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00:13Earth is a living planet.
00:19But 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?
00:35These are some of our planet's greatest mysteries.
00:44For a long time, scientists thought life could not have appeared very early in Earth's history,
00:51when the planet was under heavy bombardment by asteroids.
00:54A tremendous number of impacts, even a large one.
00:58Imagine an object the size of the Moon that could have collided with the Earth.
01:02But now, scientists are finding new clues.
01:12In ancient rocks.
01:14On the surface of the Moon.
01:16Even on space rocks hundreds of millions of miles away.
01:19And inside craters made by massive asteroid impacts.
01:26And they're wondering, instead 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.
01:41Leading some scientists to ask, could asteroids be the spark of life?
01:49Right now, on NOVA.
02:11The Barberton-Makondra Mountains in South Africa.
02:24Here lie some of the oldest and rarest rocks visible on the surface of our planet.
02:29And here, geologists Nadia Drabun and Puma Lele Masheli are searching for evidence of the conditions on the early Earth.
02:39To help solve the mystery of how life got started.
02:44So we'll be going right here.
02:47Right where you see the purple meet the orange.
02:50Right near the river?
02:51Yeah.
02:52When someone comes onto these mountains, they think, oh wow, that's a really beautiful scenery and really gorgeous.
03:03However, when I come here, I really start seeing Earth history unfolding layer by layer.
03:09Some of the Barberton-Makondra Rocks are as old as 3.6 billion years.
03:16They've only survived this long because the mountain range sits on a relatively stable part of the Earth's surface.
03:22They date back to a geological eon called the Archean.
03:30Earth itself had only formed about 900 million years before.
03:42The Archean world was alien.
03:45There was no breathable oxygen.
03:48Erupting volcanoes poured vast quantities of greenhouse gases into the atmosphere.
03:56The sun was a lot weaker than it is today.
04:00But these gases kept the planet warm.
04:03Warm enough for liquid water on its surface.
04:06In fact, some of the minerals found in Archean rocks suggest the planet was already an ocean world.
04:15So, there was water.
04:19Was there also life?
04:21These Archean rocks are some of the best preserved in the world.
04:34Could they contain signs of ancient life forms?
04:37In this vast landscape, Nadia thinks she may have found some traces.
04:46When you look at these rocks here, some of these layers look just really black.
04:53But what I'm seeing here is really the remains of life back then.
04:57People have taken a really close look through the microscope.
05:00And what they're finding is remains of single cellular organisms preserved within the rock.
05:10What did these microbes look like?
05:13Was this the first life on Earth?
05:15Far from the mountains of Barberton, in the city of Orléans, France, geologist Francis Westall examines ancient rock samples, hunting for signs of life.
05:35We have here in front of me a collection of rocks from Barberton in South Africa, and also from the Pilbara in Australia.
05:42These rocks are more than three billion years old.
05:47In 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 in the Barberton-Makonjwa Mountains.
06:05Rocks from both locations have given Francis and her colleagues some of the best evidence yet of what life may have been like in the Archean Eon over three billion years ago.
06:19To 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 translated into highly magnified images.
06:41But this rock is not a good conductor of electrons, so it's coated with a thin layer of a material that is gold.
06:56In a 3.3 billion year old sample from Barberton, Francis identifies what many believe are fossilized life forms.
07:04Here 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 for instance?
07:26One method is to compare them to microfossils of modern bacteria that Francis actually made in her lab.
07:37She entombed living microbes in silica.
07:41In nature, silica can fossilize an ancient organism by penetrating and coating its internal structure.
07:47In an extremely old rock sample from the Pilbara in Australia, Francis finds a shape that looks like one of her modern silica-coated microbes.
08:03Chemical analysis reveals signatures of what could be organic molecules, which 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.
08:25We can see, also here, cell division.
08:28These are cells that are preserved in a rock nearly three and a half billion years old.
08:34And they are exquisitely preserved.
08:37They could be some of the oldest microfossils so far found on Earth.
