All language subtitles for Jupiter Revealed BBC Horizon 2018 1080p HDTV x264 AAC MVGroup org_Subtitles01.ENG

In the outer solar system
there lurks a monster.

Everything about it is on steroids.

Its radiation is the worst, its
magnetic field is the strongest,

it's spinning the fastest.

Jupiter.

We had to build an armoured tank to
go there.

Thanks to Nasa's Juno mission,

scientists can explore what's inside
the largest planet

in the solar system for the first
time.

A few years ago all we had was
theories.

Now we get to look inside.

Enabling them to peel back the
layers

and reveal Jupiter's close-held
secrets.

We need to know what's going on in
the interior,

and that's not something we can get

by just taking pictures of the
outside.

And inside they are finding
scientific wonders.

I look at an image like that and I
say, "Wow". I just love it.

And some scientists are even trying
to create a piece of Jupiter...

All personnel are required to exit
the target bay at this time.

..here on Earth.

The power that we put in the lasers
is about 500 times the

power that is used for the entire
United States at a given moment.

This is the story of an audacious
journey

to the most extreme world we
have.

To send a spacecraft there is a
little bit insane.

But this insane mission could answer
questions that have long puzzled

planetary explorers.

It had a key role in the formation
of the solar system.

It holds the secrets to how the
whole solar system formed,

how it got started, how planets are
made.

What's the point of building a
spacecraft

if you're not going to send it
somewhere cool and interesting?

To the Romans, Jupiter was the king
of the gods,

the lord of thunder and lightning.

It ruled the sky.

And today Jupiter still holds us in
awe with its incredible beauty.

But despite centuries of studying
the swirls and stripes

we see with our telescopes, it holds
one fundamental secret.

What lies beneath these cloud tops?

What is Jupiter made of?

What sits at its very core?

Today a group of scientists are
achieving something

that would once have
been, well, completely impossible.

They are taking us on a trip beneath
the clouds, into the depths of this

alien world.

The clouds are hiding what's inside
the planet.

But they're not driven by idle
curiosity.

They believe Jupiter, the king of
the gods,

is the most important planet in the
solar system.

If we can make a good measurement of

what's at the very centre of
Jupiter,

that's going to let us figure out
what was going on

right at the start of our solar
system.

Which is when all of the planet
formation gets started.

Jupiter is big.

Very big.

And its size gives a clue.

A clue to why understanding the
planet is so important.

But for Professor Kaitlin Kratter

that word, big, doesn't do it
justice.

It's really hard to get a sense of
how big it is

in comparison to piddly little
Earth.

So what I want to do is I want to

give you a frame of reference and
show

you how big Jupiter is compared to
all the rest of the planets in the

solar system.

Kaitlin's going to measure out the
planets' masses with rocks.

This is going to be our
representation of Mercury,

the smallest planet in our solar
system.

And you can see we're starting out
with something that's pretty light.

I can throw it up and down.
It's only about one kilogram.

Next up, Mars.

And you can see Mars is a bit bigger
than Mercury.

It's about twice as massive, maybe
two kilograms.

It's still pretty light, no big
difference.

But it's a large jump to Venus at
14kg.

And our own lump of rock, the Earth,
is bigger still.

You can tell it's getting a little
heavy.

It's about 17kg, so I've got
to work a little bit now.

But in terms of the masses in the
solar system

we are just getting started.

For the outer worlds, Kaitlin needs
a little help.

Even the smallest, Uranus, is more
than ten times the Earth's mass.

That's 250kg worth of rock
there.

I'm pretty strong but I'm not quite
that strong.

Add 50 more kilograms and you've got
Uranus's twin, Neptune.

And then we reach Saturn, the second
most massive planet.

And you can see it's a whole lot
bigger

than everything else we've seen so
far.

Remember, Mercury, our tiny planet
was just one kilogram.

This is 1,700 kg.

But what about the heavyweight,
Jupiter?

It's in another league entirely.

Because on our scale Jupiter isn't a
pile of rocks,

it's the truck itself.

And you can clearly see Jupiter
out-masses them all.

So we've got 7,000 kg here for
Jupiter on our scale.

