WEBVTT

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Imagine, if you will, just spending two entire

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decades of your life traversing the cold, dark,

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totally unfathomable expanse of the outer solar

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system. You dedicate your entire existence to

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exploring a distant alien world. You're sending

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back imagery and data that completely shatters

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and rewrites our understanding of our own cosmic

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neighborhood. And then at the very end of it

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all, after fundamentally changing the textbooks,

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you intentionally orchestrate your own fiery

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spectacular demise. Yeah, it's intense. You plunge

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headfirst into a gas giant, burning up into a

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streak of light, all to protect the very secrets

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and pristine environments you just spent your

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life uncovering. It sounds exactly like the plot

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of a science fiction epic, doesn't it? Totally.

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Like a sacrificial hero's journey, but played

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out on a canvas billions of miles across. It

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really does. But this isn't fiction. Welcome

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to today's Deep Dive. We're going to be exploring

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the legacy of one of the greatest explorers in

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human history. It's a robotic marvel known as

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the Cassini -Huygens spacecraft. We have an incredibly

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detailed dossier today, drawing from the extensive

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encyclopedic record of the mission. Our mission

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today, right here with you, the listener, is

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to unpack the monumental legacy of this joint

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venture. And it was a massive one. Yeah, a huge

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collaboration between NASA, the European Space

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Agency, and the Italian Space Agency. This machine

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spent 13 years orbiting Saturn, and what it found

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there is, I mean, it's nothing short of mind

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-bending. To really grasp the gravity of this,

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we have to set the stage a bit. Launched in 1997

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and ending its run in 2017, Cassini -Huygens

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wasn't just, you know, another probe ticking

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boxes on a space exploration checklist. Right.

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As NASA's Planetary Science Division Director

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Jim Green put it, this was a mission of firsts.

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It completely redefined our search for extraterrestrial

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life in the solar system. Completely. We are

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talking about a mission that successfully landed

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a probe on a haze and shrouded alien moon, discovered

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hidden gl - oceans of liquid water and literally

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flew a spacecraft right through erupting icy

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geysers in deep space. Okay let's unpack this

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because you don't just wake up one day and decide

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to fly a multi -billion dollar piece of hardware

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through a geyser on a moon orbiting Saturn. This

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was a massive undertaking just to get off the

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ground. Let's go back to the genesis of this

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project in the 1980s. How did this even start?

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So the origins actually trace back to 1982. The

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European Science Foundation and the American

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National Academy of Sciences formed a working

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group to look into cooperative missions. Two

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European scientists proposed this paired concept,

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a Saturn orbiter and a separate probe that would

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specifically drop down into Titan, which is Saturn's

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largest moon. Wow. So way back in 82. Yeah. Then

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in 1983, NASA's Solar System Exploration Committee

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recommended this exact orbiter probe pair as

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a core project. Sally Ride, the pioneering American

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astronaut, even highlighted and approved of the

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Cassini mission in her influential 1987 report

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regarding America's future in space leadership.

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But reading through the historical context in

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our dossier, it seems like the science was, well,

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almost secondary to the political maneuvering

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required to keep it alive. Oh, absolutely. Because

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in 1988, NASA's associate administrator for space

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science pushed hard for a joint mission. But

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there was a lot of geopolitical tension at play.

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Yeah, if we connect this to the bigger picture,

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the late 1980s was a delicate time for international

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space relations. NASA was feeling the strain

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because their European partners felt they hadn't

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been treated as equals in previous collaborations.

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Europe had experienced instances where joint

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missions were suddenly canceled or, you know,

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scaled back by the US without much consultation.

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Oh, yikes. That's a quick way to lose friends.

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Exactly. So promoting Cassini -Huygens was a

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deliberate way to mend those fences to stress

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an even sharing of scientific and technological

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benefits. Furthermore, the Soviet Union had started

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cooperating more closely with Europe on space

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ventures. Ah, I see. So for the United States,

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keeping Europe as a close partner was strategically

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vital. That makes a lot of sense. So in 1988,

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the European Space Agency officially chooses

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this as its next major mission, and the US funds

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it the following year. And it's a good thing

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they tied the knot early, right? Very good thing.

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Because the US Congress almost killed the whole

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thing a few years later. They did. In 1992 and

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again in 1994, Cassini -Huygens came under severe

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political fire in the U .S. Congress, facing

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massive budget cuts across the board. The mission

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was nearly canceled. NASA essentially had to

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argue that they could not back out because the

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Europeans had already poured substantial funding

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into their portion of the spacecraft. If the

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U .S. broke that promise, it would have caused

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a massive diplomatic incident. It's incredible

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to think about the tension of international collaborations

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what made it so difficult to organize. But that

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very same reliance on international partners

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is the shield that saved it from the congressional

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chopping block. That's the irony of it. They

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get the funding and they build this thing. And

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looking at the specs, the scale of this spacecraft

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is difficult to comprehend. The physical presence

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of Cassini was imposing. At the time of its launch,

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it was the third largest uncrewed interplanetary

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spacecraft ever built, right behind the Soviet

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Phobos 1 and 2 probes sent to Mars. At launch,

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the spacecraft had a mass of 5 ,600 kilograms.

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That is over 12 ,000 pounds. The orbiter itself

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stood 6 .8 meters high, that's over 22 feet,

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and was four meters wide. To put that in perspective

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for you listening, Imagine a machine roughly

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the size of a 30 -passenger school bus, but entirely

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packed with sensitive scientific instruments.

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The dossier mentions it had 1 ,630 interconnected

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electronic components, 22 ,000 wire connections,

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and 14 kilometers of cabling. That cabling is

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essential. It's the communication network connecting

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all the disparate scientific instruments, the

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spectrometers, the radar, the cameras, to the

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central computers. 14 kilometers, that's almost

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nine miles of wiring. I like to picture that

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cabling as the nervous system of this giant metallic

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beast sending signals back and forth in the freezing,

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darker space. That's a great way to look at it.

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And the computing power itself was unique. The

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sources say it used a redundant system with a

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mill STD1750A instruction set architecture. Break

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that down for us, because it sounds like alphabet

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soup. It does sound like jargon, but it's a critical

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piece of the engineering. When you send a computer

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into deep space, you cannot use the same kind

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of processor you have in your laptop on Earth.

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Because of the environment out there. Exactly.

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Our atmosphere and magnetic field protect our

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electronics from cosmic radiation. In deep space,

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high energy particles can literally pass through

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a microchip and flip a bit from a zero to a one,

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causing a system crash. Oh, wow. The MIL -STD

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1750A architecture was a military standard designed

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to be heavily radiation hardened and incredibly

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robust. It wasn't about being the fastest computer.

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It was about being an unbreakable computer that

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could survive decades in a highly radioactive

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environment. Which brings us to perhaps the biggest

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engineering hurdle of all the power source. Because

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if you're going to Saturn, you have a massive

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problem regarding sunlight. Yes. Saturn is roughly

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1 .4 billion kilometers away from the sun. At

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that distance, For instance, the sunlight is

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roughly 1 % as intense as it is here on Earth.

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Just 1 %? Yeah. If you wanted to power a machine

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the size of Cassini using solar panels, those

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arrays would have had to be impractically massive.

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They would be too heavy to launch and too unwieldy

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to maneuver once in space. So solar power is

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out of the question. What did they use to keep

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this massive nervous system of wires running?

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They utilized radioisotope thermoelectric generators,

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commonly referred to as RTGs. Cassini was powered

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by 32 .7 kilograms of nuclear fuel. Specifically,

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it used plutonium dioxide containing about 28

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.3 kilograms of pure plutonium -238. Okay, wait.

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When most people hear plutonium, they think of

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nuclear reactors or weapons. How does a lump

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of radioactive material power a deep space probe?

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Does it have a tiny nuclear reactor inside? Not

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exactly. An RTGE is remarkably simple and contains

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no moving parts, which is why it's perfect for

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space exploration. Plutonium -238 is a highly

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unstable isotope. As it naturally decays, it

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emits a tremendous amount of heat. Okay, so it

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gets hot. Right. The RTG surrounds this glowing

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hot plutonium with specialized materials called

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thermocouples. A thermocouple takes advantage

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of the temperature difference between the hot

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radioactive material on the inside and the freezing

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cold of space on the outside and converts that

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thermal gradient directly into electricity. So

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it's essentially a nuclear battery running on

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the ambient heat of decaying plutonium. Precisely.

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The sheer volume of plutonium required, nearly

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33 kilograms, is what sparked intense controversy

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leading up to the 1997 launch. You had public

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protests, lawsuits, and citizens groups furious

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about the environmental risks. Let's talk about

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that controversy impartially, based on the records

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we have. Because the fear wasn't just about a

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rocket exploding on the launch pad in Florida.

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The real anxiety centered around the trajectory

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Cassini had to take to get to Saturn. That's

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right. To reach Saturn, Cassini required a tremendous

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amount of velocity, more than any rocket of that

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era could provide on its own. So mission planners

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utilized a technique called gravitational slingshots.

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The flight path was known as as a VVEGA trajectory.

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That stands for Venus Earth Jupiter Gravity Assist.

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Cassini would fly close to Venus twice, steal

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a little bit of its orbital momentum to speed

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up, then fly back past Earth for another boost,

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and finally head out to Jupiter for one last

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slingshot towards Saturn. It's that Earth flyby

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in August 1999 that caused the uproar. Because

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if something went wrong and Cassini crashed into

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Earth during that slingshot maneuver, you got

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over 30 kilograms of plutonium hitting the atmosphere

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at interplanetary speeds. What were the actual

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risks of that happening? NASA conducted extensive

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environmental impact studies to quantify that

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exact risk. They had to look at the absolute

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worst case scenario. That scenario involved Cassini

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hitting the Earth's atmosphere at a very specific

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acute angle. If it hit straight on, the RTGs

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were designed to survive impact and bury themselves

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in the ground or ocean. But an acute angle could

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cause the spacecraft to skip and gradually burn

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up in the upper atmosphere, vaporizing the RTGs

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and dispersing a significant fraction of the

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plutonium dioxide globally. And what would that

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mean for the people on the ground? NASA's own

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estimate stated that such a dispersal could potentially

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expose up to five billion people to trace amounts

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of radiation. Statistically, they calculated

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this could result in an estimated 5 ,000 additional

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cancer deaths over subsequent decades. Five thousand

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potential deaths. That is a heavy burden for

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a science mission to carry. How did NASA justify

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taking that risk? NASA framed the risk through

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probability. Their engineers estimated the chance

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of this specific catastrophic failure happening

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at less than one in a million. They viewed the

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risk as minuscule compared to the scientific

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payoff. Furthermore, they had heavily armored

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the RTGs with multiple layers of graphite to

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survive extreme reentry heat. But not everyone

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bought into those reassurances. No, they did

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not. Prominent critics such as the theoretical

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physicist Michio Kaku publicly argued that NASA

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was severely under... estimating the risks of

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casualties and property damage. Critics argued

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that the shielding might fail or that alternative

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energy sources like highly advanced solar arrays

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or fuel cells hadn't been thoroughly exhausted

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as options. It became a highly publicized debate

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between the drive for unprecedented scientific

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discovery and the fear of a literal nuclear fallout

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scenario. It's a profound tension. We want to

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reach the stars, but the tools required to get

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there carry immense risks. Our goal here isn't

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to take a side, but to acknowledge that this

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was a deeply complex issue at the time. Ultimately,

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the courts allowed the launch to proceed in October

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1997, and the Earth fly by. It happened on August

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18, 1999. It went perfectly. Exactly. Cassini

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executed the maneuver flawlessly, passing just

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11 ,171 kilometers above our planet. At a single

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hitch, it gained the speed it needed and headed

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out toward the outer solar system. And that long

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cruise provided a perfect opportunity to test

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the spacecraft's instruments, specifically during

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the Jupiter flyby in late 2000. Cassini made

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its closest approach on December 30, 2000. It

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wasn't a fleeting encounter. It spent six months

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observing the Jupiter system, capturing around

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26 ,000 high -resolution images of the planet,

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its faint rings, and its moons. I was reading

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about what they found at Jupiter and it's fascinating

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because it completely flipped some long -held

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assumptions about how the planet's atmosphere

00:12:47.179 --> 00:12:49.879
works. It really did. Anyone who has seen a picture

00:12:49.879 --> 00:12:52.120
of Jupiter knows it has these distinct bands.

