The Planets: Ice Worlds

Transcript

The Planets: Ice Worlds

PBS Airdate: August 14, 2019

NARRATOR: From the comfort of our home world, bathed in the warm light of our life-giving star…

…we’ve set out to explore every one of the planets. We’ve pushed further into the dark of space. But after decades of exploration, just two probes have explored the most inhospitable and distant reaches of the solar system’s strangest realm…

DERRICK H. PITTS (The Franklin Institute): This is a region of the solar system that we really had very little information about.

NARRATOR: …their instruments waking up to find astonishing vistas, unlike anything encountered before…

LEIGH FLETCHER (University of Leicester): It’s at that moment you realize you’re looking at something that’s very different.

NARRATOR: …places where all the rules are broken…

FRAN BAGENAL (University of Colorado): This was a really strange system. So why is Uranus so tipped on its side?

NARRATOR: …where everything we thought we knew is being rewritten.

NOAH HAMMOND (University of Toronto): Geysers like this one even exist on Triton, where it’s 30 times farther from the sun.

NARRATOR: Incredibly, we have pushed the frontier all the way to the solar system’s most distant outpost, Pluto.

ALAN STERN (Principal Investigator, New Horizons): Small planets should be simpler, and they should run out of energy in their internal engines and stop evolving, like the moon did billions of years ago. Pluto didn’t read any of those textbooks.

NARRATOR: The Planets: Ice Worlds, right now, on NOVA.

NARRATOR: Far, far away, beyond Mars, past the storms of Jupiter and the rings of Saturn, where the distance from the sun is measured not in millions but billions of miles, lies a region unlike anywhere else in the solar system. Out here, the planets are utterly bizarre, even unnerving.

DAVID GRINSPOON (Planetary Science Institute): Uranus is an oddity, even in a solar system of oddities.

NARRATOR: Temperatures approach absolute zero, at which everything grinds to a halt. Yet somehow, the worlds here are still teeming with activity.

FRAN BAGENAL: Neptune was a great excitement; all sorts of strange things going on.

NARRATOR: A place where cold doesn’t always mean frozen…

LEIGH FLETCHER: It’s at that moment you realize you’re looking at something that’s very different.

NARRATOR: …and even deeper into the darkness, past where the planets end, a vast expanse scattered with mysterious bodies awaits.

HAL WEAVER (Project Scientist, New Horizons): Our jaws just dropped to the floor.

DERRICK PITTS: If ever there were an object that turned out to be far more surprising than we ever would have imagined, that’s Pluto.

NARRATOR: There is no part of the solar system more puzzling. This is the realm of the ice worlds.

VOYAGER MISSION CONTROL ROOM: Sixty seconds. All continuing to go well.

NARRATOR: Travelling to the most distant planets, Uranus and Neptune, is so hard, we’ve only managed it once.

PROJECT VOYAGER TO THE GIANT PLANETS

VOYAGER MISSION CONTROL ROOM: We have ignition, and we have liftoff.

VOYAGER 2

1977

NARRATOR: This first mission to the farthest part of the solar system is only possible thanks to some help from the worlds closer to the sun…

BUILT TO EXPLORE THE

OUTER SOLAR SYSTEM

VOYAGER MISSION CONTROL ROOM: Twenty-five seconds into the launch. All continuing to go well.

NARRATOR: …making the most of a rare planetary alignment.

DAVID GRINSPOON: People realized that there was an opportunity coming up in the 1970s, that only comes up every couple of hundred years, where the planets in their orbits kind of line up in just the right way, so that you can slingshot from one to the next.

VOYAGER MISSION CONTROL ROOM: The data coming back shows that we’re right on the money.

WILLIAM MCKINNON (Co-Investigator, New Horizons): The key idea here is that you could use the gravity of each planet to accelerate the spacecraft, speed it up, and shorten the trip time.

NARRATOR: If it works, this series of planetary boosts will help Voyager cross nearly 900-million additional miles of space before reaching the first of the ice worlds.

DERRICK PITTS: This is a region of the solar system that we really had very little information about.

FRAN BAGENEL: We had excellent cameras and sensors and so on, and we used that to go out into the solar system and see things, for the first time, we had never seen before.