If you take all the other planets in
the solar system and you add them

together, Jupiter is still two and a
half times bigger than that.

You can see why Jupiter was God of
the skies.

And the planet's gargantuan size

reveals something even more
fundamental.

Because when it comes to planets,
big means old.

We think that because Jupiter's so
big, it had to form

really early in the
history of the solar system.

Jupiter isn't just a giant.

It's a gas giant, almost entirely
made up of hydrogen and helium.

And this means the planet must have
formed

when the solar system was in its
infancy.

Because whilst there was a lot of
gas in the early solar system,

it didn't stick around for long.

The gas goes away on timescales of
maybe

a million to 10 million years at
most.

So what that means is that Jupiter
has to form quickly

to be there in time to suck up all
that stuff.

Scientists now think that Jupiter is
the oldest world we have,

forged at the very dawn of the solar
system.

And inside, cloaked in swirling
clouds,

should be remnants of this earliest
time.

If we want to understand where it
all started,

how all of planet formation began,

we need to know what's going on in
the interior,

and that's not something we can get

by just taking pictures of the
outside.

But Jupiter guards its secrets
jealously.

It's an inhospitable and dangerous
world.

And delving into its depths requires
a unique machine.

Jupiter's the most extreme
environment Nasa's ever visited.

To send a spacecraft there is a
little bit insane.

We had to, you know, build an
armoured tank to go there.

Scott Bolton heads up the Juno
mission.

And this is his armoured tank.

Behind me is the Juno spacecraft,
basically life-size.

It's an enormous spacecraft.

Close to 70 feet in diameter,

as it spins around and cartwheels
through space.

This is one of the largest
spacecraft ever made.

In Roman mythology,
Juno was Jupiter's wife,

and only she could see the King's
true nature.

Juno had the special powers to see
through

a veil of clouds that Jupiter
surrounded himself with,

to hide his mischief.

Juno the spacecraft has all these
magical instruments

to see inside of Jupiter.

Juno is kitted out with 29-foot-long
solar panels to harvest the sun's

energy from half a billion miles
away.

200kg of titanium armour
protects its fragile electronics.

It also boasts a unique array of
scientific instruments.

So, almost all of the science
instruments on Juno

are situated between the
solar rays,

so, they're on this main deck of the
spacecraft.

Here you have particle instruments,
an ultraviolet camera.

That's the microwave radiometer that
looks in different wavelengths into

Jupiter's atmosphere.

There are so many firsts associated
with it,

to be able to explore Jupiter and
get that close.

Makes me very proud to be part of
the team

that designed and built that thing.

But there was almost a notable
absence from Juno's arsenal.

So, as we come around, you're seeing
JunoCam right here.

JunoCam is the only camera that
captures visible light

in colour on the spacecraft,

but at first, Nasa told them to
leave it behind.

And I just said, "I just can't
imagine going

"all that way and not having a
camera",

so the team ignored Nasa's direction
and we kept the camera on anyway.

A regular camera was almost deemed
an unnecessary luxury.

Because Juno's main mission is to
peer through the atmosphere,

not just take pretty pictures of the
cloud tops.

What Juno's doing is taking us all
inside of Jupiter to see what it's

like. We're journeying right to the
centre and passing by all these

strange phenomena on the way down.

On the 5th of August 2011, the
armoured tank was sent on its way.

It had a journey of 1.7 billion
miles ahead of it.

But it was to get a dramatic
introduction to Jupiter's might...

..whilst still 5 million miles from
its destination.

Because five years after launch,

Juno felt the power of the gas
giant.

A power that could have ended the
mission before it had really begun.

Heidi Becker is a senior scientist
at Nasa's Jet Propulsion Laboratory.

She was tasked with ensuring the
spacecraft survived

this first encounter with Jupiter's
power.

My job on Juno has always been to be
afraid of Jupiter.

I think of Jupiter as something
that's attacking us and throwing its

weapons at us, really.

Ten days before reaching the planet,

Juno's plasma wave detector recorded
this.

DEEP STATIC HISS

The sound that we're hearing is the
moment when

Juno is crossing over
into Jupiter's territory.

It's a moment called crossing the
bow shock.

