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Scientists hypothesize that the same cosmic bombardments that once reshaped the early Earth may have created the very conditions that allowed life to emerge....
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00:12Earth is a living planet.
00:18But it wasn't always that way.
00:22Life had a beginning.
00:25When and how did life emerge on this planet?
00:28What environments did it live on throughout Earth's history?
00:34These are some of our planet's greatest mysteries.
00:43For a long time,
00:45scientists thought life could not have appeared very early in Earth's history
00:50when the planet was under heavy bombardment by asteroids.
00:55A tremendous number of impacts.
00:57Even a large one.
00:58Imagine an object the size of the moon that could have collided with the Earth.
01:07But now, scientists are finding new clues.
01:11In ancient rocks.
01:13On the surface of the moon.
01:15Even on space rocks hundreds of millions of miles away.
01:20And inside craters made by massive asteroid impacts.
01:26And they're wondering.
01:28Instead of preventing life from starting.
01:31Could violent impacts like these actually be essential?
01:37Asteroids could have delivered the basic chemical building blocks of life to Earth.
01:43Leading some scientists to ask.
01:46Could asteroids be the spark of life?
01:49Right now.
01:50On NOVA.
01:51With me.
02:09This is a very special of our planet.
02:10And now here's our planet.
02:19The planet we have to reach the galaxy.
02:21parcours you and our planet,
02:21Mountains in South Africa. Here lie some of the oldest and rarest rocks visible
02:27on the surface of our planet. And here geologists Nadia Drabon and Pumalile
02:34Mashali are searching for evidence of the conditions on the early earth to
02:39help solve the mystery of how life got started.
02:44So we'll be going right here, right where you see the purple meet the orange.
02:49Right near the river? Yeah.
02:56When someone comes onto these mountains they think oh wow that's a really
03:00beautiful scenery and really gorgeous. However when I come here I really start
03:05seeing earth history unfolding layer by layer. Some of the Barberton Macandrua rocks
03:11are as old as 3.6 billion years. They've only survived this long because the
03:18mountain range sits on a relatively stable part of the earth's crust.
03:25They date back to a geological eon called the Archean. Earth itself had only formed
03:32about 900 million years before.
03:41The Archean world was alien. There was no breathable oxygen. Erupting volcanoes poured vast quantities of greenhouse gases into the
03:52atmosphere.
03:56The sun was a lot weaker than it is today. But these gases kept the planet warm. Warm enough for
04:05liquid water on its surface.
04:07In fact some of the minerals found in Archean rocks suggest the planet was already an ocean world.
04:16So there was water. Was there also life?
04:29These Archean rocks are some of the best preserved in the world. Could they contain signs of ancient life forms?
04:39In this vast landscape Nadia thinks she may have found some traces.
04:48When you look at these rocks here some of these layers look just really black. But what I'm seeing here
04:54is really the remains of life back then.
04:57People have taken a really close look through the microscope and what they're finding is remains of single cellular organisms
05:04preserved within the rock.
05:09What did these microbes look like? Was this the first life on Earth?
05:18Far from the mountains of Barbiton, in the city of Orléans, France, geologist Francis Westall examines ancient rock samples, hunting
05:27for signs of life.
05:34We have here in front of me a collection of rocks from Barbiton in South Africa and also from the
05:41Pilbara in Australia.
05:42These rocks are more than three billion years old. In these rocks I have found traces of fossil microbial life.
05:55These rocky outcrops in the arid regions of the Pilbara in the northwest of Australia are as ancient as those
06:02in the Barbiton-Makonjwa Mountains.
06:08Rocks from both locations have given Francis and her colleagues some of the best evidence yet of what life may
06:15have been like in the Archean Eon over three billion years ago.
06:24To detect ancient life forms, Francis uses a scanning electron microscope.
06:30A concentrated beam of electrons scans the sample and interacts with atoms on the surface, creating signals that can be
06:39translated into highly magnified images.
