Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomie podcast. Each episode offers a
Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
Speaker 1: unwinding after a long day. Let's travel through the mysteries
Speaker 1: of the universe as you drift off into a peaceful
Speaker 1: slumber under the night sky.
Speaker 2: If you close your eyes and try to picture the
Speaker 2: ultimate space getaway, you might imagine staring out the reinforced
Speaker 2: window of a spacecraft just watching this beautiful, pristine world
Speaker 2: slowly drifting past.
Speaker 3: Now, absolutely that classic sci fi view.
Speaker 2: Right, And I really want to paint that picture for
Speaker 2: you today, because back in February of nineteen seventy four,
Speaker 2: humanity actually got a view of something that looked exactly
Speaker 2: like that.
Speaker 3: Yeah, the Mariner ten flyby.
Speaker 2: Exactly NASA's Mariner ten spacecraft. Yeah, it's hurtling through the
Speaker 2: inner Solar System. And as it performed this fly by,
Speaker 2: a venus the camera snap this incredibly striking series of photographs.
Speaker 3: They're iconic images, really they are.
Speaker 2: And when you look at those archival images, the planet
Speaker 2: just looks entirely peaceful. I mean It's this perfectly smooth, featureless,
Speaker 2: pearly white orb just hanging there in the pitch blackness
Speaker 2: of space.
Speaker 3: It looks completely harmless, right.
Speaker 2: There are no jagged crater's visible, no raging storms tearing
Speaker 2: across the surface, no harsh colors. It just looks like
Speaker 2: a giant, pristine marble, serene quiet. I'm completely underscurbed.
Speaker 3: It really is a stunning piece of cosmic imagery. But
Speaker 3: it is also one of the greatest deceptions in our
Speaker 3: entire solar system.
Speaker 2: The ultimate catfish.
Speaker 3: Yeah, exactly. We are so conditioned as humans to look
Speaker 3: at a smooth, white, cloudy surface and associate it with calm,
Speaker 3: you know, maybe a soft winter day or a gentle fog.
Speaker 2: Right, it looks like a cloud you could just bounce on.
Speaker 3: But what Mariner ten actually captured was, well, it's essentially
Speaker 3: planetary scale camouflage, because right beneath those trenk pearly white
Speaker 3: clouds is an environment so hostiles, so thoroughly apocalyptic that
Speaker 3: it is quite literally the closest thing to Hell we
Speaker 3: have ever discovered in our cosmic neighborhood.
Speaker 2: Wow, and I think we need to completely shatter that
Speaker 2: peaceful illusion right out of the gate because the reality
Speaker 2: of what is happening under that pristine veil is almost
Speaker 2: it's hard to comprehend.
Speaker 3: It defies everyday logic, honestly, it really does.
Speaker 2: Like if you were to somehow drop down beneath that
Speaker 2: pearly white exterior in a protective suit and try to
Speaker 2: just stand on the surface, you wouldn't be standing at all.
Speaker 2: You'd be instantaneously crushed.
Speaker 3: Oh, completely flattened.
Speaker 2: Yeah, because the atmosphere of pressure down there is ninety
Speaker 2: two times greater than what we experience standing at sea
Speaker 2: level here on Earth. Ninety two times.
Speaker 3: To put the sheer physics of that into perspective, experiencing
Speaker 3: ninety two bars of atmospheric pressure is the equivalent of
Speaker 3: being nearly a kilometer or so about three thousand feet
Speaker 3: underwater in Earth's oceans.
Speaker 2: Wait, three thousand feet deep.
Speaker 3: Yeah, if you think about the kind of heavy, incredibly
Speaker 3: reenf force titanium submersibles we have to build just to
Speaker 3: survive at those depths, that is the baseline environment on
Speaker 3: the surface of Venus.
Speaker 2: That is terrifying. Just standing there as like being at
Speaker 2: the bottom of the ocean.
Speaker 3: And it gets stranger actually, because the atmosphere at the
Speaker 3: surface is so dense that it doesn't even behave like
Speaker 3: a normal gas anymore. It exists as what physicists call
Speaker 3: a supercritical fluid.
Speaker 2: Okay, wait, a supercritical fluid that sounds like something out
Speaker 2: of a sci fi reactor core. How does an entire
Speaker 2: atmosphere become supercritical?
Speaker 3: It's wild, right. It happens when you have carbon dioxide,
Speaker 3: which makes up about ninety six percent of Venus' atmosphere,
Speaker 3: and it gets subjected to extreme pressure and extreme heat simultaneously.
Speaker 2: So it's basically being squeezed and baked at the same
Speaker 2: time exactly.
Speaker 3: It passes the specific critical point where the distinct boundary
Speaker 3: between a liquid and a gas just entirely disappear. So
Speaker 3: you aren't walking through a heavy breeze.
Speaker 2: Down there, What are you walking through them?
Speaker 3: You'd be wading through this thick, soupy, viscous fluid that
Speaker 3: constantly surrounds and crushes everything at time. I mean, it
Speaker 3: flows like a gas, but it has the dissolving power
Speaker 3: in the density of a liquid.
Speaker 2: That is deeply, deeply unsettling. You're wading through a glowing,
Speaker 2: crushing soup and we haven't even brought up the temperature.
Speaker 3: Yet oh right, the heat is a whole other nightmare.
Speaker 2: Yeah, the surface of Venus sits at a staggering four
Speaker 2: hundred and sixty seven degrees celsius. That's eight hundred and
Speaker 2: seventy three degrees fahrenheit.
Speaker 3: Which is hotter than the surface of Mercury. By the way,
Speaker 3: even the mercury is much closer to the sun.
Speaker 2: Right, And just to give a practical reference for that
Speaker 2: kind of heat for you listening, if you took a
Speaker 2: solid block of lead or zinc or tin and just
Speaker 2: set it on the ground on Venus, it would instantly
Speaker 2: melt into a puddle.
Speaker 3: It would just liquify, just liquify.
Speaker 2: And to put the final terrifying touch on this whole environment,
Speaker 2: those serene clouds we talked about from the Mariner ten photos,
Speaker 2: the ones that look like a soft winter.