You hear this very different roar.

Juno was slamming into charged
particles,

trapped in the huge magnetic field
that surrounds the planet.

You're hearing the radio waves
converted into sound.

This was Jupiter greeting Juno with
the roar

of its massive magnetosphere.

It extends all the way back to
Saturn, perhaps further.

And it's the biggest structure in
the solar system

next to the Sun's magnetosphere.

It's kind of a Halloween kind of
sound,

and it's appropriate given the
strength

of the magnetosphere at Jupiter.

The first layer of Jupiter actually
sits outside the planet itself.

It's an enormous magnetic field

extending out millions of miles
above the cloud tops.

And intense magnetic fields mean
intense radiation.

Other missions have experienced the
fury of Jupiter's radiation

environment.

Four, three, two, one.

We have ignition and liftoff of
Atlantis

and the Galileo spacecraft bound for
Jupiter.

Almost three decades ago, Galileo,

the only other spacecraft to orbit
Jupiter, blasted off.

It, too, journeyed across the void.

But once at the gas giant things got
a little odd.

The spacecraft sent back some images
that were almost totally white.

And Galileo would randomly switch
into safe mode.

It didn't take long to realise that
this was radiation around Jupiter,

pummelling the spacecraft's
electronics.

Jupiter's radiation environment is
the most dangerous environment for a

spacecraft to go into.

Juno was built to be bigger and
stronger than Galileo.

An armoured tank in space.

Because it would orbit the planet
far closer than its predecessor.

And the closer it got,

the more powerful and dangerous the
radiation.

It's a region we were very afraid of
because no-one had ever been there

before.

It feels to us like sending our
spacecraft into a shooting gallery.

With bullets that are moving at
almost the speed of light.

To make things more difficult, Juno
was entering this extreme radiation

environment at 130,000 mph.

...minimum burn timer.

Almost there.

On July 4th 2016, Juno
arrived at Jupiter.

It required a perfectly timed burst
of thrusters

to get the craft into orbit.

If that doesn't fire just right you
fly right past Jupiter.

That's it. You don't go into orbit,
you don't get any science,

you go around the solar system
again.

By the time you come back to Jupiter
it's decades later.

Probably nothing's working.

Juno dived around the planet and
inside the radiation belt.

You're really just sitting there
waiting,

hoping that you'll come out all
right at the end and be in orbit.

It's a very uncomfortable situation.

The thrusters fired on cue.

All stations... We have the tone for
burn cut-off on Delta B.

Welcome, Jupiter.

And despite the shooting gallery of
particles,

the spacecraft was fully
operational.

We just did the hardest thing Nasa's
ever done.

After a decade worth of planning,

and hundreds of thousands of hours
of meticulous work...

..Juno was in orbit.

The journey to Jupiter's heart could
begin.

Every 53 days, the spacecraft swoops

north to south just 3,000 miles
from the cloud tops.

And that means Juno is rewarded with
a close-up look

at a dazzling display.

A display that hints at just how
strange the gas giant's interior is.

Because Jupiter is home to the most
powerful aurora

in the entire solar system.

Professor Fran Bagenal is
studying how the gas giant

creates these astonishing light
shows.

Here, we're looking at the aurora
on Jupiter.

This is spectacular.

But the planet doesn't produce these
aurora alone.

It gets some help from its own
moons.

Here, imaged by Juno.

So, we see Jupiter in the middle but
around Jupiter we see the moons, Io,

Europa, Ganymede, Callisto.

The innermost moon, Io, is key.

This is a moon like no other.

This footage shows a plume of
material being blasted out

from the moon's surface, 200 miles
into space.

Io is a volcanic world, and material
from its eruptions

goes straight into Jupiter's huge
magnetosphere.

The gases that come from Io become
trapped in the magnetic field.

And they become accelerated to very
high energies.

Particles are accelerated along the
field lines towards the poles with

spectacular results.

Energetic charged particles come in,

bombard the atmosphere, make it
glow.

And then we're seeing this glow in
the atmosphere of Jupiter.

Look closely and we can even see the
movement of the moons

in the aurora itself.

Those dots, you can see them there.