06:44But this rock is not a good conductor of electrons, so it's coated with a thin layer of a material
06:51that is gold.
06:56In a 3.3 billion year old sample from Barbiton, Francis identifies what many believe are fossilized life forms.
07:06Here you can see an individual filament here as well.
07:11Francis thinks each of these thread-like structures is a cell about 70 times thinner than a human hair.
07:19How do we know that they're microbial fossils and not something else that's got nothing to do with microbes, minerals
07:25for instance?
07:27One method is to compare them to microfossils of modern bacteria that Francis actually made in her lab.
07:36She entombed living microbes in silica.
07:40In nature, silica can fossilize an ancient organism by penetrating and coating its internal structure.
07:50In an extremely old rock sample from the Pilbara in Australia,
07:55Francis finds a shape that looks like one of her modern silica-coated microbes.
08:02Chemical analysis reveals signatures of what could be organic molecules,
08:08which means this might have been an ancient life form.
08:17I've been able to reveal traces of single cells.
08:22We can see cell division.
08:24We can see also here cell division.
08:27These are cells that are preserved in a rock nearly three and a half billion years old,
08:33and they are exquisitely preserved.
08:37They could be some of the oldest microfossils so far found on Earth.
08:43Traces of a variety of single-celled life forms that lived in different environments over three billion years ago
08:50have been found in Barberton and the Pilbara.
08:56Even though they were single-celled, they came in a variety of shapes.
09:01And so, this could not have been the first life.
09:07Life was extremely diversified already by three and a half billion years ago.
09:12Which tells me that it must have emerged a lot earlier than we originally thought,
09:17possibly between 4.3 and 4.2 billion years ago.
09:27That would place the origins of life within the most mysterious and inhospitable eon in Earth's history.
09:35The Hadean.
09:39This was a time even before the Archean.
09:47Archean rocks may be extremely rare, but Earth's Hadean rocks are nearly unheard of.
09:53Because most rocks on Earth eventually get destroyed, eroded away, or melted down.
10:01For most of our planet's history, Earth's crust has been broken into plates.
10:07Sometimes, when two plates collide, one will slide under the other, pushing the surface rocks down into the mantle.
10:15It's as though Earth is swallowing its past.
10:23Direct evidence of the Hadean may be long gone.
10:27But what we do know is that over four and a half billion years ago,
10:31our planet had just formed from dust and rock particles that circled our young Sun so its surface was unstable.
10:42Scientists named the eon after Hades because they believed it must have been a hellish place,
10:48covered with molten lava from erupting volcanoes.
10:54On top of that, giant asteroids left over from the formation of the solar system pummeled the planet.
11:05Could life have emerged and survived in such hellish conditions?
11:14To find the answer, scientists must first know what life actually is.
11:24Karen Rogers is an astrobiologist and geochemist.
11:32Karen and her team study the origins of life.
11:39At some point in Earth's history, there wasn't life.
11:43And there had to, from that entire planet that was abiotic, that had no life on it,
11:51there was a chemistry, or probably a series of chemistries and reactions that were intertwined,
11:56that eventually came into life.
12:01Scientists don't yet know the exact chemistry that created life.
12:05But they do know its building blocks.
12:09Molecules containing elements like carbon, hydrogen, nitrogen, and oxygen,
12:15which are found all over the solar system,
12:18can join to form organic molecules, including sugars and amino acids.
12:25These bond to make even bigger molecules.
12:29Amino acids form proteins, vital for the functions of a cell.
12:35How do we make the amino acids that turn into proteins?
12:39How are the sugars that form the backbone of DNA and RNA originally synthesized?
12:46So life has all of these ingredients.
12:48And they need to come together just right to eventually get to life as we know it.
12:55The recipe required a source of energy and one of life's most essential ingredients.
13:02Liquid water.
13:04So if life did emerge 4.3 billion years ago,
13:08then this ancient, extremely hot planet had to also be a wet planet.
13:16The rocks that could prove that might be long gone.
