MIT Geologists Uncover Traces of Earth’s Primordial Origins

<v Speaker 1>Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
<v Speaker 1>with our soothing Bedtime Astronomy podcast. Each episode offers a
<v Speaker 1>gentle journey through the stars, planets, and beyond, perfect for
<v Speaker 1>unwinding after a long day. Let's travel through the mysteries
<v Speaker 1>of the universe as you drift off into a peaceful
<v Speaker 1>slumber under the night sky.
<v Speaker 2>Okay, let's unpack this. There's this question. It's probably as
<v Speaker 2>old as thinking about planets. Really, what was Earth actually
<v Speaker 2>made of? I mean, before it became the Earth? We
<v Speaker 2>know what were the starting chemicals? Yeah, what was the
<v Speaker 2>recipe for proto Earth? And for decades, I think it's
<v Speaker 2>fair to say the scientific line has been pretty clear,
<v Speaker 2>almost absolute.
<v Speaker 3>Absolutely The standard story was that whatever Earth started as
<v Speaker 3>chemically speaking, got completely wiped out, obliterated right.
<v Speaker 2>By the formation of the moon, the constant geological churning.
<v Speaker 2>Basically the chemical slate was wiped claim. That's what I learned.
<v Speaker 3>Anyway, that was the textbook answer. The idea was that
<v Speaker 3>the heat and violence involved just homogenized everything, mixed it
<v Speaker 3>all up in the one sort of standard Earth composition.
<v Speaker 2>But now, well, now we're diving into something pretty groundbreaking.
<v Speaker 2>There's a major paper just out in Nature Geosciences that
<v Speaker 2>seems to turn that whole idea on its head.
<v Speaker 3>It really does. It's a significant challenge to that long
<v Speaker 3>held view.
<v Speaker 2>The claim, and it sounds almost like science fiction, is
<v Speaker 2>that scientists have found actual physical remnants of that original
<v Speaker 2>proto Earth material from four point five billion years ago
<v Speaker 2>before the big.
<v Speaker 3>Impact, preserved chemical fingerprints, exactly material that somehow survived the
<v Speaker 3>event that was supposed to reset everything.
<v Speaker 2>So our mission today for you listening is to figure
<v Speaker 2>out how how can a tiny chemical signal and imbalance
<v Speaker 2>in some old rocks actually rewrite our planet's entire origin story.
<v Speaker 2>It feels like a shortcut to understanding the very first
<v Speaker 2>ingredients of our solarstem.
<v Speaker 3>And it is a shortcut in a way, because, as
<v Speaker 3>you said, the giant impact theory was so central that
<v Speaker 3>collision thought to have formed the Moon was considered so
<v Speaker 3>devastating that it effectively erased any chemical memory of what
<v Speaker 3>came before.
<v Speaker 2>You couldn't look at Earth rocks and know what proto
<v Speaker 2>Earth was like.
<v Speaker 3>Precisely, the assumption was ironclad. The original stuff was gone, melted,
<v Speaker 3>mixed in. If you wanted to know about Earth's building blocks.
<v Speaker 3>You had to look outwards at meteorites, things formed elsewhere
<v Speaker 3>that didn't go through that cataclysm. But this new work,
<v Speaker 3>and it's a strong team researchers from MIT, Carnegie, ETH,
<v Speaker 3>Zurich scripts.
<v Speaker 2>They're saying, hang on, maybe some of it is still
<v Speaker 2>here exactly.
<v Speaker 3>Maybe some of those original chemical ingredients are preserved right
<v Speaker 3>here deep within the Earth. We might not need to
<v Speaker 3>look only the space. We might need to look deeper
<v Speaker 3>under our feet.
<v Speaker 2>Which takes us right back to that conventional story, the
<v Speaker 2>one that's now being challenged. Let's quickly recap that the
<v Speaker 2>early life of a planet.
<v Speaker 3>Okay, so picture of the very beginning the Solar System
<v Speaker 3>isn't planets yet. It's just this huge disk of gas
<v Speaker 3>and dust around the brand new sun, the solar nebula,
<v Speaker 3>like a cosmic soup, a very hot, very chaotic soup,
<v Speaker 3>and gravity starts doing its thing. Dust grains stick together,
<v Speaker 3>become pebbles. Pebbles clump into rock accretion right, accretion, Yes,
<v Speaker 3>building up. Layer by layer, These clumps form the first meteorites,
<v Speaker 3>the building blocks, and they keep colliding, merging, getting bigger.
<v Speaker 2>And bigger, until you get planetesimals and eventually proto Earth
<v Speaker 2>and its neighbors.