Io and Europa.

And those are because there are a
million amp electrical currents

flowing along the magnetic field
into the atmosphere,

bombarding the atmosphere and making
it glow.

But there is a mystery in these
displays.

On Earth, the aurora is caused by
the iron core at the centre of our

planet, acting like a giant bar
magnet,

pulling charged particles from the
Sun and giving us wonderful light

displays in the sky.

But Jupiter is almost entirely
hydrogen and helium.

On Earth these are gases, not
magnets.

Something strange is going on inside
the planet,

and Juno's unique orbit is designed
to help the team get answers.

We're looking down and seeing these
aurora glows.

We're flying through the magnetic
field

and measuring at the same time the
charged particles

and the fields that cause these
auroral particles to

bombard the atmosphere.

Something inside the planet is
creating this brilliant light show.

And Juno is going to take us through
the cloud tops to reveal what it is.

The outer layer of the planet is at
once familiar and yet totally alien.

Jupiter's atmosphere.

Juno beamed back abstract
masterpieces of spiralling storms.

Swirling bands of colourful wind.

It's almost as if the king of the
solar system

had wrapped himself in a majestic
cloak to guard his secrets.

Professor Andy Ingersoll has been
trying to decipher

this enigmatic layer of clouds for
five decades.

You have storms that last for
hundreds of years.

You have winds that are three times
hurricane force on Earth.

Juno gets much closer than any
spacecraft ever has been.

So we have details at a scale we
never had before.

And one of Juno's most stunning
discoveries

was hiding in plain sight.

Because the spacecraft revealed a
whole new side to the gas giant.

Quite literally.

We've never had a spacecraft over
the poles.

So it's pretty exciting.

It's new territory.

You send good instruments into a new
place

and there's stuff there to be
discovered.

JunoCam, the instrument almost left
on Earth,

revealed the polar regions of
Jupiter in glorious detail.

What we find is vortices kind of
like hurricanes.

They're all packed together.

And we've been watching them now for
a year,

and they haven't all merged into
one.

And these storms became even more
astonishing when viewed with Juno's

infrared camera.

They're packed in in this pentagonal
pattern.

There's actually six of them if you
count the one in the centre.

And they just sort of sit there.

And this is remarkable.

This is really the first time that
anyone has seen

such a geometric pattern of cyclones
on any planet or anywhere.

I look at an image like that and I
say, "Wow".

The idea that nature can make such a

geometrical structure is
fascinating.

The images being beamed back from
all over Jupiter are stunning.

But they also create more questions.

What produces the iconic stripes of
wind we see in the atmosphere?

How deep do those winds go?

Professor Tapio Schneider and Dr
Junjun Liu are planet builders.

With a little help from the
supercomputer in Caltech's basement,

they can simulate entire worlds,

and when building a planet,

the first question to ask is -
what powers it?

On Earth, the Sun powers the entire
climate system.

It sets the atmosphere in motion,

the atmosphere sets the ocean in
motion.

Everything in the climate system
starts with the Sun.

But if you want to think about winds
and climate on Jupiter there's an

additional heat source we need to
think about.

That additional heat source is
inside the planet.

Because when the gas giant formed,

an enormous amount of energy was
trapped in its centre.

For a long time people have been
puzzling,

what is the different roles played
by those two different heat sources?

You know, this is... Like, our model
is actually

the first general circulation model,

it's a global model,

taking into account both the
solar radiation

and the internal heat flux.

The pair believed the two heat
sources,

our sun and the planet's hot
interior,

worked together to power Jupiter's
atmosphere.

And armed with this information they
could create

a virtual Jupiter, winds and all.

This was the first time the heating
by the sunlight and the

internal heat flux have been
combined in a model.

After a month of number-crunching on
some of the most powerful computers

on Earth, their simulation
eventually churned out a planet.

This is the result of our general
circulation model,

which actually is a very difficult
simulation

because Jupiter's radii is very
large.

The colour shows the direction of
the wind.

I was really happy about this
result.

It looks at Jupiter in many
essential ways,

it shows one strong eastward jet
at the equator,

and alternating eastward westward,
eastward westward jets.

