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Jupiter and Its Ocean Moons · Talking Science

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You know, I feel like we've all had that one
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roommate or maybe a sibling who just completely
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takes over the house. Oh, absolutely. The one
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who just sprawls out everywhere. Right. They
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take up all the space. They control the thermostat,
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leave their stuff everywhere. And basically everyone
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else in the house just has to, you know, adapt
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to their rules. The whole environment just sort
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of bends around their gravity. I mean. literally
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and figuratively. Exactly. And when you look
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at our solar system, we have this ultimate space
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hogging roommate, which is Jupiter. I mean, it
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is the undisputed heavyweight champion of our
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cosmic neighborhood. Yeah, it really is. But
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what's truly mind bending and really the mission
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for this deep dive today is understanding why
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this incredibly hostile, massive planet. is acting
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as the anchor for a miniature solar system of
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moons that surprisingly actually hold our biggest
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hopes for finding alien life. It's a brilliant
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contradiction, really. I mean, the most dangerous
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environment imaginable is somehow generating
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the exact conditions needed for biology. And
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for you listening to really grasp how it does
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that, we have to understand its sheer incomprehensible
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scale. Jupiter is about 11 times Earth's diameter.
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Right. It has more than 300 times Earth's mass.
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Like if you took every single other planet in
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our solar system, Mars, Venus, Saturn, all of
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them, and mashed them into one giant ball, Jupiter
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would still be more than twice as massive as
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all of them combined. It is the dominant object
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in the solar system, second only to the sun itself.
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It's made of completely different material than
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a rocky planet like Earth. It's overwhelmingly
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hydrogen and helium. Which is essentially the
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exact same makeup as the sun. So I always hear
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people call Jupiter a failed star, but I struggle
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with that term a bit. Is it actually on the verge
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of bursting into a star, or is that just an exaggeration?
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It's a bit of both, but mostly an exaggeration.
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It's not a near miss. You know, you shouldn't
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picture Jupiter as being just a few pounds shy
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of lighting up the night sky. Okay, so it's not
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like adding one more asteroid will ignite it.
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No, not at all. You would need somewhere around
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80 times Jupiter's current mass before the pressure
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and temperature deep inside its core could actually
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ignite hydrogen fusion. So it falls very short
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of being a star. Got it. Okay, so it's not a
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star. But it actually radiates more heat out
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into space than it receives from the sun. If
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it's not doing fusion, how is it generating that
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much heat? Right. So that's through its own gravity.
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Yeah. Because it has so much mass, the entire
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planet is constantly pulling inward on itself.
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Like it's shrinking. Essentially, yes. That immense,
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slow gravitational contraction causes this continuous
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squeezing effect. And that physical squeezing
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generates internal heat. Which brings up a slightly
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naive question, but I think it's what everyone
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pictures when they hear the term gas giant. Sure.
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If there's absolutely no hard surface to land
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on, if I took a bowling ball and just dropped
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it into Jupiter, does it just fall forever until
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it eventually melts? Actually, that is the perfect
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way to picture it, because a planet without a
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surface is entirely counterintuitive to how we
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experience the world. Right. We're used to hitting
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the ground. Exactly. If you drop that bowling
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ball, there's no splat. It wouldn't hit a hard
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ground. As it descends through the atmosphere,
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the gas around it simply grows denser and denser
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and hotter and hotter. No clear boundary at all.
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None. Eventually, without any clear line to cross,
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the gas becomes so incredibly dense that it transitions
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and begins to behave as a liquid. Wow. So your
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bowling ball wouldn't plonk onto a surface. It
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would just sink into an increasingly thick, boiling
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hot fluid. That is deeply unsettling to think
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about. Oh, but it gets stranger. If you follow
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that bowling ball deeper still, the pressure
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becomes so extreme that we reach one of the most
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fascinating physical states in the universe,
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which is metallic hydrogen. Now, wait. Metallic
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hydrogen sounds like a complete oxymoron. Hydrogen
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is lightweight gas. How does it become a metal?
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It's all about that crushing pressure we were
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just talking about. Down in the extreme depths
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of Jupiter, the weight of the atmosphere above
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is so intense that the hydrogen atoms are violently
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squeezed together. The pressure actually strips
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the electrons away from the hydrogen nuclei.