Speaker 3: Fog, Yeah, definitely not water vapor.
Speaker 2: No, they are made of concentrated sulfuric acid.
Speaker 3: And that acid cycle is particularly vicious too. It actually
Speaker 3: rain sulfuric acid high up in the atmosphere, but the
Speaker 3: surface is so unimaginably hot that the acid rain boils
Speaker 3: and evaporates miles before it ever even hits the ground.
Speaker 2: So it's just this permanent hovering acid mist exactly.
Speaker 3: It forms a permanent corrosive haze. It is a world
Speaker 3: that seems actively designed to destroy anything that comes near it,
Speaker 3: which makes the underlying reality of Venus so bewildering for
Speaker 3: planetary scientists.
Speaker 2: Because it shouldn't be like this, right, No, not at all.
Speaker 3: By almost every metric we have. Venus shouldn't be a hellscape.
Speaker 3: It should be Earth's twin.
Speaker 2: That's the part that really boggles the mind. If you
Speaker 2: look at the rostats, Earth and Venus are practically identical,
Speaker 2: I mean, yeah, roughly the same size, they have almost
Speaker 2: the same mass, they have similar gravity.
Speaker 3: They're virtually the same age too.
Speaker 2: Right, They're located in the same general neighborhood of the
Speaker 2: inner Solar System, and they formed at the exact same
Speaker 2: time out of the exact same primordial dust and gas.
Speaker 3: If you are an alien astronomer looking at our Solar
Speaker 3: System from say a thousand light years away, you would
Speaker 3: see two blue, green, habitable looking planets right next to
Speaker 3: each other. You would assume they evolved identically.
Speaker 2: So how do you start with two identical twins made
Speaker 2: of the same stuff at the same time and end
Speaker 2: up with one being this vibrant blue marble teeming with
Speaker 2: oceans and forests, and the other being a toxic, crushing,
Speaker 2: eight hundred and seventy three degree supercritical inferno.
Speaker 3: That divergence is basically the holy grail of planetary science.
Speaker 2: I bet it's the ultimate what went wrong.
Speaker 3: Scenario exactly, And the general consensus is that you won't
Speaker 3: find the answer by looking at anything happening on Venus today.
Speaker 3: The surface has been completely scrubbed. To figure out what
Speaker 3: went so disastrously wrong, we have to look incredibly far
Speaker 3: back in time.
Speaker 2: Like to the very beginning of the Solar system.
Speaker 3: Yeah, we have to rewind the clock roughly four point
Speaker 3: five billion years to the very chaotic, incredibly violent first
Speaker 3: fifty million years of our Solar System's existence.
Speaker 2: Because the evidence points to a cataclysmic event, doesn't.
Speaker 3: It It does. It points to something massive.
Speaker 2: We're talking about a massive moon sized object acting as
Speaker 2: a cosmic wrecking ball, an event so violently profound that
Speaker 2: it permanently altered the planet's fundamental mechanics.
Speaker 3: Yeah, it fundamentally broke the planet.
Speaker 2: But to even begin to understand how we know this
Speaker 2: ancient catastrophe happened. We have to look at the strange,
Speaker 2: perplexing way Venus moves through.
Speaker 3: Space today, right, because planetary movement is essentially a massive
Speaker 3: historical record, the mechanics of how a planet spins, its tilt,
Speaker 3: its orbital speed. These aren't just random numbers that it
Speaker 3: was born with.
Speaker 2: They're like scars exactly.
Speaker 3: They are the cumulative physical result of everything that has
Speaker 3: ever happened to that body. And Venus moves in a
Speaker 3: way that defies almost everything we expect from a rocky planet.
Speaker 2: Let's get into the kinematics, you know, the study of
Speaker 2: its motion, because the numbers for Venus are just absurd.
Speaker 2: I mean, on Earth, we are entirely used to our
Speaker 2: rapid counterclockwise rotation.
Speaker 3: Sure our standard twenty four hour day.
Speaker 2: We spin on our axis once every twenty four hours.
Speaker 2: It's a brisk pace. It keeps the weather systems churning.
Speaker 2: It gives us our standard day and night cycle. But Venus,
Speaker 2: on the other hand, is moving at a pace so
Speaker 2: sluggish it almost seems broken.
Speaker 3: It's barely moving at all rotationally speaking, and its sluggishness
Speaker 3: is really only half the anomaly. The truly baffling part
Speaker 3: is that it is spinning in the wrong direction.
Speaker 2: Entirely the retrograde spin. Yes, so Earth, Mars, Jupiter, almost
Speaker 2: everything in our solar system spins counterclockwise, but Venus spins clockwise.
Speaker 2: It's the odd one out, and it does it so
Speaker 2: agonizingly slowly that a single rotation on its axis. So
Speaker 2: one single Venusian day takes two hundred and forty eight
Speaker 2: Earth days to complete.
Speaker 3: Just let that number sink in for a second. Two
Speaker 3: hundred and forty eight earth days is wild In the
Speaker 3: time it takes Venus to spin around just one single time,
Speaker 3: Earth has gone through winter, spring, summer, and fall. In fact,
Speaker 3: Venus's day is actually longer than it's year.
Speaker 2: Wait, its day is longer than it's year.
Speaker 3: Yeah, it orbits the Sun in two hundred and twenty
Speaker 3: five earth days, but it takes two hundred and forty
Speaker 3: eight days to spend on its axis once.
Speaker 2: That is just it breaks my brain a little bit
Speaker 2: if I'm trying to visualize what that practically means for
Speaker 2: the surface. Assuming you could survive the pressure in the heat,
Speaker 2: and you could somehow see through the thick sulfuric acid clouds,
Speaker 2: what would a day even look like?
Speaker 3: Well, the Sun would slowly rise in the west because
Speaker 3: of the backward spin right the west, and it would
Speaker 3: take more than one hundred earth days just to cross
Speaker 3: the sky before finally setting in the east. The sheer
Speaker 3: length of the days and nights is terrifying.
Speaker 2: So you're just sitting under the blazing sun for over
Speaker 2: three months straight.