00:12:52.580 --> 00:12:56.500
Dark brown belts and pale white zones. For decades,

00:12:56.860 --> 00:12:59.179
what did scientists think was causing those distinct

00:12:59.179 --> 00:13:01.679
colors? Prior to Cassini, the prevailing atmospheric

00:13:01.679 --> 00:13:03.899
model was based largely on how weather works

00:13:03.899 --> 00:13:06.360
here on Earth. On Earth, clouds generally form

00:13:06.360 --> 00:13:08.960
where air is rising and cooling. So scientists

00:13:08.960 --> 00:13:10.879
looked at Jupiter and assumed the pale, light

00:13:10.879 --> 00:13:13.019
-colored zones were areas of rising, upwelling

00:13:13.019 --> 00:13:15.320
air, and the dark belts were areas of sinking

00:13:15.320 --> 00:13:18.179
air. It seemed perfectly logical. But Cassini

00:13:18.179 --> 00:13:20.480
gets there, turns its highly sensitive cameras

00:13:20.480 --> 00:13:22.940
on the planet, and what does it see? What's fascinating

00:13:22.940 --> 00:13:25.940
here is how Cassini's data contradicted the established

00:13:25.940 --> 00:13:28.990
models entirely. Cassini was able to resolve

00:13:28.990 --> 00:13:31.970
individual storm cells of upwelling bright white

00:13:31.970 --> 00:13:34.370
clouds that were far too small to be seen from

00:13:34.370 --> 00:13:37.809
Earth. And almost without exception, these rising

00:13:37.809 --> 00:13:40.470
storm cells were popping up inside the dark belts.

00:13:40.690 --> 00:13:42.610
Oh wait, so the dark bands are actually the areas

00:13:42.610 --> 00:13:45.190
of rising atmospheric motion, and the light zones

00:13:45.190 --> 00:13:46.870
are where the air is sinking and clearing out.

00:13:47.169 --> 00:13:49.850
Exactly. It completely inverted the existing

00:13:49.850 --> 00:13:52.409
understanding of Jupiter's atmospheric circulation.

00:13:52.750 --> 00:13:55.350
It was a massive scientific victory, proving

00:13:55.350 --> 00:13:57.309
that Cassini's instruments were sharper, and

00:13:57.309 --> 00:13:59.529
more capable than anything we had previously

00:13:59.529 --> 00:14:01.870
sent to the outer planets. It's doing revolutionary

00:14:01.870 --> 00:14:04.190
science, rewriting the textbooks on Jupiter,

00:14:04.590 --> 00:14:06.450
and it hasn't even reached its main destination

00:14:06.450 --> 00:14:08.750
yet. Yeah, just warming up. And before we get

00:14:08.750 --> 00:14:11.230
to Saturn, we cannot skip what Cassini did in

00:14:11.230 --> 00:14:15.190
2003. The dossier notes a test of Albert Einstein's

00:14:15.190 --> 00:14:18.529
general theory of relativity. How exactly does

00:14:18.529 --> 00:14:21.110
a Saturn -bound probe test a fundamental law

00:14:21.110 --> 00:14:24.230
of physics? It utilized the radio waves transmitted

00:14:24.230 --> 00:14:26.490
between the spacecraft and the receiving dishes

00:14:26.490 --> 00:14:29.649
on Earth. In 2003, from our perspective here

00:14:29.649 --> 00:14:32.769
on Earth, Cassini passed very close to the Sun.

00:14:33.629 --> 00:14:36.570
According to Einstein's theory, a massive object

00:14:36.570 --> 00:14:39.990
like the Sun actually curves the fabric of space

00:14:39.990 --> 00:14:42.409
-time around it. So space isn't just an empty

00:14:42.409 --> 00:14:44.909
void, it's more like a trampoline with a bowling

00:14:44.909 --> 00:14:47.399
ball in the middle, creating a dip. A perfect

00:14:47.399 --> 00:14:50.139
analogy. Because of that dip, when radio waves

00:14:50.139 --> 00:14:52.980
travel through that curved space into and out

00:14:52.980 --> 00:14:55.320
of the sun's gravitational well, they should

00:14:55.320 --> 00:14:57.860
experience a frequency shift, a phenomenon known

00:14:57.860 --> 00:15:00.419
as gravitational redshift and blueshift. Hadn't

00:15:00.419 --> 00:15:02.039
previous probes already proven this, though?

00:15:02.220 --> 00:15:04.940
Yes. Earlier missions like the Viking landers

00:15:04.940 --> 00:15:07.379
on Mars and the Voyager probes had tested this,

00:15:07.679 --> 00:15:09.840
confirming Einstein's predictions to an accuracy

00:15:09.840 --> 00:15:12.440
of one part in a thousand. But Cassini's radio

00:15:12.440 --> 00:15:14.480
and communication instruments were so incredibly

00:15:14.480 --> 00:15:16.820
precise that they improved that accuracy by a

00:15:16.820 --> 00:15:19.480
massive margin. Wow. Cassini confirmed general

00:15:19.480 --> 00:15:21.840
relativity to an accuracy of about one part in

00:15:21.840 --> 00:15:24.840
51 ,000, finding absolutely no deviations from

00:15:24.840 --> 00:15:27.399
Einstein's predictions. That is just phenomenal.

00:15:27.500 --> 00:15:29.759
It's using the entire solar system as a physics

00:15:29.759 --> 00:15:32.860
laboratory. But let's use that incredible momentum

00:15:32.860 --> 00:15:36.139
it gained from Jupiter and fast forward to the

00:15:36.139 --> 00:15:40.440
grand arrival, July 1st, 2004. After a seven

00:15:40.440 --> 00:15:43.120
-year voyage, Cassini finally reaches the ring

00:15:43.120 --> 00:15:46.299
giant. This brings us to the Saturn Orbit Insertion

00:15:46.299 --> 00:15:49.679
or SOI. This was, without a doubt, one of the

00:15:49.679 --> 00:15:52.559
most complex, nerve -wracking, and dangerous

00:15:52.559 --> 00:15:54.779
maneuvers of the entire mission. I can imagine.

00:15:54.940 --> 00:15:57.000
You have to remember, Cassini is hurtling toward

00:15:57.000 --> 00:15:59.779
Saturn at immense speeds. If it doesn't hit the

00:15:59.779 --> 00:16:01.720
brakes at precisely the right moment, it will

00:16:01.720 --> 00:16:04.259
just fly past the planet and disappear into deep

00:16:04.259 --> 00:16:06.460
space. But hitting the brakes isn't as simple

00:16:06.460 --> 00:16:08.500
as tapping a pedal. It has to fly through the

00:16:08.500 --> 00:16:11.460
rings to get into orbit, right? Yes. To achieve

00:16:11.460 --> 00:16:13.379
the correct orbit, Cassini had to fly through

00:16:13.379 --> 00:16:16.980
a known gap between Saturn's F and G rings. Even

00:16:16.980 --> 00:16:19.340
in a gap, the area is filled with microscopic

00:16:19.340 --> 00:16:22.179
dust and ice particles. At the speeds Cassini

00:16:22.179 --> 00:16:24.259
was traveling, hitting a piece of ice the size

00:16:24.259 --> 00:16:26.600
of a grain of sand could sever a vital cable

00:16:26.600 --> 00:16:28.759
or destroy an instrument. So how do they protect

00:16:28.759 --> 00:16:31.669
it? To survive crossing the ring plane, mission

00:16:31.669 --> 00:16:33.850
controllers had to turn the entire spacecraft

00:16:33.850 --> 00:16:36.429
around so its large high -gain antenna faced

00:16:36.429 --> 00:16:39.750
forward. They literally used their main communication

00:16:39.750 --> 00:16:43.250
dish as a physical shield to deflect micrometeorites.

00:16:43.570 --> 00:16:46.649
So it's flying backwards, blindly holding a giant

00:16:46.649 --> 00:16:48.809
shield in front of its face as it plunges through

00:16:48.809 --> 00:16:51.190
the rings, and once it's through... Once it safely

00:16:51.190 --> 00:16:53.289
crossed the ring plane, it had to immediately

00:16:53.289 --> 00:16:55.549
rotate the spacecraft again to point its main

00:16:55.549 --> 00:16:58.240
engine forward along its flight path. Then, it

00:16:58.240 --> 00:17:00.820
fired that engine for a prolonged 96 -minute

00:17:00.820 --> 00:17:03.899
burn. This deceleration burn slowed the craft

00:17:03.899 --> 00:17:07.579
down by 622 meters per second. I can only imagine

00:17:07.579 --> 00:17:10.039
the tension in the control room at the Jet Propulsion

00:17:10.039 --> 00:17:13.000
Laboratory. It takes over an hour for radio signals

00:17:13.000 --> 00:17:15.200
to reach Earth from Saturn, so by the time they

00:17:15.200 --> 00:17:17.079
received word that the engine had fired, the

00:17:17.079 --> 00:17:19.240
maneuver was already over. Exactly. They just

00:17:19.240 --> 00:17:21.880
had to wait and hope. But it worked. On June

00:17:21.880 --> 00:17:25.119
30th, 2004 Pacific time, Cassini was officially

00:17:25.119 --> 00:17:27.380
captured by Saturn's gravity, passing within

00:17:27.380 --> 00:17:29.579
just 20 ,000 kilometers of the planet's cloud

00:17:29.579 --> 00:17:32.660
tops. And almost immediately, it starts solving

00:17:32.660 --> 00:17:35.900
puzzles. One of the biggest being, how fast does

00:17:35.900 --> 00:17:38.519
Saturn actually spin? This was a genuine mystery

00:17:38.519 --> 00:17:40.779
that had frustrated astronomers for decades.