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Meaning the electrons are just freely floating
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around, like how they behave in a copper wire.
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Precisely. Because those electrons are free to
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move, that ocean of hydrogen suddenly conducts
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electricity. which, you know, is the defining
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characteristic of a metal. Oh, I see. So you
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have this vast, swirling, liquid ocean of electrically
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conducting metallic hydrogen just churning away
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inside the planet. And that massive conducting
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ocean is almost certainly what generates Jupiter's
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colossal magnetic field. And the scale of that
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magnetic field is just absurd. It's the largest
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structure in the solar system outside of the
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sun's own magnetic influence. It really is. Like
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if you were standing outside at night and we
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could somehow see Jupiter's magnetic field from
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Earth with our naked eyes, it would appear several
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times wider than the full moon. Which is staggering
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to think about. I mean, Jupiter is hundreds of
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millions of miles away, yet its magnetic footprint
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would absolutely dominate our night sky. So this
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liquid metallic hydrogen is the engine driving
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this magnetic monster. But all that internal
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heat and energy also drives some truly wild weather
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up in the atmosphere. Oh, incredibly wild. Because
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despite being this enormous heavy beast, Jupiter
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rotates incredibly fast. A full day there is
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under 10 hours. And that rapid rotation has massive
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physical consequences. Imagine spinning a balloon
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made of liquid. It spins so fast that the planet
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physically bulges at the equator and flattens
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out at the poles. It's not even a perfect sphere.
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Right. And that intense spin takes all of its
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weather systems and stretches them out horizontally
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into those famous, beautiful stripes of clouds
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we always see in photos. And those stripes are
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moving in opposite directions, creating sheer
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chaos where they meet, which brings to mind the
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Great Red Spot. Ah, yes. It's categorized as
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an anticyclone. But I need you to explain this
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because on Earth, when the weather reporter says
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we have a high pressure system coming in, that
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usually means clear blue skies and calm weather.
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How does high pressure on Jupiter create a raging
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violent storm? That's a great distinction to
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make. So an anticyclone is a weather system where
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winds circulate around a central region, high
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atmospheric pressure. On Earth, our atmosphere
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is relatively thin and high pressure gently pushes
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air downward, which clears out clouds. But Jupiter's
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atmosphere is... immensely deep and just churning
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with internal heat. So it reacts differently.
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Very differently. When a high pressure zone forms
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there, it creates a massive swirling vortex.
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The pressure pushes outward, forcing the winds
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to race around it at hundreds of miles per hour.
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It's less of a gentle clearing system and more
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of a heavily pressurized atmospheric engine.
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And this storm is large enough to swallow the
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Earth whole. It's been observed for at least
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a century and a half, maybe much longer based
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on historical astronomy records, though it has
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been measurably shrinking and getting rounder
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in recent decades. Yeah, but longevity is what
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usually surprises people the most. Like, how
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does a single storm last for centuries? Well,
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the best way I can picture why it lasts so long
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is to think of a spinning top on a perfectly
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frictionless floor. That's a good analogy. Down
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here on Earth, a hurricane gets its energy from
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the warm ocean, but eventually it hits a landmass.
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That land creates friction, cuts off its fuel,
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and breaks the storm apart. But on Jupiter, there
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is no land surface. Right. No solid ground. The
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floor is frictionless. There's nothing to slow
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the momentum down. So this storm just keeps spinning,
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continuously fed by the neighboring jet streams
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for hundreds of years. That's exactly the mechanism.
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Without a solid surface to disrupt the fluid
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dynamics, that momentum is preserved almost indefinitely.
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And as much as we think we understand it, we
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are still discovering entirely new things under
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those clouds. Like the Juno spacecraft arrived
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at Jupiter in 2017. and it delivered data that
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completely upended our models. It really did.
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For instance, before Juno, the assumption was
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that Jupiter probably had a compact, solid core
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of rock and ice at the very center. But Juno
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revealed the core is actually fuzzy or diluted.
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Yes. Fuzzy is the exact term planetary scientists
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are using right now. What exactly is a fuzzy
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core? Like, how does rock and ice become fuzzy?