Their simulation reproduced
Jupiter's visible winds

almost perfectly.

It was very satisfying. It was
perhaps one of the most

satisfying moments in a scientific
career.

That you put together an image of
how a whole planet works,

you try to put on a
computer what you can of it,

and it comes out the way you thought
it should come out.

If their simulation is right,

the instantly recognisable stripes
of wind we see on Jupiter's surface

are powered from above by the Sun,
and from below

by heat leaking from the planet's
interior.

And their model even had a
prediction

about how deep these wind patterns
go.

We think that the equatorial region

these jets go all the way through,
deep inside Jupiter.

They believe that the visible winds
extend well below the cloud tops.

And thanks to Juno,

using its array of instruments to
peer through the atmosphere,

we can finally see if that
prediction is right.

It appears that the winds that we
measure

at the tops of the clouds have
roots that go down,

kind of parallel to the polar axis
north to south,

so that's as deep as they possibly
could go.

As predicted, Jupiter's huge bands
of wind mark just the top of great

rivers of atmosphere flowing deep
within the planet.

We're talking winds thousands of
kilometres below the cloud tops.

Even the Great Red Spot, a storm
that could swallow the Earth whole,

was found to have a root as deep as
Juno's instruments could measure.

It could go down thousands of
kilometres.

That pretty much answers the
question that we had.

"Is the red spot shallow or deep?"

And the answer is, it's deep.

This upper layer of Jupiter is
proving to be more fascinating

and dynamic than scientists dared
hope.

And the atmosphere holds one more
mystery,

one that could have important
implications for our own planet.

It is the mystery of Jupiter's
missing water.

The search for water beyond Earth is
one of the most important quests for

planetary explorers.

Jupiter, being almost entirely made
up of hydrogen and helium,

might not seem an obvious place to
look.

But, for Scott,

the hunt for water is one of Juno's
most important objectives.

Water is important throughout the
whole universe.

Everywhere we look on the Earth that
there's water, there's life.

It's thought that the water on Earth

may not have been here from the
beginning.

It's believed to have been deposited
on the young planet

by icy balls of rock.

If that were the case, Jupiter, with
its enormous gravity,

should have pulled in the lion's
share of these icy snowballs.

It should be rich in water.

Of course, few believe the giant
planet will be teeming with life.

But if we can figure out whether
there is water on Jupiter,

and how much, we can get a much
better grasp

on where our own water came from.

So, when we're seeking to understand
how much water's in Jupiter,

it's also telling us about the
history of water,

and maybe the origin of life.

But two decades ago,

this quest for water was dealt a
blow

by the only other spacecraft we've
flown around Jupiter.

Galileo will expand our knowledge of
Jupiter and its satellites.

Like Juno, Nasa's Galileo spacecraft

tried to find water in the giant
planet.

It had a probe on it.

And the probe actually went into the
atmosphere and measured directly how

much of each element there was.

Jupiter was expected to be
relatively abundant in water.

Galileo found almost none.

In the 30 minutes that it took the
Galileo probe

to make its measurements, it brought
into question every single theory

of solar system formation.

If Jupiter really is a dry world,

the origin of our own water is a
total mystery.

But could the result have been
misleading?

So, one of the weaknesses of the
Galileo probe was

it was only sampling one spot.

And if that spot didn't represent
everywhere on Jupiter,

then the measurement really couldn't
be extended to the whole planet.

We were searching for another way to
do it,

and that's when Juno came along.

The Juno team had to find a whole
new approach

to look for water on Jupiter.

It was Scott's brainwave to use the
heat trapped in the planet's centre.

Because that heat is slowly leaking
out in the form of microwaves.

Water is opaque to the microwave
part of the radio spectrum.

That's why your microwave oven heats
up wet food.

Juno is measuring how much of the
heat leaking from the planet's hot

interior is absorbed by water in the
atmosphere.

And, crucially, it doesn't just
measure this at one point.

So, we actually look all over the
whole planet

at all different angles,

measuring water at every spot.

It could be before the get a final
answer on just how wet Jupiter is.

It's a big planet.

And Juno needs to scan it all.

But its microwave detector has made
a discovery.