00:17:41.500 --> 00:17:44.779
Unlike a rocky planet like Earth or Mars, Saturn

00:17:44.779 --> 00:17:47.680
is a gas giant. It doesn't have a solid surface

00:17:47.680 --> 00:17:49.799
with mountains or craters that you can track

00:17:49.799 --> 00:17:51.859
with a telescope to see how long it takes to

00:17:51.859 --> 00:17:54.240
complete a single rotation. So how do they try

00:17:54.240 --> 00:17:56.960
to measure it before Cassini? When Voyager 1

00:17:56.960 --> 00:17:59.779
flew by in 1980, it measured Saturn's rotation

00:17:59.779 --> 00:18:02.480
by tracking periodic radio emissions generated

00:18:02.480 --> 00:18:05.380
by the planet's magnetic field. They calculated

00:18:05.380 --> 00:18:08.220
a rotational period of 10 hours, 39 minutes,

00:18:08.359 --> 00:18:11.799
and 24 seconds. But when Cassini arrived 24 years

00:18:11.799 --> 00:18:14.140
later, its radio data showed a spin rate that

00:18:14.140 --> 00:18:16.789
was roughly six minutes longer. Which is physically

00:18:16.789 --> 00:18:19.069
impossible, right? Yeah. A massive gas giant

00:18:19.069 --> 00:18:21.769
doesn't just slow down its rotation by six minutes

00:18:21.769 --> 00:18:24.730
in a couple of decades. The conservation of angular

00:18:24.730 --> 00:18:27.750
momentum wouldn't allow that. Precisely. It turns

00:18:27.750 --> 00:18:29.670
out the radio emissions were not a perfectly

00:18:29.670 --> 00:18:32.190
reliable clock. They were being affected by seasonal

00:18:32.190 --> 00:18:34.529
variations in Saturn's upper atmosphere and its

00:18:34.529 --> 00:18:36.910
ionosphere, the layer of the atmosphere filled

00:18:36.910 --> 00:18:39.730
with charged particles. The magnetic field lines

00:18:39.730 --> 00:18:42.470
were slipping relative to the planet's deep interior.

00:18:42.799 --> 00:18:45.599
The true rotational period of the bulk of the

00:18:45.599 --> 00:18:48.000
planet remained elusive for years during Cassini's

00:18:48.000 --> 00:18:50.299
mission. But they eventually figured it out.

00:18:51.240 --> 00:18:54.180
And the method they used is honestly one of the

00:18:54.180 --> 00:18:56.720
most poetic scientific concepts I've ever heard.

00:18:57.539 --> 00:19:00.920
Our dossier calls it ring seismology. Bring that

00:19:00.920 --> 00:19:02.539
down first because it sounds like they were treating

00:19:02.539 --> 00:19:04.640
the rings like an instrument. They absolutely

00:19:04.640 --> 00:19:07.759
were. Saturn's interior isn't static. It vibrates,

00:19:07.759 --> 00:19:10.740
much like a bell ringing. These internal vibrations

00:19:10.740 --> 00:19:14.400
cause tiny rhythmic oscillations in Saturn's

00:19:14.400 --> 00:19:16.839
gravitational field. Because the rings are so

00:19:16.839 --> 00:19:19.519
vast and orbit so closely to the planet, they

00:19:19.519 --> 00:19:22.220
actually absorb this subtle gravitational energy.

00:19:22.680 --> 00:19:24.740
The particles in the rings get pushed and pulled

00:19:24.740 --> 00:19:27.140
by these microscopic variations until the energy

00:19:27.140 --> 00:19:30.259
accumulates, creating visible spiral waves in

00:19:30.259 --> 00:19:32.920
the rings themselves. So the rings act like a

00:19:32.920 --> 00:19:35.619
giant hypersensitive seismograph wrapped around

00:19:35.619 --> 00:19:38.950
the planet. Exactly. By carefully studying the

00:19:38.950 --> 00:19:41.250
structure and frequency of those specific waves

00:19:41.250 --> 00:19:44.130
in the rings, using Cassini's images and stellar

00:19:44.130 --> 00:19:46.730
occultation data, scientists could mathematically

00:19:46.730 --> 00:19:49.849
work backwards. They could see the internal vibrations

00:19:49.849 --> 00:19:52.829
inside the planet and use that deep interior

00:19:52.829 --> 00:19:55.750
pulsing to calculate a precise rotational period.

00:19:55.829 --> 00:19:58.970
That's incredible. In 2019, analyzing Cassini's

00:19:58.970 --> 00:20:02.289
final data, they finally pinned it down 10 hours,

00:20:02.450 --> 00:20:05.369
33 minutes, and 38 seconds. That is beautiful.

00:20:05.589 --> 00:20:07.910
The rings aren't just a pretty visual feature.

00:20:08.049 --> 00:20:10.869
They are a diagnostic tool to read the heartbeat

00:20:10.869 --> 00:20:13.549
of the planet. And speaking of the rings, Cassini

00:20:13.549 --> 00:20:15.690
gave us some massive revelations about them,

00:20:15.750 --> 00:20:18.269
didn't it? For centuries, people assumed Saturn

00:20:18.269 --> 00:20:20.990
was just born with these rings. This raises an

00:20:20.990 --> 00:20:22.670
important question that astronomers have debated

00:20:22.670 --> 00:20:25.250
for a long time, the age and origin of the rings.

00:20:25.750 --> 00:20:27.690
Are they a primordial feature from the birth

00:20:27.690 --> 00:20:30.289
of the solar system 4 .5 billion years ago, or

00:20:30.289 --> 00:20:33.609
are they a recent addition? Cassini's data, particularly

00:20:33.609 --> 00:20:35.950
from its final orbits where it flew incredibly

00:20:35.950 --> 00:20:38.849
close, allowed scientists to determine the precise

00:20:38.849 --> 00:20:40.970
mass of the rings by measuring their gravitational

00:20:40.970 --> 00:20:43.670
pull on the spacecraft. And what does mass have

00:20:43.670 --> 00:20:46.670
to do with age? The less mass the rings have,

00:20:46.869 --> 00:20:49.329
the younger they likely are. If they were ancient,

00:20:49.450 --> 00:20:51.829
they would have accumulated much more mass from

00:20:51.829 --> 00:20:54.690
billions of years of micrometeorite bombardment,

00:20:54.690 --> 00:20:57.569
and they would look much darker and dirtier than

00:20:57.569 --> 00:21:00.400
the bright pristine ice we see today. That makes

00:21:00.400 --> 00:21:03.059
sense. The finding was stunning. The rings are

00:21:03.059 --> 00:21:05.799
incredibly light and therefore relatively young.

00:21:06.180 --> 00:21:08.920
They are estimated to be only 10 to 100 million

00:21:08.920 --> 00:21:12.200
years old. Wait a second. 10 to 100 million years

00:21:12.200 --> 00:21:14.980
old? That means when the dinosaurs were walking

00:21:14.980 --> 00:21:18.019
around on Earth, Saturn might not have had rings

00:21:18.019 --> 00:21:20.119
at all. It might have just been a bare gas giant.

00:21:20.339 --> 00:21:22.700
It completely reframes our perception of the

00:21:22.700 --> 00:21:24.960
solar system. We tend to think of the planets

00:21:24.960 --> 00:21:27.420
as static, ancient monuments that have looked

00:21:27.420 --> 00:21:30.200
exactly the same since the dawn of time. But

00:21:30.200 --> 00:21:32.640
Cassini proved that the solar system is incredibly

00:21:32.640 --> 00:21:35.759
dynamic. Moons are shattered by gravity, rings

00:21:35.759 --> 00:21:38.420
are formed from the debris, and features we consider

00:21:38.420 --> 00:21:40.480
permanent are actually just fleeting moments

00:21:40.480 --> 00:21:43.859
in cosmic time. That thought alone is worth the

00:21:43.859 --> 00:21:46.740
price of admission. It's a completely different

00:21:46.740 --> 00:21:49.359
way of looking at the night sky. And beyond the

00:21:49.359 --> 00:21:51.900
rings, Cassini spent a massive amount of time

00:21:51.900 --> 00:21:54.619
studying Saturn's weather. Here's where it gets

00:21:54.619 --> 00:21:56.700
really interesting, because Saturn's weather

00:21:56.700 --> 00:21:59.279
makes Earth's hurricanes look like a gentle breeze.

00:22:00.059 --> 00:22:02.759
Looking at the data from 2010, Cassini watched

00:22:02.759 --> 00:22:05.480
this massive storm erupt in the northern hemisphere

00:22:05.480 --> 00:22:08.819
known as the Great White Spot. What exactly was

00:22:08.819 --> 00:22:12.000
this? Saturn experiences these massive planet

00:22:12.000 --> 00:22:14.460
-encircling seasonal storms that erupt roughly

00:22:14.460 --> 00:22:17.079
every 30 Earth years, which equates to about

00:22:17.079 --> 00:22:20.000
one Saturnian year. But the 2010 storm was the

00:22:20.000 --> 00:22:22.220
first of its kind ever observed closely by a

00:22:22.220 --> 00:22:24.500
spacecraft in orbit. And because Cassini had

00:22:24.500 --> 00:22:26.480
a suite of diverse instruments, it allowed us

00:22:26.480 --> 00:22:28.480
to see the storm not just in visible light, but

00:22:28.480 --> 00:22:31.000
in thermal infrared. I was reading the dossier

00:22:31.000 --> 00:22:32.920
on this, and the dimensions and the chemistry

00:22:32.920 --> 00:22:35.779
of this storm just broke my brain. Walk us through

00:22:35.779 --> 00:22:37.599
what Cassini actually saw down there, because

00:22:37.599 --> 00:22:39.450
calling it a storm feels like an understatement.

00:22:39.579 --> 00:22:42.380
It was unprecedented in recorded observation.

00:22:43.099 --> 00:22:45.740
The storm grew so massive that it eventually

00:22:45.740 --> 00:22:48.099
wrapped completely around the entire planet,

00:22:48.359 --> 00:22:50.920
its tail catching up with its head. It created

00:22:50.920 --> 00:22:53.680
a stratospheric vortex that was initially larger

00:22:53.680 --> 00:22:56.980
than Jupiter's famous Great Red Spot. Wow. In

00:22:56.980 --> 00:22:59.619
terms of temperature, Cassini detected a massive

00:22:59.619 --> 00:23:02.119
spike in the stratosphere, 83 degrees Celsius

00:23:02.119 --> 00:23:04.119
above normal. And what about the chemistry? Because

00:23:04.119 --> 00:23:06.079
that's where the scientists really scratch their

00:23:06.079 --> 00:23:09.430
heads. Chemically, the storm was bizarre. Researchers

00:23:09.430 --> 00:23:12.069
analyzing the infrared data detected a massive

00:23:12.069 --> 00:23:15.450
discharge of ethylene gas. Ethylene. For context,

00:23:15.670 --> 00:23:17.630
ethylene is a very common molecule here on Earth.

00:23:17.750 --> 00:23:20.130
Plants naturally produce it to ripen fruit, and

00:23:20.130 --> 00:23:22.309
we manufacture it industrially to make plastics.