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Well, it means there isn't a sharp boundary where
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the metallic hydrogen ends and a solid rock begins.
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Instead, the heavy elements of rock and ice are
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dissolved and blended into the liquid metallic
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hydrogen above them. So it's just this huge,
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smeared -out transitional zone. Exactly. But
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how does that even happen? The most plausible
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explanation currently points to a major head
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-on collision very early in Jupiter's history.
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A massive planetary body, maybe 10 times the
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mass of Earth, could have slammed into Jupiter.
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Wow. Right. And it essentially shattered the
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original solid core and stirred it up like a
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spoon in a teacup, mixing those heavy elements
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permanently into the fluid layers above. That
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paints such a violent picture of the early solar
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system. And Juno didn't just look deep inside.
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It looked at the poles. It found these bizarre,
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highly stable geometric clusters of enormous
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cyclones, just perfectly arranged in geometric
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patterns like an octagon of storms surrounding
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one central storm. It looks completely artificial
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when you first see it, but it's pure. How does
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a chaotic atmosphere build perfect geometry?
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It really comes down to the physics of vortices.
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When you have multiple massive storms driven
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to the poles by Jupiter's rotation, they start
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to repel each other. So they push away. Yes,
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and they find a state of equilibrium where they
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are close enough to interact but push against
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one another just enough to lock into these stable,
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crystalline patterns. It's a delicate balance
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of fluid mechanics that we rarely ever see on
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such a colossal scale. It's alien in every sense
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of the word. But if Jupiter's gravity is strong
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enough to dictate perfect geometry at its poles,
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it's really not surprising that its gravity reaches
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out and dictates the architecture of the entire
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solar system. Oh, sure. It is the ultimate gravitational
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anchor. Right. It's shaped exactly where material
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could accumulate when the planets were first
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forming. But there's a specific narrative I want
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to challenge here. I always hear Jupiter called
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our cosmic shield. You know, the idea that its
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massive gravity deflects or captures comets and
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asteroids that would otherwise wipe out the inner
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planets, like Earth. Yeah, it's a very common
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idea. But the research also notes that Jupiter's
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gravity perturbs objects inward. So, is Jupiter
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our noble protector, taking hits for us? Or is
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it a sniper occasionally throwing rocks at our
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heads? That is the exact debate happening in
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astronomy today. The cosmic shield narrative
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is highly popular, but it's considered far too
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simplistic now. Because it does both. Right.
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It's true that Jupiter's gravity sweeps up a
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lot of dangerous debris. I mean, we actually
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watched a comet called Shoemaker -Levy 9 smash
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into it in the 1990s. I remember seeing pictures
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of that. Yeah, it was incredible. Yeah. But at
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the same time, its gravity destabilizes the orbits
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of other objects, nudging them out of safe paths
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and sending them hurtling toward the inner solar
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system. So it really is a two -way street. Exactly.
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The net effect whether Jupiter has saved Earth
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from more impacts than it has actively caused
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is hotly debated. But regardless of whether it's
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a shield or a sniper, its absolute control over
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the layout of the solar system is undeniable.
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And if Jupiter's gravity is strong enough to
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toss comets across the solar system, what does
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it do to the objects trapped right next to it?
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Which brings us to the second half of our mission
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today. The moons. The Jovian system. Yeah. Jupiter
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has over 90 confirmed moons, but we are focusing
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on the big four. Io, Europa, Ganymede, and Callisto.
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The famous Galilean moons. Right. Named because
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Galileo spotted them in 1610 with a modest early
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telescope. And you really have to appreciate
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the historical weight of that moment. He looks
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at this primitive tube of glass, sees four dots
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moving around Jupiter, and realizes they're orbiting
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the planet. Not Earth. It was a massive realization.
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It was direct, undeniable evidence that the Earth
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was not the center of all celestial motion. A
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total paradigm shift. It was essentially the
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dawn of modern astronomy. He realized he wasn't
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just looking at a planet, but an entirely distinct
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planetary system. And when you zoom in on the
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closest of those four moons, Io, you see just
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how violently that system operates. Io is the
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most volcanically active body we know of. Visually,
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it is this lurid yellow -orange color because
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it is coated in sulfur compounds. It looks a
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bit like a moldy pizza. It really does. It has
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hundreds of active volcanoes shooting plumes
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hundreds of kilometers straight up into space.
