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NARRATOR:
Our solar system is filled
with mysterious worlds...

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...wandering between
and beyond the planets.

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(collision pounds)

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MALENA RICE:
The objects that lie
between the planets

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are actually the key
to understanding

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how our solar system formed.

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NARRATOR:
Imposters, and oddballs,

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rewriting our understanding
of our place in space.

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JESSICA SUNSHINE:
It is two pieces
that are stuck together.

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It was really quite remarkable.

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(explodes)

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QUEENIE HOI SHAN CHAN:
It is possible that after
30 million years,

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Mars might have a ring
of its own.

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♪ ♪

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NARRATOR:
Studying these wandering worlds

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allows scientists to explore
regions of the solar system

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we have no chance of visiting.

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WANDA DÍAZ MERCED:
I cannot go to
the asteroid belt,

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so when a meteorite
lands on Earth,

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we will have a chunk of history
right in our hands.

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ASHLEY KING:
The Winchcombe meteorite

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was like a little treasure box
for planetary scientists.

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(geyser bursts)

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NARRATOR:
And the misfits
of our solar system

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are full of surprises.

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VERONICA BRAY DURFEY:
There are many, many worlds
out there

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that we are yet to discover

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and that we haven't
even imagined yet.

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SCOTT SHEPPARD:
It's like a box of chocolates.

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You never know what you're
gonna get in our images.

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This model of the solar system,

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it's missing all
of the most interesting bits.

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NARRATOR:
What secrets do
these wandering worlds

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reveal about our solar system?

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And what else
is lurking out there

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in the dark?

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(bursting)

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"Solar System:
Wandering Worlds,"

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right now on "NOVA."

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♪ ♪

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♪ ♪

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NARRATOR:
There's something out there
in the darkness.

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We don't know for sure
where it came from

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or how long it's been there.

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But we know it's not alone.

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It was discovered in 2018.

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A world with no official name.

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So distant,
it has been called simply

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FarFarOut.

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SHEPPARD:
FarFarOut,

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as its name implies, is very
far away.

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So, it's just a, a very faint
point of light

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that, uh, we discovered

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with one of the largest
telescopes in the world.

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JANE LUU:
Its notoriety
comes from the fact

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that it's
the most distant object

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that we have found
in the solar system.

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SHEPPARD:
And the big question is,
what do we call the next one?

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Do we just add another "far"
or not?

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LUU:
"ExtremelyFarOut,"
and then "StupendouslyFarOut,"

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and it just keeps going.
(laughs)

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♪ ♪

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NARRATOR:
12 billion miles from the sun,

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FarFarOut is not alone.

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Out here, there could be
countless other worlds

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yet to be discovered,

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wandering in the dark.

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Even closer to home,
we are only just beginning

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to explore the vast spaces
between the planets.

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Home to a myriad of worlds,

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many too small or too dark
to see.

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NANCY CHABOT:
When we think about
our solar system,

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we think about the sun,
it's in the center,

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everything else is
kind of going around it,

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and we've got the big planets,
Jupiter and Saturn,

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and the most important planet,
Earth.

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But there are so many more
secrets and mysteries

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than just these planets
that are shown in the model.

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So, to me,
the most exciting thing

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about studying the solar system
is not the planets themselves,

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but it's all the bits
in between the planets.

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NARRATOR:
These worlds could provide clues
to our own planet's story.

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RICE:
In a lot of ways,
studying the solar system

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is a way of trying
to understand ourselves.

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How did we come to be
in the first place,

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and what does it mean
that we're on this rock

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that is sailing through space?

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NARRATOR:
With distances so vast,
there's still much to discover.

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KING:
There's so much stuff

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that we just don't know
about our solar system,

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and what we do know is,
it is constantly surprising us.

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So we need to go out there,
look at these wandering worlds.

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NARRATOR:
And many questions
remain unanswered.

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LYNNAE QUICK:
Are these lost
and wandering worlds

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worthy of exploration
in their own right?

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CHABOT:
How far do these
dark regions extend

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beyond, to the edge
of our solar system?

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Are there more planets
in the dark region

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waiting to be discovered?

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♪ ♪

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(dog barking in distance)

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NARRATOR: It was the sound
that most people noticed.

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(explosion echoing in distance)

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A sonic boom in the night.

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But this was no fighter jet.

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Traveling at around
30,000 miles per hour,

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it tore through the atmosphere.

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♪ ♪

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Broke up.

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And rained down
across the fields.

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A visitor from a distant realm.

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One of the biggest chunks

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landed on a driveway
in front of a house.

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KING:
When I first saw it,
it was kind of a splat.

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I mean, it's so soft, it kind of
just made a powder

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and it threw fragments
all over the driveway.

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SARA RUSSELL:
The Winchcombe meteorite fall

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was the first U.K. meteorite
fall recovered for 30 years,

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so we've been waiting
such a long time.

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KING:
I couldn't believe that we had
a new meteorite in the U.K.

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Yeah, it was incredibly
exciting.

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And all meteorites are
scientifically priceless.

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RUSSELL:
I feel amazed and privileged

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to be able to hold something

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that may tell us about the
secrets

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of the origins of our solar
system,

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and how we got to be here.

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NARRATOR:
It's estimated as many as 50
meteorites hit Earth every day.

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Many burn up in our atmosphere,

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creating shooting stars
and meteor showers.

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But some of the largest ones
do make it to Earth.

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In 2018,
the Hamburg meteor fireball

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streaked across
the American Midwest sky.

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WOMAN:
What was that?

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Did you see a light flash
out there?

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It's particularly pristine,
because it landed

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on a frozen lake, so that
keeps it in cold storage.

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It was like the meteor selected
where to land,

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because it wanted to be studied.

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NARRATOR:
A few years later,

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a meteorite the weight
of a grand piano

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exploded in the skies
near McAllen, Texas.

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(explosion pounds in distance)

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MERCED:
Ah!

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It's like a,
like an explosion of dynamite.

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(explosion echoes)

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That big explosion,
that was a sonic boom.

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♪ ♪

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NARRATOR:
The cows weren't
the only witnesses

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that night in Winchcombe.

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Doorbell and CCTV cameras
never sleep.

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And networks of dedicated
meteor cameras

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captured it
from different angles.

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That meant it was possible
to calculate its trajectory.

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(cows mooing)

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Back over the skies of England,

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out of Earth's atmosphere,

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past the orbit of Mars,

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into the dark.

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This is where
the meteorite's journey began,

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a mysterious realm
of countless rocky worlds,

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rubble left over from the
formation of the solar system:

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asteroids.

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There could be at least
a million out here.

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But they're so dark,
reflecting little light,

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they're incredibly difficult
to detect.

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But asteroids don't always
stay in the asteroid belt.

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(collision pounds)

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When two collide,

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they blast fragments
in all directions,

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sending some out of
the asteroid belt forever.

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Sometimes wreaking havoc
on planets they encounter.

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♪ ♪

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Including our own.

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And asteroids
that leave the belt

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can transform planets nearby.

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♪ ♪

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A planet covered in scars
from the asteroid belt is Mars.

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Around 80 fresh impact sites
are found on Mars every year.

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♪ ♪

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And some amazing meteorites

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have even been snapped
by NASA's rovers.

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But there's
another dark rock here,

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imaged by
the Perseverance rover,

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00:12:03,033 --> 00:12:07,766
not on Mars's surface,
but orbiting overhead...

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00:12:07,766 --> 00:12:12,133
♪ ♪

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00:12:12,133 --> 00:12:14,000
...captured during an eclipse,

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as it passed
in front of the sun.

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This is Mars's moon Phobos.

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00:12:28,066 --> 00:12:31,566
Today, the orbiting probe
Mars Express

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00:12:31,566 --> 00:12:35,266
regularly flies
between Mars and Phobos.

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00:12:35,266 --> 00:12:39,266
♪ ♪

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00:12:39,266 --> 00:12:43,533
Its high-resolution camera

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00:12:43,533 --> 00:12:49,200
captured incredibly detailed
images of Phobos,

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00:12:49,200 --> 00:12:53,366
showing a surface covered
in strange grooves.

