Nova (1974–…): Season 46, Episode 1 - Pluto and Beyond - full transcript

Four billion miles from Earth,

a spacecraft closes in
on its target,

a mysterious object far beyond
all the known planets

that could reveal new secrets

about the birth
of the solar system.

But the mission is risky.

Even being hit

by something smaller
than a single pellet of rice

at 32,000 miles an hour

would be catastrophic,

and we would lose the mission.



The spacecraft
that brought us to Pluto

is now attempting an even more
challenging final quest.

Can it succeed?

There's only one shot,

and if you make a mistake,
that could be it.

"Pluto and Beyond."

Right now, on "NOVA."

January 1, 2019.

It's the arrival of a new year.

But here at Mission Ops,
the mood is tense.

The team is feeling
a little stressed.

A team of scientists,

along with their families
and friends,

are waiting in anticipation...



I'm getting
a little bit nervous.

For the arrival of a signal

from a tiny spacecraft
on a dangerous mission.

Its name: New Horizons.

We are really pressing
the limits here.

"New Horizons" is attempting

to fly by a mysterious object

far beyond the planets
we've come to know,

a billion miles beyond Pluto,

in the outback
of the solar system.

This is the farthest exploration
in the history of humankind,

and nobody's planning
anything like it ever again.

This is really challenging.

We're going to a small object
that we don't know a lot about.

In fact,

one of the biggest, baddest
space telescopes in our arsenal,

the Hubble,

can only capture a pixelated
image of this tiny speck.

Its official name
is 2014 M.U.69,

but the New Horizons team

also calls it by the Latin name
Ultima Thule.

We gave it this nickname
Ultima Thule

that means
"beyond the farthest frontiers."

And in fact, it really is

beyond the known world

or part of our solar system
that we have explored.

Here, objects like Ultima Thule
have been frozen in time

since the solar system formed

four-and-a-half billion years
ago.

We believe this object,
like many others out there,

are actually planetary embryos.

And to study those objects
will give us a great window

into the process
of planetary formation.

For the New Horizons team,

taking their spacecraft
into the unknown

is not only a monumental task,

it's risky.

An object the size of a pea
or even smaller

would be capable of literally
taking out the spacecraft.

Tests have revealed
that as the spacecraft travels

at 36,000 miles an hour,

even something as small
as a grain of sand

could rip a hole
right through it.

At this point in the mission,

you really have to be prepared
for anything.

♪ ♪

But for now,

all the team can do is wait,

and hope that years of work
will pay off

and that the tiny explorer
manages to stay on target...

And survive.

I love this spacecraft.

I've put my blood, sweat,
and tears

into helping
to put this thing together,

going back to 2002.

It's just made us feel so proud.

Proud, because when it comes
to exploring our solar system,

New Horizons
is already a pioneer.

January 19, 2006.

New Horizons is prepared
for launch at Cape Canaveral.

Two... one.

We have ignition and lift-off

of NASA's New Horizons
spacecraft

on a voyage to visit
the planet Pluto and beyond.

The spacecraft sets out
on a journey to reach not one,

but two distant targets.

♪ ♪

Along the way, Alice Bowman,
missions operations manager...

Also known as MOM...

Will help guide it
through a voyage

that will last
more than a decade.

We talk about the spacecraft
as if it's our child.

When we launched, you know,
we referred to it as a baby.

When it does something
that we don't expect,

we relate it perhaps
to terrible twos

or something like that,

so it really,
it becomes part of us.

78 days after launch,

New Horizons passes the orbit
of the red planet, Mars.

Just two months later, it flies
through the asteroid belt.

In a year, it passes by Jupiter,

where it captures spectacular
images of a volcanic eruption

on the gas giant's moon lo.

It was the first time
that time-lapse

had ever been made
of any volcano

anywhere in the universe
off the Earth.

So it was really unique.

The spacecraft travels another
two-and-a-half billion miles

past the orbits
of three more giant planets...

Saturn, Uranus, and Neptune.

Finally,
nine years after launch,

New Horizons closes in
on its first fly-by target...

Pluto and its moons.

They have only been observed
from billions of miles away,

our best images
nothing more than a blur.

Until, in the summer of 2015,
it slowly comes into view.