08:42Traces of a variety of single-celled life forms that lived in different environments over three billion years ago have 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.
09:04Life was extremely diversified already by three and a half billion years ago, which tells me that it must have emerged a lot earlier than we originally thought, possibly between 4.3 and 4.2 billion years ago.
09:21That would place the origins of life within the most mysterious and inhospitable eon in Earth's history.
09:36The Hadean.
09:40This was a time even before the Archean.
09:43Archean rocks may be extremely rare, but Earth's Hadean rocks are nearly unheard of.
09:54Because most rocks on Earth eventually get destroyed, eroded away, or melted down.
10:00For most of our planet's history, Earth's crust has been broken into plates.
10:06Sometimes, 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.
10:26But what we do know is that over four and a half billion years ago, our planet had just formed from dust and rock particles that circled our young Sun so its surface was unstable.
10:43Scientists named the eon after Hades because they believed it must have been a hellish place, covered with molten lava from erupting volcanoes.
10:52On top of that, giant asteroids left over from the formation of the solar system pummeled the planet.
11:06Could life have emerged and survived in such hellish conditions?
11:15To find the answer, scientists must first know what life actually is.
11:22Karen Rogers is an astrobiologist and geochemist.
11:25Karen Rogers is an astrobiologist and geochemist.
11:33Karen and her team study the origins of life.
11:40At 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, there was a chemistry or probably a series of chemistries and reactions that were intertwined that eventually came into life.
12:02Scientists don't yet know the exact chemistry that created life.
12:05created life.
12:06But they do know its building blocks.
12:08But they do know its building blocks.
12:10Molecules containing elements like carbon, hydrogen, nitrogen, and oxygen, which are found all over the solar system,
12:18can join to form organic molecules, including sugars and amino acids.
12:22These bond to make even bigger molecules.
12:29Amino acids form proteins, vital for the functions of a cell.
12:34How do we make the amino acids that turn into proteins?
12:38How are the sugars that form the backbone of DNA and RNA originally synthesized?
12:46So life has all of these ingredients.
12:49And they need to come together just right to eventually get to life as we know it.
12:56The 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, then this ancient, extremely hot planet had to also be a wet planet.
13:17The rocks that could prove that might be long gone.
13:21But for years, scientists have been gathering clues from tiny, ancient mineral crystals.
13:26When rocks erode, some minerals can survive and get incorporated into new rocks.
13:38In 2018, here in the Barberton-Macondra mountain range, Nadia 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.
14:10Zircon can withstand billions of years of weathering.
14:14So it retains evidence about the rock in which it originally formed.
14:18And that's why the zircons Nadia and her team discovered on this mountain are so special.
14:26So this here is actually my favorite rock in the entire Barberton-Greenstone belt.
14:34That is because we find zircon about 200 million years older than the oldest rock on Earth.
14:40Which means Nadia had discovered some of the rarest zircons on the planet, up to 4.2 billion years old, from the Hadean.
14:51Chemical analysis of these, along with even older Hadean zircons found in Australia in the 1980s, revealed that they had formed in the presence of a very special ingredient.
15:04By about 4.3 billion years ago, we've got evidence for liquid water preserved within these zircons.
15:17The presence of water in the Hadean 4.3 billion years ago is crucial, because water is one of the key ingredients for life.
15:31And life as we know it could not have emerged without it.
15:34That began to paint a picture of what the Hadean landscape was like.
15:41It was not exactly the hellish place scientists once thought it was.
15:48We had emergent land, but maybe not a lot of it.
16:00And 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.
16:12But 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.
16:29And volcanic activity delivered it to the surface as steam.
16:32And 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?
16:57Snuffed 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.
17:19There may be traces of impacts that happened around three and a half billion years ago, back in the Barberton-McCondral Mountains.
17:32While any craters would have been eroded away, much tinier clues can survive.
17:40I just found one.
17:42Woohoo!
17:44These 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.
17:57Spheriols 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,
18:09when that smashes into Earth, you actually have so much energy that is going to form a rock vapor cloud that it's going to be ejected out of the crater at speeds of up to 40,000 miles per hour.