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00:12:55,833 --> 00:13:01,433
Phobos looks like someone has
ridden a giant bike all over it.

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00:13:09,000 --> 00:13:13,700
Astrophysicist Sean Raymond
is investigating

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00:13:13,700 --> 00:13:17,600
how objects like Phobos
could have formed.

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00:13:23,066 --> 00:13:24,666
Phobos is a strange-looking
moon.

200
00:13:24,666 --> 00:13:28,366
Like this beach, it's covered in
grooves.

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00:13:28,366 --> 00:13:29,666
You might say it's

202
00:13:29,666 --> 00:13:31,633
the grooviest moon
in the solar system.

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00:13:33,733 --> 00:13:37,066
NARRATOR:
The magnificent grooves
here in Spain

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00:13:37,066 --> 00:13:39,566
are formed
by geological processes

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00:13:39,566 --> 00:13:43,733
and erosion
from relentless, crashing waves.

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00:13:43,733 --> 00:13:47,200
RAYMOND:
It's so cool--
the grooves are amazing here.

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00:13:47,200 --> 00:13:50,366
NARRATOR:
But Phobos isn't anything
like Earth,

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00:13:50,366 --> 00:13:53,700
so what's going on?

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00:13:53,700 --> 00:13:56,200
RAYMOND:
Phobos certainly looks
like an asteroid.

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00:13:56,200 --> 00:13:59,400
It's covered in craters,
and it's dark in color.

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00:13:59,400 --> 00:14:01,666
So you might think
it's just an asteroid that got

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00:14:01,666 --> 00:14:06,166
too close to Mars
and then was captured in orbit.

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00:14:06,166 --> 00:14:11,333
NARRATOR:
It turns out
it's not that simple.

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00:14:11,333 --> 00:14:15,000
Phobos orbits Mars
in an almost perfect circle,

215
00:14:15,000 --> 00:14:17,933
right along Mars's equator,

216
00:14:17,933 --> 00:14:19,600
and this makes us question
whether Phobos

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00:14:19,600 --> 00:14:22,800
is really the asteroid
it appears to be,

218
00:14:22,800 --> 00:14:25,900
because captured asteroids
usually orbit planets

219
00:14:25,900 --> 00:14:28,233
on very elliptical orbits

220
00:14:28,233 --> 00:14:30,733
that sometimes take them
very far from their planet

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00:14:30,733 --> 00:14:33,066
and sometimes being much closer.

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00:14:33,066 --> 00:14:36,366
NARRATOR:
So, if it's not an asteroid,

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00:14:36,366 --> 00:14:40,033
where did this funny
little moon come from?

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00:14:43,166 --> 00:14:45,166
CHABOT:
So, in planetary science,

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00:14:45,166 --> 00:14:47,500
the joke is that you just add
an impact event,

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00:14:47,500 --> 00:14:50,200
and an impact event can explain
everything.

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00:14:50,200 --> 00:14:52,533
That might actually be true in
this case, though.

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00:14:52,533 --> 00:14:54,766
 
It's this one-off event,
and it might have been

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00:14:54,766 --> 00:14:56,800
that an object hit Mars,

230
00:14:56,800 --> 00:14:59,800
and Phobos is the result
of that impact collision

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00:14:59,800 --> 00:15:03,133
between those objects,
and that's what we're seeing.

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00:15:03,133 --> 00:15:07,000
♪ ♪

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00:15:07,000 --> 00:15:13,400
NARRATOR:
Phobos may not be
a captured asteroid at all,

234
00:15:13,400 --> 00:15:16,333
but formed from debris
thrown into orbit

235
00:15:16,333 --> 00:15:21,166
after a massive asteroid impact.

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00:15:21,166 --> 00:15:24,200
However,
this still doesn't explain

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why it's covered in grooves.

238
00:15:31,900 --> 00:15:37,233
Phobos is about 3,700 miles
from Mars's surface,

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00:15:37,233 --> 00:15:42,766
and every hundred years,
moves closer by about six feet.

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00:15:42,766 --> 00:15:48,500
And as it does, the tidal forces
caused by Mars's gravity

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00:15:48,500 --> 00:15:52,000
become stronger.

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00:15:52,000 --> 00:15:55,000
RAYMOND:
So, just like the moon
pulls on the Earth,

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00:15:55,000 --> 00:15:58,533
dragging the oceans
and causing the tide,

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00:15:58,533 --> 00:16:03,066
Mars pulls on Phobos,
causing tides, as well.

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00:16:03,066 --> 00:16:05,266
So, as you can see
behind me right now,

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00:16:05,266 --> 00:16:08,133
the tide is coming in
as the moon is pulling on

247
00:16:08,133 --> 00:16:09,800
the water on the Earth.

248
00:16:09,800 --> 00:16:12,766
The same process
happens on Phobos, due to Mars,

249
00:16:12,766 --> 00:16:15,566
except on Phobos, it's sand
and rock that's moving,

250
00:16:15,566 --> 00:16:17,933
instead of water.

251
00:16:19,766 --> 00:16:24,233
NARRATOR:
Those tidal forces
are pulling Phobos apart.

252
00:16:24,233 --> 00:16:30,100
And with every orbit,
the grooves widen and deepen.

253
00:16:35,066 --> 00:16:39,566
Eventually,
Phobos will drift so close,

254
00:16:39,566 --> 00:16:44,166
Mars's gravity will destroy it.

255
00:16:44,166 --> 00:16:46,866
As Phobos breaks apart...

256
00:16:49,400 --> 00:16:53,766
...most of the debris will fall
to the surface of Mars.

257
00:16:57,433 --> 00:17:01,100
♪ ♪

258
00:17:01,100 --> 00:17:05,933
But the rest will remain
in close orbit,

259
00:17:05,933 --> 00:17:12,733
spreading out to encircle
the entire planet,

260
00:17:12,733 --> 00:17:16,766
giving Mars a wispy ring.

261
00:17:20,266 --> 00:17:22,433
CHAN:
It would be quite impressive.

262
00:17:22,433 --> 00:17:25,066
I love ring planets,
I love Saturn,

263
00:17:25,066 --> 00:17:28,933
and it's not bad to have another
ring planet in our solar system.

264
00:17:31,433 --> 00:17:35,433
NARRATOR:
It seems Mars will one day
be transformed

265
00:17:35,433 --> 00:17:38,466
by the asteroid belt.

266
00:17:43,600 --> 00:17:47,633
But the asteroid belt itself
is still an enigma.

267
00:17:50,100 --> 00:17:52,433
We've flown several spacecraft

268
00:17:52,433 --> 00:17:56,633
through this
mysterious region,

269
00:17:56,633 --> 00:17:58,866
but only one
has orbited the rocks

270
00:17:58,866 --> 00:18:02,266
in the asteroid belt itself:

271
00:18:02,266 --> 00:18:07,600
NASA's Dawn probe.

272
00:18:07,600 --> 00:18:11,666
Most of these ancient remnants
are misshapen boulders.

273
00:18:13,100 --> 00:18:16,133
But one stands out.

274
00:18:21,233 --> 00:18:23,900
Ceres is much bigger
than the others

275
00:18:23,900 --> 00:18:29,100
and almost perfectly spherical.

276
00:18:29,100 --> 00:18:30,600
QUICK:
I joined the Dawn mission

277
00:18:30,600 --> 00:18:32,700
right after it reached Ceres,

278
00:18:32,700 --> 00:18:34,033
and it was so exciting.

279
00:18:34,033 --> 00:18:38,200
Dawn collected thousands
of images of Ceres.

280
00:18:38,200 --> 00:18:40,266
They showed us areas
of the surface

281
00:18:40,266 --> 00:18:42,300
that we'd never seen before.

282
00:18:42,300 --> 00:18:43,533
We thought that it's kind of

283
00:18:43,533 --> 00:18:45,000
a dead planetary body.