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And uniquely, there are zero impact craters on
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its surface. Which is very telling. In space,
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if a surface has no craters, it means it is extremely
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young. Because it's constantly paving over itself.
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Yes. The volcanoes are erupting so constantly
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that the lava and sulfur repave the surface faster
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than meteor craters can even accumulate. It is
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just a world of endless geological violence.
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But here's what I find confusing about that.
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Io is hundreds of millions of miles away from
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the sun. It should be a frozen, dead rock. Where
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is it getting the heat to melt its entire interior?
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Ah, this brings us to the defining scientific
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concept for the entire Jupiter -Moon system,
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which is tidal heating. So how does tidal heating
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actually work? Well, it's all about gravity and
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geometry. Io's orbit around Jupiter is not a
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perfect circle. It's slightly elliptical or oval
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-shaped. And this is partly because the gravity
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of the other nearby moons tugs on Io, preventing
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its orbit from settling into a perfect circle.
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Because the orbit is elliptical, Io's physical
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distance from Jupiter is constantly changing.
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Sometimes it's a bit closer, sometimes a bit
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further away. Meaning the strength of Jupiter's
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gravitational pull on Io is constantly increasing
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and decreasing as it moves. Precisely. As it
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orbits, that immense gravity stretches and squeezes
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the solid rock of Io by varying amounts. Oh,
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wow. Just squeezing solid rock. Yeah. This continuous,
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relentless physical flexing generates massive
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amounts of internal heat through friction. The
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research provides a perfect everyday analogy.
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If you take a solid metal paperclip and rapidly
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bend it back and forth in your hands, The metal
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gets hot. That makes perfect sense. I keep picturing
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Io as this giant sulfur -flavored stress ball
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being endlessly squeezed and released by Jupiter's
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massive gravitational hand. All that kneading
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creates friction. The friction creates heat,
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and that energy has to go somewhere. Yeah, exactly.
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So it bursts out as volcanoes. A very vivid way
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to picture it, but scientifically spot on. The
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friction melts the rock itself. So if tidal heating
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causes literal fire and endless volcanoes on
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the closest moon, What does that exact same squeezing
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do to the next moon out? Because the second Galilean
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moon is Europa, and Europa happens to be entirely
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covered in ice. And this is where the story shifts
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from dramatic, fiery violence to... the profound
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potential for alien biology. Europa is slightly
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smaller than our own moon. Its surface is essentially
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water ice, and it is one of the smoothest objects
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in the solar system. Very few craters, but it
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is crisscrossed by these long, dark, mysterious
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fractures. And again, few craters means a young
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surface that is actively being renewed. Something
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is constantly cracking and resurfacing that ice,
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and all the evidence points to a stunning reality
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beneath that crust, a global subsurface ocean
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of liquid saltwater. Hiding under an ice shell
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that is estimated to be 10 to 30 kilometers thick.
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And the volume of water we are talking about
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is staggering. Europa is smaller than our moon,
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but that subsurface ocean holds roughly twice
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the amount of liquid water as all of Earth's
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oceans combined. It is arguably the most significant
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body of water in the solar system. But wait!
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We've never drilled into it. It's hidden under
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30 kilometers of ice, 400 million miles away.
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How can we possibly know it's a salty liquid
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ocean? How do we know it's not just solid ice
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all the way down? It's an absolutely brilliant
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piece of scientific deduction. And the strongest
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proof is actually magnetic. Remember Jupiter's
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massive spinning magnetic field we talked about
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earlier? The one wider than the full moon. Right.
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As Europa orbits through that invisible magnetic
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field, Jupiter's field actually induces a secondary
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magnetic field inside Europa. Oh, really? Yes,
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and the specific way Europa's magnetic field
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responds and fluctuates tells us exactly what's
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inside. It requires there to be a global, highly
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conductive layer just beneath the surface. And
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solid ice doesn't conduct electricity. Exactly.