18:24This rock vapor cloud is going to start condensing to form these spheriols that are going to rain out and blanket the entire globe.
18:29Without visible craters, these scattered spheriols may be the only remaining evidence of an impact.
18:39So it's impossible to know exactly where on Earth the asteroid hit.
18:43As 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 Puma Lele locate is very thick, almost eight inches deep.
19:07So the asteroid that created it was probably more than 20 miles across.
19:14For the impact energy, what we actually think about is the mass.
19:17And 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 the environment and life responded.
19:35Before the impact happened, about 3.26 billion years ago, here at this location, we would have been standing on the sea floor, on the shallow sea floor.
19:44And there was a little bit of life present, but not too much.
19:49And then all of a sudden, this is changing really dramatically.
19:58The asteroid hit the ocean, triggering an enormous tsunami that swept across the globe.
20:05Evidence 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.
20:20What effects did the tsunami have on the simple life that may have lived at the time?
20:24Nadia finds clues and sediments that formed not long after the impact.
20:31The rocks are red, an indication of iron, an essential nutrient for life.
20:39What we think is that the tsunami that was sweeping by was bringing iron-rich waters from the deep oceans to the surface.
20:46A 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?
21:02So what we think we see in these rocks is that these microbes are starting to respond to that increase in nutrients and iron, and are actually starting to bloom.
21:13When 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 consequences for the environment.
21:31Life was actually able to thrive.
21:32So far, evidence of several giant impacts that happened between 3.5 and 3.2 billion years ago has been found in these mountains.
21:44But what was happening earlier, during the Hadean, 4.3 billion years ago, when some scientists think the very first life emerged?
21:54Traces 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.
22:11We don't have any surviving remnants of that Hadean Earth, and so it's easy, I think, to imagine that that surface was not cratered.
22:24But the moon actually tells us otherwise.
22:27Zero, zero, five, seven, two.
22:31David Kring is an astrobiologist at the Lunar and Planetary Institute in Houston.
22:36He studies the surface of the moon to learn about the early Earth.
22:46In 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?
23:02Ignition sequence start.
23:05Almost immediately, the Apollo 11 mission answered this question.
23:10With the samples that were collected and brought back to Earth, it became evident that nearly all of those circular features must have been generated by impacting asteroids and comets.
23:21It was a turning point when scientists realized that violent asteroid impacts could reshape the surface of a planet, including our own.
23:34The 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.
23:49The older a planetary surface, the more time there has been for it to be hit by these impacting asteroids, and therefore the greater the number of craters.
24:04Thousands of craters larger than a mile wide have been counted so far.
24:15When the moon rocks from some of the craters were dated, scientists were in for a surprise.
24:22In most cases, the samples that were returned by the Apollo astronauts had very, very old ages, in what we now call the Hadean of Earth history, indicating that there was, early in solar system history, an intense period of bombardment.
24:46If the moon suffered this many violent impacts, how many and how large were the asteroids that hit the early Earth?
24:56How frequently did they impact?
24:59And how could they affect the emergence of life?
25:02Planetary scientist Simona Markey has been piecing the story together.
25:06There is one single process that's very important to me that I find very fascinating, and that is the process of collisions.
25:27Everywhere we look, everywhere in the solar system there is a solid surface, you'll find that there are craters.
25:34The craters are a reminder of our solar system's formation around 4.56 billion years ago.
25:47It began as a disk of dust and gas in orbit around the young sun.
25:54The solid materials collided and clumped together to gradually form the rocky planets.
26:01As a result of the formation of the Earth, there were still lots of debris and asteroids and other molar objects flying around the sun.
26:18Those objects kept colliding with the surface of the Earth.
26:22About four and a half billion years ago, a single object the size of Mars, or even bigger, may have crashed into the young Earth.
26:38This high-resolution simulation reveals how the collision flung enough molten and vaporized debris into space to create the Moon.
26:50I'm trying to understand the early evolution of the Earth and the effects of all those impacts that were taking place during the idea on Earth.