13:20But for years, scientists have been gathering clues from tiny, ancient mineral crystals.
13:32When rocks erode, some minerals can survive and get incorporated into new rocks.
13:46In 2018, here in the Barberton-Macondra mountain range,
13:51Nadia Drabun and her team found grains of a type of mineral known to be the Earth's oldest surviving material.
13:58Zircon.
13:59Zircon.
14:03Zircon is an extremely tough little crystal.
14:06Once it forms, it's very hard to break down.
14:09Zircon can withstand billions of years of weathering.
14:13So it retains evidence about the rock in which it originally formed.
14:20And that's why the Zircons Nadia and her team discovered on this mountain are so special.
14:30So this here is actually my favorite rock in the entire Barberton-Greenstone belt.
14:34That is because you find Zircon about 200 million years older than the oldest rock on Earth.
14:42Which means Nadia had discovered some of the rarest zircons on the planet, up to 4.2 billion years old,
14:50from the Hadean.
14:53Chemical analysis of these, along with even older Hadean zircons found in Australia in the 1980s,
15:00revealed that they had formed in the presence of a very special ingredient.
15:11Zircon.
15:12By about 4.3 billion years ago, we've got evidence for liquid water preserved within these zircons.
15:20The presence of water in the Hadean 4.3 billion years ago is crucial.
15:26Because water is one of the key ingredients for life.
15:30And life as we know it could not have emerged without it.
15:36That began to paint a picture of what the Hadean landscape was like.
15:44It was not exactly the hellish place scientists once thought it was.
15:53We had emergent land, but maybe not a lot of it.
15:59And we had an ocean covering most of the planet.
16:06For oceans to exist, the planet's crust must have cooled much faster than scientists once thought.
16:15But where did the water come from?
16:18Some scientists believe it was delivered by asteroids and comets.
16:23But Earth may also have been born with water trapped deep inside the mantle.
16:28And volcanic activity delivered it to the surface as steam.
16:35And in addition, we were regularly getting bombarded with meteorites and asteroids.
16:41And so they came in one after another, after another.
16:47Did life have to wait for a lull in the bombardments before it could spark?
16:54Or was it hardy enough to emerge despite the chaos?
16:58Snuffed out by an impact in one place, only to reemerge in another.
17:13So far, no direct evidence of these early asteroid impacts has been found on Earth.
17:22There may be traces of impacts that happened around three and a half billion years ago, back in the Barberton
17:28-Macandru Mountains.
17:31While any craters would have been eroded away, much tinier clues can survive.
17:39I just found one!
17:41Woohoo!
17:43These things are so difficult to find.
17:45Like in this whole package of rocks, these are the few that are well preserved.
17:53This tiny circle is a spheriol.
17:56Spheriols can form as a direct result of massive asteroid impacts.
18:05When you have a giant impactor, so think about 10 kilometers in diameter or bigger, when that smashes into Earth,
18:11you actually have so much energy that is going to form a rock vapor cloud that is going to be
18:16ejected out of the crater at speeds of up to 40,000 miles per hour.
18:23This rock vapor cloud is going to start condensing to form these spheriols that are going to rain out and
18:28blanket the entire globe.
18:32Without visible craters, these scattered spheriols may be the only remaining evidence of an impact.
18:38So it's impossible to know exactly where on Earth the asteroid hit.
18:50As the spheriols rain down, they form layers.
18:54The thicker the layer, the larger the original impact.
18:57And the spheriol layer that Nadia and Pumalele locate is very thick, almost eight inches deep.
19:06So the asteroid that created it was probably more than 20 miles across.
19:13For the impact energy, what we actually think about is the mass.
19:16And that would have been 50 to 200 times bigger than that of the impactor that killed the dinosaurs.
19:27These rocks tell the whole story from before the impact happened to the actual impact event and then to how
19:32the environment and life responded.
19:34Before the impact happened, about 3.26 billion years ago, here at this location, we would have been standing on
19:41the sea floor, on the shallow sea floor.