284
00:18:45,000 --> 00:18:47,400
Looking at those images,

285
00:18:47,400 --> 00:18:49,633
we could not, basically,
believe our eyes,

286
00:18:49,633 --> 00:18:52,100
and it was, like, "Uh,
what's going on over there?"

287
00:18:52,100 --> 00:18:55,800
♪ ♪

288
00:18:55,800 --> 00:18:59,466
NARRATOR:
At first, it appears dark
and heavily cratered,

289
00:18:59,466 --> 00:19:02,866
like its fellow asteroids.

290
00:19:02,866 --> 00:19:05,066
But Ceres is different.

291
00:19:06,933 --> 00:19:12,166
Its surface is peppered
with white crystals.

292
00:19:12,166 --> 00:19:15,700
But what are they?

293
00:19:15,700 --> 00:19:19,866
Clues come from another planet
in our solar system,

294
00:19:19,866 --> 00:19:24,566
where white crystals
are also found on the surface.

295
00:19:26,633 --> 00:19:29,666
Earth.

296
00:19:36,166 --> 00:19:40,666
HAKEEM OLUSEYI:
This mountain is made up
almost entirely of sea salt,

297
00:19:40,666 --> 00:19:42,833
the exact same stuff
that you put on your food

298
00:19:42,833 --> 00:19:44,033
at the dinner table.

299
00:19:45,633 --> 00:19:47,966
NARRATOR:
40 million years ago,

300
00:19:47,966 --> 00:19:52,766
this whole area
was under an ancient sea.

301
00:19:56,600 --> 00:19:59,633
Over time, it dried out,

302
00:19:59,633 --> 00:20:04,900
leaving behind a layer of salt
a mile thick.

303
00:20:06,400 --> 00:20:08,566
Holy moly!

304
00:20:08,566 --> 00:20:10,600
Whoa!

305
00:20:12,566 --> 00:20:15,433
♪ ♪

306
00:20:18,233 --> 00:20:19,900
It's definitely salty.

307
00:20:19,900 --> 00:20:21,766
And the thing about
salt deposits like this

308
00:20:21,766 --> 00:20:24,733
is that they're only formed
in the presence of water.

309
00:20:24,733 --> 00:20:28,400
So, that raises
an intriguing possibility.

310
00:20:28,400 --> 00:20:32,733
Could the white spots on Ceres
also be salts

311
00:20:32,733 --> 00:20:36,700
that were deposited by water?

312
00:20:36,700 --> 00:20:39,466
NARRATOR:
Finding water on Ceres today

313
00:20:39,466 --> 00:20:41,633
would be
an astonishing discovery.

314
00:20:41,633 --> 00:20:45,033
♪ ♪

315
00:20:45,033 --> 00:20:49,066
Dawn made tight orbits
of Ceres.

316
00:20:50,700 --> 00:20:54,400
And by bouncing light
off the crystal deposits,

317
00:20:54,400 --> 00:21:00,333
it determined
what they were made of:

318
00:21:00,333 --> 00:21:04,433
sodium carbonate,
a common type of salt.

319
00:21:06,666 --> 00:21:10,166
A tantalizing sign that Ceres,

320
00:21:10,166 --> 00:21:12,966
which is 13 times smaller
than Earth,

321
00:21:12,966 --> 00:21:17,233
had an ocean in the past.

322
00:21:17,233 --> 00:21:21,833
Flying just over 20 miles
from the surface,

323
00:21:21,833 --> 00:21:27,466
Dawn finds something else
in the white spots:

324
00:21:27,466 --> 00:21:30,333
hydrohalite crystals,

325
00:21:30,333 --> 00:21:36,166
another salt found on Earth
in the presence of water.

326
00:21:36,166 --> 00:21:39,833
Could Ceres still be
a water world today?

327
00:21:42,800 --> 00:21:45,400
So, "hydro" is water
and "halite" is salt--

328
00:21:45,400 --> 00:21:46,400
table salt.

329
00:21:46,400 --> 00:21:48,900
So, if you imagine a table salt

330
00:21:48,900 --> 00:21:51,733
that's got water molecules
in the structure,

331
00:21:51,733 --> 00:21:54,300
that's what hydrohalite is.

332
00:21:54,300 --> 00:21:56,566
It was very surprising
that there were hydrohalites

333
00:21:56,566 --> 00:21:58,566
on the surface of Ceres.

334
00:21:58,566 --> 00:22:00,900
CHAN:
Hydrohalite would be
very unstable

335
00:22:00,900 --> 00:22:03,233
at the surface of Ceres.

336
00:22:03,233 --> 00:22:05,233
At that pressure,

337
00:22:05,233 --> 00:22:08,400
the water molecule
would have been vaporized.

338
00:22:08,400 --> 00:22:12,500
That implies that water
was recently emplaced on Ceres,

339
00:22:12,500 --> 00:22:16,133
bound to salt crystals within
the past few hundred years.

340
00:22:16,133 --> 00:22:17,866
This replenishment
of hydrohalite

341
00:22:17,866 --> 00:22:20,166
at Ceres' surface
leads us to wonder

342
00:22:20,166 --> 00:22:21,966
if Ceres might be an ocean world

343
00:22:21,966 --> 00:22:24,733
that's masquerading
as an asteroid.

344
00:22:24,733 --> 00:22:28,400
♪ ♪

345
00:22:28,400 --> 00:22:32,133
NARRATOR:
Scientists suspect
that pools of salty water exist

346
00:22:32,133 --> 00:22:36,666
about 25 miles underground,

347
00:22:36,666 --> 00:22:39,000
raising another question:

348
00:22:39,000 --> 00:22:43,166
how did these salts
end up on the surface?

349
00:22:43,166 --> 00:22:47,500
A clue lies in Ceres' location,

350
00:22:47,500 --> 00:22:50,533
right in the heart
of the asteroid belt,

351
00:22:50,533 --> 00:22:52,600
where collisions are common...

352
00:22:52,600 --> 00:22:54,933
(collision pounds)

353
00:22:54,933 --> 00:22:58,866
...and incoming asteroids
can form cracks in the surface

354
00:22:58,866 --> 00:23:02,600
reaching the pools below.

355
00:23:02,600 --> 00:23:04,933
Exposed to the vacuum of space,

356
00:23:04,933 --> 00:23:10,333
the water vaporizes,

357
00:23:10,333 --> 00:23:14,933
leaving its cargo of salt behind

358
00:23:14,933 --> 00:23:18,833
and peppering Ceres
with white spots.

359
00:23:21,000 --> 00:23:23,000
QUICK:
There's still one big twist

360
00:23:23,000 --> 00:23:24,833
to the story of Ceres' past.

361
00:23:24,833 --> 00:23:28,566
The Dawn spacecraft found
ammonia salts on the surface.

362
00:23:30,233 --> 00:23:33,900
NARRATOR:
Ammonia salts could be traces
of ammonia ices

363
00:23:33,900 --> 00:23:37,266
that once covered
Ceres' surface.

364
00:23:37,266 --> 00:23:39,766
Frozen ammonia is common
in colder parts

365
00:23:39,766 --> 00:23:44,100
of the solar system,
but not here.

366
00:23:44,100 --> 00:23:49,966
CHAN:
Ammonia doesn't really exist
as ice at where Ceres is now.

367
00:23:49,966 --> 00:23:52,966
It has to be formed
at a distance

368
00:23:52,966 --> 00:23:55,433
further away from the sun,

369
00:23:55,433 --> 00:23:57,900
where the distance
is cold enough

370
00:23:57,900 --> 00:24:00,800
for ammonia to exist as ice.

371
00:24:00,800 --> 00:24:02,966
This suggests
that Ceres didn't form

372
00:24:02,966 --> 00:24:05,133
where it stands currently
in our solar system.

373
00:24:06,466 --> 00:24:11,033
NARRATOR:
Instead, scientists think
it formed much farther out,

374
00:24:11,033 --> 00:24:13,733
and as it wandered
towards the sun,

375
00:24:13,733 --> 00:24:16,333
the ammonia ices melted,

376
00:24:16,333 --> 00:24:21,933
leaving behind the ammonia salts
we see today.