27:03So we do this by building models.
27:04One of the most important sources of data comes from NASA's Lunar Reconnaissance Mission.
27:16This robotic spacecraft has made a 3D map of the Moon's surface at extremely high resolution.
27:22The first thing that we do is to look at the surface of the Moon.
27:29It is much older than the surface of the Earth.
27:32The surface of the Moon is full of impact creators.
27:35All the impact creators.
27:37And 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 model.
27:47It took an international team decades to collect the data.
27:53But they finally created a computer model that took what happened on the Moon during the Hadean,
27:59and simulated the asteroids that would have hit the Earth during the same stretch of time.
28:07And the outcome of that first modeling was staggering.
28:11We 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. It's a collision.
28:34The prediction was that there were a tremendous number of impacts.
28:37Even a large one. Imagine 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,
28:56and melted a large portion of the crust of the Earth.
28:59This series of apocalyptic bombardments might look like it created a chaotic hellscape on Earth.
29:07But 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 a foothold.
29:21If life started on Earth around perhaps 4.2 billion years ago or thereabouts, then the question is how that was connected to the impacts that were taking place at the same time.
29:37The origins of life community rarely thought about impacts as part of the origin story.
29:46It's really hard to not think about them.
29:50We really had to change our sort of frame of mind.
29:53And I certainly did.
29:54To investigate what effects the asteroid impacts had on the emergence of life,
30:03Karen Rogers is recreating the conditions of the Hadean Earth in her lab.
30:11In some ways, the early Earth was a big experimental laboratory doing prebiotic chemistry.
30:17We can do experiments that were similar to what the early Earth was doing and hopefully discover the chemistry that eventually led to life.
30:34Karen's team can create tiny Hadean environments with the same temperatures, pressures, gases, water composition and types of rocks that may have existed at the time.
30:48Echoing the places which may have had the chemistry needed for simple molecules to join and eventually lead to the first cell.
31:04So what we think about the origins of life, there are a few different ideas that have been around for a while that people have been studying for quite some time.
31:12One of them is a hydrothermal system origin of life.
31:15These 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 the chemistry that allows life to emerge.
31:35Hydrothermal systems can appear on land where magma pushes towards the surface creating hot springs and geysers like the ones at Yellowstone.
31:43And in the deep sea.
31:47Here, the cold seawater descends into fractures in the rock and interacts with the minerals.
31:52Heated by magma, it re-emerges through chimney-like structures, now enriched with the types of organic molecules necessary for life.
32:01We have really hot hydrothermal fluid coming out of a chimney.
32:12It's full of metals and it's mixing with seawater.
32:15And so when those two fluids come together, they could also provide energy to do organic chemistry that might lead to life.
32:25So 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?
32:40Or somewhere else?
32:41Was that even possible under a steady barrage of asteroids?
32:50When we think about life surviving on the Earth, we think about things that allow it to thrive and things that might actually destroy it.
32:58And probably one of the most prominent sort of events that destroyed life was the impact that killed the dinosaurs.
33:0566 million years ago, long after the Hadean ended, a space rock bigger than Mount Everest hurtled toward our planet.
33:20It was a moment that would change the evolution of life on Earth.
33:25A vivid reminder of the havoc and devastation that an asteroid impact can wreak.
33:30That one impact alone wiped out 75% of Earth's species after it hit the Yucatan Peninsula.
33:51The Chicxulub impact crater was produced by an asteroid.
33:55It hit with an energy equivalent to 100 million megatons of energy.
34:03That's a tremendous blast.
34:11David Kring has studied rocks from beneath the Chicxulub impact crater.
34:14Looking at tiny slices of the rock under a microscope, he found quartz crystals that had been shocked and deformed by the intense pressure generated by the impact.
34:31But he also saw something much more surprising.
34:41Minerals like anhydrite, which are produced hydrothermally in the presence of very hot water.
34:47So this is evidence that the impact event heated the Earth's crust, heating the water within the Earth's crust, and then generated a vast circulating hydrothermal system.