19:43And there was a little bit of life present, but not too much.
19:48And then all of a sudden, this is changing really dramatically.
19:57The asteroid hit the ocean, triggering an enormous tsunami that swept across the globe.
20:04Evidence of the big wave is in the rocks.
20:10And that's what we see here, these big chunks that were ripped up from the sea floor right below.
20:19What effects did the tsunami have on the simple life that may have lived at the time?
20:25Nadia finds clues in sediments that formed not long after the impact.
20:30The rocks are red, an indication of iron and a central nutrient for life.
20:38What we think is that the tsunami that was sweeping by was bringing iron-rich waters from the deep oceans
20:44to the surface.
20:48A closer look at the iron-bearing rocks reveals another surprise.
20:55Signs that life bounced back very quickly after the impact.
21:00How could this happen?
21:03So, what we think we see in these rocks is that these microbes are starting to respond to that increase
21:09in nutrients and iron.
21:11And they're actually starting to bloom.
21:17When people think about giant meteorite impacts, they first think about the extinction of the dinosaurs.
21:23What we think, what we are seeing here is that life was not only able to survive these really disastrous
21:29consequences for the environment.
21:30Life was actually able to thrive.
21:34So far, evidence of several giant impacts that happened between 3.5 and 3.2 billion years ago has been
21:42found in these mountains.
21:45But what was happening earlier, during the Hadean, 4.3 billion years ago, when some scientists think the very first
21:54life emerged?
21:58Traces of that time on Earth are long gone, but there's another place that can tell the story.
22:05The moon, whose surface has retained the kinds of scars that once covered Earth.
22:12We don't have any surviving remnants of that Hadean Earth, and so it's easy, I think, to imagine that that
22:20surface was not cratered.
22:22But the moon actually tells us otherwise.
22:26Zero, zero, five, seven, two.
22:31David Kring is an astrobiologist at the Lunar and Planetary Institute in Houston.
22:37He studies the surface of the moon to learn about the early Earth.
22:49In the early and mid-20th century, scientists debated the origin of the circular structures on the lunar surface.
22:57Were they huge volcanoes, or were they impact craters?
23:01Ignition sequence start.
23:05Almost immediately, the Apollo 11 mission answered this question.
23:09With the samples that were collected and brought back to Earth, it became evident that nearly all of those circular
23:16features must have been generated by impacting asteroids and comets.
23:23It was a turning point when scientists realized that violent asteroid impacts could reshape the surface of a planet, including
23:31our own.
23:35The craters on the moon were beautifully preserved, undisturbed by erosion or plate tectonics like we have here on Earth.
23:47Scientists started to count them.
23:51The older a planetary surface, the more time there has been for it to be hit by these impacting asteroids,
24:01and therefore the greater the number of craters.
24:10Thousands of craters larger than a mile wide have been counted so far.
24:17When the moon rocks from some of the craters were dated, scientists were in for a surprise.
24:26In most cases, the samples that were returned by the Apollo astronauts had very, very old ages.
24:34In what we now call the Hadean of Earth history, indicating that there was, early in solar system history, an
24:43intense period of bombardment.
24:48If the moon suffered this many violent impacts, how many and how large were the asteroids that hit the early
24:54Earth?
24:55How frequently did they impact?
24:58And how could they affect the emergence of life?
25:03Planetary scientist, Simona Markey, has been piecing the story together.
25:19There is one single process that's very important to me that I find very fascinating, and that is the process
25:25of collisions.
25:29Everywhere you look, everywhere in the solar system there is a solid surface, you'll find that there are craters.
25:38The craters are a reminder of our solar system's formation around 4.56 billion years ago.
25:48It began as a disk of dust and gas in orbit around the young sun.
25:56The solid materials collided and clumped together to gradually form the rocky planets.
26:09As a result of the formation of the Earth, there were still lots of debris and asteroids and other smaller
26:16objects flying around the sun.