<v Speaker 3>Right, And this proto Earth in its earliest stage wasn't
<v Speaker 3>like Earth today. It was likely rocky, yes, but incredibly hot,
<v Speaker 3>constantly bombarded by more material, probably covered in bubbling lava.
<v Speaker 3>A global magma.
<v Speaker 2>Ocean sounds pretty inhospitable.
<v Speaker 3>Definitely not a place for life as we know it.
<v Speaker 3>It was still accumulating mass, still forming, chemically different from
<v Speaker 3>the planet we live on.
<v Speaker 2>And then the event, the catastrophe, And this happened fast,
<v Speaker 2>geologically speaking.
<v Speaker 3>Extremely fast. We're talking less than one hundred million years
<v Speaker 3>after the planet first started forming, very early in its life.
<v Speaker 2>And this wasn't just another collision. This was the collision
<v Speaker 2>the giant impact, the.
<v Speaker 3>One that's thought to have created our moon. The leading theory,
<v Speaker 3>the giant impact hypothesis, posits that a massive object, something
<v Speaker 3>roughly the size of Mars, often called thea thea Yes,
<v Speaker 3>slammed into this young, molten proto Earth.
<v Speaker 2>The energy involved must have been well unimaginable.
<v Speaker 3>Truly astronomical. Heating an already superheated molten planet was something
<v Speaker 3>that big. It would have favorized huge amounts of rock.
<v Speaker 3>The mantle the crest through enormous plumes of debris into orbit.
<v Speaker 2>Which eventually clumped together to form the Moon.
<v Speaker 3>That's the prevailing model, but the key consequence for our
<v Speaker 3>story today. The reason this new finding is so radical
<v Speaker 3>is what that impact supposedly did to Earth itself. It
<v Speaker 3>scrambled everything completely. The conventional view, the one taught for decades,
<v Speaker 3>is that the impact energy in the subsequent remelting led
<v Speaker 3>to total planetary homogenization. The planet's interior got mixed like
<v Speaker 3>a cake batters the chemistry exactly. Any original chemical signature
<v Speaker 3>from proto Earth was thought to be utterly obliterated, mixed
<v Speaker 3>inseparably with the material from the impactor. Thea gone forever.
<v Speaker 2>Which again makes total sense when you think about the
<v Speaker 2>sheer violence so natural A scientists concluded, look to meteorites,
<v Speaker 2>They're the only pristine witnesses left.
<v Speaker 3>It was the logical conclusion. If everything here got scrambled,
<v Speaker 3>or reseaid, the only way to guess the original ingredients
<v Speaker 3>was to analyze things that weren't here during the impact,
<v Speaker 3>untouched samples from the early Solar System.
<v Speaker 2>So the assumption was you pick up any rock on
<v Speaker 2>Earth from the crust, the mantle, wherever it should basically
<v Speaker 2>have the same post impact.
<v Speaker 3>Chemical fingerprint, correct a homogenized signature. Finding something different, something
<v Speaker 3>that harks back to the pre impact era suggests a
<v Speaker 3>part of the planet somehow escaped that total mixing. It
<v Speaker 3>implies some deep reservoir remained isolated.
<v Speaker 2>Which sounds almost impossible.
<v Speaker 3>It sounds incredibly unlikely given the scale of the impact.
<v Speaker 3>That's why this new result is so startling. Nicole Ney,
<v Speaker 3>one of the lead authors on the paper, really captured this.
<v Speaker 3>She said, this is amazing because we would expect this
<v Speaker 3>very early signature to be slowly erased through Earth's.
<v Speaker 2>Evolution, even if it survived the impact. You'd think billions
<v Speaker 2>of years of geology would smooth it out.
<v Speaker 3>You'd think so. Convection in the mantle, melting plate, tectonics,
<v Speaker 3>all these processes tend to mix things up over geological time.
<v Speaker 3>The fact that they found any remnant implies we need
<v Speaker 3>to seriously reconsider how effective the giant impact was as
<v Speaker 3>a chemical eraser.
<v Speaker 2>And maybe maybe parts of our planet are chemically distinct
<v Speaker 2>zoned and have been that way for four and a
<v Speaker 2>half billion years.
<v Speaker 3>That's the profound implication here. Maybe Earth isn't as well
<v Speaker 3>mixed as we assumed.
<v Speaker 2>Okay, so if the impact didn't completely erase everything, how
<v Speaker 2>did they find the leftover bits? What's the chemical code
<v Speaker 2>the tracer they used to unlock this?
<v Speaker 3>You mentioned isotopes, right, It all comes down to isotopes,
<v Speaker 3>and specifically isotopes of potassium.
<v Speaker 2>Let's break that down. Isotopes Okay, I remember this from chemistry.