NARRATOR: Almost nine years into its mission, Voyager begins its approach to an entirely unexplored planet and reveals a world weirder than we had ever imagined…

URANUS

1.8 BILLION MILES FROM THE SUN

NARRATOR: …a vast ball of gas, 14 times the mass of Earth and four times its diameter. Sensors detect an atmosphere of 83 percent hydrogen and 15 percent helium. But it’s the 2.3 percent methane that, by absorbing red light and reflecting blue, lends Uranus its color.

DAVID GRINSPOON: …just this giant, pretty much featureless blue-green ball. It seemed unreal.

LEIGH FLETCHER: They could see none of the activity that you’re familiar with on Jupiter. And it’s at that moment you realize you’re looking at something that’s very different.

FRAN BAGENAL: Poor Uranus. It has got rather boring clouds, truth be told, so there wasn’t a lot to see with the cameras.

NARRATOR: Uranus spins on its axis once every 17 hours, which should generate dramatic storms, so why is it so featureless? Voyager detects a clue.

-371 DEGREES FAHRENHEIT

NARRATOR: Temperatures here are the coldest of any planet in the solar system. There’s simply not enough heat to drive the storms seen on Jupiter and Saturn. Uranus is an entirely new class of planet, an “Ice Giant.”

And more surprises are to come. Uranus has rings.

FRAN BAGENAL: We knew, long ago, from telescopic observations, the rings were there at Uranus; we didn’t know their configuration or their shape.

NARRATOR: Voyager begins to explore the ring system and spots something curious in the shadows. Two moons, Cordelia, on the inner edge of the brightest ring, and Ophelia, on the outer edge, helped to organize the system.

CORDELIA

OPHELIA

LEIGH FLETCHER: Particles within the rings can be moved inwards or outwards, as these tiny objects, called “shepherd moons,” whose gravitational force can shape and sculpt the rings themselves.

NARRATOR: But it’s the orientation of the orbits of these moons and the rings themselves that singles out Uranus as the strangest of worlds.

LEIGH FLETCHER: Uranus looks bizarre. The rings, rather than looking like that, when you look through a telescope, they’re actually orbiting up and over the top of the planet. The whole thing is tipped, like a spinning top.

NARRATOR: A bizarre orientation that hints at an unusual past.

THE SOLAR SYSTEM

4.6 BILLION YEARS AGO

NARRATOR: Since the beginning, everything in the solar system has been circling in the same direction. It begins with the vast cloud of material that orbits the young sun. Over time, the material draws together, forming each of the planets. Today, they all orbit the sun and spin on their axes in the same counterclockwise direction as that primordial cloud, except for Venus and Uranus, which spin in the opposite direction. But Uranus is even stranger because the entire planet is on its side.

FRAN BAGENAL: This was a really strange system. So why is Uranus so tipped on its side?

DAVID GRINSPOON: If a roughly Earth-sized object smashed into Uranus late in its formation history, then that would’ve had the proper amount of momentum to, basically, knock it on its side.

NARRATOR: Not only did the collision tip the planet over, but it may also help to explain another of Uranus’ mysteries: why the planet is so cold.

LEIGH FLETCHER: That impact presumably relinquished all of that internal energy that the planet had when it first formed and has left it as a relatively dead and sluggish world.

NARRATOR: We learned so much during this brief encounter, but Uranus still holds many mysteries.

And Voyager’s strangest discoveries are yet to come. After Uranus, it must cover another billion miles of empty space before it will see another world.

DAVID GRINSPOON: We can say the numbers, but can we really wrap our heads around something that large? In order to help ourselves do this, we can make scale models.

NARRATOR: At the center of the solar system is our sun, a ball of fire 850,000 miles in diameter. But if we scale the whole system down by a factor of 600-million, the sun becomes the size of this light. And walking out, you pass all the rocky inner worlds within the first 500 yards.

MERCURY

VENUS

EARTH

MARS

NARRATOR: But to get to the outer solar system, is far harder.

SUN

MERCURY

VENUS

EARTH

MARS

NARRATOR: On our scale, we have to cross the harbor to reach the next planet, nearly a mile away.