Every day, it was getting bigger
and bigger and bigger

and starting to reveal
this world.

It was an incredible ride.

The mission is proceeding
without a hitch.

All is working as planned,

but then...

On July 4, 2015, just ten days
before the Pluto fly-by...

I got a call

from the New Horizons principal
investigator, Alan Stern.

I could hear
that he was panting.

He was running down the hallway
here at APL.

He said, "We lost contact
with the spacecraft,"

and I said,
"You've got to be kidding."

You know, this has
never happened before.

You just feel, you know,

that pit in the bottom
of your stomach.

Your pulse goes up a little bit.

Could it be, you know,

these millions of miles away,
we hit something?

Is the spacecraft
still in one piece?

The team races to figure out
what's gone wrong.

It took a little while,
but we realized

exactly what had happened is,
we had overloaded the computer.

That's sort of like

your worst nightmare

a week before an encounter.

We knew that we could fix it.

The question was:

Were we going to be able
to do that in enough time?

Alice, I swear, didn't get
any sleep,

but she said
she slept on the floor

for a few minutes one night.

For a couple of nights,
slept there,

you know,
just like a child that's sick.

You want to be there to help it
recover along the way.

The team works round the clock,

re-uploading instructions
to the spacecraft's computer.

Alice Bowman,
our mission operations manager,

and her team

did a fantastic job

of putting everything
back together again

with only six hours to spare.

Just in time for the fly-by.

♪ ♪

Okay, we're in lock
with carrier.

July 14, 2015.

Three billion miles from Earth,

New Horizons should have just
flown above Pluto's surface,

taking pictures
and gathering data.

But did it make it?

Stand by for telemetry.

Alice waits to hear back
from the spacecraft...

A sign it has safely completed
the fly-by.

New Horizons is so far away,

it takes four-and-a-half hours

for that signal to reach Earth.

MOM on Pluto 1.

We have a healthy spacecraft.

We've recorded data
of the Pluto system.

It was a huge sense of relief
and accomplishment.

I think mostly accomplishment.

We did it.

- We did, we did.
- It's just great.

♪ ♪

The first up-close images
come in.

And they shock the world.

♪ ♪

When the images first came down
from New Horizons,

I was stunned, excited, tired...

Every emotion and feeling
you can imagine,

but really just amazed
at what they looked like.

This tiny world, with a diameter
less than 1,500 miles,

turns out to be
incredibly complex,

with mountains
more than a mile high.

The Rocky Mountains here
are beautiful,

and the Flatirons
in the background,

but instead of rock,

the mountains on Pluto
were made of ice,

and at those temperatures,

ice is so cold,
it's like bedrock.

Pluto's most famous feature,
its heart,

contains a massive glacier
that flows across its surface.

I certainly did not expect

a glacier of nitrogen
and methane ices.

Never in a million years
did I expect that.

We're seeing processes,

some of which look
quite familiar from the Earth,

but are happening in a
completely alien environment

with completely alien materials.

Pluto even has volcanoes
made of ice.

There is something that looks
very much like an ice volcano

on Pluto.

We didn't see it erupt, but
it sure looks like a volcano.

Using images and data collected
by the spacecraft,

the team created this simulation
of what it would feel like

to fly over Pluto's surface.

Some of the geologists
on our team

have taken to calling Pluto
the new Mars,

because it's every bit
as complicated as Mars.

What could be driving
such geological diversity

on such a tiny world?

Pluto's surface
may change with the seasons.

Pluto doesn't really have
the sort of four seasons

that we have.

We have very even seasons:

We have a hot summer
and a cold winter

that's about the same length
of time in each one,

because Earth is in
a circular orbit around the sun.

Pluto's not.

It's in this very eccentric
orbit around the sun.

As Pluto, along with its
largest moon, Charon,

gets closer to the sun,

its surface warms.

But as it continues
on its 248-year orbit,

getting farther and farther
from the sun,

its surface becomes colder.

So there are
these extreme seasons.

In summer, ices on the surface
can evaporate.

In winter, they can re-condense,

so when you see it today,
it is not going to look the same

as it looks in a hundred years,

when it's in
the opposite season.