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Solid ice is a terrible conductor. But liquid
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saltwater is a fantastic conductor. When you
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combine that magnetic signature with the visually
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fractured mobile ice surface, plus observations
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that look very much like water vapor plumes venting
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into space, the case for a vast liquid saltwater
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ocean is incredibly strong. So we have a massive
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salty ocean kept liquid in the freezing depths
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of space by that same tidal heating we saw in
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Io. Yes, exactly. It's just a gentler version
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of the stress ball effect. The squeezing isn't
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strong enough to melt rock into lava, but it
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is strong enough to melt ice into an ocean. Yes.
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The orbital flexing warms the interior just enough
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to maintain that liquid state beneath the insulating
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ice shell. And this leads us to the most exciting
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concept of this entire deep dive. Chemosynthesis.
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This is the biology part. Right. On Earth, we
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are heavily biased toward photosynthesis. Yeah.
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We think of life as depending on energy from
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the sun, plants use sunlight, animals eat plants,
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and so on. But deep down in Earth's own oceans,
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thousands of feet below the surface in total
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pitch black darkness, we find entire complex
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ecosystems thriving around hydrothermal vents.
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Like underwater volcanoes. Exactly. Where hot,
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mineral -rich water from the planet's interior
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meets the cold ocean water, life flourishes without
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a single drop of sunlight. The organisms there
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survive on chemosynthesis. They extract their
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vital energy directly from the chemical reactions
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happening at those vents. And we think Europa
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has those vents. Well, think about the ingredients.
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Europa has a massive liquid ocean sitting directly
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on top of a rocky seafloor. That rocky seafloor
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is being actively needed and warmed by Jupiter's
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tidal heating. It is highly plausible that Europa
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has active hydrothermal events on its ocean floor.
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It is a complete paradigm shift. It's honestly
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amazing to me. We spend so much time and billions
18:29
of dollars looking at Mars, hoping to maybe find
18:32
the fossilized remains of a dried up microbe
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in the red dust. Right, looking for past life.
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But it turns out the absolute prime real estate
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for living, breathing alien life in our solar
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system might be in permanent pitch black darkness
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under 20 kilometers of solid ice. Europa is genuinely
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regarded as a top candidate for life, arguably
18:53
ahead of Mars. It forces us to completely redefine
18:56
our understanding of where life can exist. It
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proves that a planet doesn't need to be in the
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Goldilocks zone of a star to be habitable. It
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just needs a heat source, liquid water, and the
19:07
right chemistry. So as we move even further out
19:10
from Jupiter, rounding out the Galilean family,
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we start to see that tidal heating effect fade
19:14
away. But it leaves behind a very different world.
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We do. The third moon out is Ganymede, which
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is a record breaker. It is the largest moon in
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the solar system. It's physically larger than
19:24
the planet Mercury. And it generates its own
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magnetic field, right? It is the only moon we
19:28
know of that generates its own internal magnetic
19:31
field. Why does that matter so much? Because
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a magnetic field requires a churning, liquid,
19:35
conductive core. So Ganymede almost certainly
19:38
has a liquid iron core deep inside. And it also
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has a subsurface ocean. But because it is further
19:44
away from Jupiter, it experiences less tidal
19:47
heating than Europa. So the ice freezes deeper.
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Precisely. The data suggests Ganymede's ocean
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is buried much deeper beneath a much thicker
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ice crust. The heat isn't strong enough to keep
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the water close to the surface. And finally,
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we reach the outermost of the Big Four, Callisto.
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And Callisto is basically the exact opposite
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of Io. It is heavily cratered and geologically
20:08
dead. It's essentially an ancient relic. Because
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it orbits the furthest out, it largely escaped
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the intense, violent gravitational squeezing
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that drives Io and Europa. So it just kind of
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sits there. Yeah, it just sits there, preserving
20:20
the ancient, battered history of the early solar
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system. Though incredibly, even Callisto might
20:26
hide a deep, frozen ocean of its own. So when
20:28
you step back and look at this single planetary
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system, you have a moon being continuously torn
20:34
apart by volcanoes, a moon with a hidden ocean
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that might harbor life, a moon larger than a
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planet with its own iron core, and an ancient
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battered relic, all of them anchored by this
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massive churning gas giant. It's an incredibly
20:50
diverse neighborhood. So naturally, for you listening,
20:52
the question is, what comes next? Are we going
20:56
to look closer? Humanity is absolutely heading
20:58
back. NASA recently launched the Europa Clipper
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mission. It's designed to make repeated, incredibly
21:04
close flybys of Europa. That's exciting. It won't
21:07
be looking for life directly, but it will map
21:09
the ice shell in extreme detail, characterize
21:12
the ocean below, and officially assess its habitability.