<v Speaker 2>They're like different versions of the same element exactly.
<v Speaker 3>Same element means the same number of protons in the
<v Speaker 3>nucleus that defines what the element is. So potassium symbol
<v Speaker 3>K always has nineteen proton.
<v Speaker 2>Isotopes have different numbers of neutrons.
<v Speaker 3>Correct, same protons, different neutrons. This changes the mass slightly,
<v Speaker 3>but not the chemical behavior mostly okay, And this slight
<v Speaker 3>mass difference is absolutely critical when you're dealing with really
<v Speaker 3>high energy events like planets forming or smashing into each other.
<v Speaker 2>Ah. Okay, So potassium, what are its isotopes?
<v Speaker 3>Potassium has three main naturally occurring ones, potassium thirty nine
<v Speaker 3>K thirty nine, potassium forty K forty and potassium forty
<v Speaker 3>one K forty one.
<v Speaker 2>Got it, thirty nine forty forty one.
<v Speaker 3>Now, on what we consider standard modern Earth the stuff
<v Speaker 3>that makes up the bulk of the crust and mantle.
<v Speaker 3>K thirty nine and K forty one are overwhelmingly dominant.
<v Speaker 3>They make up almost all the potassium and K forty.
<v Speaker 3>K forty is there, but it's a tiny, tiny fraction
<v Speaker 3>of vanishingly small percentage compared to the other two.
<v Speaker 2>Okay, so that specific ratio that balance loads of thirty
<v Speaker 2>nine and forty one hardly any forty that's the chemical
<v Speaker 2>signature of normal post impact earth.
<v Speaker 3>That's the homogenized signature. Yes, But why potassium? Why is
<v Speaker 3>it the key?
<v Speaker 2>Good question? Why not iron or silicon or something more common.
<v Speaker 3>It comes down to volatility. Potassium is what's called a
<v Speaker 3>moderately volatile.
<v Speaker 2>Element, meaning it evaporates relatively easily when heated.
<v Speaker 3>Exactly think about the giant impact again, immense heat, vaporized rock. Yeah,
<v Speaker 3>volatile elements like potassium should have been strongly affected. They
<v Speaker 3>might have been lost to space or fractionated, meaning that
<v Speaker 3>different isotopes might have behaved slightly differently in that extreme heat.
<v Speaker 2>Okay, So it's volatility makes it sensitive to these huge.
<v Speaker 3>Events, very sensitive. If the impact truly mixed everything perfectly,
<v Speaker 3>then the potassium isotupe ratio should be the same everywhere,
<v Speaker 3>reflecting that final homogenization event. But if some material didn't
<v Speaker 3>go through that intense heating and mixing, it might.
<v Speaker 2>Have preserved a different potassium isotope ratio from before the impact.
<v Speaker 3>That's the hypothesis, and this team led by me actually
<v Speaker 3>laid the groundwork for this in a previous study back
<v Speaker 3>in twenty twenty three. They weren't looking at earth rocks then,
<v Speaker 3>they were looking.
<v Speaker 2>Outwards at meteorites.
<v Speaker 3>Yes, they analyzed a whole range of major meteorite types,
<v Speaker 3>carbonaceous chondrites and statipe chondrites, ordinary chondrides. These are like
<v Speaker 3>snapshots of the different chemical reservoirs that existed in the
<v Speaker 3>early Solar System, the potential building blocks of planets.
<v Speaker 2>And what did they find in those meteorites.
<v Speaker 3>They found that the potassium isotope ratios were different, different
<v Speaker 3>from standard Earth and different from each other.
<v Speaker 2>Ah so not the standard Earth mix of K thirty nine,
<v Speaker 2>forty and forty one exactly.
<v Speaker 3>Some meteorite groups had slightly more K forty one relative
<v Speaker 3>to K thirty nine, others slightly less. They showed distinct
<v Speaker 3>potassium isotopic anomalies.
<v Speaker 2>An anomaly, meaning just different from the Earth standard.
<v Speaker 3>Different from the bulk Earth standard. Yes, and this wasn't
<v Speaker 3>just random noise. It varied systematically between different classes of meteorites.
<v Speaker 2>Okay, this is clicking now. The different meteorite types represent
<v Speaker 2>different Early Solar System ingredients, and they have unique potassium
<v Speaker 2>isotope barcodes.
<v Speaker 3>You got it. That was the breakthrough concept, this isotopic anomaly.
<v Speaker 3>The specific balance of K thirty nine, K forty and
<v Speaker 3>K forty one tells you something about the conditions, the temperature,
<v Speaker 3>the pressure under which that material formed. It acts as
<v Speaker 3>a tracer.
<v Speaker 2>A tracer for Earth's original building blocks.