00:23:23.009 --> 00:23:25.450
But it is supposed to be extremely rare in the

00:23:25.450 --> 00:23:27.589
hydrogen and helium atmosphere of Saturn. Yet

00:23:27.589 --> 00:23:30.650
this storm produced a concentrated spike of ethylene

00:23:30.650 --> 00:23:33.930
gas 100 times greater than what was previously

00:23:33.930 --> 00:23:36.309
thought possible for Saturn's atmospheric conditions.

00:23:37.150 --> 00:23:39.470
It forced atmospheric chemists back to the drawing

00:23:39.470 --> 00:23:41.970
board. It showed us that the deep atmospheric

00:23:41.970 --> 00:23:44.630
chemistry of these gas giants churning hundreds

00:23:44.630 --> 00:23:47.650
of miles beneath the visible cloud tops is far

00:23:47.650 --> 00:23:50.309
more violently active and complex than we imagined.

00:23:50.609 --> 00:23:52.890
And if a storm wrapping around the entire planet

00:23:52.890 --> 00:23:55.500
emitting ethylene isn't crazy enough, Let's talk

00:23:55.500 --> 00:23:58.319
about the poles. Specifically, the South Pole

00:23:58.319 --> 00:24:01.359
hurricane. Cassini finds a literal hurricane

00:24:01.359 --> 00:24:04.200
locked at the South Pole of Saturn. It has a

00:24:04.200 --> 00:24:06.180
distinct eyewall, just like a hurricane over

00:24:06.180 --> 00:24:09.859
the Atlantic Ocean on Earth. But the scale, it's

00:24:09.859 --> 00:24:12.720
just monstrous. It is an Earth -like meteorological

00:24:12.720 --> 00:24:15.019
phenomenon, but scaled up to alien proportions.

00:24:15.440 --> 00:24:17.880
The eye of the hurricane is 8 ,000 kilometers

00:24:17.880 --> 00:24:20.519
across. That is wide enough to comfortably swallow

00:24:20.519 --> 00:24:22.880
the entire Earth. Swallowing the Earth. Let that

00:24:22.880 --> 00:24:25.410
sink in. The winds at the eyewall are blowing

00:24:25.410 --> 00:24:29.170
at 560 kilometers per hour. And unlike hurricanes

00:24:29.170 --> 00:24:31.430
on Earth, which drift across the oceans guided

00:24:31.430 --> 00:24:34.369
by trade winds, this storm is completely stationary.

00:24:34.710 --> 00:24:37.890
It just sits at the geographic South Pole, perpetually

00:24:37.890 --> 00:24:39.910
spinning. It's mesmerizing. And the North Pole

00:24:39.910 --> 00:24:41.609
is equally strange, right? It doesn't have a

00:24:41.609 --> 00:24:44.289
hurricane. It has the hexagon. Yes, the North

00:24:44.289 --> 00:24:47.490
Polar Hexagon is a persistent, six -sided cloud

00:24:47.490 --> 00:24:50.049
pattern. It was originally spotted by the Voyager

00:24:50.049 --> 00:24:52.230
probes, but Cassini gave us an unprecedented

00:24:52.230 --> 00:24:55.150
long -term view of it. The hexagon is essentially

00:24:55.150 --> 00:24:58.029
a massive jet stream following a geometric path.

00:24:58.549 --> 00:25:01.009
What Cassini observed over its 13 -year mission

00:25:01.009 --> 00:25:03.670
was something entirely unexpected. The hexagon

00:25:03.670 --> 00:25:06.289
changed color. Wait, a geometric cloud pattern

00:25:06.289 --> 00:25:08.150
the size of a planet? Just decided to change

00:25:08.150 --> 00:25:11.980
color. Why? Between 2012 and 2016, the interior

00:25:11.980 --> 00:25:14.240
of the hexagon shifted from a mostly pale blue

00:25:14.240 --> 00:25:17.539
color to a distinct golden hue. The leading theory

00:25:17.539 --> 00:25:19.880
among planetary scientists is seasonal change.

00:25:20.140 --> 00:25:23.259
A year on Saturn takes nearly 30 Earth years.

00:25:23.519 --> 00:25:26.140
As Saturn's north pole slowly swiveled toward

00:25:26.140 --> 00:25:29.440
the Sun, the extended exposure to solar radiation

00:25:29.440 --> 00:25:31.880
likely initiated photochemical reactions in the

00:25:31.880 --> 00:25:34.759
upper atmosphere. The sunlight reacted with methane

00:25:34.759 --> 00:25:37.660
and other trace gases, creating a thick, golden

00:25:37.660 --> 00:25:41.099
haze of aerosols over the pole. Again, it highlights

00:25:41.099 --> 00:25:43.960
that Saturn is a deeply dynamic, shifting world,

00:25:44.339 --> 00:25:47.220
driven by seasons just like Earth. It's a living,

00:25:47.420 --> 00:25:50.119
breathing meteorological system. But as much

00:25:50.119 --> 00:25:52.819
as Saturn was the main event, the expert maneuvering

00:25:52.819 --> 00:25:55.279
of Cassini allowed it to treat the Saturnian

00:25:55.279 --> 00:25:58.019
system like a miniature solar system. It didn't

00:25:58.019 --> 00:25:59.880
just study the planet, it studied the moons.

00:26:00.000 --> 00:26:01.640
And there are dozens of them. Yeah, and there

00:26:01.640 --> 00:26:04.079
are so many. In fact, Cassini discovered seven

00:26:04.079 --> 00:26:06.400
completely new ones, like Daphnis and Anthy,

00:26:06.579 --> 00:26:08.279
which were found hiding right inside the tiny

00:26:08.279 --> 00:26:10.500
gaps of the rings. But if we're talking about

00:26:10.500 --> 00:26:12.799
the established moons it visited, the flybys

00:26:12.799 --> 00:26:15.200
were wild. Let's start with Phoebe. What did

00:26:15.200 --> 00:26:17.559
we learn there? Phoebe was actually the very

00:26:17.559 --> 00:26:20.339
first targeted moon flyby of the mission, happening

00:26:20.339 --> 00:26:23.819
in June 2004, just weeks before Cassini even

00:26:23.819 --> 00:26:26.619
fired its engines to enter orbit around Saturn.

00:26:27.160 --> 00:26:29.799
It was a one -time shot due to the specific orbital

00:26:29.799 --> 00:26:32.680
mechanics required to get to Saturn. From Earth,

00:26:32.799 --> 00:26:34.940
Phoebe looks incredibly dark, reflecting very

00:26:34.940 --> 00:26:37.059
little light. Like a piece of charcoal in space.

00:26:37.339 --> 00:26:39.940
Exactly. But when Cassini's high -resolution

00:26:39.940 --> 00:26:42.799
images and spectrometer data came back, scientists

00:26:42.799 --> 00:26:45.640
realized Phoebe was far more complex. It was

00:26:45.640 --> 00:26:48.480
heavily cratered, but the bright spots exposed

00:26:48.480 --> 00:26:51.119
inside those deep craters revealed a massive

00:26:51.119 --> 00:26:54.099
amount of water ice hiding just beneath its dark,

00:26:54.279 --> 00:26:57.799
dusty exterior. Furthermore, Phoebe orbits Saturn

00:26:57.799 --> 00:27:00.460
backwards, a retrograde orbit compared to most

00:27:00.460 --> 00:27:02.279
of the other moons. So what does that tell us

00:27:02.279 --> 00:27:04.079
about its origin? Because a retrograde orbit

00:27:04.079 --> 00:27:06.000
usually means the object wasn't formed there

00:27:06.000 --> 00:27:08.950
alongside the planet. The consensus is that Phoebe

00:27:08.950 --> 00:27:12.009
is a captured centaur or a Kuiper belt object.

00:27:12.589 --> 00:27:15.349
It's an interloper from the icy outer reaches

00:27:15.349 --> 00:27:17.829
of the solar system beyond Neptune that wandered

00:27:17.829 --> 00:27:20.650
too close to Saturn millions of years ago and

00:27:20.650 --> 00:27:23.289
was ensnared by its gravity. It's essentially

00:27:23.289 --> 00:27:26.890
a primordial dirty snowball offering a pristine

00:27:26.890 --> 00:27:29.210
glimpse into the building blocks of the early

00:27:29.210 --> 00:27:31.670
solar system. That's a great find. But the flyby

00:27:31.670 --> 00:27:34.029
that really sounds like a thriller movie was

00:27:34.029 --> 00:27:38.180
Iapetus in September 2007. Iapetus is a bizarre

00:27:38.180 --> 00:27:41.099
moon. Our sources describe it as two -toned,

00:27:41.240 --> 00:27:43.420
where one half of the moon is pitch black and

00:27:43.420 --> 00:27:45.819
the trailing hemisphere is bright white like

00:27:45.819 --> 00:27:48.029
snow. And on top of that, it's shaped like a

00:27:48.029 --> 00:27:50.549
walnut. Yes. The walnut shape is perhaps its

00:27:50.549 --> 00:27:52.549
most defining feature, aside from the coloring.

00:27:53.190 --> 00:27:55.809
That shape comes from a massive equatorial ridge.

00:27:56.049 --> 00:27:58.109
It's a continuous mountain range reaching up

00:27:58.109 --> 00:28:00.769
to 20 kilometers high and 10 kilometers wide

00:28:00.769 --> 00:28:03.150
that wraps almost perfectly around the moon's

00:28:03.150 --> 00:28:06.329
equator. That's massive. It is. It looks astonishingly

00:28:06.329 --> 00:28:08.470
geometric, making the moon look like it was manufactured

00:28:08.470 --> 00:28:10.589
from two separate halves stitched together at

00:28:10.589 --> 00:28:12.869
the seam. It's the kind of visual that immediately

00:28:12.869 --> 00:28:15.920
makes you wonder how geology could possibly create

00:28:15.920 --> 00:28:19.680
such a specific shape. So Cassini flies by, takes

00:28:19.680 --> 00:28:21.940
these incredible high -resolution images from

00:28:21.940 --> 00:28:24.819
just 1 ,600 kilometers away, and prepares to

00:28:24.819 --> 00:28:27.500
beam all this gold mine of data back to Earth.

00:28:28.180 --> 00:28:31.059
But right at the climax of the flyby disaster

00:28:31.059 --> 00:28:33.440
strikes. It was a moment of incredibly bad timing

00:28:33.440 --> 00:28:36.460
that highlights the perils of deep space exploration.

00:28:37.119 --> 00:28:39.440
Right in the middle of data transmission following

00:28:39.440 --> 00:28:41.980
the closest approach, the spacecraft was hit

00:28:41.980 --> 00:28:45.230
by a galactic cosmic ray. We talked earlier about

00:28:45.230 --> 00:28:47.230
why they needed a radiation -hardened computer.

00:28:47.349 --> 00:28:49.369
Is this exactly what they were afraid of? What

00:28:49.369 --> 00:28:52.210
actually is a galactic cosmic ray? A galactic

00:28:52.210 --> 00:28:54.450
cosmic ray is not a ray of light. It's a high

00:28:54.450 --> 00:28:56.809
-energy atomic nucleus traveling at nearly the

00:28:56.809 --> 00:28:59.150
speed of light, often originating from outside

00:28:59.150 --> 00:29:01.630
our solar system, perhaps from a distant supernova.