JUPITER

SUN

DAVID GRINSPOON: And we’ve reached the orbit of Jupiter, the largest of the planets and the first of the gas giants.

NARRATOR: Even farther, at almost twice the distance from the sun as Jupiter, we reach Saturn.

SATURN

JUPITER

DAVID GRINSPOON: Now, as we approach Saturn, the light is getting noticeably dimmer. And yet, from Earth, we still see it, because it’s a big bright planet, and it’s surrounded by those bright, reflective rings that act as a mirror, sending so much light back towards us.

NARRATOR: Beyond here, the planets are separated by hundreds of millions of miles of dark empty space. Now, we are three miles from our model sun.

DAVID GRINSPOON: We’re reaching the orbit of Uranus, twice again as far from the sun as Saturn.

URANUS

DAVID GRINSPOON: Out here, at Uranus, there’s only about .2 percent of the light that we get at Earth from the sun.

NARRATOR: Heading out into the dark, 1.7-billion miles from the sun…

NEPTUNE

NARRATOR: …and we begin to fully understand the distances Voyager faces on its journey to the farthest reaches of the solar system.

DAVID GRINSPOON: Now, finally, we’ve reached the realm of Neptune, the outermost of the giant planets. Back there, on that little island, where Earth and the other planets are basking in the warmth and the glow of the nearby sun, it feels as though we’ve come quite a long way.

NARRATOR: In 1989, after 12 long years, Voyager finally crosses the great expanse of space between Earth and its most distant planned objective…

SCIENTISTS AT VOYAGER MISSION CONTROL: Ooh! Aah!

NEPTUNE

2.8 BILLION MILES FROM THE SUN

NARRATOR: …Neptune, an ice giant, 17 times the mass of Earth. A billion miles farther from the sun than Uranus, Neptune is almost chemically identical.

80% HYDROGEN

19% HELIUM

1.5% METHANE

NARRATOR: Yet, bizarrely, it couldn’t be more different.

DAVID GRINSPOON: Neptune, in a way, was almost a relief, because it wasn’t featureless, you know? It was like, “Oh, good! A planet with clouds and features again.”

FRAN BAGENAL: Neptune was a great excitement. It’s got swirling clouds, really strong winds: at 1,500 miles an hour, incredibly fast, the fastest winds that we’ve got in the solar system.

LEIGH FLETCHER: One of the things that Voyager discovered was an immense dark vortex within the atmosphere, a huge swirling dark spot.

SOUTHERN HEMISPHERE

GREAT DARK SPOT

DAVID GRINSPOON: We say it’s a “giant storm,” but just those words don’t fully contain…we’re talking about a storm the size of a planet Earth or larger.

NARRATOR: And the surprises keep coming. Even though it’s much further out, Voyager discovers Neptune is warmer than Uranus. It emits two and a half times the amount of heat it receives from the sun.

AVERAGE TEMPERATURE -353 DEGREES FAHRENHEIT

NARRATOR: And the source of the heat is another oddity of this strange planet.

DERRICK PITS: In fact, when we look at this dynamic activity in these extraordinarily cold regions, we really are at a loss to understand just what’s going on here.

NARRATOR: One theory is that the buildup of pressure beneath the thick layers of cloud turns the carbon in the methane into a rain made of diamonds; they then melt as they fall into the interior of the planet, producing the extra heat.

As the heat makes its way out into the frozen cold of space, it churns the entire atmosphere, whipping up winds around the globe.

LEIGH FLETCHER: There are no mountain ranges, no valleys, no continental boundaries to get in the way of the perfect fluid dynamical flows. What that means is that when you start a weather pattern going, when you start a vortex spinning or you start a plume rising, there’s very little to get in the way of it.

FRAN BAGENAL: So, those winds that develop and go around, they just keep going around and around. There is nothing to slow them down, no friction with the surface.

NARRATOR: And the extreme cold here makes the atmosphere less viscous, allowing the gases to move faster, creating supersonic winds that outpace anything seen on Jupiter or Saturn.

Voyager 2 has almost completed its grand tour, but the spacecraft’s visit to Neptune includes an encounter with another puzzling world.