<v Speaker 3>Precisely. THEE and her colleagues realized that if they could
<v Speaker 3>find material on Earth that showed one of these non
<v Speaker 3>standard potassium isotope ratios, especially one that matched some meteorite group,
<v Speaker 3>it would be strong evidence that this material predates the
<v Speaker 3>final homogenization it survived.
<v Speaker 2>So the twenty twenty three study established potassium isotopes as
<v Speaker 2>the tool, the chemical barcode.
<v Speaker 3>Yes, it gave them the crucial tool. What's fascinating is
<v Speaker 3>how it shifted the search instead of just looking at
<v Speaker 3>space rocks to guess Earth's original makeup.
<v Speaker 2>They started looking for the signature of those space rocks
<v Speaker 2>or something like them hidden within Earth itself.
<v Speaker 3>Exactly, find the barcode on Earth and you've potentially found
<v Speaker 3>a piece of proto Earth.
<v Speaker 2>Right. Okay, so you have the tool of the potassium isotopenomaly.
<v Speaker 2>You suspect some proto Earth materials survived. Where on Earth
<v Speaker 2>do you even begin to look for something like that,
<v Speaker 2>something four point five billion years old that somehow dodged
<v Speaker 2>a planetary scale cataclysm.
<v Speaker 3>That's the next critical piece. You need a strategy. You
<v Speaker 3>can't just drill anywhere. The logic has to be fine,
<v Speaker 3>the most isolated, the oldest or the deepest materials accessible,
<v Speaker 3>places that might have been shielded.
<v Speaker 2>Shielded from the impacts mixing, and shielded from billions of
<v Speaker 2>years of geological reprocessing. Makes sense. So where did they target.
<v Speaker 3>They focused on two main categories of samples, hitting both
<v Speaker 3>deep time and deep Earth.
<v Speaker 2>Okay, deep time first, what does that mean?
<v Speaker 3>That means looking at the oldest preserved rocks on the
<v Speaker 3>Earth's surface. They collected samples from ancient crustal areas in
<v Speaker 3>Greenland and Canada. There specifically, those regions contain cretons cretons
<v Speaker 3>are the incredibly old stable cores of continents. Some of
<v Speaker 3>these rocks are billions of years old, among the most
<v Speaker 3>ancient materials we have access to. On the crust, they've
<v Speaker 3>largely avoided being recycled back into the mantle through processes
<v Speaker 3>like subduction.
<v Speaker 2>So potentially little pockets of very old crusts that might
<v Speaker 2>remember an earlier time.
<v Speaker 3>That was the hope for the deep time samples. Then
<v Speaker 3>for deep Earth, they looked at lava.
<v Speaker 2>Lava, But isn't lava relatively new rock?
<v Speaker 3>The lava itself cools into new rock, Yes, but where
<v Speaker 3>the lava comes from is key. They specifically analyze samples from.
<v Speaker 2>Hawaii, Okay, Hawaii famous for volcanoes. Why Hawaiian lava.
<v Speaker 3>Because Hawaiian vulcanism is different from say, volcanism at tectonic
<v Speaker 3>plate boundaries. Hawaii sits on a hotspot. It's fed by
<v Speaker 3>a deep mantle plume.
<v Speaker 2>A plume like a conveyor belt of hot rock rising
<v Speaker 2>from deep inside the Earth.
<v Speaker 3>Exactly. These plumes are thought to originate from way down,
<v Speaker 3>perhaps even from the boundary between the core in the mantle,
<v Speaker 3>a region called the D's layer D double prime. It's
<v Speaker 3>about as deep as you can sample material from. Wow.
<v Speaker 2>So the idea is if any proto Earth material got
<v Speaker 2>trapped deep inside the planet, protected from the mixing, a
<v Speaker 2>mantle plume like the one feeding Hawaii might bring tiny
<v Speaker 2>samples of it up to the surface.
<v Speaker 3>That's the hypothesis. These plumes could be tapping into a deep, ancient,
<v Speaker 3>potentially unmixed reservoir. So you have the ancient surface rocks
<v Speaker 3>from cratons and deep mantle material brought up by plumes.
<v Speaker 3>Two prime candidates.
<v Speaker 2>Okay, they've got their target samples Greenland, Canada, Hawaii. What
<v Speaker 2>happens next? This isn't like a simple chemistry test. I
<v Speaker 2>imagine measuring tiny isotope differences. It sounds incredibly difficult.
<v Speaker 3>It's extraordinarily difficult. The analytical process here is painstaking, requiring
<v Speaker 3>extreme precision and cleanliness.
<v Speaker 2>Walk us through it. What do they do with these rocks?