35:04This system would have been similar to volcanically driven hydrothermal systems, where some scientists believe life first emerged.
35:18But this one was much larger.
35:20Much larger.
35:23As David probed further, he found something else locked inside the minerals.
35:33Signs that ancient microbes were living in Chicxulub's hydrothermal system, just after the impact.
35:38We now have evidence that it hosted a microbial ecosystem.
35:47They provided the habitat in which these organisms thrived and grew throughout the crust of the Earth, beneath the floor of the Chicxulub impact crater.
36:00And it wasn't just Chicxulub.
36:06As scientists surveyed the 200 known impact craters and structures on Earth, they discovered that about a third of them show signs of the same type of hydrothermal activity.
36:19And so we began to realize that this was a common process that would have occurred in impact craters throughout the Hadean period.
36:27What did these ancient hydrothermal systems look like?
36:34There could be clues inside one of Earth's best preserved craters.
36:39About 15 million years ago, an asteroid hit southern Germany, making an almost 16-mile-wide crater known as Rhys.
36:47The impactor was about the same size as a medieval town called Nördlingen, built inside the crater, which is nearly invisible today.
37:01Even from the highest tower, the rim is hard to make out.
37:05But 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.
37:20Planetary geologist Livio Tornabene is at Rhys Crater to learn more about these formations, which are visible as rust-colored rock.
37:34It's really bounding, this pipe structure.
37:45I mean, it looks like it disappears, but it probably goes into the rock.
37:49You probably have to see this in three dimensions, and it would be sort of branching out and trying to find the quickest route up to the surface.
37:57After decades of research, scientists believe they know how these pipes were formed.
38:05Here, 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, it would have produced a lot of melt that would have been superheated.
38:22The heat from the melt released water from the rock and turned it into gas.
38:33The energy of the escaping steam forged pathways up through the hardening rock, creating what scientists call degassing pipes.
38:40The darker color of the pipes is evidence that liquids and gases once flowed through them.
38:57We know that there was fluid here running through these rocks, there was heat, there were available nutrients.
39:04And that is definitely the combination that you want to look for when looking for life here on Earth, or 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.
39:25So how large were the hydrothermal systems that formed during the Hadean?
39:32The Chicxulub crater may help scientists in their estimates.
39:38So Chicxulub is a good model for some of the smaller impact events that occurred during the Hadean.
39:47At the Southwest Research Institute, geologist Amanda Alexander runs one of the latest Chicxulub models.
39:56The blue-green color shows the areas where the impact would have fractured the rock, allowing water to flow through, creating a hydrothermal system.
40:06It was much bigger than scientists thought.
40:13About 10 times larger than was previously expected, and about 100 times larger than we think is the current Yellowstone hydrothermal system.
40:23And this astonishing estimate is for only one crater.
40:27So the Chicxulub impactor was about 14 kilometers in size, but 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.
40:48So at some point, vast hydrothermal systems might have covered much of the planet.
41:00All of this research is leading to a remarkable idea.
41:05It's looking more and more like asteroid impacts were double-edged swords.
41:09While they were certainly bringers of chaos and destruction, they might have created ideal conditions for life.
41:20But what about the raw ingredients?
41:23How can we know if they were present at asteroid impact sites?
41:26Danny 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.
42:04In 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.
42:16This meteorite was a treasure trove containing hundreds of amino acids and other fundamental building blocks of life.
42:25The way we extract these meteorite samples to look for the chemical building blocks of life is we start with a small chunk, maybe the size of a sugar cube.
42:39Start chopping it up, grinding it up. We make kind of a meteorite flower.
42:44And then we take that powder and we put it in a test tube with water to extract it.
42:51So 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 detecting them.
43:06And then the final step is we inject that liquid into a mass spectrometer to separate out the individual amino acid peaks and identify them by name.
43:18But there's a problem with studying meteorites that have made their way to Earth's surface.
43:22One of the challenges with meteorites is that as soon as they hit the atmosphere and hit the ground, they immediately become contaminated.
