too
21:21well we think we need this kind of primitive cell membrane to keep the genetic molecules trapped
21:28inside you can't just have everything diffusing around you have to have things compartmentalized
21:35jack shostak at harvard medical school is on a quest to solve one of life's biggest mysteries
21:41how the earliest life forms walled themselves in define me from not me
21:49so modern cell membranes are really tough they're stable they're great barriers they allow cells to
21:58control everything that gets in and out but that requires a lot of fancy highly evolved machinery
22:05which wasn't around by definition for the first cells so those membranes had to be really different
22:12but what might these primitive skins around cells have looked like jack found inspiration
22:19in soap bubbles so these are delicate they really illustrate the idea that there's an encapsulated
22:31space that was pretty good
22:37soap bubbles are made from molecules called fatty acids primitive chemicals that jack thinks were produced
22:45on the primeval earth inside hydrothermal geysers the right kinds of minerals could catalyze the
22:52assembly of fatty acids from simple things like carbon monoxide methane water one kind of nice way that
23:02that could happen is in in a hydrothermal vent system and then they could bubble up to the surface
23:15so jack set about recreating the chemistry of a geyser in his lab and eventually created fatty acids
23:25now he mixes them into a primordial chemical soup made of water salt and amino acids and he watches as a
23:35remarkable transformation takes place so membranes form in sheets and they're they're kind of wavy and the edges are
23:43kind of high energy so what happens is they they close up on themselves and they make little round
23:48structures so they're closed structures like tiny soap bubbles
23:55these little dots are actually hollow bubbles less than a thousandth of an inch across
24:04this is what the first living cells may have looked like four billion years ago
24:08jack may have recreated the seeds of life right under his microscope
24:18but it is impossible for life to evolve unless cells can pull off one crucial task
24:24they must be able to grow and divide this is how seeds blossom into flowers how a caterpillar becomes a
24:34butterfly and how a baby becomes an adult
24:40soap bubbles grow and divide with nothing more than a puff of air
24:44so jack slightly jiggles the vesicles and watches something incredible happen
24:51the membrane will start to grow spontaneously what we see in the microscope is is that it grows in a very
24:57peculiar way the whole initial vesicle turned into a long flexible tube these fatty acid membranes are
25:07achieving one of evolution's most essential jobs self-replication and they appear to do it automatically
25:15to jack this is a sure sign he's getting close to understanding how the miracle of life began
25:21so we have a cycle of growth and division that's very much like primitive cell growth and division
25:31jack may very well have found the recipe for life's earliest cell structure but to be truly alive
25:38those cells need one vital ingredient genes genes are the molecular identity that can pass from a cell
25:48to its copy all modern life does this with the double helix of dna it's the most complex chemical molecule
25:57we know made up of tens of billions of atoms dna controls every detail of every living thing the color of
26:06our eyes the shape of the leaves on a tree the way even the most simple bacterium swims and every time a cell
26:13divides it places a copy of its dna in both cells of the new generation
26:23at the university of manchester in england chemist john sutherland is trying to discover how dna came to be
26:32the key to discovering how we came to be for me the really interesting point here is the transition
26:38between chemistry and biology it's always been assumed that you need to have an informational
26:42molecule you can't really have life unless you can have inheritance so you need to have something
26:47which you can inherit the information stored in a molecule a molecule as complex as dna could never
26:54have formed all by itself in a primordial pond but there is a simpler version of it a single-stranded
27:01informational molecule called ribonucleic acid or rna scientists studying the origin of life have long
27:11believed that rna might be the precursor of dna a simpler carrier of life's genetic code so the name
27:20of the game if you like is to make rna from very very simple precursor chemicals using simple organic
27:27chemistry under conditions which could have prevailed on the early earth rna is a giant molecular
27:33string made up of four different basic building blocks the order in which these blocks are arranged
27:41forms a genetic code when you look at rna you as an as a chemist you just you you're in sort of
27:49astonishment really and just what a wonderful molecule it is it's complex it's a really beautiful
27:54structure and you inevitably wonder how on earth did that structure arise how on earth did chemistry
28:00produce it rna's structure looks simple but looks can deceive each building block is actually made of
28:09two parts a sugar molecule and a nuclear base chemists found they could make the nuclear bases and so when
28:18they then realized they could actually make the sugars they just thought we must be able to join them
28:22together and so they tried for many years but the problem was chemically you just can't join them
28:27together for years scientists tried and failed to whip up some rna by placing a sugar and a base in a pot
28:37and heating it up but john realized that the primordial soup metaphor was too narrow early earth's kitchen
28:46it had more than just a stove top it had an oven a steamer and the freezer this is like a pond that's sitting
28:54there for a while and then the temperature goes up and the pond starts to evaporate and the residue that's left after the pond is
29:00evaporated is then heated for a period and then it rains again and after it's rained the sun comes out so it's a