00:29:02.410 --> 00:29:05.329
When this tiny, incredibly energetic particle

00:29:05.329 --> 00:29:07.910
slammed into Cassini's circuitry, the impact

00:29:07.910 --> 00:29:11.190
tripped a solid -state power switch. The spacecraft's

00:29:11.190 --> 00:29:13.900
computer systems detected the anomaly and force

00:29:13.900 --> 00:29:16.519
the probe into safe mode. Safe mode, meaning

00:29:16.519 --> 00:29:19.930
it just shuts everything down. Yes. Safe Mode

00:29:19.930 --> 00:29:21.970
is a protective state where the computer shuts

00:29:21.970 --> 00:29:25.309
down all non -essential functions, stops transmitting

00:29:25.309 --> 00:29:28.009
science data, and points its antenna toward Earth

00:29:28.009 --> 00:29:31.009
to wait for instructions. It's a self -preservation

00:29:31.009 --> 00:29:33.190
instinct designed to prevent the glitch from

00:29:33.190 --> 00:29:48.759
causing permanent hardware damage. statistical

00:29:48.759 --> 00:29:51.279
bad luck of that moment. It is the definition

00:29:51.279 --> 00:29:54.440
of statistical bad luck, but it is simultaneously

00:29:54.440 --> 00:29:56.660
a brilliant testament to the robust engineering

00:29:56.660 --> 00:29:58.880
of the Jet Propulsion Laboratory team back in

00:29:58.880 --> 00:30:02.339
the 1990s. How so? Despite the main systems going

00:30:02.339 --> 00:30:04.920
into safe mode, the onboard solid state memory

00:30:04.920 --> 00:30:06.859
recorders had done their job. They had saved

00:30:06.859 --> 00:30:09.299
all the data collected during the flyby. Once

00:30:09.299 --> 00:30:11.539
the engineers on Earth carefully diagnosed the

00:30:11.539 --> 00:30:13.720
problem and coaxed Cassini out of safe mode over

00:30:13.720 --> 00:30:16.700
the next few days, all of the IPDIS imagery and

00:30:16.700 --> 00:30:19.440
radar data was recovered and transmitted back

00:30:19.440 --> 00:30:22.619
home. That is a massive sigh of relief. And as

00:30:22.619 --> 00:30:24.920
incredible as that icy mountain on Iapetus is,

00:30:25.240 --> 00:30:27.519
or the dark secrets of Phoebe, if we're talking

00:30:27.519 --> 00:30:29.819
about the real crown jewels of this mission,

00:30:30.240 --> 00:30:32.099
the places that fundamentally changed our search

00:30:32.099 --> 00:30:35.460
for life, We have to look beneath the smog. We

00:30:35.460 --> 00:30:37.539
have to talk about Titan and Enceladus. Let's

00:30:37.539 --> 00:30:40.759
start with Titan. This moon is an absolute behemoth.

00:30:40.839 --> 00:30:43.099
It's larger than the planet Mercury, but you

00:30:43.099 --> 00:30:45.140
can't see its surface because it is completely

00:30:45.140 --> 00:30:48.119
shrouded in the thick, dense, orange atmosphere.

00:30:48.519 --> 00:30:50.940
Titan is unique. It's the only moon in the solar

00:30:50.940 --> 00:30:53.079
system with a dense atmosphere. In fact, its

00:30:53.079 --> 00:30:56.440
atmosphere is 50 % thicker than Earth's. Exploring

00:30:56.440 --> 00:30:58.920
what lay hidden beneath that opaque orange haze

00:30:58.920 --> 00:31:01.279
was the primary reason the European Space Agency

00:31:01.279 --> 00:31:05.099
built the Huygens probe. Huygens was a 350 -kilogram

00:31:05.099 --> 00:31:07.740
robotic laboratory shaped somewhat like a flying

00:31:07.740 --> 00:31:10.640
saucer designed specifically to plunge into Titan's

00:31:10.640 --> 00:31:13.140
atmosphere, survive the fiery descent and land

00:31:13.140 --> 00:31:15.460
on the completely unknown surface. On Christmas

00:31:15.460 --> 00:31:18.839
Day 2004, Cassini finally releases the Huygens

00:31:18.839 --> 00:31:22.390
probe. They detach, and Huygens coasts in silence

00:31:22.390 --> 00:31:25.329
for 20 days until it slams into Titan's upper

00:31:25.329 --> 00:31:30.089
atmosphere on January 14, 2005. This was the

00:31:30.089 --> 00:31:31.990
first landing ever accomplished in the outer

00:31:31.990 --> 00:31:35.279
solar system. But reading the dossier, There

00:31:35.279 --> 00:31:38.039
was a critical, near -fatal flaw discovered long

00:31:38.039 --> 00:31:40.599
after launch that almost ruined the entire endeavor.

00:31:40.859 --> 00:31:43.740
Yes. It's one of the most harrowing stories of

00:31:43.740 --> 00:31:46.259
the entire mission and a master class in orbital

00:31:46.259 --> 00:31:49.079
problem solving. Years after the spacecraft launched

00:31:49.079 --> 00:31:51.220
from Earth, engineers running simulated tests

00:31:51.220 --> 00:31:53.819
discovered a critical design flaw in the communication

00:31:53.819 --> 00:31:56.240
system between the Huygens probe and the Cassini

00:31:56.240 --> 00:31:58.849
orbiter. The plan is for Huygens to descend through

00:31:58.849 --> 00:32:01.250
the atmosphere and transmit its data continuously

00:32:01.250 --> 00:32:03.470
up to Cassini, which would act as a relay station,

00:32:03.789 --> 00:32:05.529
recording the data and eventually beaming it

00:32:05.529 --> 00:32:07.430
to Earth. It sounds like a standard relay maneuver.

00:32:07.549 --> 00:32:09.589
What was the flaw? The problem was rooted in

00:32:09.589 --> 00:32:12.430
the Doppler shift. Think of how a police siren

00:32:12.430 --> 00:32:15.049
changes pitch as the car speeds past you on the

00:32:15.049 --> 00:32:17.849
highway. The sound waves compress, making the

00:32:17.849 --> 00:32:20.190
pitch higher as it approaches, and then stretch

00:32:20.190 --> 00:32:22.769
out, making the pitch lower as it speeds away.

00:32:23.019 --> 00:32:25.980
The exact same physics applied to radio waves.

00:32:26.890 --> 00:32:29.549
As the Huygens probe descended, Cassini would

00:32:29.549 --> 00:32:32.769
be flying overhead at tremendous orbital speeds.

00:32:33.549 --> 00:32:35.769
The relative speed between the two spacecraft

00:32:35.769 --> 00:32:38.670
would cause a massive Doppler shift in the radio

00:32:38.670 --> 00:32:41.170
frequency transmitted by the probe. And the receiver

00:32:41.170 --> 00:32:43.650
on Cassini wasn't designed to handle that shift.

00:32:43.869 --> 00:32:46.890
Exactly. The bandwidth of Cassini's signal processing

00:32:46.890 --> 00:32:49.890
electronics was too narrow. The anticipated Doppler

00:32:49.890 --> 00:32:53.089
shift caused by Cassini rushing toward and then

00:32:53.089 --> 00:32:55.289
away from the probe would push the radio signal

00:32:55.289 --> 00:32:57.180
completely out of of the receiver's readable

00:32:57.180 --> 00:33:00.200
range. Cassini would literally be deaf to the

00:33:00.200 --> 00:33:02.799
perbs transmission. All of Europe's work, the

00:33:02.799 --> 00:33:04.539
entire purpose of the landing would have been

00:33:04.539 --> 00:33:08.150
lost in a sea of unreadable static. Oh man, so

00:33:08.150 --> 00:33:11.410
what did they do? You are a billion miles away.

00:33:11.730 --> 00:33:14.890
You cannot send a mechanic with a wrench to Saturn

00:33:14.890 --> 00:33:17.650
to swap out a radio receiver on a spacecraft

00:33:17.650 --> 00:33:20.309
traveling at thousands of miles an hour. What's

00:33:20.309 --> 00:33:23.150
fascinating here is the sheer ingenuity of the

00:33:23.150 --> 00:33:25.450
orbital mechanics fix they came up with. Since

00:33:25.450 --> 00:33:27.349
they could not physically alter the hardware

00:33:27.349 --> 00:33:29.970
to widen the bandwidth, they had to use physics

00:33:29.970 --> 00:33:32.569
to reduce the Doppler shift itself. How do you

00:33:32.569 --> 00:33:35.349
do that? They did this by altering Cassini's

00:33:35.349 --> 00:33:39.099
entire trajectory. They meticulously recalculated

00:33:39.099 --> 00:33:42.059
the orbital path, changing the angle and altitude

00:33:42.059 --> 00:33:44.539
at which Cassini flew past Titan during the descent.

00:33:45.180 --> 00:33:47.539
Instead of flying low and rushing straight toward

00:33:47.539 --> 00:33:49.859
and away from the probe, they adjusted the orbit

00:33:49.859 --> 00:33:51.960
so Cassini flew much higher and more parallel

00:33:51.960 --> 00:33:55.119
to the probe's descent. I see. So by flying parallel,

00:33:55.279 --> 00:33:57.339
you minimize the speed at which the two craft

00:33:57.339 --> 00:33:59.140
are closing the distance between each other.

00:33:59.400 --> 00:34:01.640
It's like driving perfectly alongside the police

00:34:01.640 --> 00:34:03.799
car so the siren's pitch remains constant to

00:34:03.799 --> 00:34:07.180
your ears. Precisely. This brilliant trajectory

00:34:07.180 --> 00:34:09.400
adjustment reduced the relative line of sight

00:34:09.400 --> 00:34:12.219
velocity just enough to keep the pitch of the

00:34:12.219 --> 00:34:14.760
radio signal within the narrow, readable range

00:34:14.760 --> 00:34:17.900
of Cassini's receiver. That is human ingenuity

00:34:17.900 --> 00:34:20.159
at its finest. And thank goodness they figured

00:34:20.159 --> 00:34:22.500
it out, because the two and a half hour parachute

00:34:22.500 --> 00:34:25.579
ride down through Titan's atmosphere gave us

00:34:25.579 --> 00:34:28.059
some of the most surreal, mind -bending images

00:34:28.059 --> 00:34:31.280
in the history of spaceflight. I want you, the

00:34:31.280 --> 00:34:34.289
listener. to try and visualize this. As Huygens

00:34:34.289 --> 00:34:36.449
breaks through the orange haze, its cameras start

00:34:36.449 --> 00:34:39.150
snapping pictures. What exactly was it seeing?