And it's not one the team were
expecting.

This is the signal from the
microwave radiometer.

And it is measuring the heat of the
planet, and

every now and then we get a spike.

Bam! And then it goes back to normal

in measuring this heat of the
planet.

It was a little puzzle at first, one
of these spikes.

And it was possible that

there was some cosmic ray hitting
the instrument.

But it became very clear very soon
that this was radio signals from the

lightning in Jupiter's atmosphere.

Maybe 1,000 times brighter than the
lightning on earth.

Jupiter, lord of thunder and
lightning, didn't disappoint.

The planet's atmosphere is alive
with

flashes of lightning of unimaginable
power.

And though these signals were
a surprise,

it could be evidence for the huge
quantities of water

the theories had predicted.

To have lightning, the theory is
you need all three phases of water.

Liquid, gas and solid.

So, inside Jupiter's atmosphere
there's a layer

where the pressure and temperature
are just right to form clouds.

The lightning strikes Juno has
detected

suggest the Galileo probe must have
fallen into a dry spot.

Jupiter is a water world, after all.

And some of the water might even be
visible.

We see these little white clouds.

Little compared to Jupiter,

but they're actually 50km
going across.

And we see them at the very top of
the atmosphere,

you can tell it at the top, because
it's casting shadows.

These, we believe, are ammonia water
ice thunderstorms.

It's hailing or snowing on Jupiter.

These thunderstorms are just the tip
of a whole layer of water,

hidden beneath the cloud tops.

Perhaps just 100 miles down.

And once Juno has figured out
exactly how much is inside Jupiter,

scientists can better understand

how water was delivered to our own
planet.

But Juno's instruments have allowed

scientists to travel even further
into Jupiter.

And beneath the upper atmosphere and
the water clouds...

..is almost pure hydrogen.

The most abundant element in the
universe.

And it's this hydrogen that holds
the key to the intense aurora

and vast magnetic fields Juno
encountered

on arrival to the planet.

Because of the intense pressure
inside Jupiter,

something strange starts to happen.

At the National Ignition Facility in
Northern California,

Marius Millot is finding out what
happens to hydrogen

when it finds itself in Jupiter's
extreme interior.

So, here we're trying to replicate

the extreme conditions inside
Jupiter.

Before, it was only possible with
theory or simulations.

But now we are able to assess,
actually, those conditions

in the laboratory, and do the real
experiment.

So, basically, we are creating a

little planet interior inside our
laboratory.

The National Ignition Facility is
home to

192 of the most powerful lasers
on the planet.

And they're all focused on a point
in space

just a few millimetres wide.

So, this is the target that we put
inside this target chamber.

We fill a little portion inside its
cone here with liquid hydrogen,

about 20,000,000th of a gram.

And then we shine 80 laser beams
from the top,

and 80 laser beams from the bottom.

The lasers create a shock wave,

crushing the hydrogen to the same
intense pressure

we'd find 10,000 miles inside
Jupiter.

But it takes a lot of power to get
there.

So, the power that we've put in the
lasers when we shine the laser onto

the target is about 500 times the
power

that is used for the entire United
States at a given moment.

May I have your attention,

all personnel are required to exit
the Target Bay at this time.

It is believed that when hydrogen is
crushed to such extremes,

it takes on a form that has almost
mythical status here on Earth.

The hydrogen becomes a metal.

It's an extraordinary experiment.

-170 and counting.

PCU's charge complete.

There could be a lot of extra
radiation,

high-power voltage,

a lot of laser light could leak if
there was a problem.

So, you don't want to be there
during the experiment.

Precision is everything.

The hydrogen sample is carefully
manoeuvred into position.

-60 and counting.

It takes an army of scientists and
engineers

to ensure the laser shot goes off
without a hitch.

-30 and counting.

With everything set, it's time to
fire the lasers.

T minus five, four, three, two, one,
shot...

What's happening?
The shot just happened.

We create the condition inside
Jupiter

for a few billionths of a second.

After each blast of the laser, the
sample is completely destroyed.

So, to find out what happened to the
hydrogen,

the team shone light at the sample
throughout the experiment.

Hydrogen is normally a clear gas.