377
00:24:21,933 --> 00:24:26,133
An imposter
lurking in the asteroid belt,

378
00:24:26,133 --> 00:24:30,966
exposed by its salty secrets.

379
00:24:30,966 --> 00:24:33,666
Ceres has
a journey of relocation

380
00:24:33,666 --> 00:24:36,900
just written
all across the surface.

381
00:24:39,900 --> 00:24:44,766
NARRATOR:
But just how did Ceres end up
where it is today?

382
00:24:44,766 --> 00:24:47,100
OLUSEYI:
The best explanation
is that it wandered.

383
00:24:47,100 --> 00:24:48,700
Well, actually, it was pulled.

384
00:24:48,700 --> 00:24:49,933
So let's say this is Ceres.

385
00:24:49,933 --> 00:24:50,966
Okay?

386
00:24:50,966 --> 00:24:53,500
We think that Ceres
formed beyond

387
00:24:53,500 --> 00:24:55,100
what is known
as the ice line

388
00:24:55,100 --> 00:24:56,866
for ammonium ices.

389
00:24:56,866 --> 00:24:58,666
NARRATOR:
Beyond this ice line,

390
00:24:58,666 --> 00:25:00,766
ammonia freezes,

391
00:25:00,766 --> 00:25:04,500
and this is where Ceres
likely started forming,

392
00:25:04,500 --> 00:25:07,600
alongside Neptune
and Uranus.

393
00:25:07,600 --> 00:25:09,866
OLUSEYI: And here we have
Saturn and Jupiter.

394
00:25:09,866 --> 00:25:11,666
Now, normally, these planets

395
00:25:11,666 --> 00:25:12,866
aren't lined up
like this.

396
00:25:12,866 --> 00:25:14,700
They're moving
around the solar system.

397
00:25:14,700 --> 00:25:17,833
And what happens is,
as Ceres

398
00:25:17,833 --> 00:25:19,833
orbited the solar system,

399
00:25:19,833 --> 00:25:22,633
Jupiter tugged on it
with its gravity,

400
00:25:22,633 --> 00:25:25,400
and Ceres ended up
right there,

401
00:25:25,400 --> 00:25:28,133
in the asteroid belt,
where we find it today.

402
00:25:30,433 --> 00:25:32,766
NARRATOR:
In the heart
of the asteroid belt,

403
00:25:32,766 --> 00:25:36,066
Ceres, once a much icier world,

404
00:25:36,066 --> 00:25:40,100
has migrated
far from where it formed,

405
00:25:40,100 --> 00:25:44,766
evidence that our solar system
is ever changing.

406
00:25:44,766 --> 00:25:46,733
♪ ♪

407
00:25:46,733 --> 00:25:50,633
Ceres isn't
the only displaced world.

408
00:25:50,633 --> 00:25:54,100
Farther from the sun,
there is another icy world

409
00:25:54,100 --> 00:25:57,700
that doesn't seem to belong
where it's found today.

410
00:25:59,133 --> 00:26:03,633
Beyond Jupiter,

411
00:26:03,633 --> 00:26:06,833
the space between the planets
gets wider

412
00:26:06,833 --> 00:26:09,200
and wider.

413
00:26:10,333 --> 00:26:13,433
And temperatures plummet.

414
00:26:15,933 --> 00:26:20,200
♪ ♪

415
00:26:20,200 --> 00:26:25,700
And a billion miles past Uranus,

416
00:26:25,700 --> 00:26:29,633
we finally reach the farthest
planet from the sun.

417
00:26:32,433 --> 00:26:35,466
Neptune.

418
00:26:35,466 --> 00:26:41,466
♪ ♪

419
00:26:41,466 --> 00:26:45,700
Wrapped in a dense blue blanket,

420
00:26:45,700 --> 00:26:51,566
Neptune has
no detectable surface,

421
00:26:51,566 --> 00:26:55,600
with clouds
of methane and ammonia.

422
00:26:57,900 --> 00:27:02,600
But there are rocky worlds
nearby.

423
00:27:02,600 --> 00:27:06,833
Neptune has at least 16 moons.

424
00:27:06,833 --> 00:27:11,333
And one is very unusual.

425
00:27:16,466 --> 00:27:21,300
Triton is the largest
of Neptune's moons.

426
00:27:21,300 --> 00:27:24,066
Its surface is coated with ice.

427
00:27:28,100 --> 00:27:30,833
And, unlike the other moons,

428
00:27:30,833 --> 00:27:33,600
Triton is an active world.

429
00:27:33,600 --> 00:27:37,733
(geyser bursts)

430
00:27:37,733 --> 00:27:40,633
Geyser-like plumes
of gas and dust

431
00:27:40,633 --> 00:27:44,566
stretch five miles high
into Triton's atmosphere...

432
00:27:46,400 --> 00:27:48,433
...which flattens them abruptly

433
00:27:48,433 --> 00:27:51,033
by 90 degrees,

434
00:27:51,033 --> 00:27:55,500
creating a vista so strange,

435
00:27:55,500 --> 00:27:58,666
it's hard to believe it's real.

436
00:28:03,066 --> 00:28:08,900
How did a moon
2.8 billion miles from the sun

437
00:28:08,900 --> 00:28:11,933
become so active?

438
00:28:17,200 --> 00:28:20,200
A clue lies
with how the planets and moons

439
00:28:20,200 --> 00:28:23,866
move around each other
in the solar system.

440
00:28:28,133 --> 00:28:30,000
CARLY HOWETT:
Every day, the sun rises
in the east

441
00:28:30,000 --> 00:28:32,133
and sets in the west.

442
00:28:32,133 --> 00:28:34,333
And the moon follows
the same course.

443
00:28:34,333 --> 00:28:36,000
And there's a reason for that.

444
00:28:37,366 --> 00:28:39,233
NARRATOR:
To understand why,

445
00:28:39,233 --> 00:28:42,966
we need to go all the way back.

446
00:28:45,066 --> 00:28:49,233
To the birth
of the solar system.

447
00:28:49,233 --> 00:28:51,200
DURFEY:
In the beginning of our
solar system,

448
00:28:51,200 --> 00:28:52,633
the sun was surrounded

449
00:28:52,633 --> 00:28:55,066
by a disc of dust and gas.

450
00:28:55,066 --> 00:28:58,433
And it was within
this spinning disc

451
00:28:58,433 --> 00:29:01,300
that the planets formed.

452
00:29:01,300 --> 00:29:02,733
PAREKH:
So that's the reason

453
00:29:02,733 --> 00:29:04,366
the planets and the moon
continued

454
00:29:04,366 --> 00:29:06,233
orbiting also
in the same direction

455
00:29:06,233 --> 00:29:09,200
around the sun.

456
00:29:09,200 --> 00:29:11,666
NARRATOR:
Moons that form
around their planets

457
00:29:11,666 --> 00:29:14,866
tend to follow this pattern,

458
00:29:14,866 --> 00:29:17,033
orbiting and spinning
in the direction

459
00:29:17,033 --> 00:29:20,900
of the planet's rotation.

460
00:29:20,900 --> 00:29:25,233
But while the inner moons orbit
Neptune in the same direction,

461
00:29:25,233 --> 00:29:28,533
Triton goes the other way,

462
00:29:28,533 --> 00:29:33,700
suggesting it didn't form
alongside Neptune,

463
00:29:33,700 --> 00:29:38,500
but came from elsewhere.

464
00:29:42,666 --> 00:29:44,200
HOWETT:
What a planet's made from

465
00:29:44,200 --> 00:29:47,033
can tell you where it formed
in our solar system.

466
00:29:47,033 --> 00:29:49,300
And that's because,
in our early solar system,

467
00:29:49,300 --> 00:29:51,800
the ingredients that
a planet could be built from

468
00:29:51,800 --> 00:29:54,200
varied as the distance
from the sun.

469
00:29:54,200 --> 00:29:57,133
So if we take Earth,
for example,

470
00:29:57,133 --> 00:29:58,800
it's got a lot of rocks and
metals, too:

471
00:29:58,800 --> 00:30:00,833
aluminium and iron.