TRITON

LARGEST OF NEPTUNE’S 14 KNOWN MOONS

NARRATOR: Roughly the size of our own moon, but scarred by deep cracks and pits, Triton is covered by a sheen of icy nitrogen. We expected it to be a frozen, silent world, but one incredible image that Voyager sends back contains something entirely unexpected. Here, nearly three-billion miles from the sun, huge geysers erupt nearly five miles into space.

NOAH HAMMOND: Geysers like this one even exist on Triton, where it’s 30 times farther from the sun and it is so cold, yet you still have this intense geologic activity going on.

NARRATOR: At -391 degrees Fahrenheit, Voyager found Triton to be one of the coldest places in the solar system. So, what could be causing these eruptions to burst from the frozen depths?

NOAH HAMMOND: The surface of Triton is covered in a thin layer of nitrogen ice, and it is so cold on Triton that nitrogen, which is a gas on Earth, is frozen solid to the surface. But right where the sun is striking, it starts to vaporize a little bit in the sub-surface.

NARRATOR: As weak sunlight passes through the nitrogen ice surface, it heats up a layer of darker particles several feet below. And in some spots that heat is just enough to vaporize the frozen nitrogen.

NOAH HAMMOND: A lot of gas builds up, and then it bursts through and creates a geyser that goes 8,000 meters into the sky.

NARRATOR: But, although the faint light of the sun is just strong enough to power Triton’s geysers, it is likely too weak to explain the cracks and pits elsewhere on the surface, rugged features that cover half the moon. What caused them is thought to be linked to Triton’s odd path around Neptune.

NOAH HAMMOND: Its orbit is really unusual. It orbits in the opposite direction that the planet spins. Now, most moons orbit in the same direction that the planet spins, because we think most moons form at the same time as the planet in a disk of material around the planet. And since Triton is going the opposite way, we think it must have formed in a different way.

OUTER REACHES

OF THE SOLAR SYSTEM

NARRATOR: One theory is that billions of years ago Triton wasn’t a moon at all. It formed way beyond Neptune, a huge wandering object that eventually ends up close enough to Neptune to be drawn in by its gravity and trapped in its unusual orbit.

NOAH HAMMOND: So, when Triton first goes into orbit around Neptune, it’s not going to be a perfectly circular orbit. We expect it to be highly eccentric, where it’s getting closer to and further from Neptune. And when that happens, Triton is going to get stretched and squeezed by the immense changes in gravity as it moves in and out. And that stretching and squeezing is going to put an intense amount of heat into Triton.

NARRATOR: The ancient molten interior then explodes up through faults in the moon’s crust. Over time, Triton’s orbit becomes more and more circular. No longer stretched and squeezed, the moon cools, leaving the rugged surface we see today.

As it leaves Triton and Neptune behind, Voyager’s mission is over. It will never encounter another planet. But as it heads out of our solar system to the ocean of stars beyond, it carries with it an interstellar “message in a bottle,” should it ever encounter something or someone else.

ARCHIVE: These unique disks contain photographs of everyday life as well as voices, the music of Beethoven and Chuck Berry, a baby crying and a heartbeat.

NARRATOR: On its lonely journey into darkness, Voyager passes through an unknown region of space that in just a few years will be described for the first time.

ALAN STERN: The discovery of the Kuiper Belt, in the 1990s, is probably the single most important discovery of the space age. It completely changed everything. It was as if we had a map of the earth without the Pacific Ocean on it, because we didn’t know it was there.

NARRATOR: The Kuiper Belt is the remotest part of the solar system. Here, trillions of frozen lumps of water, ammonia and methane circle the distant sun.

HAL WEAVER: The Kuiper Belt is what we call the third zone of the solar system. This is what we think is the most primitive region, a zone of icy objects beyond Neptune’s orbit.

PLUTO

HUBBLE SPACE TELESCOPE

NARRATOR: Incredibly, by the early 2000s, our telescopes become powerful enough for us to just make out these unbelievably distant objects.

QUAOAR DISCOVERED 2002

SEDNA DISCOVERED 2003

HAUMEA DISCOVERED 2003

MAKEMAKE DISCOVERED 2005

ALAN STERN: We found Sedna and Eris, Makemake and Haumea and Ixion and more.