But, by replicating the pressure
inside Jupiter,

something astonishing happens to it.

A few nanoseconds after the
beginning of the experiment,

hydrogen starts to get compressed,
but it's still transparent.

And as time evolves, we increase the
pressure.

And this time, the pressure got so
high

that the light is now reflecting off
the shiny surface of the hydrogen.

Hydrogen transformed from being
transparent to opaque,

and then becomes a metal, like a
shiny metal.

And, because of the blistering
temperatures inside Jupiter...

..this metal isn't solid.

It's a liquid.

If we were to go deep inside
Jupiter,

we would see a deep ocean of fluid,
shiny metal.

This is the first time that we can
actually do this kind of experiment

and recreate the exact condition
inside a planet.

This is the next layer of Jupiter.

A vast ball of liquid, metallic
hydrogen.

In fact, it could make up as much of
50% of the planet's huge mass.

Jupiter is not so much a gas giant
as a liquid metal giant.

And this strange substance explains

the incredible electrical phenomena

we saw outside Jupiter's clouds.

Because, as the metal flows, it acts
like a huge magnet,

creating the enormous magnetic
field.

And a blinding aurora.

It's time to descend to the final
layer.

Juno was designed to tell us once
and for all

what lies at Jupiter's heart.

Is there a core?

And if there is, how big is it?

And what is it made of?

At Nice Observatory,

Prof Tristan Guillot is using
Jupiter's unique orbit

to get answers to these questions.

OK, so, I'm going to use these three
chalks to represent Juno.

Pretty accurate? Juno has this
special orbit,

it's coming very close to the planet
where,

depending on what's inside Jupiter,

Juno will move in slightly different
ways.

It's doing something like that.

So, that's how we will be able to
measure what's inside Jupiter.

They're using gravity to probe
Jupiter.

Because, if there is a dense core
at the planet's centre,

Juno will find it by measuring its
gravitational pull.

We're able to measure the gravity
shield of Jupiter

100 times better than
what has been done before.

We were very excited to get the
results back.

And we're already starting to get
answers.

The answers the team are finding

take us back to the early days of
the solar system.

Because at Jupiter's ancient heart

could be the blueprint for building
a planet.

Finding out what's inside would tell
us a lot about not only how planets

like Jupiter form,

but maybe about the early history of
our own solar system,

and potentially about a lot of other
extrasolar planetary systems that

we're starting to discover now.

We know what the planets were formed
from.

A giant cloud of gas,

and perhaps dust left over from
earlier generations of star systems.

But the mechanism is still a
mystery.

For a long time, it was thought that

each world formed by a gradual
process.

You start with dust grains, those
dust grains somehow smush together,

they get bigger and bigger and
bigger

until you get pebbles and rocks and
boulders.

And we sort of keep walking up the
size ladder.

And then those big bodies smash
together

to make the cores of planets.

But it's not clear that that process
is going to work fast enough to

explain something like Jupiter.

Because one of the big problems with
that model is that it takes a long

time to go from little tiny stuff
like this,

to a big honking planet like
Jupiter.

Scientists believe that Jupiter
formed

perhaps just a few million years
after the Sun.

So, there needs to be a mechanism
that works quickly.

On top of that, it's really hard to
make rocks stick together.

You know, what happens if you throw
two rocks together?

Nothing, right? They didn't grow,
they don't stick together.

The same kind of thing happens in
the early solar nebula.

So, how do you go from a dust cloud

to a giant planet like Jupiter in
the cosmological blink of an eye?

There are two opposing theories,
and, crucially,

they give two different predictions

as to what to expect at
the planet's centre.

The first suggests that Jupiter
ultimately

started life as a cloud of pebbles.

You take these little rocks,

and instead of trying to squish them
together

to make slightly bigger rocks...

..you take a whole bunch of them,

and you let them interact with the
gas

that we know is there in the early
solar nebula.

And just like when you throw a ball
on a windy day,

it slows down faster,

those little pebbles, they feel the
gas drag

from the gas that's also
going around the star.

And because of a combination of gas
drag and gravity,

we can actually get them to clump
together for little things like this

directly to 100km bodies.