472
00:30:00,833 --> 00:30:02,233
And Mars is pretty
similar.

473
00:30:02,233 --> 00:30:05,066
Iron, metals, and other rocks.

474
00:30:05,066 --> 00:30:08,033
So these can be paired together.

475
00:30:08,033 --> 00:30:10,066
If we do the same thing

476
00:30:10,066 --> 00:30:13,766
for the ice giants,
Neptune and Uranus,

477
00:30:13,766 --> 00:30:15,800
with big atmospheres
made of hydrogen,

478
00:30:15,800 --> 00:30:17,566
helium, and a bit of methane,

479
00:30:17,566 --> 00:30:19,233
they're huge, too.

480
00:30:19,233 --> 00:30:21,733
So we can pair those together.

481
00:30:21,733 --> 00:30:23,933
So how does Triton fit in?

482
00:30:23,933 --> 00:30:25,800
Well, its surface
is mainly nitrogen ice,

483
00:30:25,800 --> 00:30:27,200
and it's much smaller.

484
00:30:27,200 --> 00:30:30,166
It doesn't fit with either
of these two groupings.

485
00:30:30,166 --> 00:30:32,300
To understand
where it could fit,

486
00:30:32,300 --> 00:30:33,966
we have to look at Pluto.

487
00:30:33,966 --> 00:30:37,633
Pluto has a, a nitrogen
ice surface with methane,

488
00:30:37,633 --> 00:30:40,033
carbon monoxide, and water ice.

489
00:30:40,033 --> 00:30:43,000
And it's about the same size
as Triton, too.

490
00:30:43,000 --> 00:30:44,766
These are a good pairing.

491
00:30:44,766 --> 00:30:47,866
NARRATOR:
With such similar ingredients,

492
00:30:47,866 --> 00:30:51,700
Triton and Pluto could've
formed in the same place,

493
00:30:51,700 --> 00:30:55,100
but they aren't
anywhere near each other today.

494
00:30:55,100 --> 00:30:58,433
HOWETT:
Triton's located
one billion miles from Pluto.

495
00:30:58,433 --> 00:30:59,966
So how did that happen?

496
00:31:01,566 --> 00:31:05,900
NARRATOR:
Neptune might be the farthest
planet from the sun,

497
00:31:05,900 --> 00:31:09,900
but it's not the edge
of our solar system.

498
00:31:09,900 --> 00:31:13,833
Not even close.

499
00:31:13,833 --> 00:31:17,233
Almost a billion miles
farther out

500
00:31:17,233 --> 00:31:19,700
lies Pluto.

501
00:31:19,700 --> 00:31:22,700
And it's not alone.

502
00:31:22,700 --> 00:31:28,100
There are hundreds of thousands
of other worlds out here.

503
00:31:28,100 --> 00:31:32,533
This is the Kuiper Belt,

504
00:31:32,533 --> 00:31:37,433
a vast, doughnut-shaped ring
of icy bodies

505
00:31:37,433 --> 00:31:39,466
billions of miles wide.

506
00:31:41,566 --> 00:31:43,300
So dark and distant,

507
00:31:43,300 --> 00:31:49,233
it remained undiscovered
until 1992.

508
00:31:49,233 --> 00:31:51,466
LUU: We had been searching for,
uh, the Kuiper Belt

509
00:31:51,466 --> 00:31:54,500
for, uh, for five years
before we finally found it.

510
00:31:54,500 --> 00:31:57,966
So when we spotted
the first Kuiper Belt object,

511
00:31:57,966 --> 00:32:00,333
1992 QB1,

512
00:32:00,333 --> 00:32:02,300
there was jumping up
and down, and there was...

513
00:32:02,300 --> 00:32:04,966
I think we gave each other
a high five.
(laughs)

514
00:32:04,966 --> 00:32:06,833
The discovery of the Kuiper Belt

515
00:32:06,833 --> 00:32:09,133
helped us to better understand
our solar system

516
00:32:09,133 --> 00:32:11,900
as it is now,
and also its history.

517
00:32:11,900 --> 00:32:15,333
LUU:
The Kuiper Belt is
really the frontier

518
00:32:15,333 --> 00:32:18,200
if you want to understand
the solar system.

519
00:32:18,200 --> 00:32:20,366
But it is very difficult
to study it,

520
00:32:20,366 --> 00:32:24,233
because it is so far away.

521
00:32:24,233 --> 00:32:26,833
NARRATOR:
Despite the challenges,

522
00:32:26,833 --> 00:32:29,300
more than 4,000
Kuiper Belt objects

523
00:32:29,300 --> 00:32:32,300
have been discovered to date.

524
00:32:35,233 --> 00:32:37,300
And scientists estimate

525
00:32:37,300 --> 00:32:40,366
there may be 200 dwarf planets.

526
00:32:43,533 --> 00:32:47,333
Some have rings and moons.

527
00:32:47,333 --> 00:32:52,666
Some are bizarre and misshapen.

528
00:32:52,666 --> 00:32:55,200
But they
all share one thing in common.

529
00:32:57,933 --> 00:33:01,566
They're made of icy materials,
similar to Triton.

530
00:33:04,466 --> 00:33:08,733
This is where Triton belongs.

531
00:33:08,733 --> 00:33:12,000
So how did it end up
around a billion miles away,

532
00:33:12,000 --> 00:33:16,333
in orbit around Neptune?

533
00:33:16,333 --> 00:33:20,366
♪ ♪

534
00:33:24,866 --> 00:33:27,166
HOWETT:
So, to understand Triton,

535
00:33:27,166 --> 00:33:29,200
you have to understand
the Kuiper Belt.

536
00:33:29,200 --> 00:33:30,800
If this is our sun,

537
00:33:30,800 --> 00:33:33,500
the one population
of Kuiper Belt objects

538
00:33:33,500 --> 00:33:36,833
orbit it in a nice circle.

539
00:33:36,833 --> 00:33:39,600
Another population
of Kuiper Belt objects

540
00:33:39,600 --> 00:33:42,933
have a highly elliptical orbit.

541
00:33:42,933 --> 00:33:45,500
So the question is,
why are these so different?

542
00:33:45,500 --> 00:33:48,933
What caused them to be
in this weird orbit?

543
00:33:48,933 --> 00:33:50,933
Well, the answer is,
some of these objects

544
00:33:50,933 --> 00:33:53,866
are in resonance with
another planet, Neptune.

545
00:33:53,866 --> 00:33:57,133
Resonance is when two objects
have paths

546
00:33:57,133 --> 00:33:59,233
that meet up occasionally.

547
00:33:59,233 --> 00:34:01,300
And we see this
throughout the solar system.

548
00:34:01,300 --> 00:34:03,300
If you look, for example,
at Pluto,

549
00:34:03,300 --> 00:34:04,600
it'll go around

550
00:34:04,600 --> 00:34:07,533
on this elliptical orbit
twice

551
00:34:07,533 --> 00:34:11,433
in the same time Neptune has
gone around three times.

552
00:34:11,433 --> 00:34:14,200
And this resonance is an
important clue

553
00:34:14,200 --> 00:34:16,700
in understanding
how disruptive

554
00:34:16,700 --> 00:34:19,100
Neptune is to Kuiper
Belt objects.

555
00:34:23,366 --> 00:34:25,600
♪ ♪

556
00:34:25,600 --> 00:34:27,966
NARRATOR:
Scientists think Neptune formed

557
00:34:27,966 --> 00:34:31,566
much closer to the sun,

558
00:34:31,566 --> 00:34:33,966
then slowly drifted out.

559
00:34:37,533 --> 00:34:40,366
Its huge gravity
disrupted the orbits

560
00:34:40,366 --> 00:34:43,366
of the Kuiper Belt worlds
it encountered,

561
00:34:43,366 --> 00:34:45,800
kicking them into
the elliptical orbits

562
00:34:45,800 --> 00:34:49,133
we see today.