26:18Those objects kept colliding with the surface of the Earth.
26:30About four and a half billion years ago, a single object the size of Mars, or even bigger, may have
26:37crashed into the young Earth.
26:40This high-resolution simulation reveals how the collision flung enough molten and vaporized debris into space to create the Moon.
26:54I'm trying to understand the early evolution of the Earth and the effects of all those impacts that were taking
26:59place during the idea on Earth.
27:02So we do this by building models.
27:05One of the most important sources of data comes from NASA's Lunar Reconnaissance Mission.
27:15This robotic spacecraft has made a 3D map of the Moon's surface at extremely high resolution.
27:24The first thing that we do is to look at the surface of the Moon.
27:28It is much older than the surface of the Earth.
27:31The surface of the Moon is full of impact creators, all the impact creators.
27:36And so we can use that information by mapping how many there are and their sizes and their ages.
27:42And that will provide us the primary information that we need to build our models.
27:48It took an international team decades to collect the data.
27:52But they finally created a computer model that took what happened on the Moon during the Hadean and simulated the
27:59asteroids that would have hit the Earth during the same stretch of time.
28:06And the outcome of that first modeling was staggering.
28:14We are seeing the entire surface of the Earth that is strongly affected by impacts.
28:21Every single circle that you see here is an impact, is a collision.
28:33The prediction was that there were a tremendous number of impacts, even a large one.
28:38Imagine an object the size of the Moon that could have collided with the Earth.
28:50That would have basically wiped out almost entirely perhaps the oceans, vaporized the oceans and melted a large portion of
28:58the crust of the Earth.
28:59This series of apocalyptic bombardments might look like it created a chaotic hellscape on Earth.
29:08But fossil evidence suggests that life did emerge during the Hadean.
29:13So even during asteroid impacts, there must have been enough habitable conditions somewhere on the planet for life to get
29:21a foothold.
29:24If life started on Earth around perhaps 4.2 billion years ago or thereabouts, then the question is how that
29:33was connected to the impacts that were taking place at the same time.
29:40The origins of life community rarely thought about impacts as part of the origin story.
29:45It's really hard to not think about them.
29:49We really had to change our sort of frame of mind, and I certainly did.
29:57To investigate what effects the asteroid impacts had on the emergence of life,
30:02Karen Rogers is recreating the conditions of the Hadean Earth in her lab.
30:10In some ways, the early Earth was a big experimental laboratory.
30:15We're doing prebiotic chemistry.
30:22We can do experiments that were similar to what the early Earth was doing,
30:27and hopefully discover the chemistry that eventually led to life.
30:33Karen's team can create tiny Hadean environments with the same temperatures, pressures, gases,
30:41water composition, and types of rocks that may have existed at the time.
30:51Echoing the places which may have had the chemistry needed for simple molecules to join and eventually lead to the
30:59first cell.
31:03So what we think about the origins of life, there are a few different ideas that have been around for
31:08a while that people have been studying for quite some time.
31:11One of them is a hydrothermal system origin of life.
31:17These are hot water systems heated by volcanic activity.
31:22One of the really special things about hydrothermal systems is that they can provide energy either for life or maybe
31:30the chemistry that allows life to emerge.
31:34Hydrothermal systems can appear on land where magma pushes towards the surface, creating hot springs and geysers like the ones
31:43at Yellowstone and in the deep sea.
31:46Here, the cold sea water descends into fractures in the rock and interacts with the minerals.
31:53Heated by magma, it re-emerges through chimney-like structures, now enriched with the types of organic molecules necessary for
32:01life.
32:07We have really hot hydrothermal fluid coming out of a chimney.
32:11It's full of metals and it's mixing with seawater.
32:17And so when those two fluids come together, they could also provide energy to do organic chemistry that might lead
32:24to life.
32:29So did the very first primitive cells emerge and survive in hydrothermal systems?
32:35And if so, where?
32:37On land?
32:38In the deep sea?