Speaker 3: Yes, it creates a thermal dynamic that is profoundly alien
Speaker 3: because when a planet spins that slowly, the side facing
Speaker 3: the Sun is subjected to a relentless, unending bombardment of
Speaker 3: solar radiation for months on end.
Speaker 2: So all that heat just bakes into the atmosphere in
Speaker 2: one spot.
Speaker 3: Exactly Meanwhile, the dark side is plunged into an equally
Speaker 3: long stagnant night. You completely lose all the rapid atmosphere
Speaker 3: mixing and the daily thermal relief that a fast spinning
Speaker 3: planet like Earth enjoys.
Speaker 2: Man, if you're trying to picture how anomalous this backward
Speaker 2: spin really is, think of Earth like a beautifully balanced
Speaker 2: spinning top.
Speaker 3: I like that analogy.
Speaker 2: Yeah, So you pull the string and it hits the table,
Speaker 2: and it's just humming along, spinning rapidly and smoothly in
Speaker 2: a nice counterclockwise direction. It has all this wonderful, stable momentum.
Speaker 2: It's happy, right, it's happy. But Venus looks like a
Speaker 2: spinning top that was violently kicked, like something hit it
Speaker 2: with such immense force that it completely killed its natural
Speaker 2: forward momentum, stopped it dead, and left it slowly, drunkenly
Speaker 2: spinning in the opposite direction.
Speaker 3: That visual is remarkably accurate to the physics involved. Actually,
Speaker 3: and the reason planetary scientists have been so obsessed with
Speaker 3: this retrograde anomaly for decades is that planets do not
Speaker 3: just spontaneously decide to hit the brakes and reverse.
Speaker 2: Course because of the laws of physics, right.
Speaker 3: Right, The laws of physics strictly forbid it.
Speaker 2: Why is that exactly what dictates the defeat vault spin
Speaker 2: of a planet in the first place. Why counterclockwise?
Speaker 3: It all comes back to how a solar system forms.
Speaker 3: If you picture a giant, formless cloud of cold gas
Speaker 3: and dust floating in space. Eventually gravity causes this cloud
Speaker 3: to collapse in on itself.
Speaker 2: Okay, so it starts squishing together.
Speaker 3: Right, and as it collapses, it starts to spin, And
Speaker 3: just like an ice skater pulling their arms in during
Speaker 3: a spin, the more it collapses the faster it spins,
Speaker 3: eventually flattening out into a massive swirling disk. We call
Speaker 3: it the protoplanetary disk, like.
Speaker 2: A giant cosmic pizza.
Speaker 3: Do yes, exactly. The star forms in the center and
Speaker 3: the planets form from the leftover dust swirling around it
Speaker 3: in the disk.
Speaker 2: So, because the entire massive dust cloud was already spinning
Speaker 2: in one direction, let's say counterclockwise, everything that forms out
Speaker 2: of that dust should also be spinning counterclockwise.
Speaker 3: Precisely. It is called the conservation of angular momentum. The
Speaker 3: planets are basically inheriting the spin of the original dust cloud.
Speaker 2: They don't have a choice, no choice at all.
Speaker 3: So for a planet the size and mass of Venus
Speaker 3: to completely violate that inherited momentum to just stop and
Speaker 3: spin backward, an external force of unimaginable power must have intervened.
Speaker 3: It is literally the only way the math works.
Speaker 2: You need a massive energetic event to essentially grab the
Speaker 2: planet and physically force it into reverse. You do, which
Speaker 2: is where the work of Cedric Gilman and his team
Speaker 2: at ETH Zurich comes in. They are planetary scientists who
Speaker 2: recently presented some really groundbreaking models at the European Geoscience's
Speaker 2: Union General Assembly, and they basically took on the task
Speaker 2: of figuring out exactly what kind of force it takes
Speaker 2: to stop a world.
Speaker 3: And their approach to solving this mystery is fascinating because
Speaker 3: they essentially had to treat the Solar System like a
Speaker 3: four point five billion year old crime scene.
Speaker 2: Right, you can't just go dust for prints exactly.
Speaker 3: They couldn't just guess what happened. They had to work backward.
Speaker 3: They started with the slow rotating observation, so the two
Speaker 3: hundred and forty eight day backward crawl we see today,
Speaker 3: and they fed at endpoint into highly advanced computer simulations.
Speaker 2: So they're reverse engineering the apocalypse.
Speaker 3: Yeah. They use these models to test millions of permutations,
Speaker 3: just trying to find the exact initial conditions that could
Speaker 3: produce the venus we see now.
Speaker 2: They're essentially running the physics engine of the universe in reverse.
Speaker 2: They're asking what happens when you throw a ridiculously large
Speaker 2: rock at another ridiculously large rock.
Speaker 3: And not just any rock. The simulations revealed that to
Speaker 3: alter the momentum of a planet that massive, you need
Speaker 3: an impactor roughly one tenth the mass of Venus itself.
Speaker 2: One tenth of the entire planet's mass. To give that
Speaker 2: some scale for you listening, we aren't talking about a
Speaker 2: standard asteroid here. We aren't talking about the six mile
Speaker 2: wide Metia that wiped out the dinosaurs.
Speaker 3: No, that would barely be a scratch, right.
Speaker 2: An object that is one tenth the mass of Earth
Speaker 2: or Venus is roughly the size of our moon. You
Speaker 2: have a solid, rocky, fully formed planetary body thousands of
Speaker 2: miles across, hurtling through the dark void of the early
Speaker 2: Solar System.
Speaker 3: It is terrifying amount mass, just.
Speaker 2: A rogue moon on a collision course exactly.
Speaker 3: But the model showed that the mass alone wasn't enough
Speaker 3: to solve the mystery. The geometry of the collision was
Speaker 3: absolutely critical, because if that moon sized object had struck
Speaker 3: Venus dead center like a perfect bullseye, it wouldn't have
Speaker 3: caused the retrograde spin.
Speaker 2: Wait, really, why not? Wouldn't a direct hit transfer the
Speaker 2: most energy, Well, it.