But there could be another
strikingly different reason

for Pluto's complex surface.

Based on measurements

of its density
and chemical composition,

scientists believe
it has a rocky core.

All rock contains
radioactive elements,

which as they decay,
release heat.

So there's a continual flow
of heat

from the interior of Pluto
to the, to the outside.

But it's a very small
amount of heat,

because Pluto is pretty small...

It doesn't have
that much rock in it.

But we think that even that
tiny amount of internal heat

is enough to move mountains,
literally.

And it may also be enough heat

to create something
extraordinary

beneath Pluto's icy crust.

Right now,

Pluto is covered in frozen water
and frozen nitrogen

and a few other compounds.

It's quite possible
that in the past,

there was enough heat
internal to Pluto

to melt some of that ice
and create a layer of ocean.

We suspect that Pluto
has an ocean of liquid water

deep in the interior,

hundreds of miles
below the surface.

It raises what seems like

an extraordinary possibility,

that if you have liquid water
and rock deep inside Pluto

in contact with each other,

well, that's an environment
that life could exist in.

I think one of the most
mind-blowing things

is to hear the astrobiologists
talk about the fact

that that could be an abode
for life, potentially.

Here we have a world
whose surface is just 40 degrees

above absolute zero.

It's three billion miles
from the sun.

You would never expect life
at those kinds of temperatures.

Whatever's causing
the extraordinary geology

on Pluto's surface

will be debated
for years to come.

There are a lot of theories

and there are a lot of ideas,

and we don't know
which one is right

or if none of them are right.

We're in this wonderful position
of knowing volumes

compared to what we knew before,

but it's maddening,
because unlike Mars,

which is around the corner,

and you could fly to
very quickly again,

it's a big undertaking to cross
the entire solar system.

♪ ♪

As its historic fly-by
comes to an end,

and the tiny spacecraft
leaves Pluto,

New Horizons looks back

to take one last
breathtaking image.

My real favorite, favorite
picture

is one after we flew by Pluto,

and we're looking back
and we see the horizon of Pluto,

with the sun lighting
the atmosphere from behind.

You can see layers of haze
and shadows of mountains

streaming across the surface,

and that is where
you really understand

that Pluto is a world.

Whenever I see that picture,

it's as if I'm sitting
on the spacecraft,

looking out the window
as Pluto goes whizzing by,

and it, more than any other
picture that we took,

puts me there.

That photograph for me
is the crowning achievement.

We were really there

and we really did it.

And we made our own
little contribution

not just to science,
but actually to history.

That history begins
back in 1930,

when Pluto is discovered
by Clyde Tombaugh,

a young farm boy
with a passion for astronomy.

For nearly a century,
Clyde has the honor

of being the only American
to discover a planet.

But almost from the get-go,

many astronomers
aren't buying it,

because when it comes
to being a planet,

size matters.

When you discover
an astronomical object

far, far away,

you have no direct way
of measuring its mass.

You don't actually know
how massive it is.

And so people speculated about,

maybe Pluto was one Earth mass,

and then people kept revising
their estimate

down and down and down.

Until people realized,
"Oh, my gosh,

this thing is really, really
small."

It turns out Pluto is smaller
than Earth's moon,

but size wasn't Pluto's
only problem.

So was its location.

A tiny little planet
in the outer solar system

just didn't make sense.

Pluto was regarded as a planet,

but it was always regarded
as a kind of funny planet,

a weird planet,
somewhat out of place.

So the sun sits in the middle.

The sun is this massive body
made of hydrogen,

it's a million times
the mass of the Earth

and about a hundred times
the diameter of the Earth,

and it's orbited by planets,

which are moving
in nearly circular orbits.

And then at the very edge,

the outer edge
of this system of planets,

we knew of Pluto.

Pluto is not really like
a terrestrial planet,

because it's got
quite a bit of ice in it.

Pluto is not at all
like a giant planet,

because it's tiny
and it's not made of gas...

It's made of solid material.

And it also has
a very strange orbit

with a high ellipticity
and a high inclination.

It's tilted up relative to
the plane of the solar system.

Beyond Pluto, uh...

there was nothing,

and people actually didn't think
about that in general,

because it's just
an empty space.