00:34:39.550 --> 00:34:42.329
It revealed a landscape that was shockingly unnervingly

00:34:42.329 --> 00:34:45.190
familiar, yet totally alien. As it descended,

00:34:45.449 --> 00:34:47.889
it photographed complex topography branching

00:34:47.889 --> 00:34:50.690
drainage networks, rugged hills and deep river

00:34:50.690 --> 00:34:52.929
valleys that looked exactly like the aerial topography

00:34:52.929 --> 00:34:55.190
of Earth. But those rivers weren't carved by

00:34:55.190 --> 00:34:58.289
water, were they? No, they were not. At minus

00:34:58.289 --> 00:35:01.360
290 degrees Fahrenheit, Water on Titan is frozen

00:35:01.360 --> 00:35:03.980
as hard as granite. It acts as the bedrock of

00:35:03.980 --> 00:35:07.739
the moon. Titan possesses a full active hydrological

00:35:07.739 --> 00:35:10.900
cycle. It has clouds, it rains, rivers flow across

00:35:10.900 --> 00:35:14.199
the surface, and evaporation occurs. But the

00:35:14.199 --> 00:35:16.960
fluid driving this entire cycle is liquid natural

00:35:16.960 --> 00:35:19.719
gas, specifically liquid methane and ethane.

00:35:19.760 --> 00:35:21.860
It rains liquid natural gas, so the rivers are

00:35:21.860 --> 00:35:25.409
flowing with gasoline that is just... Staggering

00:35:25.409 --> 00:35:27.369
to think about. And then the probe finally hits

00:35:27.369 --> 00:35:29.510
the ground. It doesn't crash at lambs. Yes. The

00:35:29.510 --> 00:35:31.309
penetrometer in the bottom of the probe measured

00:35:31.309 --> 00:35:34.409
the impact force. It indicated that Huygens landed

00:35:34.409 --> 00:35:36.690
in a material with the physical consistency of

00:35:36.690 --> 00:35:39.650
wet sand or soft clay. It had landed in a muddy

00:35:39.650 --> 00:35:42.090
floodplain of liquid methane. And amazingly,

00:35:42.090 --> 00:35:44.730
it survived the impact. Incredible. It sat on

00:35:44.730 --> 00:35:46.750
the freezing surface and transmitted continuous

00:35:46.750 --> 00:35:49.630
data and images for about 90 minutes before Cassini

00:35:49.630 --> 00:35:52.050
finally dropped below the horizon, severing the

00:35:52.050 --> 00:35:55.139
relay link. Meanwhile, from orbit, Cassini is

00:35:55.139 --> 00:35:58.000
not done with Titan. Over the next decade, Cassini

00:35:58.000 --> 00:36:00.320
used its powerful radar instruments to peer through

00:36:00.320 --> 00:36:02.820
the smog and map the rest of the moon. And what

00:36:02.820 --> 00:36:05.119
they found in the northern polar latitudes changed

00:36:05.119 --> 00:36:08.809
everything. They found lakes and seas, massive

00:36:08.809 --> 00:36:12.690
standing bodies of liquid hydrocarbons. In 2006

00:36:12.690 --> 00:36:15.690
and 2007, radar images confirmed the presence

00:36:15.690 --> 00:36:18.909
of numerous lakes ranging from one to 100 kilometers

00:36:18.909 --> 00:36:21.550
across. As they continued mapping, they found

00:36:21.550 --> 00:36:24.869
actual seas, bodies of liquid like Kraken Mare

00:36:24.869 --> 00:36:27.210
and Ligea Mare, which are significantly larger

00:36:27.210 --> 00:36:29.750
than the Great Lakes in North America. This remains

00:36:29.750 --> 00:36:32.530
the first and currently the only discovery of

00:36:32.530 --> 00:36:34.769
stable existing liquid lakes anywhere in the

00:36:34.769 --> 00:36:37.119
universe. besides Earth. Think about the philosophical

00:36:37.119 --> 00:36:39.699
weight of that discovery. You have this world,

00:36:39.920 --> 00:36:42.440
Titan, which is essentially a deep freeze version

00:36:42.440 --> 00:36:45.860
of a prebiotic Earth. It has incredibly complex

00:36:45.860 --> 00:36:48.019
organic chemistry happening in the atmosphere,

00:36:48.360 --> 00:36:51.199
creating the haze. It has liquids pooling on

00:36:51.199 --> 00:36:54.039
the surface, carving geology. It really forces

00:36:54.039 --> 00:36:57.079
you to wonder, if a world is this geologically

00:36:57.079 --> 00:37:00.460
and chemically active at minus 290 degrees, could

00:37:00.460 --> 00:37:03.760
there be some form of weird exotic life that

00:37:03.760 --> 00:37:07.130
uses methane instead of water as its biological

00:37:07.130 --> 00:37:09.730
solvent. It drastically expands our definition

00:37:09.730 --> 00:37:12.449
of habitability. Life as we know it. Earth -centric

00:37:12.449 --> 00:37:15.730
life requires liquid water. But Titan forces

00:37:15.730 --> 00:37:18.849
astrobiologists to ask if life as we don't know

00:37:18.849 --> 00:37:20.989
it could exist in a completely different chemical

00:37:20.989 --> 00:37:23.710
paradigm. Could cell membranes form in liquid

00:37:23.710 --> 00:37:26.289
methane? Titan is the ultimate laboratory for

00:37:26.289 --> 00:37:28.389
answering that question. Titan gave us an Earth

00:37:28.389 --> 00:37:31.079
-like surface with deeply alien chemistry. But

00:37:31.079 --> 00:37:33.239
then, as the mission progressed, another moon

00:37:33.239 --> 00:37:35.159
stepped into the spotlight. A moon that gave

00:37:35.159 --> 00:37:36.940
us Earth -like chemistry in an alien setting.

00:37:37.579 --> 00:37:39.820
Let's pivot to the true crown jewel of the Cassini

00:37:39.820 --> 00:37:42.400
mission in syllabus. Enceladus is a tiny moon,

00:37:42.659 --> 00:37:45.440
only about 500 kilometers across. To put that

00:37:45.440 --> 00:37:47.260
in perspective, it could fit comfortably within

00:37:47.260 --> 00:37:49.679
the borders of the state of Arizona. Initially,

00:37:49.820 --> 00:37:51.719
it wasn't a major focus of the mission planners.

00:37:52.119 --> 00:37:54.519
From a distance, it looks like a bright, frozen,

00:37:54.820 --> 00:37:57.539
geologically dead ball of ice. It reflects almost

00:37:57.539 --> 00:37:59.920
100 % of the sunlight that hits it, making it

00:37:59.920 --> 00:38:02.059
one of the brightest objects in the solar system.

00:38:02.539 --> 00:38:06.079
But during the early flybys in 2005, Cassini's

00:38:06.079 --> 00:38:08.670
instruments picked up something strange. The

00:38:08.670 --> 00:38:11.230
magnetometer detected a deflection in the local

00:38:11.230 --> 00:38:14.050
magnetic field around the moon. Why was that

00:38:14.050 --> 00:38:16.369
a smoking gun for the scientists? Saturn has

00:38:16.369 --> 00:38:19.590
a massive rotating magnetic field. As it sweeps

00:38:19.590 --> 00:38:22.090
past its moons, the magnetic field lines should

00:38:22.090 --> 00:38:24.329
pass right through them without much disturbance

00:38:24.329 --> 00:38:27.719
if the moon is just a dead rock. But Cassini's

00:38:27.719 --> 00:38:29.760
magnetometer detected that the magnetic field

00:38:29.760 --> 00:38:32.659
lines were bending around Enceladus. This is

00:38:32.659 --> 00:38:34.539
a telltale signature that the moon is pushing

00:38:34.539 --> 00:38:36.380
back, and the only way it can push back is if

00:38:36.380 --> 00:38:39.099
it has an atmosphere containing ionized particles.

00:38:39.539 --> 00:38:42.099
Which is physically perplexing, right? A moon

00:38:42.099 --> 00:38:44.460
that tiny does not have nearly enough gravity

00:38:44.460 --> 00:38:47.119
to hold onto a permanent atmosphere. The gas

00:38:47.119 --> 00:38:50.059
would just escape into space. Unless the atmosphere

00:38:50.059 --> 00:38:51.900
is constantly being replenished by something.

00:38:52.159 --> 00:38:54.619
Precisely. The atmosphere had to be actively

00:38:54.619 --> 00:38:57.460
venting from the moon itself. So mission controllers

00:38:57.460 --> 00:38:59.800
commanded Cassini to turn its high -resolution

00:38:59.800 --> 00:39:02.199
cameras to look specifically at the south pole

00:39:02.199 --> 00:39:04.659
of Enceladus. And that's when they caught it.

00:39:04.880 --> 00:39:07.840
Erupting from massive parallel tectonic fractures

00:39:07.840 --> 00:39:10.139
at the moon's south pole features, scientists

00:39:10.139 --> 00:39:13.019
nicknamed tiger stripes were towering, continuous

00:39:13.019 --> 00:39:15.679
geysers shooting water ice and vapor hundreds

00:39:15.679 --> 00:39:18.300
of miles into deep space. Imagine that visual.

00:39:18.760 --> 00:39:21.780
A tiny frozen moon shooting massive jets of water

00:39:21.780 --> 00:39:24.159
out of its south pole. In fact, these geysers

00:39:24.159 --> 00:39:26.820
are so prolific, the dossier note, they are actually

00:39:26.820 --> 00:39:29.179
the source material for Saturn's entire E -Ring.

00:39:29.599 --> 00:39:31.639
The E -Ring is just a massive trail of frozen

00:39:31.639 --> 00:39:34.519
water vapor left behind by Enceladus. Cassini

00:39:34.519 --> 00:39:36.619
was essentially tracing the ring back to a leak

00:39:36.619 --> 00:39:39.769
in a moon. It was a total paradigm shift in planetary

00:39:39.769 --> 00:39:42.449
science. If there are geysers shooting water

00:39:42.449 --> 00:39:45.389
vapor into space at supersonic speeds, mission

00:39:45.389 --> 00:39:47.869
scientists realized there must be pockets of

00:39:47.869 --> 00:39:51.170
liquid water beneath the icy crest, fueling these

00:39:51.170 --> 00:39:54.309
eruptions. So the Cassini team did something

00:39:54.309 --> 00:39:57.630
incredibly daring. They altered Cassini's orbital

00:39:57.630 --> 00:40:00.409
trajectory to fly directly through the erupting

00:40:00.409 --> 00:40:02.889
plumes. Think about the sheer audacity of that

00:40:02.889 --> 00:40:06.369
maneuver. You take a multi -billion dollar robotic

00:40:06.369 --> 00:40:08.849
spacecraft, traveling at thousands of miles an

00:40:08.849 --> 00:40:11.170
hour, and you intentionally fly it through a

00:40:11.170 --> 00:40:14.489
geyser erupting from an alien moon just so you

00:40:14.489 --> 00:40:17.070
can taste the water. It's wild! What did they

00:40:17.070 --> 00:40:18.789
find when they flew through the plume? It was

00:40:18.789 --> 00:40:20.989
a spectacular and highly rewarding maneuver.