Speaker 3: Transfers the most energy into the core. Yes, if you
Speaker 3: have a dead center impact, the kinetic energy goes straight inward,
Speaker 3: driving a massive shockwave through the center of the planet. Okay,
Speaker 3: but it doesn't give you leverage. If you want to
Speaker 3: change how a massive sphere spins, you need torque. You
Speaker 3: need to hit it on the edge. So the models
Speaker 3: concluded that the impactor had to strike Venus at a
Speaker 3: very high angle. It had to be a tangential off
Speaker 3: center grazing blow.
Speaker 2: So instead of a hit on car crash, it's more
Speaker 2: like a side swipe, but at tens of thousands of
Speaker 2: miles per hour.
Speaker 3: Precisely, that glancing blow acts like a giant cosmic hand.
Speaker 2: It grabs the edge of the rapidly spinning planet and
Speaker 2: violently wrenches it the other way.
Speaker 3: Yes, the models show that this specific type of tangential
Speaker 3: strike could take a young, healthy, rapidly spinning Venus, slam
Speaker 3: the brakes on its rotation and induce a faster backward spin.
Speaker 2: And then over time it slowed down.
Speaker 3: Exactly over billions of years of gravitational friction, that initial
Speaker 3: backward spin slowly decayed into the sluggish two hundred and
Speaker 3: forty eight day crawl we see today.
Speaker 2: Okay, but I'm struggling with the mechanics of survivability here,
Speaker 2: because if an object the size of the Moon, traveling
Speaker 2: at thirty or forty kilometers a second, slams into a planet,
Speaker 2: wouldn't the planet just cease to exist? You'd think so, right,
Speaker 2: I mean, how does a rocky sphere take a punch
Speaker 2: of that magnitude and not just shatter into a billion
Speaker 2: pieces of gravel floating in orbit, like the Death Star
Speaker 2: exploding or something.
Speaker 3: It's a completely natural question, because our daily intuition tells
Speaker 3: us that a high speed collision of that size should
Speaker 3: be totally destructive. But this is where planetary physics really
Speaker 3: diverges from our everyday experience. It all comes down to
Speaker 3: a concept called gravitational binding energy. When a planet gets
Speaker 3: to be the size of Venus, its gravity is so
Speaker 3: intensely powerful that it holds its own mass together with
Speaker 3: incredible force, so.
Speaker 2: It's basically squeezing itself into a ball.
Speaker 3: Yes, To permanently shatter a planet that big, to actually
Speaker 3: blast its pieces so far apart that they don't just
Speaker 3: immediately fall back together, requires an energy threshold that is
Speaker 3: truly astronomical, much more than even a moon sized impactor
Speaker 3: can deliver.
Speaker 2: So even if it fractures into pieces, the gravity just
Speaker 2: pulls all the pieces right back into a sphere exactly.
Speaker 3: But furthermore, the tangential angle we talked about actually saves
Speaker 3: the planet from total obliteration.
Speaker 2: Oh, because it wasn't a dead center hit right in.
Speaker 3: A head on collision. All that energy plunges directly into
Speaker 3: the core, which can literally unbind the planet and blow
Speaker 3: it apart, but with a high angle, grazing blow. A
Speaker 3: vast amount of the impactor's kinetic energy is spent on friction,
Speaker 3: on shearing off the outer layers, and on altering the
Speaker 3: angle momentum.
Speaker 2: So it bleeds off the energy on the surface exactly.
Speaker 3: The impactor itself might be completely vaporized and its material
Speaker 3: merged with the planet's outer crust, but the host planet's
Speaker 3: core remains intact. It survives structurally.
Speaker 2: That paints just a wild picture. The planet takes the hit,
Speaker 2: the moon sized rock is pulverized and absorbed into the crust,
Speaker 2: and Venus remains a single intact.
Speaker 3: Sphere, battered but intact.
Speaker 2: But you know, just because it stayed in one piece
Speaker 2: doesn't mean it walked away unharmed. Surviving the kinetic impact
Speaker 2: was just the beginning, because the physical consequences on the
Speaker 2: interior of the planet were.
Speaker 3: Apocalyptic, beyond apocalyptic, really, because when an object that large
Speaker 3: strikes a planet, the laws of thermodynamics take over immediately,
Speaker 3: right The energy has go somewhere exactly. You have a
Speaker 3: staggering amount of kinetic energy the sheer motion of a
Speaker 3: moon sized rock traveling at cosmic speeds. That energy cannot
Speaker 3: just vanish when the rock stops. It has to convert
Speaker 3: into another form, and in a high speed planetary collision,
Speaker 3: kinetic energy instantly converts into heat.
Speaker 2: And we are not talking about a modest heat wave here,
Speaker 2: not at all. We are talking about the surface of
Speaker 2: the planet literally melting into a global ocean of glowing rock.
Speaker 2: The simulations dive deep into the immediate aftermath of this collision,
Speaker 2: and depending on the exact speed and angle, the heat
Speaker 2: transformation is unimaginable.
Speaker 3: The models run a whole spectrum of scenarios. On the
Speaker 3: mild end of the collision parameters, if you can even
Speaker 3: call it mild, you still get a shallow melt layer
Speaker 3: covering the entire globe, maybe one hundred kilometers thick.
Speaker 2: Wait, one hundred kilometers.
Speaker 3: Yeah, so that is sixty two miles deep of pure,
Speaker 3: sloshing liquid magma coating every single inch of the planet.
Speaker 2: Sixty two miles deep of lava is the mild.
Speaker 3: Scenario, right, that's if it barely clips it. The extreme scenario,
Speaker 3: which the researcher's note is highly likely given the immense
Speaker 3: energy required to actually reverse the planet's rotation, is that
Speaker 3: the kinetic heat transfer melted ninety nine percent of Venus's mantle.
Speaker 2: Ninety nine percent, yes mantle being for context, the vast
Speaker 2: rocky interior of the planet that sits right between the
Speaker 2: dense iron core in the center and the thin outer
Speaker 2: crust on the surface. It is the bulk of the
Speaker 2: planet's volume.
Speaker 3: It's almost the entire planet, and.
Speaker 2: The model suggests that ninety nine percent of that solid
Speaker 2: rock was instantly turned into a liquid. The entire planet
Speaker 2: essentially became a giant droplet of glowing molten magma floating
Speaker 2: in space.