And next stop, uh, the stars.

Is the solar system's
little misfit

really alone out there?

For decades to come,

astronomers look
for another planet beyond Pluto.

But as hard as they look...

And they look hard...

No one finds anything.

Until two astronomers,
David Jewitt and Jane Luu,

take on the challenge.

The original thought that we had

was simply that the outer
solar system is weirdly empty.

David and Jane get access

to one of the most powerful
telescopes on the planet,

and they start a search
that will take a lot longer

than either one of them expects.

While it's easy to see
distant stars,

because they radiate
their own light,

other celestial bodies
are much harder to see.

That's because light
has to travel all the way

from our sun to the object,

reflect off its surface,

and then make the long journey
back to Earth.

By then, it's barely visible.

David and Jane hope that
advances in digital detectors,

which are far more sensitive
to light than film,

will help them see
a whole lot more.

August 1992,
Mauna Kea Observatory, Hawaii.

After searching for six years,
they finally find an object

moving in the night sky.

Here is the set

of discovery images
for the first object.

So you can see this object

drifting from this picture

to this one to this one.

It's drifting slowly
to the left.

A tiny object beyond Pluto
orbiting the sun.

Then they find more.

And more.

So the space beyond Neptune
is basically,

is full of objects that
we just didn't know about before

because they're too faint.

David and Jane discover

an entirely new region
of the solar system.

Now known as the Kuiper Belt,

it's believed to be home
to hundreds of thousands,

possibly millions,
of icy objects...

Including Pluto.

The Kuiper Belt has a thousand
times more objects in it

than we have
in the asteroid belt,

completely unknown
until these first observations.

The Kuiper Belt stretches out
billions of miles.

It is just difficult to imagine

how expansive
this field of icy debris is.

Think of it as a giant doughnut
surrounding the planets,

on average,
each Kuiper Belt object

separated from the next
by a million miles.

That's how massive
the Kuiper Belt is.

The day that the first new
Kuiper Belt object

was discovered
by Dave Jewitt and Jane Luu,

it clicked in everybody who was
paying attention's head,

it was, like, "Oh there's a ton
of objects out there.

"That's what Pluto is part of,
Pluto's part of the Kuiper Belt.

It suddenly all makes sense."

For me, Pluto was the harbinger
of things to come.

We didn't realize

that its being an oddball
was telling us something,

it was telling us the secret

of the third zone
of the solar system.

This really sort of restructures
our understanding

of how our solar system is built
and how we should think

about the membership
of our solar system.

♪ ♪

August 2006, Prague.

Just a few months
after New Horizons set out

to explore the ninth planet
of the solar system,

an international association
of astronomers

votes to demote Pluto.

And the official planet count
goes back down to eight.

While some members of the public
are outraged,

not everyone sees this
as a demotion.

One could argue

that Pluto actually made out
better with this change,

because in its previous
instance,

it was the smallest planet
of the solar system.

It now has become
the king of the Kuiper Belt,

and so, in a sense,
its status has gone up.

Over the last few decades,
astronomers have discovered

that Kuiper Belt objects
vary in size, shape,

and also in their orbits.

There are larger objects,
like Pluto.

These are known
as dwarf planets.

We've discovered
that the outer solar system

is littered with small planets.

These are typically
rocky and icy objects.

Many have atmospheres,
many, possibly most, have moons.

There's a great variety in terms
of their physical properties,

their colors,
their compositions...

Many of the things we're used to

in the planets
we're familiar with,

but in miniature.

I think a decent analogy is,
when you see a Chihuahua,

it's still a dog,

because it has
the characteristics

of the canine species,

just in miniature.

Then there are objects
like Ultima Thule.

Astronomers think these objects
have been frozen in time

since the birth
of our solar system

four-and-a-half billion
years ago.

So what we think we're seeing
is a fossil structure

that's left over from the
formation of the solar system.

It's this tiny remnant of the
ancient past that we can visit.

Objects like M.U.69
retain the pristine conditions

of the early solar system.

This now lets us

look at these objects
with the idea

that an examination of them
will help us better understand

what the early solar system
was like.

Unfortunately, our best images
of these primordial objects

are only single pixels
of dim light,

almost impossible to see.