32:39Or somewhere else?
32:41Was that even possible under a steady barrage of asteroids?
32:49When we think about life surviving on the Earth, we think about things that allow it to thrive and things
32:55that might actually destroy it.
32:56And probably one of the most prominent sort of events that destroyed life was the impact that killed the dinosaurs.
33:0966 million years ago, long after the Hadean ended, a space rock bigger than Mount Everest hurtled toward our planet.
33:19It was a moment that would change the evolution of life on Earth.
33:24A vivid reminder of the havoc and devastation that an asteroid impact can wreak.
33:33That one impact alone wiped out 75% of Earth species after it hit the Yucatan Peninsula.
33:50The Chicxulub impact crater was produced by an asteroid.
33:55It hit with an energy equivalent to 100 million megatons of energy.
34:02That's a tremendous blast.
34:10David Kring has studied rocks from beneath the Chicxulub impact crater.
34:18Looking at tiny slices of the rock under a microscope,
34:24he found quartz crystals that had been shocked and deformed by the intense pressure generated by the impact.
34:37But he also saw something much more surprising.
34:41Minerals like anhydrite, which are produced hydrothermally in the presence of very hot water.
34:51So this is evidence that the impact event heated the Earth's crust, heating the water within the Earth's crust,
35:00and then generated a vast circulating hydrothermal system.
35:10This system would have been similar to volcanically driven hydrothermal systems, where some scientists believe life first emerged.
35:17But this one was much larger.
35:22As David probed further, he found something else locked inside the minerals.
35:32Signs that ancient microbes were living in Chicxulub's hydrothermal system, just after the impact.
35:41We now have evidence that it hosted a microbial ecosystem.
35:46They provided the habitat in which these organisms thrived and grew throughout the crust of the Earth beneath the floor
35:57of the Chicxulub impact crater.
36:03And it wasn't just Chicxulub.
36:05As scientists surveyed the 200 known impact craters and structures on Earth,
36:10they discovered that about a third of them show signs of the same type of hydrothermal activity.
36:18And so we began to realize that this was a common process that would have occurred in impact craters throughout
36:26the Hadean period.
36:30What did these ancient hydrothermal systems look like?
36:34There could be clues inside one of Earth's best preserved craters.
36:38About 15 million years ago, an asteroid hit southern Germany, making an almost 16-mile-wide crater known as Rhys.
36:52The impactor was about the same size as a medieval town called Nördlingen,
36:57built inside the crater, which is nearly invisible today.
37:01Even from the highest tower, the rim is hard to make out.
37:06But human-made quarries have exposed the secrets that lie beneath the crater.
37:14All along the rock walls, excavation has exposed strange, vertical, pipe-like structures.
37:26Planetary geologist Livio Tornabene is at Rhys Crater to learn more about these formations,
37:31which are visible as rust-colored rock.
37:41It's really bounding, this pipe structure.
37:44I mean, it looks like it disappears, but it probably goes into the rock.
37:48You probably have to see this in three dimensions,
37:50and it would be sort of branching out and trying to find the quickest route up to the surface.
37:59After decades of research, scientists believe they know how these pipes were formed.
38:06Here, we're actually below the surface of the deposit, as it would have been 15 million years ago.
38:14It's really well preserved, and for a crater this size,
38:18it would have produced a lot of melt that would have been superheated.
38:24The heat from the melt released water from the rock and turned it into gas.
38:32The energy of the escaping steam forged pathways up through the hardening rock,
38:37creating what scientists call degassing pipes.
38:46The darker color of the pipes is evidence that liquids and gases once flowed through them.
38:56We know that there was fluid here running through these rocks,
39:00there was heat, there were available nutrients,
39:03and that is definitely the combination that you want to look for when looking for life here on Earth,
39:11or on Mars, or elsewhere in the solar system.
39:17These degassing pipes were like the plumbing of a vast hydrothermal system.
39:22With every excavation, more are exposed.