563
00:34:49,133 --> 00:34:52,566
DURFEY:
The early solar system
was complete chaos,

564
00:34:52,566 --> 00:34:56,433
filled with small bodies
growing larger

565
00:34:56,433 --> 00:34:58,233
and smashing into each other,

566
00:34:58,233 --> 00:35:01,100
sometimes destroying.

567
00:35:01,100 --> 00:35:03,266
Complete chaos.

568
00:35:04,333 --> 00:35:06,333
NARRATOR:
During all the commotion,

569
00:35:06,333 --> 00:35:11,000
Triton became trapped
by Neptune's gravity,

570
00:35:11,000 --> 00:35:15,300
slipping into its
backward orbit.

571
00:35:15,300 --> 00:35:20,600
And being this close
to a giant has consequences.

572
00:35:22,200 --> 00:35:25,800
Just as our moon raises tides
on Earth,

573
00:35:25,800 --> 00:35:30,400
Neptune raises tides on Triton,

574
00:35:30,400 --> 00:35:33,866
stretching and squashing it
like a stress ball,

575
00:35:33,866 --> 00:35:38,733
heating it up.

576
00:35:38,733 --> 00:35:41,433
HOWETT:
Triton being captured
by Neptune

577
00:35:41,433 --> 00:35:44,000
fundamentally changed
how it works.

578
00:35:44,000 --> 00:35:46,933
On Earth, we experience energy
every day.

579
00:35:46,933 --> 00:35:48,900
You might be able to hear it
in the roar

580
00:35:48,900 --> 00:35:51,666
that comes from the tide
coming in underneath us.

581
00:35:51,666 --> 00:35:53,900
(waves pounding)

582
00:35:53,900 --> 00:35:55,900
Tidal energy can force water
up through cracks

583
00:35:55,900 --> 00:35:57,400
in the Earth, like the one
in front of us,

584
00:35:57,400 --> 00:36:02,600
creating plumes
erupting up to the sky.

585
00:36:02,600 --> 00:36:07,733
NARRATOR:
On Triton, the plumes are
even more spectacular.

586
00:36:07,733 --> 00:36:11,466
HOWETT:
The plumes on Triton
would be magnificent to behold.

587
00:36:11,466 --> 00:36:15,900
Erupting from the surface,
cracks like this,

588
00:36:15,900 --> 00:36:20,000
but going five miles
into the sky.

589
00:36:20,000 --> 00:36:21,900
I mean, it'd just be
absolutely phenomenal.

590
00:36:21,900 --> 00:36:24,100
(geyser bursts)

591
00:36:24,100 --> 00:36:27,566
NARRATOR:
What creates Triton's plumes
is a mystery.

592
00:36:27,566 --> 00:36:33,000
But one theory lies
in its unusual orbit.

593
00:36:33,000 --> 00:36:36,400
HOWETT:
It's highly tilted,
and Triton orbits backwards.

594
00:36:36,400 --> 00:36:38,500
Meaning as it goes
around Neptune,

595
00:36:38,500 --> 00:36:40,666
its pull and push
that it receives

596
00:36:40,666 --> 00:36:42,566
from Neptune and its moons
changes.

597
00:36:42,566 --> 00:36:44,666
This creates a kind of friction,

598
00:36:44,666 --> 00:36:46,233
similar to the one
that you get

599
00:36:46,233 --> 00:36:48,466
when you rub your hands together
on a cold day.

600
00:36:48,466 --> 00:36:51,100
Your hands warm up,
and so might Triton.

601
00:36:51,100 --> 00:36:54,266
We call that kind of energy
tidal heating.

602
00:36:56,900 --> 00:37:00,433
NARRATOR:
As Neptune's gravity
stretches and squashes

603
00:37:00,433 --> 00:37:02,466
its giant moon...

604
00:37:02,466 --> 00:37:05,366
(plume roaring)

605
00:37:05,366 --> 00:37:07,466
...the tidal heating produced

606
00:37:07,466 --> 00:37:11,333
melts Triton's frozen
interior...

607
00:37:11,333 --> 00:37:14,433
♪ ♪

608
00:37:14,433 --> 00:37:19,466
...powering its spectacular
plumes.

609
00:37:19,466 --> 00:37:21,233
DURFEY:
Triton is a great example

610
00:37:21,233 --> 00:37:24,600
of how interconnected
our solar system is.

611
00:37:24,600 --> 00:37:26,733
And it also serves as a good
example

612
00:37:26,733 --> 00:37:30,200
of how a large, giant planet

613
00:37:30,200 --> 00:37:32,166
straying into a belt of objects

614
00:37:32,166 --> 00:37:35,266
can really mess up your system.

615
00:37:43,266 --> 00:37:48,233
NARRATOR:
Triton was plucked
from the Kuiper Belt,

616
00:37:48,233 --> 00:37:53,566
a distant realm
filled with mysterious worlds

617
00:37:53,566 --> 00:37:56,033
so far away

618
00:37:56,033 --> 00:38:00,466
we can't make them out
in much detail.

619
00:38:00,466 --> 00:38:03,233
But we have sent one spacecraft.

620
00:38:09,066 --> 00:38:13,366
It took over nine years
for New Horizons to get here

621
00:38:13,366 --> 00:38:16,900
and home in
on its primary target.

622
00:38:23,200 --> 00:38:25,266
♪ ♪

623
00:38:25,266 --> 00:38:29,900
The tiny spacecraft captured
the first close-up images

624
00:38:29,900 --> 00:38:34,833
of this Kuiper Belt world,

625
00:38:34,833 --> 00:38:37,600
revealing unexpectedly complex

626
00:38:37,600 --> 00:38:41,566
and dynamic surface features:

627
00:38:41,566 --> 00:38:45,833
mountains as high as the Alps,
made from water,

628
00:38:45,833 --> 00:38:51,166
frozen as hard as granite.

629
00:38:51,166 --> 00:38:54,933
But there's something else odd
out here.

630
00:38:54,933 --> 00:38:58,100
Another world close by.

631
00:39:06,933 --> 00:39:11,900
How did Charon and Pluto
end up almost touching?

632
00:39:16,466 --> 00:39:18,533
Charon orbits about 12,000 miles

633
00:39:18,533 --> 00:39:19,933
from the surface of Pluto,

634
00:39:19,933 --> 00:39:21,900
which sounds like a really large
number,

635
00:39:21,900 --> 00:39:23,500
but is actually really close

636
00:39:23,500 --> 00:39:25,766
for the scale
of the Kuiper Belt.

637
00:39:25,766 --> 00:39:28,466
It's very common
in our solar system

638
00:39:28,466 --> 00:39:33,433
for moons that are close enough
to their parent body

639
00:39:33,433 --> 00:39:35,666
to become tidally locked.

640
00:39:35,666 --> 00:39:38,166
And that is where one orbit

641
00:39:38,166 --> 00:39:41,300
will also be one spin,

642
00:39:41,300 --> 00:39:43,800
so that the same face
of that moon

643
00:39:43,800 --> 00:39:46,866
is presented to the planet
at all times.

644
00:39:51,366 --> 00:39:54,133
NARRATOR:
All large moons
in the solar system,

645
00:39:54,133 --> 00:39:57,600
including our own,
are tidally locked,

646
00:39:57,600 --> 00:40:02,666
only showing one face
to their parent planet.

647
00:40:02,666 --> 00:40:05,500
But in the case of Pluto
and Charon,

648
00:40:05,500 --> 00:40:10,266
it isn't just Charon that is
tidally locked to Pluto.

649
00:40:10,266 --> 00:40:14,300
Pluto is also tidally locked
to Charon.

650
00:40:14,300 --> 00:40:19,200
Both worlds constantly
face each other at all times.

651
00:40:21,566 --> 00:40:24,066
RICE:
And what that means is,
if you're on the side of Pluto

652
00:40:24,066 --> 00:40:26,166
where you're able to see Charon,

653
00:40:26,166 --> 00:40:29,533
then it'll look like it's just
hanging there all the time.

654
00:40:29,533 --> 00:40:31,433
It's not going to rise,
it's not going to set.