If only we could get
a spacecraft

out to the Kuiper Belt
to take a closer look.

But of course,
there's one already out there.

When we launched
the New Horizons spacecraft

back in 2006,

we knew we wanted to fly
to an object beyond Pluto,

but we didn't have
a particular object

that we knew we could reach
with our spacecraft.

So we started doing
deep searches of the sky

beyond Pluto.

April 2011.

While New Horizons is traveling

through the solar system,

at the Southwest Research
Institute in Boulder, Colorado,

Marc Buie leads the search
for New Horizons' next target.

But the teams faces
extraordinary limitations.

The region their spacecraft can
safely reach is extremely small.

There's certain things
we don't have

an infinite supply of,

like fuel.

And our thrusters,

we only want to put
so many thruster counts on them.

Thrusters make it possible
to redirect your spacecraft

as you zero in on a target.

Without them, there's no way
to steer the ship.

If you use them
beyond the lifetime

that they were designed for,

they could have a failure.

But an aging spacecraft
is just one of many challenges.

Where you need to look

is probably one of the hardest
spots in the sky to look.

It's right in the middle
of the Milky Way.

The densest star fields
in the entire sky,

where you would see
a million stars brighter

than the objects
you were looking for,

and you had to try and sift it
out between all those stars.

They search for several years,

and find nothing.

We were starting to say,
"What's going to happen?

"We have to find an object
in 2014.

"If we don't find one in 2014,

"we won't know well enough
where the object is

to redirect the spacecraft
to get there."

The clock is running out.

It's time for the big guns.

It's time for Hubble.

From its vantage point far
beyond the Earth's atmosphere,

the Hubble space telescope
has a better chance

of spotting faint objects,

and that makes
all the difference.

After a big effort
with the Hubble telescope

in the summer of 2014,

we found an object.

Wow, it was truly exhilarating.

Yay, we've done it!

This is kind of a first,

to discover an object
while you're in flight,

and then redirect the spacecraft
to fly by it,

and determine its orbit
along the way.

Nailing down
Ultima Thule's orbit

is critical for the success
of the mission.

Think of it like skeet shooting.

You have to predict
where your target will be...

in the future.

So we do shooting and targeting
in the outer solar system.

You're going to tell me here

how you do shooting
and targeting on Earth.

New Horizons team member
Anne Verbiscer

and sharpshooter
J.R. Pierce

demonstrate.

It's not a space vehicle, but...

We'll get our point across here.

♪ ♪

Pull.

If J.R. aims
directly at the target...

He's gonna miss.

Launch.

I'm initiating
the launch sequence.

Pull.

But if he aims
ahead of the target...

It's a hit.

Again and again.

And again.

You need to focus on where
your target is going to be,

not where your target is.

So this reminds me
of when I was a child

and watching
the Apollo launches.

All engines running.

We have a lift-off.

It fascinated me

that they were targeting
where the moon was going to be

three days after
the launch happened,

and that's when the astronauts
would arrive

to try and land on it.

So for New Horizons, the concept
is basically the same

as it was for Apollo,

but the distances
are far greater.

We have to intercept where
it will be years down the road.

So we have to calculate

where it will end up
on the exact day and hour

and literally minute
of the fly-by

from years in advance.

Images taken
by the Hubble space telescope

help the team
track Ultima Thule's orbit.

But they still need
to know more.

They don't know how big it is,
or even what shape it is.

Ultima Thule is a completely,
almost unknown object.

This is terra incognita.

It's a new world.

Details we don't know.

But there may be a way
to find out more

by observing
a rare celestial event.

An occultation
in its simplest form

is when something gets in front
of something else.

If you've ever been on a beach,

and you're just enjoying
a nice sunny day,

and then all of a sudden
the sun goes away

because somebody just walked
in between you and the sun,

and there's that shadow
passes across your face,

the same exact thing
is happening here,

except instead of our sun,
it's a star,

and if the star is hidden
from your view,

you are in the shadow
of the Kuiper Belt object.

♪ ♪

If you can measure
the edge of that shadow,

it shows the shape and size
of the object.

Suppose it's moving 20 miles
per second across the sky,

and the star disappears
for one second,

now you know that
it's 20 miles across... easy.