HAL WEAVER: We now know of more than 2,000, you know, Kuiper Belt objects.

NARRATOR: This is the solar system’s new frontier. And in 2006, a new probe is primed to leave Earth on a mission to explore it.

NEW HORIZONS MISSION CONTROL: Five, four, three, two, one, we have ignition, and liftoff…

NEW HORIZONS 2006

NEW HORIZONS MISSION CONTROL: …of NASA’s New Horizons spacecraft, on a decade long voyage to visit the planet Pluto and then beyond.

DAVID GRINSPOON: It just shoots up so fast. It’s the fastest launch ever from Earth.

ALAN STERN: As soon as we were launched, we had to test all the backup systems and plan the most sophisticated flyby of Jupiter that had ever taken place.

NARRATOR: Even with the extra kick from Jupiter’s gravity, it will still take 10 long years to reach the Kuiper Belt.

DAVID GRINSPOON: In order to ensure that it was going to last for the decade, they built in a lot of redundancy, there were actually two of everything, computers and the guidance systems. And they figured out how to hibernate…the first spacecraft that, that hibernated.

ALAN STERN: But it had really never been done before, to put the spacecraft largely to sleep, let the spacecraft just silently coast. Then we could extend the life of the electronics. No spacecraft mission had ever really used hibernation as a day-to-day way to cross the solar system.

DAVID GRINSPOON: That was scary because you know, you turn it off, and you hope that it comes back on again.

NARRATOR: New Horizon’s first target is the Kuiper Belt’s most famous resident.

HAL WEAVER: The discovery of Pluto was back in 1930, by Clyde Tombaugh, a Kansas farm boy who was using the telescope at the Lowell observatory in Arizona.

CATHY OLKIN (Deputy Project Scientist, New Horizons): Every clear night Clyde would go out and, and take images of the sky on photographic plates. And when it was cloudy or during the day, he would compare those plates.

HAL WEAVER: When you’re looking out at the sky, how do you tell something is a star versus a planet? Well, planets actually move, relative to the stars, and that’s because they’re much closer to us than the stars. So, Clyde Tombaugh noticed that there was this little speck moving across the stars.

CATHY OLKIN: And then Clyde Tombaugh discovered Pluto.

NARRATOR: It is crowned the ninth planet, a title Pluto enjoys for 76 years. But while New Horizons continues its decade-long voyage, a debate rages back on Earth, one that will challenge Pluto’s very status as a planet.

DAVID GRINSPOON: According to the International Astronomical Union, a planet has to be orbiting the sun.

NOAH HAMMOND: It needs to be large enough and massive enough that its gravity can pull itself into spherical shape.

DAVID GRINSPOON: And it has to have cleared its zone, meaning that it is sort of a gravitational bully of its, of its own realm.

NARRATOR: The problem is Pluto’s region of the Kuiper Belt is packed with hundreds of icy objects.

NOAH HAMMOND: Pluto doesn’t meet the criteria for being a planet, because it hasn’t cleared its orbit.

DAVID GRINSPOON: By that definition, Pluto clearly belongs to a different sort of grouping.

NARRATOR: Pluto is now classified as a “dwarf planet,” along with the other larger worlds of the Kuiper Belt. But the debate still continues.

DAVID GRINSPOON: But I think planetary scientists really never stopped calling Pluto a planet.

HAL WEAVER: Pluto is what it is; it doesn’t make any difference whether we call it a planet, a full-fledged planet versus a dwarf planet.

FRAN BAGENAL: Defining them and labeling is really a side thing; it’s a periphery to the important thing, which is exploration.

CATHY OLKIN: We are searching for frequency. Stand by.

NARRATOR: After nine years of flight, NASA attempts to reawaken New Horizons from hibernation.

ALAN STERN: The first words he said were, “Alan, we have lost contact with the spacecraft.”

CATHY OLKIN: All of a sudden, I get a message that the spacecraft had shut down. I couldn’t believe it.

ALAN STERN: It was, it was heart-stopping. And here we had just days until the flyby was to begin to put Humpty Dumpty back together again.