655
00:40:31,433 --> 00:40:35,233
It's just going to
constantly be in your sky.

656
00:40:35,233 --> 00:40:41,300
♪ ♪

657
00:40:41,300 --> 00:40:47,466
NARRATOR:
This isn't just a dwarf planet
and its moon,

658
00:40:47,466 --> 00:40:50,666
but a binary pair.

659
00:40:50,666 --> 00:40:55,233
♪ ♪

660
00:40:55,233 --> 00:41:00,466
New Horizons is still studying
Kuiper Belt worlds today.

661
00:41:04,100 --> 00:41:07,733
During the most distant
fly-by in history,

662
00:41:07,733 --> 00:41:13,500
it encountered Arrokoth,

663
00:41:13,500 --> 00:41:16,433
a bizarre snowman-shaped
object.

664
00:41:23,466 --> 00:41:25,600
SUNSHINE:
It is two pieces
that are stuck together,

665
00:41:25,600 --> 00:41:29,766
and those two pieces must have
come together very gently.

666
00:41:29,766 --> 00:41:32,400
To actually see it
was really quite remarkable.

667
00:41:32,400 --> 00:41:35,600
Any time you see a new world,
it's remarkable.

668
00:41:39,000 --> 00:41:42,400
NARRATOR:
Why do the worlds out here
in the Kuiper Belt

669
00:41:42,400 --> 00:41:46,533
form these partnerships?

670
00:41:46,533 --> 00:41:48,600
LUU:
Things become slower and slower

671
00:41:48,600 --> 00:41:50,500
as you go further away
from the sun.

672
00:41:50,500 --> 00:41:53,633
In the Kuiper Belt,
things might collide

673
00:41:53,633 --> 00:41:56,866
at the speed of a few
hundred feet per second.

674
00:41:56,866 --> 00:42:00,733
They occur at such
low-impact velocity

675
00:42:00,733 --> 00:42:03,200
that a lot of the collisions
are constructive

676
00:42:03,200 --> 00:42:08,200
rather than destructive.

677
00:42:08,200 --> 00:42:14,000
NARRATOR:
At some point in their history,
Pluto and Charon collided.

678
00:42:20,200 --> 00:42:24,633
But their slow movements

679
00:42:24,633 --> 00:42:27,900
meant this was less of an impact

680
00:42:27,900 --> 00:42:31,333
and more of an embrace.

681
00:42:36,366 --> 00:42:41,200
The Kuiper Belt is so vast
and far from the sun

682
00:42:41,200 --> 00:42:44,700
that many mysteries
still remain.

683
00:42:47,600 --> 00:42:49,800
I am often pretty amazed
that we're actually able

684
00:42:49,800 --> 00:42:52,533
to study things
like the Big Bang

685
00:42:52,533 --> 00:42:54,800
and the early universe
and distant galaxies,

686
00:42:54,800 --> 00:42:57,533
and yet we still actually
don't know everything

687
00:42:57,533 --> 00:42:59,100
that there is to know
about our own solar system

688
00:42:59,100 --> 00:43:00,600
and our own backyard.

689
00:43:00,600 --> 00:43:04,166
I'm very confident that
there are many, many worlds

690
00:43:04,166 --> 00:43:06,633
out there that we are yet
to discover,

691
00:43:06,633 --> 00:43:10,233
and that we haven't even
imagined yet.

692
00:43:10,233 --> 00:43:15,800
♪ ♪

693
00:43:22,200 --> 00:43:26,233
NARRATOR:
We can see distant stars
in the night sky

694
00:43:26,233 --> 00:43:30,066
because they burn so bright.

695
00:43:30,066 --> 00:43:32,366
Telescopes can detect planets

696
00:43:32,366 --> 00:43:36,800
as they pass in front
of their parent stars.

697
00:43:36,800 --> 00:43:39,733
Seeing worlds
in our own solar system

698
00:43:39,733 --> 00:43:42,433
is much harder,

699
00:43:42,433 --> 00:43:45,433
but not impossible.

700
00:43:45,433 --> 00:43:49,533
♪ ♪

701
00:43:49,533 --> 00:43:51,666
In 2018,

702
00:43:51,666 --> 00:43:54,766
a faint point of light
was detected

703
00:43:54,766 --> 00:43:59,566
about 12 billion miles
from the sun.

704
00:43:59,566 --> 00:44:03,100
It's thought to be
a dwarf planet

705
00:44:03,100 --> 00:44:06,133
nicknamed FarFarOut.

706
00:44:11,500 --> 00:44:16,233
This is the most distant object
yet seen in our solar system

707
00:44:16,233 --> 00:44:20,766
by some of our most
powerful telescopes.

708
00:44:20,766 --> 00:44:25,600
But it's not the limit
of what could be out there.

709
00:44:25,600 --> 00:44:31,200
♪ ♪

710
00:44:31,200 --> 00:44:34,800
OLUSEYI:
How far do you expect
the solar system to extend?

711
00:44:34,800 --> 00:44:36,533
You may imagine that it ends

712
00:44:36,533 --> 00:44:38,700
at the last major planet,
Neptune.

713
00:44:38,700 --> 00:44:40,833
However, that's not
exactly the case,

714
00:44:40,833 --> 00:44:42,200
and let me show you why.

715
00:44:42,200 --> 00:44:44,633
Here I'm gonna make a model
of the solar system.

716
00:44:44,633 --> 00:44:47,500
This rock is my sun,

717
00:44:47,500 --> 00:44:49,233
and I'm gonna place it
right there,

718
00:44:49,233 --> 00:44:51,600
and an inch away,
I'm gonna place the Earth.

719
00:44:51,600 --> 00:44:53,866
And so this will be my scale,
one inch equals

720
00:44:53,866 --> 00:44:56,800
the average distance
between the Earth and the sun.

721
00:44:56,800 --> 00:44:59,066
So now, if I go a second inch,

722
00:44:59,066 --> 00:45:02,566
I arrive at the asteroid belt.

723
00:45:02,566 --> 00:45:06,800
And to get to the most distant
major planet, Neptune,

724
00:45:06,800 --> 00:45:09,133
that's gonna be about 30 inches.

725
00:45:09,133 --> 00:45:11,300
Now, we have to keep
going and going,

726
00:45:11,300 --> 00:45:12,833
because out here is

727
00:45:12,833 --> 00:45:15,366
the most distantly
observed object ever

728
00:45:15,366 --> 00:45:17,133
in the history
of our solar system,

729
00:45:17,133 --> 00:45:18,933
11 feet away from the sun,

730
00:45:18,933 --> 00:45:20,833
132 inches,

731
00:45:20,833 --> 00:45:22,300
12 billion miles,

732
00:45:22,300 --> 00:45:25,633
is FarFarOut.

733
00:45:25,633 --> 00:45:29,500
NARRATOR:
But the solar system
doesn't end here.

734
00:45:29,500 --> 00:45:32,533
OLUSEYI:
I have to walk
another 50 paces...

735
00:45:41,433 --> 00:45:45,933
...another 186 billion miles,

736
00:45:45,933 --> 00:45:48,066
and now we've reached
our destination,

737
00:45:48,066 --> 00:45:50,900
a vast region known
as the Oort Cloud.

738
00:45:50,900 --> 00:45:54,000
♪ ♪

739
00:45:54,000 --> 00:45:56,566
NARRATOR:
Clinging on at the very edge

740
00:45:56,566 --> 00:46:00,000
of the sun's
gravitational influence,

741
00:46:00,000 --> 00:46:03,866
the Oort Cloud is
our solar system's largest

742
00:46:03,866 --> 00:46:06,900
and most mysterious realm.

743
00:46:12,066 --> 00:46:14,700
It's so deep into the darkness,

744
00:46:14,700 --> 00:46:17,900
it's almost impossible
to imagine,

745
00:46:17,900 --> 00:46:20,533
let alone see,

746
00:46:20,533 --> 00:46:23,600
filled with billions
upon billions

747
00:46:23,600 --> 00:46:27,400
of strange worlds.