You just have to be in the
right place at the right time.

But how do you get

to precisely the right place
at the right time?

There's two pieces to this.

You need to know
where the object is,

and that's what Hubble does
for us,

but you also need to know
where the stars are.

And that's where
the Gaia Mission comes in.

The Gaia Space Observatory
has been creating

the most precise
three-dimensional star map

of our galaxy

that has ever been made.

And we knew that when
we had those star positions,

we had a chance
of actually predicting

an occultation with M.U.69.

In the summer of 2017,

the New Horizons team
finds a match.

The two best places to view
this occultation...

Where their telescopes
can detect Ultima's shadow...

Are in the mountains
of Argentina

and the countryside
of South Africa.

Much like the solar eclipse
that many people saw in 2017,

you have to be

in the right place
at the right time

to be in the path of the shadow.

So we're here.

Let's hit that first.

54 people going
to two different continents

to watch an event that takes
two seconds to happen?

Overwhelming.

♪ ♪

The teams set up
their telescopes

in the middle of nowhere...

And hope for clear skies.

We sent 13 telescopes
to South Africa.

12 telescopes
to Mendoza, Argentina.

Searching for a blink

four billion miles away.

And saw nothing.

All of that work and nothing.

It turns out

that their estimations
of Ultima Thule's orbit

are off.

The star that was supposed
to blink continued to shine.

Everybody was a little depressed
about that.

♪ ♪

A month later,
they get a second chance

to find out whatever they can

about Ultima Thule's
size and shape,

but to be in the right place
at the right time

is going to be even harder.

On July 10, of 2017,
there was another occultation

observable only
over the South Pacific Ocean,

and really accessible
only to the SOFIA aircraft.

The SOFIA Airborne Observatory

is a specially modified
Boeing 747,

with a telescope on its side.

What we're doing here with SOFIA

is putting a very large
telescope

into the occultation path

at just the time
the shadow is there.

The reality is
there are so many details,

what are the winds doing,

we had to worry
about a turbulence zone

that we might have
to fly around.

The moment of truth arrives.

They wait for the star
to blink out.

Are they in the right place
at the right time?

Again, they see nothing.

So everybody is kind of
depressed again.

Okay, we've done it a second
time and we've got nothing.

After two misses,
reality sets in.

We thought we struck out twice.

Okay.

What's going to happen next?

But they get another chance.

The next occultation
in Patagonia

was only seven days later,
on July 17.

So really had to shift gears
quickly and get ready

to do this next
ground-based effort.

The stellar occultations
that we have been attempting,

are the most challenging
stellar occultations

ever attempted in history.

Because Ultima
is so much further away

than anything else,

and it's tiny.

The night of the occultation,
winds were, were pretty bad.

These telescopes we use
are really great

however, they are
very wind-sensitive.

We wanted to shield
that telescope

from every possible vibration,
and that meant we had to do

whatever it took

to get the data
and observe the star

without it jiggling around
all over the place.

For that,
they need a few volunteers.

If you just started out with,
"We're from NASA,"

people just come out
of the woodwork.

We had two people show up...
A father and his daughter.

They brought a spare battery.

Perfect, so we put them to work.

♪ ♪

Together, for 45 minutes,

they blocked the wind with a
truck, some plywood, and a tarp.

Did they catch it?

We spent hours after people
came back with the data

to see whether we got it or not.

Does the star blink
or have they failed again?

We'd finally had success
and saw the star blink out.

This is what we came for.

This is it.

Oh, my God.

That's what's it's all about.

Six months worth of work.

Just two frames
and the star is gone.

Unbelievable.

In fact, five telescopes
capture the blink.

Each from a different
perspective.

When pieced together,
their data suggests that Ultima

is about 20 miles long,

but its shape is more complex
than anyone expected.

Immediately I could tell
this is not just

some simple spherical object
that we're looking at.

It's a much more complicated
shape.

They come up with
three possibilities.

One is, you have
two circular objects

that are close to each other
but they're orbiting each other.

Or it could be just some
lumpy potato-shaped thing.

♪ ♪

And then the third is
what we call a contact binary...

Two balls stuck together.