39:27So how large were the hydrothermal systems that formed during the Hadean?
39:33The Chicxulub crater may help scientists in their estimates.
39:39So Chicxulub is a good model for some of the smaller impact events that occurred during the Hadean.
39:48At the Southwest Research Institute, geologist Amanda Alexander
39:53runs one of the latest Chicxulub models.
39:58The blue-green color shows the areas where the impact would have fractured the rock,
40:03allowing water to flow through, creating a hydrothermal system.
40:08It was much bigger than scientists thought.
40:13About 10 times larger than was previously expected,
40:16and about 100 times larger than we think is the current Yellowstone hydrothermal system.
40:23And this astonishing estimate is for only one crater.
40:30So the Chicxulub impactor was about 14 kilometers in size,
40:34but the impacts that were happening on the Hadean were much larger and much more frequent.
40:43Impacts like these would have been occurring over the half-a-billion-year duration of the Hadean.
40:54So at some point, vast hydrothermal systems might have covered much of the planet.
41:00All of this research is leading to a remarkable idea.
41:04It's looking more and more like asteroid impacts were double-edged swords.
41:09While they were certainly bringers of chaos and destruction,
41:13they might have created ideal conditions for life.
41:20But what about the raw ingredients?
41:22How can we know if they were present at asteroid impact sites?
41:34Danny Glavin is an astrobiologist at NASA's Goddard Space Flight Center near Washington, D.C.
41:42He's been looking for the ingredients of life in space rocks.
41:49Meteorites are really fascinating objects.
41:51These are fragments of asteroid material that are constantly bombarding the Earth.
41:57Something like 5,000 metric tons of material is falling to the Earth each year.
42:03In 1969, what would become one of the world's most studied meteorites fell to Earth in Southeast Australia.
42:12It was named Murchison after a nearby town.
42:17This meteorite was a treasure trove containing hundreds of amino acids and other fundamental building blocks of life.
42:32The way we extract these meteorite samples to look for the chemical building blocks of life is we start with
42:37a small chunk,
42:38maybe the size of a sugar cube, start chopping it up, grinding it up.
42:42We make kind of a meteorite flower.
42:45And then we take that powder and we put it in a test tube with water to extract it.
42:50So we're making kind of a meteorite tea, if you will.
42:54We take the liquid water, we purify it through several steps.
42:59We want to remove the salts from the extract so that we can really focus on the amino acids and
43:05detecting them.
43:06And then the final step is we inject that liquid into a mass spectrometer to separate out the individual amino
43:13acid peaks and identify them by name.
43:18But there's a problem with studying meteorites that have made their way to Earth's surface.
43:26One of the challenges with meteorites is that as soon as they hit the atmosphere and hit the ground, they
43:32immediately become contaminated.
43:37Lift off of OSIRIS-REx to boldly go to the asteroid metric and back.
43:43We really do need to go to space to go to asteroids and bring back pristine samples that have never
43:50seen the Earth's biosphere.
43:55In 2016, NASA's OSIRIS-REx mission headed to the asteroid Bennu.
44:04Bennu is slightly taller than the Empire State Building, and from a distance, it looked like it would have had
44:10the same kind of rocky makeup as meteorites like Murchison.
44:20In October 2020, OSIRIS-REx bounced off Bennu and grabbed a sample of its surface material.
44:29We fired the nitrogen to collect the sample.
44:32There was a huge plume of material.
44:34When we imaged the sample collector, we saw there was a bounty of material from asteroid Bennu in the collector.
44:41So we had done our job.
44:44It took just under three years for the sample to be returned to Earth.
44:49Altogether, the mission brought back about 122 grams, the largest sample ever collected from an asteroid.
44:59The precious space dust was divided up and sent to labs around the world for analysis.
45:07Danny's lab got about five grams.
45:11So you're looking at a very tiny speck of Bennu.
45:15Even in a particle as small as a half a millimeter, we can extract these samples and look for amino
45:21acids and other chemical building blocks of life.