43:34Lift off of OSIRIS-REx to boldly go to the asteroid veterans and back.
43:44We really do need to go to space to go to asteroids and bring back pristine samples that have never seen the Earth's biosphere.
43:51In 2016, NASA's OSIRIS-REx mission headed to the asteroid Bennu.
44:04Bennu is slightly taller than the Empire State Building.
44:08And from a distance, it looked like it would have had the same kind of rocky makeup as meteorites like Murchison.
44:13In October 2020, OSIRIS-REx bounced off Bennu and grabbed a sample of its surface material.
44:28We fired the nitrogen to collect the sample. There was a huge plume of material.
44:33When 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.
44:56The precious space dust was divided up and sent to labs around the world for analysis.
45:08Danny's lab got about five grams.
45:11So you're looking at a very tiny speck of Bennu.
45:16Even in a particle as small as a half a millimeter, we can extract these samples and look for amino acids and other chemical building blocks of life.
45:24Bennu 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 bases of our genetic code.
45:44Which begs the question, what would happen if an asteroid that created a vast hydrothermal system on impact
45:51also delivered the building blocks of life directly to that site?
46:01Could those building blocks survive such a violent, destructive event?
46:04Nobody really knew what happened to these organic compounds once they got delivered.
46:18And 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.
46:40Mary takes a mineral thought to be on the Hadean Earth and found in impact craters today.
46:54To this, she adds a mixture of simulated Hadean water and soluble organic compounds, including amino acids, like those present in some meteorites.
47:09She then places these ingredients into a chamber where they're exposed to the conditions typical of a hydrothermal system made by an impact.
47:25It requires liquid water, energy, and heat.
47:28Hydrothermal systems made by impacts cool over a long period of time.
47:45So the experiments are conducted using a range of temperatures.
47:48Mary conducted hundreds of these trials, each lasting seven days.
48:08I remember the first time that I looked at all the experiments that needed to be done, it was 180, and I thought that that was a lot.
48:13But the actual thing is, I ended up doing probably more than double or triple that.
48:28After the tests, Mary used a nuclear magnetic resonance spectrometer to help identify the structures of any molecules that may have formed during the experiment.
48:37The results were beyond surprising.
48:44The first time I saw the results of a successful experiment, I did not believe what I was seeing.
48:51I thought 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 system?
49:11There was always a possibility that they just broke down and never led to life.
49:16But what we found is instead, these molecules actually got together and made new and bigger molecules.
49:22Now we're still trying to figure out what those new and bigger molecules are, but as you make bigger molecules, you really are pushing in the right direction to build the complex chemistry that could eventually lead to life.
49:38Exactly where and when that complex chemistry made the leap to biology and life first emerged remains a mystery.
49:54Many scientists still believe that hydrothermal systems created by volcanic activity deep in the sea or on the surface are the best candidates.
50:04But some scientists are rethinking what role asteroid impacts might have played in the origins of life.
50:13We always think about asteroids colliding with the surface of the Earth as a very negative event.
50:23Maybe that's what we needed in order to get the chemistry necessary for life to form.
50:28Those 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.
50:44Many lines of evidence have led to a remarkable hypothesis that life might have begun as a result of those huge impacts rather than in spite of them.
50:56Perhaps over four billion years ago, a space rock laden with the building blocks of life hit the Earth, creating a vast hydrothermal system, one of hundreds of thousands that covered our planet, each one with the water, the energy and the ingredients to brew the chemistry of life.
51:19And 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.
51:37And inside one four-billion-year-old crater, NASA's Perseverance rover has collected the most tantalizing evidence yet of potential microbial 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 finally reveal once and for all that we are not alone.
52:11When the crash of the galaxy and the sea rocks were bolted, NASA's Perseverance rover is the latest in theZA, NASA's Perseverance rover now.
52:18Israel-爆笑, NASA's Perseverance rover, NASA's Perseverance rover, NASA's Perseverance rover
52:19Transcription by CastingWords
52:49CastingWords
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