NARRATOR: Nine years of faultless space travel would all be a waste, if New Horizons couldn’t be brought back online.

ALAN STERN: It wasn’t easy, but they pulled it off with precisely three-and-a-half hours to spare.

NEW HORIZONS MISSION CONTROL: We’re in contact.

PLUTO

3.7 BILLION MILES FROM THE SUN

NARRATOR: New Horizons gives us our first close up glimpses of the most distant world ever visited, a world that, until now, had only appeared as a fuzzy blob.

NOAH HAMMOND: We thought the surface would be geologically dead, because Pluto is so small.

EDGARD RIVERA-VALENTÍN (Lunar and Planetary Institute): When New Horizons came by and took all of these pictures, it literally broke everything we thought about it.

DAVID GRINSPOON: Pluto was a shock and a revelation, in so many ways.

DERRICK PITTS: It’s turned out to be one of the most fascinating objects in our entire solar system.

TENZING MONTES 4 MILES HIGH

HAL WEAVER: Giant water-ice mountains, as high as the Rocky Mountains in the United States…

BLADES OF ICE

TARTARUS DORSA REGION

HAL WEAVER: …bladed terrain.

MORE THAN 1,000 IMPACT CRATERS

VEGA TERRA REGION

HALO CRATERS

ED RIVERA: We are seeing ancient parts of Pluto, but also ridiculously young parts of Pluto.

NOAH HAMMOND: We even think we see dunes, which get blown around by the very thin atmosphere.

ALAN STERN: Small planets should be simpler, and they should run out of energy in their internal engines and stop evolving, like the moon did billions of years ago. Pluto didn’t read any of those textbooks.

NARRATOR: One of the most fascinating features beamed back by New Horizons is the region named after the planet’s discoverer: Tombaugh Regio.

TOMBAUGH REGIO

PLUTO’S HEART

HAL WEAVER: We got our first full frame view of Pluto and saw this this region that looked like a heart, this heart shaped region.

NARRATOR: The western lobe of the heart is called Sputnik Planitia, a giant plain of frozen nitrogen, methane and carbon monoxide that stretches for over 330,000 square miles. And at its edge lies a range of mountains made of frozen water-ice. They rise nearly four miles into the dark skies above the plain.

As odd as that is, there is something even weirder about the region.

ALAN STERN: It’s the size of the states of Texas and Oklahoma combined, and we can’t find any craters on its surface.

NOAH HAMMOND: There are almost no impact craters on this, which means something is happening on the surface.

NARRATOR: Pluto’s heart is young, fresh ice. So, what’s creating it?

BILL MCKINNON: It’s smooth, but it wasn’t completely smooth. It had this beautiful pattern of, sort of, cells or polygons.

NARRATOR: Detailed imagery beamed back by New Horizons reveals a puzzling network of hexagon and pentagon shapes that crisscross the frozen nitrogen surface.

FRAN BAGENAL: It looks like there’s material that is convecting underneath, like soup on the stove. You have these things turning over, making these shapes on the top. So, we scratched our heads and wondered what could be making this strange behavior.

NARRATOR: Our working theory is that somewhere deep in Pluto’s interior are radioactive elements that generate heat as they decay, warming up a liquid layer beneath the planet’s crust.

BILL MCKINNON: We think underneath the exotic ices on Pluto’s surface and underneath the water-ice crust, which could easily be 100 kilometers thick, that there’s actually a layer of liquid water that surrounds the rock core.

NARRATOR: This sunless ocean of water that has existed for billions of years beneath the surface of Pluto is being gently warmed by heat from the interior.

JOHN SPENCER (Deputy Project Scientist, New Horizons): That little bit of heat that’s leaking out, we think is enough to drive the convection and these exotic patterns that we see on Sputnik Planitia. And that’s because nitrogen is, it’s very soft; it doesn’t take very much heat to make it move.

NARRATOR: As the nitrogen slowly bubbles up, the area is constantly being resurfaced, scouring away any impact craters.

CATHY OLKIN: It’s warmer underneath, so then the glacial ices are upwelling in the middle and then spread out, and then down-well on the side. And that’s what make those, makes those polygonal patterns that we see on the surface. We had no idea to expect that.