00:40:21.269 --> 00:40:23.789
In 2008, and again in much deeper dives, like

00:40:23.789 --> 00:40:26.389
in 2015 where the spacecraft passed a mere 49

00:40:26.389 --> 00:40:28.369
kilometers above the surface of the tiger stripes,

00:40:28.929 --> 00:40:31.110
Cassini's mass spectrometers tasted the chemical

00:40:31.110 --> 00:40:33.230
makeup of the plume. And a mass spectrometer

00:40:33.230 --> 00:40:35.250
is basically a device that sniffs out the chemical

00:40:35.250 --> 00:40:37.550
fingerprints of whatever it flies through. Yes,

00:40:37.949 --> 00:40:40.829
it ionizes the particles and sorts them by mass,

00:40:41.050 --> 00:40:43.530
allowing scientists to identify the exact molecules

00:40:43.530 --> 00:40:46.070
present. They detected a tremendous amount of

00:40:46.070 --> 00:40:48.409
water vapor, carbon dioxide, carbon monoxide,

00:40:48.550 --> 00:40:51.070
and various simple hydrocarbons like methane.

00:40:52.230 --> 00:40:54.610
Furthermore, as Cassini conducted more flybys,

00:40:54.989 --> 00:40:57.429
they analyzed the tiny gravitational tugs the

00:40:57.429 --> 00:40:59.889
moon exerted on the spacecraft. That gravitational

00:40:59.889 --> 00:41:02.489
data proved conclusively that this wasn't just

00:41:02.489 --> 00:41:04.449
a localized puddle of water beneath the South

00:41:04.449 --> 00:41:08.289
Pole. Enceladus possesses a global salty subsurface

00:41:08.289 --> 00:41:11.110
ocean sandwiched between the icy outer crust

00:41:11.110 --> 00:41:13.730
and a rocky interior core. Okay, stop right there.

00:41:13.889 --> 00:41:16.769
A salty ocean in direct contact with a rocky

00:41:16.769 --> 00:41:20.090
core. Why is that specific combination of factors

00:41:20.090 --> 00:41:23.179
so massively important for astrobiology? Because

00:41:23.179 --> 00:41:25.559
it completely rewrites the textbook on habitable

00:41:25.559 --> 00:41:27.739
zones in astrophysics. For decades, we operated

00:41:27.739 --> 00:41:29.400
under the assumption that a planet had to be

00:41:29.400 --> 00:41:31.659
at the perfect distance from its star, the Goldilocks

00:41:31.659 --> 00:41:34.619
zone, for water to exist in a liquid state. But

00:41:34.619 --> 00:41:36.780
Enceladus is a billion miles away from the sun.

00:41:36.800 --> 00:41:39.460
It receives almost no solar heat. The heat keeping

00:41:39.460 --> 00:41:41.920
that vast ocean liquid is generated by tidal

00:41:41.920 --> 00:41:44.460
heating. Tidal heating. That's the gravitational

00:41:44.460 --> 00:41:47.559
tug -of -war, right? Yes. Enceladus orbits Saturn

00:41:47.559 --> 00:41:50.239
in an elliptical path, and it's also in an orbital

00:41:50.239 --> 00:41:53.610
resonance with another moon, Dione. The massive

00:41:53.610 --> 00:41:56.289
shifting gravity of Saturn constantly stretches

00:41:56.289 --> 00:41:59.309
and squishes the tiny moon as it orbits. This

00:41:59.309 --> 00:42:02.329
continuous physical deformation generates massive

00:42:02.329 --> 00:42:05.670
internal friction and heat within the rocky core.

00:42:05.849 --> 00:42:07.590
Just like bending a paperclip back and forth

00:42:07.590 --> 00:42:10.829
makes it hot. Exactly. That heat radiates outward,

00:42:10.949 --> 00:42:13.289
keeping the global ocean liquid. More importantly,

00:42:13.469 --> 00:42:15.510
where that warm water interacts with the rocky

00:42:15.510 --> 00:42:18.690
core at the ocean floor, it likely creates hydrothermal

00:42:18.690 --> 00:42:21.309
vents. And if we look at our own planet, hydrothermal

00:42:21.309 --> 00:42:23.590
vents at the bottom of the oceans, down the pitch

00:42:23.590 --> 00:42:26.349
black Mariana Trench, are teeming with life.

00:42:26.550 --> 00:42:29.789
You have entire complex ecosystems, two worms,

00:42:30.250 --> 00:42:32.809
crabs, bacteria thriving entirely on the chemical

00:42:32.809 --> 00:42:35.050
energy provided by the vents completely cut off

00:42:35.050 --> 00:42:37.489
from sunlight. This raises an important question.

00:42:37.789 --> 00:42:40.050
If life could originate and thrive at the bottom

00:42:40.050 --> 00:42:42.849
of Earth's oceans around hydrothermal vents utilizing

00:42:42.849 --> 00:42:45.710
chemosynthesis, why couldn't a similar process

00:42:45.710 --> 00:42:48.869
occur on Enceladus? And the data we have continues

00:42:48.869 --> 00:42:52.280
to get better. Just recently, based on a meticulous

00:42:52.280 --> 00:42:54.980
reanalysis of Cassini's mass spectrometer data

00:42:54.980 --> 00:42:58.099
published in late 2023, researchers discovered

00:42:58.099 --> 00:43:00.599
the definitive signature of hydrogen cyanide

00:43:00.599 --> 00:43:03.780
in the plumes. Hydrogen cyanide? That sounds

00:43:03.780 --> 00:43:05.860
terrifying. Isn't that a highly toxic poison?

00:43:06.139 --> 00:43:08.639
To biology as it currently exists on Earth, yes,

00:43:08.639 --> 00:43:11.079
it can be highly toxic. But in the context of

00:43:11.079 --> 00:43:12.860
prebiotic chemistry, the chemistry that leads

00:43:12.860 --> 00:43:15.840
to the origin of life hydrogen cyanide is a crucial,

00:43:16.059 --> 00:43:18.659
incredibly versatile building block. It readily

00:43:18.659 --> 00:43:21.739
reacts to form amino acids and nucleobases, the

00:43:21.739 --> 00:43:24.480
essential components for proteins and DNA. They

00:43:24.480 --> 00:43:26.860
also found a rich array of other complex organic

00:43:26.860 --> 00:43:29.500
molecules. As the researchers noted, these chemical

00:43:29.500 --> 00:43:31.880
compounds carry the potential energy needed to

00:43:31.880 --> 00:43:34.539
support extant microbial communities, or at the

00:43:34.539 --> 00:43:36.840
very least drive the complex organia synthesis

00:43:36.840 --> 00:43:39.119
that leads to the origin of life. So underneath

00:43:39.119 --> 00:43:43.699
that dead, bright, icy crust is a warm, pitch

00:43:43.699 --> 00:43:47.239
-black, chemically rich, salty ocean that literally

00:43:47.239 --> 00:43:49.400
contains all the ingredients we think are necessary

00:43:49.400 --> 00:43:52.900
to spark life. Energy, liquid water, and organics.

00:43:53.039 --> 00:43:56.280
That is profound. Enceladus went from being a

00:43:56.280 --> 00:43:58.639
boring ice ball on a list of secondary targets

00:43:58.639 --> 00:44:00.760
to becoming the prime real estate in the search

00:44:00.760 --> 00:44:02.679
for extraterrestrial life in our solar system.

00:44:02.920 --> 00:44:05.360
It is a stunning transformation of our understanding,

00:44:05.460 --> 00:44:07.880
and ironically, it was the discovery of these

00:44:07.880 --> 00:44:10.199
incredibly habitable conditions that ultimately

00:44:10.199 --> 00:44:12.440
signed Cassini's death warrant. Which brings

00:44:12.440 --> 00:44:14.599
us to the final act of this incredible saga,

00:44:14.920 --> 00:44:17.860
the cultural impact and the grand finale. But

00:44:17.860 --> 00:44:19.679
before we get to the fiery end, we have to talk

00:44:19.679 --> 00:44:21.780
about a moment that really captured the public's

00:44:21.780 --> 00:44:25.760
imagination. July 19, 2013, a day known as the

00:44:25.760 --> 00:44:28.300
day the Earth smiled. This was a brilliant public

00:44:28.300 --> 00:44:30.260
engagement event orchestrated by the Cassini

00:44:30.260 --> 00:44:33.460
imaging team, specifically led by planetary scientist

00:44:33.460 --> 00:44:36.679
Carolyn Porco. Because Cassini was orbiting far

00:44:36.679 --> 00:44:39.179
out at Saturn, it occasionally passed directly

00:44:39.179 --> 00:44:43.119
into Saturn's shadow, eclipsing the Sun. By positioning

00:44:43.119 --> 00:44:45.559
the spacecraft in the shatter of the giant planet,

00:44:45.940 --> 00:44:48.019
the sensitive cameras were shielded from the

00:44:48.019 --> 00:44:51.400
blinding glare of the Sun. From this unique vantage

00:44:51.400 --> 00:44:54.179
point, Cassini took a sprawling multi -image

00:44:54.179 --> 00:44:57.320
natural light portrait of the entire Saturn system.

00:44:57.519 --> 00:45:00.280
A family photo. It's great. The mosaic showed

00:45:00.280 --> 00:45:03.079
the massive planet, the intricately backlit rings

00:45:03.079 --> 00:45:05.260
glowing with scattered light, and several of

00:45:05.260 --> 00:45:07.679
the moons. But off in the distance, captured

00:45:07.679 --> 00:45:09.940
in the lower right of the frame, was a tiny pale

00:45:09.940 --> 00:45:12.579
blue dot. Earth, just a pixel of light suspended

00:45:12.579 --> 00:45:15.019
in the blackness. Yes. But what made this image

00:45:15.019 --> 00:45:17.400
uniquely powerful was that NASA notified the

00:45:17.400 --> 00:45:19.920
public well in advance. They told people all

00:45:19.920 --> 00:45:21.800
around the world to go outside at a specific

00:45:21.800 --> 00:45:23.960
time, look up at the sky in the direction of

00:45:23.960 --> 00:45:26.679
Saturn, smile and wave, knowing with absolute

00:45:26.679 --> 00:45:29.420
certainty that a robotic emissary a billion miles

00:45:29.420 --> 00:45:32.219
away was actively taking their picture. So what

00:45:32.219 --> 00:45:35.159
does this all mean? To me, it was this incredible

00:45:35.159 --> 00:45:38.650
fleeting moment of global unity. For 15 minutes,

00:45:38.989 --> 00:45:40.829
people all over the Earth stopped what they were

00:45:40.829 --> 00:45:43.750
doing, ignored their terrestrial problems, and

00:45:43.750 --> 00:45:45.610
thought about their place in the massive cosmic

00:45:45.610 --> 00:45:48.610
void. It was an orchestrated moment of planetary

00:45:48.610 --> 00:45:51.730
self -reflection facilitated by a robot. It's

00:45:51.730 --> 00:45:54.570
beautiful. But as we know, robots run on fuel.