<v Speaker 3>First, the rock samples had to be crushed into a
<v Speaker 3>very fine powder, think like halcmpowder consistency.
<v Speaker 2>Ok.
<v Speaker 3>Then this powder is dissolved, usually using very strong acids
<v Speaker 3>like hydrofluoric acid to break down all the silicate minerals.
<v Speaker 3>Everything has to go into solutions.
<v Speaker 2>So you end up with a liquid containing all the
<v Speaker 2>elements from the.
<v Speaker 3>Rock correct, and then comes the really tricky part isolating
<v Speaker 3>the potassium. You need to separate the potassium atoms from
<v Speaker 3>everything else in that complex chemical soup, the iron, the silicon,
<v Speaker 3>the magnesium, calcium, trace elements, everything.
<v Speaker 2>How do they even do that?
<v Speaker 3>Typically using a technique called ion exchange chromatography. It involves
<v Speaker 3>passing the solution through special columns pack with resins that
<v Speaker 3>selectively grab onto certain elements. It's a multi step process,
<v Speaker 3>carefully washing away the unwanted elements until ideally you're left
<v Speaker 3>with just the potassium, and it has to.
<v Speaker 2>Be incredibly Pureric contamination would ruin.
<v Speaker 3>The measurement, absolutely critical. We're looking for minuscule variations in
<v Speaker 3>isotope ratios. Even a tiny bit of potassium contamination from
<v Speaker 3>the lab environment, dust, glassware reagents could completely skew the results.
<v Speaker 3>This requires working in ultra clean laboratory conditions.
<v Speaker 2>Okay, so they've powdered, dissolved, and painstakingly isolated pure potassium
<v Speaker 2>from these ancient or deep samples. Now what how do
<v Speaker 2>you measure the isotopes?
<v Speaker 3>That requires a very specialized instrument called a mass spectrometer.
<v Speaker 3>Specifically often a thermal ionization mass spectrometer to me ANDS
<v Speaker 3>or a multi collector inductively coupled plasma mass spectrometer MCICPMS
<v Speaker 3>sounds complex, it is Basically, you load the purified potassium
<v Speaker 3>sample into the machine. It gets ionised turned into charged atoms.
<v Speaker 3>Then these ions are accelerated through a magnetic field.
<v Speaker 2>And because the isotopes have slightly different masses.
<v Speaker 3>They get deflected differently by the magnetic field. Heavier isotopes
<v Speaker 3>like K forty one bend less, lighter ones like K
<v Speaker 3>thirty nine ben more. The instrument has detectors precisely positioned
<v Speaker 3>to count the ions of each mass arriving.
<v Speaker 2>So it can measure the exact ratio of K thirty
<v Speaker 2>nine to K forty to K forty one with incredible precision.
<v Speaker 3>Extraordinary precision down to parts permit billion or even better.
<v Speaker 3>That's the level you need to detect the subtle anomalies
<v Speaker 3>they were looking for and the results.
<v Speaker 2>After all that work on the Greenland, Canada, and Hawaii samples.
<v Speaker 3>The results were well remarkable consistent across these specific samples.
<v Speaker 3>They found a potassium isotopic signature that was clearly measurably
<v Speaker 3>different from the standard homogenized bulk earth signature found in
<v Speaker 3>most other rocks.
<v Speaker 2>Different how what was the anomaly?
<v Speaker 3>Specifically? They found a deficit in the potassium forty isotope, a.
<v Speaker 2>Deficit so even less K forty than the already tiny
<v Speaker 2>amount we expect in normal earth rocks exactly.
<v Speaker 3>Remember, K forty is already the runt of the litter
<v Speaker 3>isotope wise a very small percentage. These samples from the
<v Speaker 3>Creightons in the Hawaiian plume source had an even smaller
<v Speaker 3>fraction of K forty relative to K thirty nine and
<v Speaker 3>K forty one than the standard earth value. Wow, that
<v Speaker 3>is subtle, incredibly subtle. The paper used it a great
<v Speaker 3>analogy to try and convey this. Detecting this tiny deficit
<v Speaker 3>is like imagine a whole bucket of sand that's overwhelmingly yellow,
<v Speaker 3>but you expect maybe one small scoops with a brown
<v Speaker 3>sand mixed in.
<v Speaker 2>Okay, that's the standard earth K forty level of the
<v Speaker 2>tiny bit.
<v Speaker 3>Of brown, right. What they found in these samples was
<v Speaker 3>like finding only a single grain of brown sand in
<v Speaker 3>that whole bucket instead of the scoopful an even tinier
<v Speaker 3>deficit within an already trace.
<v Speaker 2>Amount That really puts the required precision into perspective. It's
<v Speaker 2>amazing they could measure that reliably.