748
00:46:27,400 --> 00:46:30,133
Most are thought to be
icy objects

749
00:46:30,133 --> 00:46:33,133
the size of mountains.

750
00:46:33,133 --> 00:46:38,133
But it's likely
some are made of rock.

751
00:46:38,133 --> 00:46:43,166
And if we were able to go there,
we'd discover they are pristine.

752
00:46:43,166 --> 00:46:46,500
♪ ♪

753
00:46:46,500 --> 00:46:51,366
Barely changed since the dawn
of the solar system.

754
00:46:51,366 --> 00:46:55,433
It's thought some could be older
than the sun.

755
00:46:57,433 --> 00:46:59,733
The Oort Cloud's existence
is hypothetical,

756
00:46:59,733 --> 00:47:01,933
but science doesn't deal
in fairy tales,

757
00:47:01,933 --> 00:47:06,100
so how do we know it's actually
there if we've never seen it?

758
00:47:06,100 --> 00:47:10,533
♪ ♪

759
00:47:10,533 --> 00:47:14,233
NARRATOR:
For as long as we've been
looking into the night sky,

760
00:47:14,233 --> 00:47:18,833
we've seen signs
that the Oort Cloud is real.

761
00:47:18,833 --> 00:47:21,866
And this is one of them.

762
00:47:27,533 --> 00:47:29,666
For hundreds of years,

763
00:47:29,666 --> 00:47:33,700
it's been locked in a deep,
frozen slumber.

764
00:47:36,133 --> 00:47:38,800
♪ ♪

765
00:47:38,800 --> 00:47:41,333
But now it stirs.

766
00:47:41,333 --> 00:47:45,200
♪ ♪

767
00:47:45,200 --> 00:47:48,800
As it nears the sun,

768
00:47:48,800 --> 00:47:51,533
warm rays bathe its surface...

769
00:47:56,566 --> 00:47:59,600
...and it begins to thaw.

770
00:47:59,600 --> 00:48:04,966
(hissing)

771
00:48:16,900 --> 00:48:19,866
♪ ♪

772
00:48:19,866 --> 00:48:25,466
So much debris is torn
from the surface,

773
00:48:25,466 --> 00:48:29,066
it stretches out,
forming a tail...

774
00:48:30,800 --> 00:48:34,833
...around 14 million miles long.

775
00:48:36,533 --> 00:48:40,566
This is the comet Nishimura.

776
00:48:45,300 --> 00:48:50,033
It's visible from Earth
for just a few weeks,

777
00:48:50,033 --> 00:48:55,033
before eventually heading back
into the darkness,

778
00:48:55,033 --> 00:48:59,700
just the latest in a long line
of icy visitors.

779
00:49:05,066 --> 00:49:07,100
Hale-Bopp.

780
00:49:10,100 --> 00:49:13,466
Neowise.

781
00:49:13,466 --> 00:49:19,466
They lit up our skies for weeks,
or even months, on end.

782
00:49:19,466 --> 00:49:21,300
Humans have been
captivated by comets

783
00:49:21,300 --> 00:49:23,166
because, frankly,
they're spectacular.

784
00:49:23,166 --> 00:49:25,833
CHABOT:
And the fact that they do wander

785
00:49:25,833 --> 00:49:28,400
around the solar system
from time to time

786
00:49:28,400 --> 00:49:31,700
really is a unique scientific
opportunity.

787
00:49:35,333 --> 00:49:37,666
NARRATOR:
When scientists followed
the trajectories

788
00:49:37,666 --> 00:49:39,700
of these comets back,

789
00:49:39,700 --> 00:49:43,833
they discovered they came
from the same region,

790
00:49:43,833 --> 00:49:49,333
more than 200 billion miles
from the sun.

791
00:49:49,333 --> 00:49:50,666
SUNSHINE:
If you calculate

792
00:49:50,666 --> 00:49:53,533
where the orbit
took you back to,

793
00:49:53,533 --> 00:49:55,033
it was way out,

794
00:49:55,033 --> 00:50:00,266
unbelievably far out,
what we now call the Oort Cloud.

795
00:50:00,266 --> 00:50:04,366
NARRATOR:
It's thought the gravity
of other objects in the galaxy

796
00:50:04,366 --> 00:50:09,666
can occasionally knock
these icy objects inwards.

797
00:50:09,666 --> 00:50:11,233
SUNSHINE:
But the really interesting thing

798
00:50:11,233 --> 00:50:14,466
was that they were coming
from all directions in space,

799
00:50:14,466 --> 00:50:16,733
and there had to be a cloud.

800
00:50:16,733 --> 00:50:20,200
♪ ♪

801
00:50:20,200 --> 00:50:23,400
NARRATOR:
Although we can't see
this far out,

802
00:50:23,400 --> 00:50:26,400
comets with orbits
starting in the Oort Cloud

803
00:50:26,400 --> 00:50:30,966
streak across our skies.

804
00:50:30,966 --> 00:50:33,166
RICE:
The Oort Cloud is
kind of incredible.

805
00:50:33,166 --> 00:50:34,700
No one's actually been there,

806
00:50:34,700 --> 00:50:37,200
no one's actually observed
anything within the Oort Cloud.

807
00:50:37,200 --> 00:50:40,000
They've only seen the wanderers
that have escaped

808
00:50:40,000 --> 00:50:42,100
from the Oort Cloud
for a brief moment,

809
00:50:42,100 --> 00:50:43,433
which I think is what makes it

810
00:50:43,433 --> 00:50:46,766
so spectacular
and so exciting to me.

811
00:50:46,766 --> 00:50:50,700
CHABOT:
If I could visit
one of those dark regions,

812
00:50:50,700 --> 00:50:52,900
I would have to choose
the Oort Cloud.

813
00:50:52,900 --> 00:50:54,800
We don't know that region
at all,

814
00:50:54,800 --> 00:50:57,700
we haven't ever explored it,
so for me,

815
00:50:57,700 --> 00:51:00,200
that would be
the most exciting place to go.

816
00:51:00,200 --> 00:51:03,100
♪ ♪

817
00:51:03,100 --> 00:51:04,766
NARRATOR:
We think of the solar system

818
00:51:04,766 --> 00:51:10,333
as the sun and all the planets.

819
00:51:10,333 --> 00:51:12,933
But that's just
what's close to Earth.

820
00:51:16,133 --> 00:51:19,033
As wandering worlds give us
rare glimpses

821
00:51:19,033 --> 00:51:21,833
into what is beyond

822
00:51:21,833 --> 00:51:25,333
and technology improves,

823
00:51:25,333 --> 00:51:30,766
we're discovering
more and more.

824
00:51:30,766 --> 00:51:32,800
RUSSELL:
We're really only
scratching the surface,

825
00:51:32,800 --> 00:51:35,800
so there are millions
of these tiny bodies out there,

826
00:51:35,800 --> 00:51:39,866
and we still have so many
secrets to unlock from them.

827
00:51:39,866 --> 00:51:43,833
MERCED:
There is so much information
in darkness.

828
00:51:43,833 --> 00:51:45,833
If we pay more attention

829
00:51:45,833 --> 00:51:49,566
and we trust what we perceive

830
00:51:49,566 --> 00:51:53,433
with all our senses,

831
00:51:53,433 --> 00:51:56,733
we will gain
much more information

832
00:51:56,733 --> 00:52:00,833
from those dark regions
of not only our solar system,

833
00:52:00,833 --> 00:52:02,966
but of the universe.

834
00:52:02,966 --> 00:52:05,033
This model of the solar system,

835
00:52:05,033 --> 00:52:08,966
it's missing all of the most
interesting bits.

836
00:52:08,966 --> 00:52:13,000
♪ ♪

837
00:52:35,100 --> 00:52:37,966
♪ ♪

838
00:52:38,900 --> 00:52:46,433
♪ ♪

839
00:52:50,266 --> 00:52:57,800
♪ ♪

840
00:53:01,700 --> 00:53:09,233
♪ ♪

841
00:53:10,866 --> 00:53:18,400
♪ ♪

842
00:53:20,033 --> 00:53:27,566
♪ ♪