21:15
And the European Space Agency has a mission called
21:17
JUICE, the Jupiter Icy Moons Explorer, which
21:20
is going to focus heavily on Ganymede, eventually
21:22
entering orbit right around it. But this brings
21:25
up a massive point of frustration for me. If
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we know Europa has a massive ocean and we strongly
21:30
suspect it has hydrothermal vents, why are we
21:32
just flying by? Why aren't we bringing a drill
21:34
right now? It's a completely fair question. But
21:37
we really have to appreciate the staggering technical
21:40
realities. Neither of these missions will land
21:43
and neither will drill. Think about the logistics.
21:46
Drilling through 20 kilometers of rock -hard
21:49
ice is profoundly difficult to do here on Earth,
21:52
even with a human crew standing right there in
21:55
unlimited power. And here we are talking about
21:57
doing it autonomously. Right. You are trying
21:59
to engineer an autonomous robotic drill to melt
22:03
or bore through miles of alien ice in an incredibly
22:08
intense radiation environment 400 million miles
22:11
away from the sun, where a single communication
22:13
signal takes nearly an hour just to travel back
22:16
and forth. Yeah, that's a lot of hurdles. If
22:18
the drill gets stuck, a human can't fix it. It's
22:21
a monumental engineering challenge that is, frankly,
22:23
a problem for a future generation of missions.
22:26
Fair enough. It's easy to look at an animation
22:28
on a screen and forget we are trying to thread
22:30
a needle millions of miles away in the dark.
22:33
But still, within the next decade, we are going
22:35
to know considerably more about this tidal warmed
22:38
ocean. We are going to have a much clearer picture
22:40
of whether our cosmic backyard hosts an environment
22:44
truly capable of supporting biology. So let's
22:47
pull all of this together. We started with this
22:49
gargantuan gas giant. hundreds of times the mass
22:52
of Earth, radiating its own heat, churning with
22:56
liquid metallic hydrogen, sporting geometric
22:58
polar storms, and a fuzzy core from an ancient
23:01
collision. And we discovered that its immense
23:04
gravity doesn't just dictate where planets form,
23:06
it violently needs its closest moons, generating
23:09
the friction and heat required to melt ice and
23:12
create vast, hidden oceans of liquid water. It
23:16
really changes how you experience the night sky.
23:19
The next time you look up on a... a clear night
23:21
and spot Jupiter and it's very bright, you can't
23:24
miss it. Remember, you aren't just looking at
23:25
a dot of light or even just the planet. You are
23:27
looking at a dynamic, violent, incredibly watery
23:30
mini solar system all its own. And if we connect
23:33
all this to a bigger picture, it raises a truly
23:35
profound question. For a century, we have been
23:38
conditioned to think that life requires a planet
23:41
exactly like Earth, a rock with a surface ocean
23:44
bathed in warm sunlight. The Goldilocks zone.
23:47
Right. But if the most promising place for life
23:49
in our solar system is actually found in pitch
23:51
darkness, under 20 kilometers of ice, kept warm
23:55
not by a star, but by the gravitational squeezing
23:58
of a gas giant, well, what if that is how life
24:02
usually exists in the universe? Oh, wow. I never
24:04
thought about it like that. What if rocky planets
24:07
with surface oceans and warm sunlight are actually
24:10
the rare weird outliers? What if the universe
24:13
is actually teeming with life, but it's entirely
24:15
hidden away inside icy moons orbiting giant planets?
24:19
That is an incredible thought to leave on. It
24:22
turns out that giant space -hogging roommate
24:24
who dictates all the rules for the rest of the
24:26
house, they might actually be the one hosting
24:28
the most interesting party in the entire neighborhood.
24:31
Think about that the next time you look up at
24:32
the stars.