Speaker 3: It's an event of such violence that it resets the
Speaker 3: entire geological clock of the world.
Speaker 2: Wow.
Speaker 3: But here is where the story takes a fascinating and
Speaker 3: frankly incredibly frustrating turn for scientists. You would assume that
Speaker 3: an event that violently melts an entire planet would leave
Speaker 3: behind some obvious glaring physical scar.
Speaker 2: Yeah, a crater the size of a continent, or a
Speaker 2: weird wabble or a massive.
Speaker 3: DNSE something right, a strange density anomaly, something we could
Speaker 3: point our instruments at today and s eight. There it is.
Speaker 3: There's the proof of the impact. Right.
Speaker 2: If you hit a planet with the moon, there should
Speaker 2: be a bruise, but there isn't. And that leads to
Speaker 2: a really profound observation about how planets actually cool down
Speaker 2: in the vacuum of space.
Speaker 3: It's all about insulation, or rather the complete lack of it.
Speaker 3: When a planet has a solid, rocky crust like Earth does,
Speaker 3: that crust acts like a heavy blanket.
Speaker 2: It keeps the heat in exactly.
Speaker 3: It traps the internal heat of the core and mantle
Speaker 3: inside the planet, and that heat escapes very slowly over
Speaker 3: billions of years through volcanoes and tectonic vents. But when
Speaker 3: you melt ninety nine percent of the mantle, you destroy
Speaker 3: the crust entirely. The blanket is gone.
Speaker 2: It's just ripped away.
Speaker 3: Yep. You just have raw liquid magma directly exposed to
Speaker 3: the freezing vacuum of space.
Speaker 2: And liquid magma is incredibly efficient at radiating heat away.
Speaker 3: Isn't it extremely efficient without a solid crust to trap
Speaker 3: the energy. The heat from that unimaginable collision just vents
Speaker 3: directly out into the void. Because the heat transfer is
Speaker 3: so efficient, a global magma ocean actually cools down and
Speaker 3: solidifies back into rock remarkable quickly on a geological timescale.
Speaker 2: How quickly are we talking.
Speaker 3: We're talking maybe a few hundred million years, which is
Speaker 3: a blink of an eye in the life of a
Speaker 3: solar system.
Speaker 2: Wow. So the rock cools, it solidifies, it forms a
Speaker 2: completely new crust, and as the models point out, once
Speaker 2: that heat is efficiently radiated away and the magma turns
Speaker 2: back into a solid surface, the thermal signature of the
Speaker 2: planet looks exactly like a planet that was never hit
Speaker 2: at all.
Speaker 3: It normalizes completely.
Speaker 2: That is so wild.
Speaker 3: Yeah, the heat is gone, the rock is solid, the
Speaker 3: planet settles back into a perfect sphere, and to any
Speaker 3: telescope or probe, it looks thermally completely standard.
Speaker 2: It is the ultimate cosmic cover up, like a perfect crime.
Speaker 2: I was thinking about this, and if you imagine someone
Speaker 2: has an incredibly detailed, beautifully carved ice.
Speaker 3: Sculpture, Okay, an ice sculpture.
Speaker 2: Right, and it has all these intricate ridges and cuts
Speaker 2: which represent the craters and the early geological history of
Speaker 2: a young planet. Now someone comes along and hits that
Speaker 2: sculpture with an industrial blow torch until it melts entirely
Speaker 2: into a puddle of water.
Speaker 3: It's just gone.
Speaker 2: Then they take that water poured into a smooth spherical
Speaker 2: mold and freeze it back into a standard block of ice.
Speaker 3: That's a great analogy. All the physical evidence of the
Speaker 3: original trauma, all the unique carving marks, the impact points,
Speaker 3: they are completely erased by the melting and refreezing process.
Speaker 3: You are left with a pristine, smooth block of ice exactly.
Speaker 2: A detective examining that ice later would have absolutely no
Speaker 2: way of knowing what the original sculpture look like, or
Speaker 2: that a blowtorch was ever used. The melting process covers.
Speaker 3: The tracks perfectly, it really does.
Speaker 2: But even though the obvious physical bruise healed and the
Speaker 2: heat dissipated, the mechanical damage was done. The planet was
Speaker 2: now spinning at a drastically reduced backward speed, and that
Speaker 2: one mechanical change triggered a terrifying cascade of consequences for
Speaker 2: the planet's climate.
Speaker 3: This is where we bring in the insights of planetary astrophysicists,
Speaker 3: particularly people like Stephen Kine, who have dedicated their research
Speaker 3: to understanding the found connection between a planet's rotation and
Speaker 3: its ability to harbor life.
Speaker 2: And it's a connection we often overlook.
Speaker 3: Honestly, it really is. When we talk about finding life
Speaker 3: in the universe, we always focus on the presence of
Speaker 3: liquid water or the distance from a star. We never
Speaker 3: really think about the spin rate as a vital ingredient
Speaker 3: for habitability.
Speaker 2: Why is rotation so critical? Why does the spin matter
Speaker 2: so much for the climate.
Speaker 3: Because rotation dictates how a planet manages its energy. A
Speaker 3: planet is constantly receiving massive amounts of heat from its star.
Speaker 3: If it wants to maintain a stable climate, it has
Speaker 3: to have a mechanism to redistribute that heat.
Speaker 2: Okay, so it has to move the heat.
Speaker 3: Around exactly On Earth, our rapid twenty four hour rotation
Speaker 3: acts like a massive atmospheric whisk. It drives the Coriolis effect.
Speaker 3: It creates vast weather systems that constantly churn the atmosphere,
Speaker 3: moving intense heat away from the equator toward the freezing
Speaker 3: poles and dragging cool airback.
Speaker 2: So it's a constant global mixing system.