<v Speaker 3>It's a testament to the advancements in mass spectrometry and
<v Speaker 3>clean lab techniques. But the consistency across these geographically distinct
<v Speaker 3>samples representing both ancient crust and deep mantle pointing to
<v Speaker 3>something real.
<v Speaker 2>The conclusion being these materials were built different.
<v Speaker 3>Build different chemically speaking, they carry a different potassium isotope signature,
<v Speaker 3>specifically this K forty deficit Compared to the vast majority
<v Speaker 3>of accessible Earth materials. They hadn't been fully processed or
<v Speaker 3>homogenized like the.
<v Speaker 2>Rest okay hold on. Finding a difference is one thing,
<v Speaker 2>proving its primordial, that it's actually from proto Earth and
<v Speaker 2>not caused by something else. Later that seems like a
<v Speaker 2>huge leap.
<v Speaker 3>It is the absolute crucial next step. You find an anomaly,
<v Speaker 3>you have to ask, could anything else explain this? Could
<v Speaker 3>some geological process create this K forty deficit over billions
<v Speaker 3>of years?
<v Speaker 2>Right, Like maybe some weird chemical reaction deep in the
<v Speaker 2>mantle preferentially removes K forty, or maybe interaction with seawater
<v Speaker 2>altered the Greenland rocks you have to rule out secondary processes.
<v Speaker 3>Exactly, and the researchers knew this. This moves us into
<v Speaker 3>the valivation phase, which is arguably the most rigorous part
<v Speaker 3>of the study. They had to try and break their
<v Speaker 3>own hypothesis.
<v Speaker 2>How did they do that? Through simulations?
<v Speaker 3>Yes, through sophisticated and numerical modeling. They started with the assumption,
<v Speaker 3>let's assume these samples are leftover proto Earth material, and
<v Speaker 3>that proto Earth was originally deficient in K forty.
<v Speaker 2>Okay, start with that premise.
<v Speaker 3>Then they simulated everything major that happened after that, all
<v Speaker 3>the potential alteration processes. They threw the geological kitchen sink
<v Speaker 3>at this hypothetical K forty deficient material in their minds.
<v Speaker 2>What kind of processes did they simulate?
<v Speaker 3>Two main categories, First, the big one, the giant impact itself,
<v Speaker 3>and subsequent smaller but still significant meteorite impacts throughout Earth's history.
<v Speaker 3>They used the known compositions of different meteorite types to
<v Speaker 3>see if mixing that stuff in could dilute or change
<v Speaker 3>the signature, Could.
<v Speaker 2>The impact of somehow created the deficit.
<v Speaker 3>Or could mixing with impact or material explain it. That
<v Speaker 3>was one set of tests. The second category was simulating
<v Speaker 3>long term geological processing within.
<v Speaker 2>The Earth, like the mantle convection, heating, melting we talked about.
<v Speaker 3>Precisely, they modeled the effects of high pressures and temperatures
<v Speaker 3>deep in the mantle. Processes like partial melting were only
<v Speaker 3>some minerals, melt, fluid circulation, basically, anything that could chemically
<v Speaker 3>alter rocks over billions of years. Could those processes generate
<v Speaker 3>a K forty deficit?
<v Speaker 2>Okay, So they simulated impacts and internal geology acting on
<v Speaker 2>this hypothetical K forty four starting material. What did the
<v Speaker 2>simulations show?
<v Speaker 3>The results were in incredibly clear and strongly supportive of
<v Speaker 3>the primordial origin. How So, in every simulation they ran
<v Speaker 3>where the original K forty deficient material was subjected to
<v Speaker 3>either impact, mixing, or long term geological heating and processing,
<v Speaker 3>the end result was a composition with a higher proportion.
<v Speaker 2>Of K forty higher, not lower.
<v Speaker 3>Higher, or at least it evolved towards the standard modern
<v Speaker 3>earth K forty ratio. The processing, the mixing, the heating
<v Speaker 3>it always tended to increase the relative amount of K forty,
<v Speaker 3>bringing it in line with the homogenized bulk earth value.
<v Speaker 3>We see almost everywhere else, and crucially crucially, none of
<v Speaker 3>the simulations could reproduce the persistent K forty deficit that
<v Speaker 3>they actually measured in the Greenland, Canada and Hawaii's samples.
<v Speaker 3>No known impact scenario, no known geological process acting over
<v Speaker 3>time could explain why these specific rocks have less K
<v Speaker 3>forty than everything else.
<v Speaker 2>Wow. Okay, So if later processes only make the K
<v Speaker 2>forty level go up towards the standard value.