NARRATOR: But why all this activity here and nowhere else? Perhaps Pluto’s heart is the site of a huge impact that long ago punched a large hole in the surface, almost down to the vast ocean beneath, a great hole that slowly filled with soft nitrogen ice and now gently churns just above a warmer ocean.

DAVID GRINSPOON: So, there’s a lot more going on on Pluto than we had ever imagined.

JOHN SPENCER: You don’t have to be a giant planet or a terrestrial planet to be an amazing place in the solar system.

ALAN STERN: It just completely changed our view of how small planets operate and how they can be as, as complex as big ones.

NARRATOR: New Horizons’ closest encounter with Pluto lasts just hours. Its fleeting visit reveals the tiny speck Clyde Tombaugh saw moving across the sky to be a dynamic, vibrant world.

But Tombaugh died nine years before New Horizons left Earth, so he never saw Pluto up close.

ALAN STERN: He had asked if a mission ever did get launched some of his ashes could be sent on the journey.

HAL WEAVER: And to think that Clyde’s ashes, you know, flew by Pluto, and you know he was finally visiting the place that he discovered, that was pretty cool.

NARRATOR: And Pluto holds a final surprise. As New Horizons turns its camera back for one last look, it captures an image of Pluto’s atmosphere glowing in the dark.

ALAN STERN: There is the blue ring of its atmosphere looking hauntingly familiar, like the earth’s atmosphere.

DERRICK PITTS: Not only can we see a number of layers in the atmosphere, but we can also see mountains on the surface of the planet, sticking up into that atmosphere.

NARRATOR: A thin blue sky over a hidden ocean of water, three-billion miles from Earth.

CATHY OLKIN: That image just epitomized everything we had done.

ALAN STERN: That’s my favorite picture from the entire flyby. And I took to saying that the solar system had saved the best for last.

NARRATOR: But New Horizons isn’t done. It expands its exploration of the Kuiper Belt by continuing on, towards a new target.

DERRICK PITTS: This was an opportunity for the New Horizons spacecraft to now look at a different object out in the Kuiper Belt, something that might be much more typical of what could be found out in this region.

ULTIMA THULE

19 MILES LONG

NARRATOR: On January 1st, 2019, it beamed back pictures of the most distant object ever visited…

HAL WEAVER: This object may be the most primitive object every encountered by a spacecraft.

NARRATOR: …two icy rocks frozen in the moment of collision...

HAL WEAVER: By looking at Ultima Thule today, we think we’re looking back in time to the origin of the solar system.

NARRATOR: …a window into the processes that created the solar system that we call home. New Horizons gives us a glimpse of our own origins, before it follows Voyager on an eternal journey out into the stars.

Just six decades ago, we left the earth for the first time. Since then, we’ve gone on to explore the whole expanse of the solar system. With each flight, curiosity has driven us further.

ED RIVERA: For us to continue doing something that is very natural and intrinsic to all of us, and that is answering the big questions and exploring the unknown.

NARRATOR: And as our technology has evolved, each encounter has taken us closer.

BILL MCKINNON: I think exploring the planets is just, it’s a great adventure that we can all participate in.

NARRATOR: We’ve landed robotic explorers on Mars, Venus and even a distant moon of Saturn.

DAVID GRINSPOON: I feel as though we’re absolutely just at the beginning of planetary exploration.

NARRATOR: These first steps have only scratched the surface, but they reveal a solar system of limitless wonder and beauty…

DERRICK PITTS: There’s still more for us to discover. There’s still more surprises out there.

CATHY OLKIN: There is a lot of exploration left for us.

NARRATOR: …as we continue to push farther and stay longer in our quest to piece together one of the greatest stories ever told: the story of the planets.

Broadcast Credits

PRODUCED AND DIRECTED BY

Martin Johnson

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Kimberley Bartholomew

DIRECTOR OF PHOTOGRAPHY

Tom Hayward

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Fran Bagenal, Leigh Fletcher, David Grinspoon, Noah Hammond, William McKinnon, Cathy Olkin, Derrick Pitts, Edgard Rivera-Valentín, John Spencer, Alan Stern, Hal Weaver

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