Speaker 3: Right. It prevents any one side of the Earth from
Speaker 3: baking excessively while the other side freeze is solid. The
Speaker 3: energy is spread out evenly. But when you violently slow
Speaker 3: that spin down to a two hundred and forty eight
Speaker 3: day crawl, that rapid mixing engine just breaks down entirely. Well,
Speaker 3: stops the heat, stops moving efficiently. You have one side
Speaker 3: of the planet staring directly into the intense radiation of
Speaker 3: the Sun for months on end. The solar energy hits
Speaker 3: the atmosphere and just pools there, creating immense stagnant zones
Speaker 3: of thermal radiation.
Speaker 2: And that completely messes up the.
Speaker 3: Weather, oh completely. That lack of rotation fundamentally alters the
Speaker 3: way clouds can form and circulate because you.
Speaker 2: Don't get the protective swirling storm systems that can reflect
Speaker 2: solar radiation back into space. The energy just gets trapped. Right.
Speaker 2: But the slow rotation is really only the first domino
Speaker 2: in this climate catastrophe, because the impact that stopped the
Speaker 2: spin and melted the mantle likely had a devastating effect
Speaker 2: on Venus's geology too. Specifically, it's plate tectonics.
Speaker 3: Yes, and this is a crucial piece of the puzzle. Now,
Speaker 3: it's import want to know that scientists are still heavily
Speaker 3: debating the exact mechanism by which the impact halted Venus's tectonics.
Speaker 2: There are a few theories, right yeah.
Speaker 3: Some believe the magma ocean depleted the crust of water,
Speaker 3: making it too dry and rigid to slide around. Others
Speaker 3: think the extreme surface heat prevented the crust from cooling
Speaker 3: enough to become dense, which is needed to subduct back
Speaker 3: into the mantle.
Speaker 2: But regardless of the exact mechanism, the end result is
Speaker 2: the same exactly.
Speaker 3: The undeniable reality we see today is that Venus has
Speaker 3: absolutely no plate tectonics. Its entire surface is a single, unbroken,
Speaker 3: stagnant lid of rock, and.
Speaker 2: A stagnant lid is a death sentence for a planet's
Speaker 2: climate because without plate tectonics, you lose the planet's most
Speaker 2: important recycling.
Speaker 3: System, specifically carbon recycling. This is the mechanism that keeps
Speaker 3: Earth habitable today. Earth actually has a massive amount of carbon,
Speaker 3: just like Venus does.
Speaker 2: But on Earth it doesn't all sit in the atmosphere.
Speaker 3: Right our plate tectonics act as a giant planetary thermostat.
Speaker 2: Does that thermostat actually work? Like? How does shifting rock
Speaker 2: control the atmosphere.
Speaker 3: It's a really beautiful cycle. Honestly. Carbon dioxide in Earth's
Speaker 3: atmosphere dissolves into rain water that slightly acidic rain falls
Speaker 3: onto rocks, weathering them and washes carbon rich minerals down
Speaker 3: into the rivers and eventually into the oceans.
Speaker 2: Okay, so the carbon washes into.
Speaker 3: The sea yep, and in the oceans, marine organisms use
Speaker 3: it to build shells, or it just precipitates out naturally
Speaker 3: and settles on the ocean floor as limestone. Eventually, because
Speaker 3: Earth has shifting tectonic plates, that ocean floor is dragged
Speaker 3: down subducted deep into the Earth's mantle, locking the carbon
Speaker 3: away safely inside the planet.
Speaker 2: It literally buries it.
Speaker 3: It does. Volcanos will eventually release some of it back out,
Speaker 3: but the cycle keeps the overall atmospheric levels completely balanced.
Speaker 2: It's this elegant self regulating loop. But on Venus that
Speaker 2: loop was completely severed because the crust is a single, solid,
Speaker 2: stagnant lid. There are no shifting plates, there is no subduction,
Speaker 2: which there is nowhere for the carbon.
Speaker 3: To go exactly. Venus still had active volcanoes constantly pumping
Speaker 3: carbon dioxide out of the interior but with the recycling
Speaker 3: system broken, that carbon just built up in the atmosphere
Speaker 3: century after century, millennium after millennium.
Speaker 2: And carbon dioxide is greenhouse gas. It is incredibly efficient
Speaker 2: at letting sunlight in but preventing the resulting heat from
Speaker 2: radiating back out into space.
Speaker 3: It acts exactly like a greenhouse, so you enter.
Speaker 2: This terrifying feedback loop, known as the runaway greenhouse effect.
Speaker 2: The volcanoes pump out carbon, the carbon traps the heat,
Speaker 2: The planet gets hotter, the heat bakes the surface, perhaps
Speaker 2: releasing even more trapped gases the vicious cycle, and because
Speaker 2: there is no tectonic recycling, the carbon just keeps piling up,
Speaker 2: thickening the atmosphere, trapping exponentially more heat. Over millions of years,
Speaker 2: this runaway train compounds until you arrive at the monstrous
Speaker 2: environment we see today. An atmosphere is so incredibly dense
Speaker 2: with trapped carbon that the pressure crushes you and the
Speaker 2: trapped heats guy rockets to an ambient four hundred and
Speaker 2: sixty seven degrees celsius.
Speaker 3: And as if a broken carbon cycle and a stagnant
Speaker 3: backward spinning atmosphere weren't enough, Venus was also fighting a
Speaker 3: losing battle against the Sun itself.
Speaker 2: Right, Because of its location in the inner Solar System,
Speaker 2: Venus is significantly closer to the Sun than Earth is,
Speaker 2: and the Sun isn't just a static light bulb. It
Speaker 2: is an evolving star, which guarantees a brutally difficult timeline
Speaker 2: for any planet in its inner orbit.
Speaker 3: Stellar evolution is a relentless force. Our Sun is a
Speaker 3: main sequence star, and as it ages and burns through
Speaker 3: its hydrogen fuel, its core actually becomes denser and hotter.
Speaker 3: As a result, the Sun steadily increases in luminosity, it
Speaker 3: gets brighter. Yeah, it gets roughly ten percent brighter and
Speaker 3: hotter every billion years, ten.
Speaker 2: Percent every billion years. So even if Venus had somehow
Speaker 2: miraculously managed to maintain a stable climate early on, even
Speaker 2: if it had struggled through the impact and kept a
Speaker 2: fragile balance, the relentless assault of an ever brightening Sun
Speaker 2: was constantly turning up the dial on the heat.