♪ ♪

And we think it could happen
for Kuiper Belt objects.

We don't know, we've never seen
one of these things before.

But when New Horizons finally
brings Ultima Thule into focus,

the results could be profound.

This elusive object could
revolutionize our understanding

of how the planets
in our solar system formed.

If the solar system
is an intricate

and complicated castle,
then MU69 is a brick,

and you don't know
how this castle was made

until you understand
what the brick looks like.

Four and a half
billion years ago,

the planets in our solar system

formed from a massive disk
of gas and dust.

Scientists have detected
the beginning of this process

in striking images of distant
solar systems like this one

known as HL Tauri,

a young star about
450 light years from Earth.

We have these
beautiful observations

of disks of gas and dust

around other stars.

So we know that planet formation
starts from small dust grains.

In our own solar system,

scientists theorize that through
a process called accretion,

gas and dust stuck together,

a lot like those
clumps of dust and dirt

that collect under your bed.

Dust bunnies, held together
by a powerful force...

Static electricity.

So you can think of

planet formation,
the initial stages,

very similar to just letting
your dust bunnies

under your bed
grow for millions of years

into bigger and bigger objects.

If you don't vacuum,

those dust bunnies
will just keep getting bigger.

But for the seeds
of planets to grow,

they need more.

They need the power of gravity.

After objects reach a certain
threshold in their mass,

they can grow more rapidly
than they could before,

because they have
substantial gravity.

But there's a catch:

There's a gap between
making something this big

and making something
the size of a planet.

How does an object grow
from the size of a marble

to the size of a planet?

In the last decade
a new theory has emerged.

A stream of marbles

will come along

and as it's moving around the
sun and some of them will clump

and you'll suddenly get
a huge amount of clumping action

and that's called
pebble accretion.

And one of the things we can do
by looking at Ultima Thule

is look to see whether it was
formed by pebble accretion.

If we see lots of
BB-to marble-sized pieces

on the surface of MU69,

we're gonna go "A-ha, this is
a loose collection of pebbles."

And pebble accretion argues
for things that are

elongated or potato-shaped,
which is what we seem to see

for Ultima Thule from
our ground base occultation.

We're interested scientifically
how planets formed,

although in our hearts
we're also interested about

where we came from,
how we got here.

What were the elements?

And the outer solar system
objects like Ultima Thule

are the raw materials.

And so we're getting a chance
to look back

at these well-preserved
raw materials

to see really what was
the starting point,

what were the ingredients

that went in to the magic recipe
that makes life.

October 4, 2018.

89 days before fly-by,

New Horizons is 30 million miles
from Ultima Thule

and closing.

Fred Pelletier

and a group
of vigilant navigators

are tracking Ultima's orbit
to ensure their spacecraft

won't miss the mark
on New Year's Eve.

They rely on images like this
taken by New Horizons'

long-range telescope,
named Lorri.

But at this distance,

tracking tiny Ultima
among a dense field of stars

is no easy task.

It's a very crowded

star field... these are all stars

and Ultima is in the center
right there.

So what we do is we have
a catalog of the starfield

that we use to remove the stars.

We end up with this image
that highlights our target,

Ultima Thule, here.

Next they zoom in
to take a closer look

and discover their estimate
of Ultima Thule's orbit is off.

The yellow cross represents
where we thought Ultima Thule

would be before we
took the picture,

and the blue greenish one

represents, well,
where it actually is.

So, as you can see,
we're a little bit off.

And the difference here

doesn't seem too much
on this scale,

but it's actually 600 miles
from the target.

Because this object
is so very, very small,

it's possible that
if we are a little bit off,

we could just miss
seeing the object

and we certainly
don't want to do that.

There's only one shot

and if you make a mistake,
that could be it.

For the next few weeks,

the navigators will carefully
follow Ultima's path,

examine every pixel
of every frame

to help guide New Horizons
to its target on New Year's.

If their calculations are right

the spacecraft will fly

just 2,200 miles
above Ultima's surface.

This is a comparison
of about 30 days out.

What Pluto looked like

and what Ultima Thule
looks like right now.

So you're asking me what the
challenges are of this mission,

this image is worth
a thousand words.