29:06sequence of events rather than one static set of conditions so john and his team recreate the sequence of
29:14wetting drying heating and cooling that would have taken place on early earth and incredibly for the
29:21first time these chemists achieve what none before them ever did they create two of the four basic building
29:31blocks of rna well now that we have to find a way to make the other two and i think we're pretty close
29:37to doing that and then we want to string them together to make an rna polymer molecule and we've
29:42actually recently found some ways in which we think we can string them together we know our incredibly
29:49complex biology could not have been the first form of life on earth what was life like before the life
29:56we know finding that life might help us understand how we got here and the answer could be right under
30:03our noses all life so far studied is the same life but it's never been clear to me that you can't have
30:10more than one form of life on the planet at the same time i think it's entirely likely that we share this
30:16planet with a genuinely alien type of life alien not because it necessarily came from space but because it
30:22belongs to a different tree of life from you and me remarkably enough it turns out that nobody has
30:29really thought to look for life on earth as we don't know it paul davies is one of the world's leading
30:36cosmologists he's the first to admit he's not a biologist but he's not afraid to venture into their
30:42territory and ask questions no one else thought to ask we don't know how a mix of non-living chemicals
30:50turns itself into a living thing we don't even know whether this is a very likely sequence of
30:54events or very unlikely sequence of events but let's suppose it's very likely uh then shouldn't
31:00it have happened many times over right here on earth paul's term for possible homegrown alien life
31:08is the shadow biosphere and he has a plan for how we might discover it we could look at places on earth
31:17which where conditions are so extreme so harsh they're beyond the reach of life as we know it to
31:22see if there's some hardy alien type of microorganism living there
31:31one of paul's colleagues felisa wolf simon is looking for a shadow biosphere by digging through the mud
31:39so the life that we might find in let's say this much mud we could have billions of different
31:47microbes that are as different as you and i are to a mosquito in fact we're more closely related to
31:54mosquitoes than they are to each other that's how different these microbes are felisa works at the u.s
31:59geological survey in menelow park california but it's nasa's astrobiology program that pays her to study
32:07mud so one of the things i always do when i go to a new environment regardless of where it is in the
32:14world i take samples to set up a winogradsky column a winogradsky column is like a potted history of the
32:21earth a breeding ground for all kinds of strange microbes you take your sample of mud and you just
32:31fill say a glass jar and you put it in the window you'll see over time beautiful colors evolve
32:38in this winogradsky column the progression of colors reveals distinct types of microbes
32:46that are inhabiting the column every type of microbe needs specific elements to survive
32:53some feed on sunlight others on carbon more exotic bugs feed on sulfur
32:59but one mud sample felicia took in 2009 revealed bugs stranger than she could have ever imagined
33:10it came from a place that is highly toxic to almost all life on earth mono lake in california
33:19you can't talk about mono lake without being a little wistful you feel like you're on another planet it also
33:24contains very interesting compounds of particular interest to me was very high levels of arsenic
33:30there's roughly 40 000 times or so the recommended arsenic from say the epa so it seemed to me
33:38logically that it could harbor potentially the vestiges of a shadow biosphere felicia was not
33:45disappointed when she dug in the mud of mono lake she did indeed find bugs that could survive these highly
33:54toxic doses of arsenic and her newfound interest in this poison didn't just cause ripples with her
34:00scientific colleagues i came home one day and i brought all these books in and i put them on
34:05on my counter my husband said so what are you interested in arsenic for and i said well i'm
34:10interested in how it dissolves where you might find it and my husband a little disturbed but but you
34:19don't study arsenic and then i started to giggle because i realized he was getting a bit nervous
34:25arsenic arsenic is an effective poison to most organisms because it closely resembles the element
34:36phosphorus it tricks our cells into substituting one element for the other since phosphorus forms the
34:44backbone of dna its effects are devastating but not the bugs that felicia found no matter how big a dose
34:52of arsenic she gave them even many times more than the sky high levels in mono lake the microbes just
34:59kept on growing so these are microbes using what seems to be poison or toxic substances and these this
35:07biology is thriving it can cope with hundreds of thousands of times what would be say an okay level
35:15of arsenic for a human to be exposed to could this microbe be part of the shadow biosphere
35:22our own homegrown alien life could its rules of biology be different from ours so perhaps
35:31maybe they use a similar kind of dna only it's a little different maybe parts of it are different
35:36maybe they use similar proteins to ours but maybe they use different amino acids than we do
35:42if arsenic atoms are somehow replacing phosphorus atoms in these microbes
35:46then these bugs do not fit on our tree of life they may not look any different from life as we know
35:55it but these bugs could be the descendants of an entirely separate genesis so if we found something
36:05that even did something a little different it could mean that here on earth there was not just one tree of