If this theory is correct,

before Jupiter became the giant we
see today,

it was a small, rocky world,

created by a cloud of pebbles.

And Juno could find the evidence at
its centre,

because all those pebbles should
still be there.

But there is an opposing theory.

One that suggests not even pebbles
are needed.

Instead of worrying about pebbles or
rocks or planetesimals,

you just take the gas in the early
solar nebula

and you collapse it down
under its own gravity

to form one big object.

So, it's kind of more like the way
we think stars might form,

rather than thinking about growing
up from rocky things.

In this theory,

in which Jupiter formed straight
from

the gas of the early solar system,

there would be no core at all.

You don't really need rocks, they're
not really part of the picture.

Two theories with two predictions.

The truth has been concealed beneath
these clouds for 4.5 billion years.

But, thanks to Juno, we finally have
an answer.

By analysing small changes in Juno's
trajectory,

Tristan and the team have been able
to map

what they think sits at Jupiter's
heart.

This is the outline of Jupiter.

And, basically, what we're seeing
there are just the cloud tops.

But what we want to know is what's
inside Jupiter.

And what we're finding is that
around here...

..there's something denser.

It's probably like 5-10 Earth
masses.

What Juno is telling them is that
there seems to be a mass of dense

material, too massive to be just
hydrogen or helium.

So, this is the core of Jupiter.

It's mostly made of rocks at very
high pressures and temperatures.

So, that shows that Jupiter started
its life as a rocky, icy world,

and that it captured the gas that
was around, the hydrogen and helium.

And that formed the giant planet
that is Jupiter now.

It's now thought that inside Jupiter
is a vast sphere of rocky material,

big enough to be a planet in its own
right,

perhaps ten times the mass of Earth.

It seems that Jupiter was once a
primordial, rocky world.

The vast cloak of gas came later.

But Juno found something else.

To the team's surprise,

there appeared to be an extra layer
around the core,

neither rock nor hydrogen.

So, this is a fuzzy core, made of
rocks, ices,

mixed with metallic hydrogen.

And that's a really important thing.

Because it really tells us about the
formation of the planet,

and this is something we did not
consider before.

Tristan believes that this
fuzzy core

is evidence of an astonishing and
unexpected stage

in planet formation.

A clue to what he thinks happened
can be found

in shooting stars.

Shooting stars are little grains
that float in space and are

captured by the Earth.

And when it burns, this creates
light.

Most of the material is actually
deposited in the atmosphere itself.

So, it doesn't reach the ground.

The unexpected fuzzy layer suggests
to Tristan that there was a dramatic

period in the planet's formation,

when Jupiter was a rocky world with
a growing atmosphere.

And from the heavens, the rocks fell
like rain.

There must have been
millions of shooting stars.

It must have been very bright,
but also very hot.

And as the shooting stars and
fireballs burnt up on the planet's

atmosphere, that's where this rocky
material stayed.

That's how they formed a mixture of
hydrogen and rocks.

That's probably what led to this
fuzzy core that we see today.

This final layer of Jupiter is a
surprise.

A fuzzy mixture of rock and liquid
metallic hydrogen

enveloping the core.

And it marks the end of our journey
into this giant.

But the mission goes on.

Juno will continue to send back
insights

into the wonders inside Jupiter.

It's always better if we can really
change

the direction of the field with
something like Juno.

Eventually, the radiation will
become too much.

The spacecraft will be damaged
beyond use,

and plunge into Jupiter's atmosphere
to safely burn up.

It will be a sentimental moment.

The longer you work with a machine,

and with the people,
the more you get attached to it.

But scientists will long pore over
its results,

perhaps for decades...

Juno has been a great success.

We've made a lot of discoveries.

Jupiter is quite unlike what we
thought it was before.

..continuing to explore the heart of
this vast and wondrous world.

We've discovered so many things
already,

and it's an adventure when you get
to go discover

things that you don't know.

Juno, mythical wife of the god
Jupiter,

saw through the veil of clouds he
used to hide his mischief.

And, thanks to Juno the spacecraft,

we're finally making the king of the
solar system lift his veil, too,

revealing his secrets to us all.