Speaker 3: Exactly you come. I find an aging, brightening star with
Speaker 3: a stagnant atmosphere that can't recycle carbon, and a runaway
Speaker 3: greenhouse becomes completely inevitable.
Speaker 2: It's a total convergence of catastrophes, but all of these
Speaker 2: cascading failures, the slow rotation, the stagnant lid, the runaway greenhouse,
Speaker 2: They all trace back to the changes induced by that
Speaker 2: initial primeval impact, which brings up a profoundly tragic scientific question.
Speaker 3: The big what if.
Speaker 2: Yes, the what if that keeps planetary scientists awake at night,
Speaker 2: because Stephen Kane and others have pointed out that rotation
Speaker 2: rate is key to habitability. If the backward two hundred
Speaker 2: and forty eight day crawl was caused by an impact,
Speaker 2: is it possible that before the moon size rock smashed
Speaker 2: into it, Venus was spinning normally.
Speaker 3: It's highly likely.
Speaker 2: And if it was spinning normally, was it actually a paradise.
Speaker 3: It is a deeply haunting possibility, and the models completely
Speaker 3: support it. If we look at the initial conditions of
Speaker 3: the Solar system before all the chaotic impacts altered their paths,
Speaker 3: Venus very likely had a rapid forward rotation, just like
Speaker 3: her Earth. It likely had a functioning climate system. It
Speaker 3: is entirely scientifically plausible that early Venus had vast oceans
Speaker 3: of liquid water, a stable, breathable atmosphere, and conditions that
Speaker 3: were perfectly suitable for the emergence of life.
Speaker 2: Wow, it completely reframes how we view the planet. That
Speaker 2: impact four point five billion years ago wouldn't have just
Speaker 2: been a neat geological event where rocks smashed together. It
Speaker 2: would have been the ultimate sudden extinction event, the instant
Speaker 2: erasure of a fully habitable, thriving twin Earth.
Speaker 3: It really is chilling to think about that a world
Speaker 3: right next door could have been a vibrant paradise and
Speaker 3: it was essentially murdered by a random, chaotic strike from
Speaker 3: the dark.
Speaker 2: It highlights the extreme fragility of planetary evolution, and this
Speaker 2: tantalizing ghost of a past habitable Venus leads directly into
Speaker 2: the final lingering mystery that scientists are currently agonizing over today.
Speaker 2: It is a puzzle locked deep inside the planet's core.
Speaker 3: Yes, going back to the models developed by the team
Speaker 3: at ETH Zurich, they have managed to model the mass
Speaker 3: of the impact, or the angle of the strike, the
Speaker 3: depth of the magma ocean, but there is one major
Speaker 3: unresolved variable in their equations.
Speaker 2: A question that completely alters how we view the planet's.
Speaker 3: History exactly, and it all comes down to water. The
Speaker 3: question is is the interior of Venus still wet?
Speaker 2: It sounds like a simple binary question, but the implications
Speaker 2: of the answer are staggering. Let's look at the two
Speaker 2: divergent realities here. First, the dry scenario. If the deep
Speaker 2: interior Venus is completely dry today, then the story makes logical.
Speaker 3: Sense, right, neat and tidy. Yeah.
Speaker 2: It means that the violent impact, the ninety nine percent
Speaker 2: mample melt and the subsequent runaway greenhouse effect successfully baked
Speaker 2: every single drop of moisture out of the planet. Venus
Speaker 2: lost all its water to the vacuum space, and it
Speaker 2: is a dead, desiccated rock all the way down to
Speaker 2: its iron core.
Speaker 3: It's a tragic story, but a closed book.
Speaker 2: But the alternative scenario, the wet scenario, is where the
Speaker 2: physics get incredibly complicated and incredibly excas What if despite
Speaker 2: the cataclysm, despite the magma oceans, there is still a
Speaker 2: massive reservoir of water locked deep inside the interior.
Speaker 3: Of the planet, which is what Cedric Gilman considers the
Speaker 3: most perplexing unanswered question today.
Speaker 2: I have to admit I have a really hard time
Speaker 2: visualizing how that is even physically possible. Let's just review
Speaker 2: the timeline we just established. A moon sized object hits
Speaker 2: the planet at thousands of miles an hour. The sheer
Speaker 2: kinetic energy instantly liquefies ninety nine percent of the rocky mantle.
Speaker 2: You now have a global ocean of glowing liquid rock
Speaker 2: that is directly exposed to the freezing vacuum of space,
Speaker 2: radiating intense heat. If there was any water in that rock,
Speaker 2: wouldn't it instantly boil, turn into vapor and vent off
Speaker 2: into the void. How in the universe could water possibly
Speaker 2: survive inside a molten planet.
Speaker 3: It seems utterly counterintuitive. I agree. If you boil a
Speaker 3: pot of water on a stove, the water evaporates, So
Speaker 3: a boiling planet should lose its water. But we have
Speaker 3: to fundamentally redefine what wet means in a geological sense.
Speaker 2: Okay, so we're not talking about puddles.
Speaker 3: No, we aren't talking about some terranean lakes of liquid
Speaker 3: water splashing around in caverns. We are talking about water
Speaker 3: molecules hydrogen and oxygen that are chemically bound within the
Speaker 3: actual crystalline lattice of the rock itself.
Speaker 2: So the water is physically part of the mineral structure.
Speaker 3: Correct minerals deep in a planet's mantle, like ringwoodite or
Speaker 3: wadsleyite can absorb water like a sponge, trapping it within
Speaker 3: their chemical bonds. Now, when the impact melted the mantle,
Speaker 3: you are right, a massive amount of those bonds would
Speaker 3: break and the water would violently degas into the atmosphere
Speaker 3: and escape to space. But the interior of a planet
Speaker 3: is subjected to crushing, unimaginable pressure from the sheer weight
Speaker 3: of the rock above it.
Speaker 2: So gravity steps in again.