36:10life that there could be multiple trees out of life humanity has spent an eternity thinking about
36:17the loneliness of being us it would provide for us an example of something else some other form of life
36:25that was also successful if we found those microorganisms then bingo we could say life on earth
36:33has happened at least twice two out of two on one earth-like planet surely means that the universe is
36:39teeming with life it would be inconceivable life had happened twice on one earth-like planet and not at
36:44all on all the other earth-like planets
36:46if felice's bugs are the offspring of a second genesis here on earth then life could be a cosmic norm
36:56we would not be alone in the universe but that leads us to an even more intriguing possibility
37:03life on earth may not be from earth at all
37:07the scientific quest to discover the origin of life has revealed something totally unexpected
37:23that might have been more than one genesis our planet might harbor not one but two or more trees
37:31of life each growing from a separate seed where did these seeds come from that question is forcing us to
37:42reassess who we really are because the answer could be out of this world
37:55planetary scientist ben weiss has pieces of another world in his lab
37:59they're rocks that have traveled from mars to earth and he thinks microscopic martians may have
38:07hitched a ride on some of them about a ton of martian rocks lands on earth every year and over the
38:14history of the of the solar system billions of tons of materials have been transferred so it's possible
38:20that we in fact are martians four billion years ago when earth was being pounded by meteorites and
38:28comets so was mars shrapnel from those impacts was flying all over the early solar system
38:37scientists have found one martian rock that dates back to those days of interplanetary violence
38:43it's called alh 84001 alh 84001 is a a martian meteorite that formed on the surface of mars and then was knocked
38:56off the planet it wandered around in space and then landed on the earth about 11 000 years ago and was
39:01found in antarctica by some u.s scientists in 1984. this rock is very special
39:08in the 1990s the discovery of tiny worm-like structures in the rock turned alh 84001 into
39:18an international celebrity the claims that these were fossilized remains of martian microbes
39:25have since been discredited but ben's investigation of this meteorite might still offer proof of life on
39:33mars because the rock is magnetized you see all these little uh dots and little features that's
39:42magnization that originated on mars in fact it's four billion year old magnization so that must mean
39:47that was that there was a magnetic field a global magnetic field on mars four billion years ago or
39:52earlier a global magnetic field acts like a protective cocoon it has kept earth's atmosphere safe since day
40:01one without a magnetic field the planet has no protection from the solar wind an intense stream
40:08of particles from the sun over hundreds of millions of years it can blow a planet's atmosphere clean away
40:17mars has no magnetic field now and almost no atmosphere the magnetization embedded in alh 84001
40:27proves that four billion years ago mars had both alh 84001 contains some trapped we think atmospheric gases from
40:40early mars the composition of these gases do not resemble the composition of the martian atmosphere today
40:46but they do resemble what you might think early mars had in its atmosphere even though today it's cold and dry
40:55and not very hospitable for life on the surface we think in its early days that it had climate which
41:01was much more like the earth's today you know it was presumably um significantly warmer and wetter there
41:08might even have been standing bodies of liquid water on its surface its atmosphere was thicker
41:14and it might have been a better place for life to originate
41:17since mars is only half the size of earth it would have cooled from a molten ball of lava much quicker
41:25than earth in other words mars could have harbored life sooner than earth and ben's most recent study
41:35is closing the link between the biology of two planets he's discovering that microscopic martians
41:41could indeed have survived the hot and bumpy ride on a space rot from mars to earth so what you see here
41:50is this is a slice of the meteorite in fact on the very outside of it over here on the left there's a
41:57little melted zone and that's the zone that got heated to high temperatures when it passed through
42:02more earth's atmosphere but most of the meteorite was barely heated at all by passage to the atmosphere
42:08as mars was slowly cooling and losing the ability to support life the last martians may have jumped ship
42:16to our warmer wetter planet organisms could have hitched a ride on this material that was being
42:22exchanged between mars and the earth that even potentially seeded the planet on which they landed
42:27on it and there's every reason to think that you know if there was an origin of life on mars
42:33billions of years ago that it probably made it to the earth multiple times
42:45if ben is right the best place to look for clues to the origin of life might be on the surface of a
42:51planet that's now dead fossils of primitive life on mars dating back billions of years
42:58could still be there perhaps the next space probe we send to mars will stumble across them and we'll
43:05be able to study our long lost ancestors but it's also possible the first living things on earth are
43:13still here lurking in the shadow biosphere you and i are the latest chapter of a story that's been
43:22unfolding for billions of years how that story begins is still unknown did comets seed the earth with the raw
43:32ingredients of life was mars our original birthplace before we jumped to a new planet or are we the earth's
43:41second or third incarnation of life aliens might be living among us we might all be martians in the end
43:52the stuff of science fiction might lead us to a cosmic truth and answer that eternal question
43:58how did we get here