The size of Ultima Thule

is a small dot still,
and it will be the case

until a few days
before the fly-by.

That makes it very different
from Pluto.

As the weeks go by,

New Horizons sends back
more images of the distant dot.

December 29, 2018.

Three days away from the fly-by

and the anticipation
is certainly building.

We thought we'd know
a lot more by now.

I think everyone
would have said,

"You'll know how fast
it's rotating,

can get an idea
of what the shape is like.

But so far, answers remain
tantalizingly out of reach.

It s holding its secrets

to the last possible minute.

I mean we keep saying,

"Well, we're gonna know
eventually, right?"

But right now,
it's still a mystery.

As the fly-by approaches,

preparations continue all night.

This evening I'll be sleeping
in my office,

so I brought
my little backpacking tent in.

I'll have time for sleep later.

Things have been happening
so fast.

Don't ask us what day it is.

Most of us cannot remember

whether it's Monday, Tuesday,
or whatever.

We know how many days it is
to fly-by.

Ten...

Nine...
Eight...

January 1, 2019.

12:33 AM.

One!

Go New Horizons!

As the world brings in
the new year,

the New Horizons team celebrates
the moment

of the spacecraft's closest
approach to Ultima Thule.

But it will be hours
before anyone knows

if the fly-by is successful.

Ultima Thule is so far away

that it takes six hours
to send a signal

from the spacecraft to Earth.

Which is crazy,
it's a really long time to wait.

Later that morning,

team members,
family, and friends

wait anxiously
for New Horizons' signal

to finish crossing four billion
miles of space and reach Earth.

Go ahead, RF.

What the green screens
will tell you

and RF is in fantastic shape.

Copy that, RF is green.

The signal comes in.

But Alice Bowman,
New Horizons' MOM,

waits for confirmation

that each system
on the spacecraft is working.

Copy thermal is reporting
green status.

Most crucially,
she wants to hear

if the digital recorders
are full of precious data.

Go ahead, CNDH.

CNDH is nominal.

Our SSR pointers are right
where we predicted.

Copy that.

Whoo!

What that means is that
the solid state recorder,

the pointers are where
they should be,

that tells me that
we observed something.

Something filled that camera.

We have a healthy spacecraft.

We've just accomplished
the most distant fly-by

of our solar system.

♪ ♪

The first close-up image
of this distant object comes up.

Well, what we saw today
blows out of the water

anything we've seen.

The first image was
two or three pixels across.

Yesterday, you could see
kind of two lobes.

And today's image we see it
for what it really is:

basically two spheres
stuck together.

Like this really is
two things that formed

as two different objects.

It's confirmation of what we saw

in the occultation.

The shape that
was predicted from that

was almost exactly correct.

It's the kind of thing
we were looking to see

is planetary formation
frozen in time

and here it is
right in front of us

it's just wonderful.

We got what we came for.

I think it's tending to

substantiate the ideas that
these objects form as clumps,

as pebble accretion.

I think it's so far looking like

a really nice confirmation
of those theories.

♪ ♪

I just was staring at it
with tears in my eyes

because we've been working
for so long to do this,

and it worked,

and I just couldn't
get over that yet,

I still haven't
gotten over that.

Absolutely amazing to see that.

This is exploration
at its purest.

When you think about it,
it's remarkable.

We didn't know this object
even existed

when we were building
the spacecraft.

Going into the unknown
is fundamentally important

for the human spirit
from every aspect...

From scientific, to artistic,

to just wondering where we came
from and why we're here.

It will take 20 months
for New Horizons to send back

all the data and images
collected of Ultima Thule.

And with many years of power
left on the spacecraft,

the team hopes it will continue

to explore the far regions
of the solar system.

But already, this tiny probe,

and the humans who built
and guided it on its journey,

have made gigantic discoveries,
taking us to new worlds,

making the unknown known,

and bringing the impossibly
distant finally within reach.

♪ ♪

The exploration continues
on "NOVA's" website,

where you can watch this
and other "NOVA" programs,

see expert interviews,
interactives,

video extras, and more.

To order this "NOVA" program
on DVD,

visit ShopPBS
or call 1-800-PLAY-PBS.

This program is also available
on Amazon Prime Video.

♪ ♪