Speaker 3: Exactly. The mystery scientists are trying to solve is whether
Speaker 3: the intense heat of the magma ocean was enough to
Speaker 3: overcome that confining pressure entirely, or if the sheer crushing
Speaker 3: weight of the deep interior managed to hold onto some
Speaker 3: of the those chemical bonds, keeping the deepest layers of
Speaker 3: rock chemically wet.
Speaker 2: So even when it turns to liquid magma, the pressure
Speaker 2: thousands of miles down might be so intense that it
Speaker 2: forces the water to stay trapped inside the melt.
Speaker 3: That's the theory. And then when the magma cools and
Speaker 3: solidifies back into that perfect crime block of ice we
Speaker 3: talked about, the water is still locked inside the solid minerals.
Speaker 2: Precisely, and if the interior is indeed still wet, it
Speaker 2: means our fundamental understanding of how planets survive apocalyptic trauma
Speaker 2: is incomplete. It means a planet can take a direct
Speaker 2: hit from a moon, melt entirely, and still harbor the
Speaker 2: essential ingredients for life deep within its mantle.
Speaker 3: It means Venus might still be holding on to the
Speaker 3: ghost of its ancient oceans, completely hidden beneath the stagnant
Speaker 3: crust and the acidic four hundred and sixty seven degree surface.
Speaker 2: The fact that we have these incredibly advanced supercomputers and
Speaker 2: we can model the exact trajectory and kinetic energy of
Speaker 2: an impactor from four point five billion years ago, but
Speaker 2: we still don't know the answer to this incredibly basic
Speaker 2: question about whether our closest planetary neighbor is wet or
Speaker 2: dry on the inside. It just proves how deeply alien
Speaker 2: Venus truly is.
Speaker 3: We've barely scratched the surface, literally and metaphorically.
Speaker 2: It is a stark and humbling reminder of the limits
Speaker 2: of our knowledge. It shows as just how effectively a
Speaker 2: single chaotic event and the infancy of a solar system
Speaker 2: can permanently obscure a planet's true nature. We look at
Speaker 2: Venus and see a smooth, white cloud, entirely blind to
Speaker 2: the violent history underneath.
Speaker 3: It's the ultimate disguise.
Speaker 2: Let's take a step back and just marvel at the
Speaker 2: staggering sequence of events we've explored today. You start with
Speaker 2: this peaceful looking, pearly white orb hanging serenely in space,
Speaker 2: But beneath that illusion is a toxic, crushing reality of
Speaker 2: supercritical fluids and melting lead. And we've traced that nightmare
Speaker 2: all the way back to a single moment of cosmic violence.
Speaker 2: A rotch, a tenth the mass of the planet, comes
Speaker 2: hurling through the dark and strikes a grazing blow. That
Speaker 2: one tangential hit transfers enough rotational torque to violently stop
Speaker 2: a rapidly spinning world in its tracks and throw it
Speaker 2: backward into a sluggish two hundred and forty eight day crawl.
Speaker 3: And the sheer energy of that hit melts ninety nine
Speaker 3: percent of the solid planet into a glowing magma ocean.
Speaker 3: The molten surface destroys the crust, effectively halting the tectonic
Speaker 3: mechanisms needed to.
Speaker 2: Recycle carbon, so the thermostat breaks. Right.
Speaker 3: With the thermostat broken, the atmosphere chokes on carbon dioxide,
Speaker 3: setting off a runaway greenhouse effect that, combined with the
Speaker 3: relentless heat of an aging sun, bakes the world completely
Speaker 3: beyond recognition.
Speaker 2: And the cruelest part is that as the magma ocean
Speaker 2: rapidly cools in the vacuum of space, all physical evidence
Speaker 2: of the impact is seamlessly erased, leaving behind only the
Speaker 2: mechanical scars of a backward spin and a silent, stagnant crust.
Speaker 3: It is a terrifying chain reaction on a planetary scale,
Speaker 3: a paradise murdered by a random.
Speaker 2: Rock, and I really want to leave you with a
Speaker 2: chilling perspective to mull over. Right now, humanity is constantly
Speaker 2: looking up at the night sky, peering through our most
Speaker 2: advance telescopes, scanning the galaxy for Earth like exoplanets.
Speaker 3: We're obsessed with finding them.
Speaker 2: We are. We find these distant worlds, and we get
Speaker 2: incredibly excited. Classifying them is habitable based primarily on two
Speaker 2: main factors, their size and their distance from their host star.
Speaker 2: If they sit in that perfect sweet spot, the Goldilock zone,
Speaker 2: where water could theoretically pool on the surface, we assume
Speaker 2: they might be teeming with life.
Speaker 3: But we have to remember Venus is in that exact
Speaker 3: sweet spot. Venus is Earth's twin in size and distance exactly.
Speaker 2: Venus checks all the boxes on our habitability checklist. If
Speaker 2: the tragic history of Venus teaches us anything, its inhabitability
Speaker 2: is not just about real estate. It is not just
Speaker 2: about being the right size at the right distance.
Speaker 3: Location isn't everything.
Speaker 2: If a single random grazing cosmic collision billions of years
Speaker 2: ago is the only difference between Earth's vibrant oceans and
Speaker 2: Venus's toxic, supercritical healthscape, we have to ask ourselves a
Speaker 2: very dark question. How many of those incredibly promising Earth
Speaker 2: like exoplanets we are discovering out there in the deep
Speaker 2: galaxy are actually just dead, backward spinning infernos hiding behind serene,
Speaker 2: pearly white clouds.
Speaker 3: It completely reframes our entire search for life in the universe.
Speaker 3: It serves as a stark reminder that surviving the chaotic
Speaker 3: rock strew environment of a young solar system isn't just
Speaker 3: about physics. It is a terrifying game of cosmic roulette.
Speaker 2: It really is. The margin for error is basically non existent.
Speaker 2: The next time you see a picture of Venus or
Speaker 2: spotted shining brightly in the evening sky. Take a moment
Speaker 2: to remember the apocalyptic history hiding beneath that beautiful camouflage.
Speaker 2: Thank you so much for joining us on this journey today.
Speaker 2: We appreciate you taking the time to explore the mysteries
Speaker 2: of our solar system with us. Keep looking up, keep
Speaker 2: asking questions, and we'll catch you on the next one.