<v Speaker 3>Then the only logical explanation left is that the deficit
<v Speaker 3>is intrinsic to the material. It started out that way
<v Speaker 3>and has somehow remained largely unchanged.
<v Speaker 2>It's a primary future, not something created a later.
<v Speaker 3>Exactly, the inescapable conclusion is that the K forty deficit
<v Speaker 3>must be a relic, a chemical memory of the material's
<v Speaker 3>formation conditions before the giant impact, before the great homogenization event.
<v Speaker 2>So these rocks, the ancient cretons the deep mantle source
<v Speaker 2>tapped by Hawaii, they really are leftover pieces of proto Earth,
<v Speaker 2>preserved somehow.
<v Speaker 3>Preserved, perhaps sequestered deep in the mantle, may be stabilized
<v Speaker 3>in the ancient crust, escaping the main mixing bowl for
<v Speaker 3>four point five billion years. This tiny isotopic deficit is
<v Speaker 3>like a surviving echo from a lost world.
<v Speaker 2>That is quite stunning. It opens a window we thought
<v Speaker 2>was welded shut. But the story doesn't quite end there,
<v Speaker 2>does it. There is another twist, a contradiction.
<v Speaker 3>Almost yes, and this is in many ways just as
<v Speaker 3>profound and maybe even more mysterious. It leads to some
<v Speaker 3>big unanswered questions.
<v Speaker 2>While these samples confirm that some kind of proto Earth
<v Speaker 2>material survived the specific chemical fingerprint they found that exact
<v Speaker 2>K forty deficit combined with the K thirty nine K
<v Speaker 2>forty one ratio.
<v Speaker 3>It doesn't perfectly match any known type of meteorite in
<v Speaker 3>our collections.
<v Speaker 2>Wait, really, after the whole setup was about using meteorte
<v Speaker 2>anomalies as.
<v Speaker 3>A guide, isn't that fascinating? Remember the twenty twenty three
<v Speaker 3>study showed different meteorite groups had different potassium anomalies that
<v Speaker 3>gave them the idea to look for an anomaly on Earth.
<v Speaker 3>They found one, the K thirty deficit. Yeah, but when
<v Speaker 3>they compared the specific isotopic ratio of this proto Earth
<v Speaker 3>material to all the known meteorite groups, no match.
<v Speaker 2>Not carbonaceous chondrites, not n statype chondrites, nothing.
<v Speaker 3>No precise match. It's unique, it's clearly ancient, clearly distinct
<v Speaker 3>from bulk Earth. But it doesn't align perfectly with any
<v Speaker 3>of the standard meteorite proxies we use for early Solar
<v Speaker 3>System ingredients.
<v Speaker 2>What does that mean? It feels like a major curveball.
<v Speaker 3>It's huge. It implies that the specific type of material,
<v Speaker 3>the particular chemical building block that came together to form
<v Speaker 3>the bulk of proto Earth, we haven't actually found a
<v Speaker 3>sample of it yet in our meteorite collections.
<v Speaker 2>So the stuff that made us predominantly is missing from
<v Speaker 2>our samples of the early Solar System.
<v Speaker 3>That seems to be the implication. Meteorites help point the
<v Speaker 3>way by showing anomalies exist, but the specific flavor of
<v Speaker 3>anomaly that characterizes photo Earth appears to be from a
<v Speaker 3>type of material we haven't yet identified or sampled out there.
<v Speaker 2>That throws a massive wrench into models of planet formation,
<v Speaker 2>doesn't it. Scientists have spent ages trying to figure out
<v Speaker 2>Earth's composition by mixing different known meteorite types in various proportions.
<v Speaker 3>Right, they try to create recipes. You know, eighty percent
<v Speaker 3>this chondrict, fifteen percent that one five percent of another
<v Speaker 3>to match Earth's overall chemistry. But if the main ingredient,
<v Speaker 3>the photo Earth stuff itself, isn't represented in those known
<v Speaker 3>meteorite groups.
<v Speaker 2>Then those recipes are fundamentally incomplete. They're missing the primary component.
<v Speaker 3>It suggests our sampling of the early Solar System based
<v Speaker 3>on the meteorites that happen to Faulder Earth might be
<v Speaker 3>bias or incomplete. There could have been distinct chemical reservoirs
<v Speaker 3>back then that we just don't have good samples.
<v Speaker 2>Of, which makes sense. Maybe the stuff that preferentially formed
<v Speaker 2>Earth in this region of the Solar System wasn't the
<v Speaker 2>same stuff that ended up forming asteroids further out, which
<v Speaker 2>are the source of most meteorites.