00:45:54.800 --> 00:45:58.360
And by 2017, Cassini's fuel tanks, the hydrazine

00:45:58.360 --> 00:46:00.440
used for its maneuvering thrusters to keep its

00:46:00.440 --> 00:46:02.280
antenna pointed at Earth and adjust its orbit,

00:46:02.639 --> 00:46:04.800
were finally running dry. And this is where the

00:46:04.800 --> 00:46:06.880
strict rules of planetary protection come into

00:46:06.880 --> 00:46:09.780
play. Because Cassini had proven that Enceladus

00:46:09.780 --> 00:46:11.900
and Titan are dynamic environments that could

00:46:11.900 --> 00:46:15.019
potentially harbor life, astrobiologists mandate

00:46:15.019 --> 00:46:17.760
that we cannot risk contaminating them. Even

00:46:17.760 --> 00:46:19.800
after spending two decades bathed in the harsh

00:46:19.800 --> 00:46:22.360
vacuum and radiation of deep space, there remains

00:46:22.360 --> 00:46:25.739
a minuscule non -zero chance that hardy microbial

00:46:25.739 --> 00:46:27.579
spores from Earth's stowaways from the cleanroom

00:46:27.579 --> 00:46:29.719
in Florida where the probe was assembled might

00:46:29.719 --> 00:46:31.800
still be dormant inside the warm interior of

00:46:31.800 --> 00:46:35.429
the spacecraft. Right. Because if a dead, unpowered

00:46:35.429 --> 00:46:37.690
Cassini eventually lost its orbit years from

00:46:37.690 --> 00:46:40.650
now, it could randomly crash into Enceladus,

00:46:40.949 --> 00:46:43.369
fracturing the ice and plunging into that pristine

00:46:43.369 --> 00:46:45.550
ocean. If that happened, we could accidentally

00:46:45.550 --> 00:46:48.570
introduce highly resilient, invasive Earth bacteria

00:46:48.570 --> 00:46:52.670
into a pristine alien ecosystem. If we later

00:46:52.670 --> 00:46:55.289
sent a mission to Enceladus and discovered microbial

00:46:55.289 --> 00:46:57.550
life, we would never be able to definitively

00:46:57.550 --> 00:47:00.670
prove if it was a true alien genesis or just

00:47:00.670 --> 00:47:02.750
the descendants of a terrestrial microbe that

00:47:02.750 --> 00:47:05.030
hitched a ride on Cassini. It would ruin everything.

00:47:05.309 --> 00:47:07.750
Exactly. The scientific integrity of the entire

00:47:07.750 --> 00:47:10.710
solar system was at stake. To prevent that contamination

00:47:10.710 --> 00:47:13.530
scenario, NASA made the hard but scientifically

00:47:13.530 --> 00:47:16.389
responsible decision to safely dispose of the

00:47:16.389 --> 00:47:19.110
spacecraft by deliberately plunging it into Saturn's

00:47:19.110 --> 00:47:21.000
crushing atmosphere. But they didn't just pointed

00:47:21.000 --> 00:47:23.639
at the planet and hit the gas, they wrung every

00:47:23.639 --> 00:47:26.559
last drop of scientific data out of it in a daring

00:47:26.559 --> 00:47:29.559
month -long phase called the Grand Finale. Beginning

00:47:29.559 --> 00:47:33.380
in April 2017, the navigation team used one final,

00:47:33.619 --> 00:47:36.159
precisely calculated gravity assist from Titan

00:47:36.159 --> 00:47:39.480
to alter Cassini's orbit one last time. This

00:47:39.480 --> 00:47:41.840
put the spacecraft on a ballistic projectory

00:47:41.840 --> 00:47:44.199
to dive repeatedly through an incredibly narrow

00:47:44.199 --> 00:47:48.239
gap only about 1900 miles wide between Saturn's

00:47:48.239 --> 00:47:50.860
upper cloud tops and the inner edge of its innermost

00:47:50.860 --> 00:47:54.289
D ring. A gap no spacecraft had ever flown through.

00:47:54.650 --> 00:47:57.289
It's threading a cosmic needle at thousands of

00:47:57.289 --> 00:47:59.650
miles per hour. And it didn't just do it once.

00:47:59.929 --> 00:48:03.769
It made 22 daring proximal orbits diving through

00:48:03.769 --> 00:48:06.190
that gap over and over. They were mapping the

00:48:06.190 --> 00:48:08.809
gravity field to unprecedented resolution, measuring

00:48:08.809 --> 00:48:11.289
the mass of the rings directly and taking ridiculously

00:48:11.289 --> 00:48:13.510
close images of the swirling clouds and auroras

00:48:13.510 --> 00:48:16.070
at the poles. It was the definition of high risk,

00:48:16.230 --> 00:48:18.769
high reward science. If a stray piece of ice

00:48:18.769 --> 00:48:21.030
or rock from the inner ring had clipped the spacecraft,

00:48:20.969 --> 00:48:23.170
during those high -speed passes, it could have

00:48:23.170 --> 00:48:25.409
been destroyed prematurely. But it survived all

00:48:25.409 --> 00:48:28.710
22 dives flawlessly. And then came the 23rd orbit.

00:48:29.130 --> 00:48:32.230
On September 15, 2017, Cassini's orbit finally

00:48:32.230 --> 00:48:34.170
intersected directly with the thickening upper

00:48:34.170 --> 00:48:36.289
atmosphere of Saturn. I remember watching this

00:48:36.289 --> 00:48:39.949
live on NASA TV. The emotional bond humans form

00:48:39.949 --> 00:48:43.110
with the machines we send into the dark is so

00:48:43.110 --> 00:48:46.650
remarkably profound. NASA actually won an Emmy

00:48:46.650 --> 00:48:49.170
Award for their multi -platform presentation

00:48:49.170 --> 00:48:52.030
of the grand finale. The control room was packed

00:48:52.030 --> 00:48:54.309
with scientists who had spent their entire careers

00:48:54.309 --> 00:48:57.349
working on this one machine. It really felt like

00:48:57.349 --> 00:49:00.030
watching the loss of a devoted old friend. The

00:49:00.030 --> 00:49:02.409
final seconds of the mission were a final testament

00:49:02.409 --> 00:49:05.010
to the sheer resilience of the engineering. As

00:49:05.010 --> 00:49:07.190
Cassini plunged into the upper atmosphere at

00:49:07.190 --> 00:49:09.989
meteoric speeds, atmospheric drag began to aggressively

00:49:09.989 --> 00:49:12.570
twist and tumble the spacecraft. But Cassini

00:49:12.570 --> 00:49:15.199
was programmed to fight. It fired its maneuvering

00:49:15.199 --> 00:49:18.179
thrusters at a 100 % capacity, fearfully battling

00:49:18.179 --> 00:49:20.440
the aerodynamic forces to keep its high -gain

00:49:20.440 --> 00:49:22.840
antenna pointed precisely at Earth. It was fighting

00:49:22.840 --> 00:49:24.980
to survive just long enough to send the last

00:49:24.980 --> 00:49:27.619
bits of data. It was using its mass spectrometer

00:49:27.619 --> 00:49:30.099
to literally taste the atmosphere of Saturn and

00:49:30.099 --> 00:49:32.599
stream that data back in real time. It fought

00:49:32.599 --> 00:49:34.699
the atmosphere for about 30 seconds longer than

00:49:34.699 --> 00:49:37.239
the aerodynamic models predicted. But eventually,

00:49:37.400 --> 00:49:39.559
the atmospheric friction and density were simply

00:49:39.559 --> 00:49:41.920
too great. The thrusters couldn't compensate,

00:49:42.280 --> 00:49:44.219
the spacecraft tumbled, the antenna pointed away

00:49:44.219 --> 00:49:46.280
from Earth, and the signal telemetry abruptly

00:49:46.280 --> 00:49:50.840
flatlined at 11 .55 .46 UTC. About 45 seconds

00:49:50.840 --> 00:49:52.880
later, the immense heat and pressure vaporized

00:49:52.880 --> 00:49:55.659
the spacecraft completely. Cassini was disassembled

00:49:55.659 --> 00:49:58.079
atom by atom, becoming a permanent part of the

00:49:58.079 --> 00:50:01.769
giant planet it had studied for 13 years. setting

00:50:01.769 --> 00:50:03.889
us postcards right up to the very last second.

00:50:04.289 --> 00:50:06.710
What a staggeringly epic journey. Let's look

00:50:06.710 --> 00:50:09.190
back at what this machine accomplished. From

00:50:09.190 --> 00:50:11.369
a controversial launch hampered by geopolitical

00:50:11.369 --> 00:50:14.230
tension and environmental protests to an epic

00:50:14.230 --> 00:50:17.630
multi -year cruise past Venus, Earth, and Jupiter.

00:50:17.949 --> 00:50:20.949
It arrived at Saturn and unveiled the complex

00:50:20.949 --> 00:50:23.769
mysteries of a dynamic rings giant. It dropped

00:50:23.769 --> 00:50:26.670
a European probe onto a moon that rains gasoline,

00:50:27.289 --> 00:50:29.849
and it discovered a hidden global ocean that

00:50:29.849 --> 00:50:32.409
just might harbor the ingredients for extraterrestrial

00:50:32.409 --> 00:50:35.239
life. Cassini -Huygens didn't just add a few

00:50:35.239 --> 00:50:37.039
footnotes to our textbooks. It fundamentally

00:50:37.039 --> 00:50:39.139
rewrote our understanding of planetary science.

00:50:39.579 --> 00:50:41.380
It expanded our understanding of our place in

00:50:41.380 --> 00:50:43.780
the cosmos in ways we never could have anticipated

00:50:43.780 --> 00:50:46.480
when it launched in the 90s. It leaves an absolutely

00:50:46.480 --> 00:50:49.679
indelible mark on human history. But as we reflect

00:50:49.679 --> 00:50:52.420
on this immense legacy, the mission's dramatic

00:50:52.420 --> 00:50:55.260
end leaves us with a profound paradox based on

00:50:55.260 --> 00:50:57.780
these intertwined themes of discovery and planetary

00:50:57.780 --> 00:51:00.639
protection. Cassini was intentionally destroyed

00:51:00.639 --> 00:51:04.070
to protect the pristine potential habitable environments

00:51:04.070 --> 00:51:06.429
of Enceladus and Titan from our own microbes.

00:51:07.070 --> 00:51:09.650
But as we design future robotic missions to literally

00:51:09.650 --> 00:51:12.989
land on these icy worlds, to perhaps drill or

00:51:12.989 --> 00:51:15.090
melt through their frozen crusts, to directly

00:51:15.090 --> 00:51:17.250
sample the oceans and search for the life we

00:51:17.250 --> 00:51:20.469
suspect is there, how do we observe a fragile

00:51:20.469 --> 00:51:23.030
alien ecosystem without fundamentally altering

00:51:23.030 --> 00:51:26.239
it? Are we destined by our very nature as explorers

00:51:26.239 --> 00:51:28.619
to contaminate the very genesis we are trying

00:51:28.619 --> 00:51:31.659
to discover? It's the ultimate paradox of exploration.

00:51:32.219 --> 00:51:33.900
Something for you to ponder the next time you

00:51:33.900 --> 00:51:36.400
look up at the night sky and spot that pale yellow

00:51:36.400 --> 00:51:39.760
point of light wandering through the stars. That's

00:51:39.760 --> 00:51:41.820
our deep dive for today. Thank you so much for

00:51:41.820 --> 00:51:43.699
joining us on this incredible, expansive journey

00:51:43.699 --> 00:51:45.719
to the outer edges of the solar system. Keep

00:51:45.719 --> 00:51:47.559
wandering, keep looking up, and we will catch

00:51:47.559 --> 00:51:48.659
you on the next deep dive.