45:26Bennu was rich in carbon, the element of life.
45:31Fourteen of the 20 amino acids found in life on Earth were also detected, along with all of the chemical
45:38bases of our genetic code.
45:44Which begs the question, what would happen if an asteroid that created a vast hydrothermal system on impact also delivered
45:53the building blocks of life directly to that site?
46:01Could those building blocks survive such a violent, destructive event?
46:12Nobody really knew what happened to these organic compounds once they got delivered.
46:17And we do know that when impactors hit the Earth, they create hydrothermal systems.
46:23And nobody asked, gee, what happens to those organic compounds in those hydrothermal systems?
46:27So we did lots and lots of experiments.
46:36Mary Herrero Perez conducts the experiments under early Earth conditions.
46:49Mary takes a mineral thought to be on the Hadean Earth and found in impact craters today.
46:59To this, she adds a mixture of simulated Hadean water and soluble organic compounds, including amino acids, like those present
47:08in some meteorites.
47:15She then places these ingredients into a chamber, where they're exposed to the conditions typical of a hydrothermal system made
47:23by an impact.
47:25It requires liquid water, energy, and heat.
47:37Hydrothermal systems made by impacts cool over a long period of time.
47:44So the experiments are conducted using a range of temperatures.
47:56Mary conducted hundreds of these trials, each lasting seven days.
48:07I remember the first time that I looked at all the experiments that needed to be done, it was 180,
48:11and I thought that that was a lot.
48:13But the actual thing is I ended up doing probably more than double or triple that.
48:27After the tests, Mary used a nuclear magnetic resonance spectrometer to help identify the structures of any molecules that may
48:35have formed during the experiment.
48:40The results were beyond surprising.
48:45The first time I saw the results of a successful experiment, I did not believe what I was seeing. I
48:51thought I had done it wrong.
48:53And then I spoke with Karen and we could understand that there was more complex chemistry happening that we envisioned.
49:02Our question was, did these molecules start to react with each other as they went through this impact-generated hydrothermal
49:10system?
49:10There was always a possibility that they just broke down and never led to life.
49:15But what we found is instead, these molecules actually got together and made new and bigger molecules.
49:24Now we're still trying to figure out what those new and bigger molecules are, but as you make bigger molecules,
49:31you really are pushing in the right direction to build the complex chemistry that could eventually lead to life.
49:45Exactly where and when that complex chemistry made the leap to biology and life first emerged remains a mystery.
49:53Many scientists still believe that hydrothermal systems created by volcanic activity deep in the sea or on the surface are
50:03the best candidates.
50:05But some scientists are rethinking what role asteroid impacts might have played in the origins of life.
50:15We always think about asteroids colliding on the surface of the Earth as a very negative event.
50:22Maybe that's what we needed in order to get the chemistry necessary for life to form.
50:30Those very same impact events were perfect crucibles for the origin and early evolution of life.
50:38They really generated an environmental life that allowed it to evolve to what it is today.
50:46Many lines of evidence have led to a remarkable hypothesis that life might have begun as a result of those
50:54huge impacts rather than in spite of them.
50:59Perhaps over 4 billion years ago, a space rock laden with the building blocks of life hit the Earth, creating
51:07a vast hydrothermal system.
51:09One of hundreds of thousands that covered our planet.
51:13Each one with the water, the energy, and the ingredients to brew the chemistry of life.
51:22And these asteroid impacts were happening all over the solar system.
51:31On Mars, the remains of hydrothermal systems have been discovered beneath many asteroid impact craters.
51:39And inside one 4 billion-year-old crater, NASA's Perseverance rover has collected the most tantalizing evidence yet of potential
51:49microbial life on the Red Planet.
51:55Who knows what discoveries may await on distant rocky surfaces elsewhere in our own solar system and beyond that might
52:05finally reveal once and for all that we are not alone.
52:35We'll see you next time.
52:40We'll see you next time.
52:51Bye.
52:53Bye.