<v Speaker 3>That's a strong possibility. Maybe there were compositional gradients in
<v Speaker 3>the early Solar negula. This finding really highlights that gap
<v Speaker 3>in our knowledge. It's what Nicole Ney alluded to in
<v Speaker 3>her final quote. They shared, our study shows that the
<v Speaker 3>current meteorite inventory is not complete and there is much
<v Speaker 3>more to learn about where our planet came from.
<v Speaker 2>We found the ghost of proto Earth, but we haven't
<v Speaker 2>found the ghost of its specific parent material in space.
<v Speaker 3>Well put, the material that built our world seems chemically
<v Speaker 3>distinct from the common samples we get from space. It
<v Speaker 3>raises huge questions, why did this type of material accumulate here,
<v Speaker 3>where does it come from? And is any of it
<v Speaker 3>still out there?
<v Speaker 2>Okay, let's try and bring this all together as we
<v Speaker 2>wrap up. This has been a pretty mind bending journey
<v Speaker 2>to deep time and.
<v Speaker 3>Deep Earth, it really has.
<v Speaker 2>We started with the idea that proto Earth's chemical memory
<v Speaker 2>was erased, but this new research, using incredibly precise measurements
<v Speaker 2>of potassium isotopes in very specific rock.
<v Speaker 3>Samples, samples from ancient Greenland in Canada and deep mantle
<v Speaker 3>lavas from Hawaii.
<v Speaker 2>They found a consistent deficit in potassium forty, a tiny
<v Speaker 2>chemical flaw.
<v Speaker 3>A flaw that couldn't be explained by the giant impact
<v Speaker 3>or subsequent geological mixing, according to their simulations.
<v Speaker 2>Proving that it must be a primordial signature, a leftover
<v Speaker 2>piece of the original pre impact planet that somehow survived
<v Speaker 2>the cataclysm and billions of years of churning.
<v Speaker 3>Its direct chemical evidence that parts of proto earth are
<v Speaker 3>still here, hidden within the modern planet.
<v Speaker 2>And this isn't just a cool historical factoid for geochemists
<v Speaker 2>as you listen to this, understand that this fundamentally rewrites
<v Speaker 2>the opening chapter of our planet story.
<v Speaker 3>It absolutely does. It tells us the giant impact wasn't
<v Speaker 3>a perfect reset button, and it suggests the building blocks
<v Speaker 3>available in the early Solar System were more diverse than
<v Speaker 3>we knew based on meteorites alone.
<v Speaker 2>It also implies that our planet's interior, particularly the deep mantle,
<v Speaker 2>might not be the well mixed soup we often imagine.
<v Speaker 2>There could be these ancient, chemically distinct blobs or reservoirs down.
<v Speaker 3>There, holding onto secrets from the dawn of the Solar System,
<v Speaker 3>right beneath our feet, which dramatically shifts the focus of
<v Speaker 3>future research. How so well, for decades, the primary way
<v Speaker 3>to study Earth's origins was looking outward, analyzing meteorites, modeling
<v Speaker 3>accretion from known space materials.
<v Speaker 2>Now, now the search turns inward.
<v Speaker 3>Exactly We need to explore the deep Earth with new tools,
<v Speaker 3>new perspectives. We need to look for other isotopic tracers,
<v Speaker 3>other chemical anomalies that might be preserved in these deep
<v Speaker 3>isolated mantle reservoirs potentially sampled by plumes like Hawaii's. The
<v Speaker 3>mantle becomes a geological archive.
<v Speaker 2>Okay, and here's the final thought, the real provocation, perhaps
<v Speaker 2>to leave you with we found evidence for proto Earth
<v Speaker 2>material identified by its unique potassium signature. Yes, but that
<v Speaker 2>signature doesn't match any meteorite we've ever found. The specific
<v Speaker 2>stuff that came together to build this world, our home.
<v Speaker 3>It's precise starting ingredient remains a mystery in terms of samples.
<v Speaker 2>We hold, which means that the most fundamental component that
<v Speaker 2>created us is either still out there somewhere in the
<v Speaker 2>Solar System, maybe locked up in asteroids or planets we
<v Speaker 2>haven't sample properly, waiting to be found, or maybe it
<v Speaker 2>was mostly used up or destroyed in the chaos of
<v Speaker 2>planet formation.
<v Speaker 3>It's a profound unknown. We're standing on the evidence of
<v Speaker 3>our origins, yet the perfect match for that starting material
<v Speaker 3>is elusive. It forces us to wonder, if this potassium
<v Speaker 3>signature survived, what other ancient chemical secrets might be locked
<v Speaker 3>away deep inside Earth, just waiting for us to find
<v Speaker 3>the right isotopic key to unlock them. What else don't
<v Speaker 3>we know about the very foundations of our own planet?
<v Speaker 3>Choos