All language subtitles for Solar.System.2024.S01E05.1080p.BluRay.x264-DRCOX_track3_[eng]

We all know the familiar faces
of our solar system.

The worlds we grew up with.

But there's another side
to our solar system

we're now discovering.

The misfits and oddballs.

Worlds of freakish shape
and size.

Of extreme landscapes...

.. mysterious phenomena...

...and hidden secrets.

Our neighbourhood is far
stranger than we ever imagined.

So, how did
all these weird worlds

come about?

Well, to answer that question,

we'll have to explore the force
that sculpted

and created them - gravity -

and the forces that resist
its relentless inward pull.

And also, at a deeper level -

cos there's always
a deeper level -

we'll be forced to contemplate

why there is
anything of complexity

and beauty in our universe
at all.

Welcome to the solar system
of the weird.

From a cloud of gas and dust,

gravity, the great sculptor
of our universe,

fashioned our star
and all the worlds

and moons around it...

... creating the solar system.

And gravity has continued
to shape these myriad worlds

ever since.

Let me give you a little
30-second lecture on gravity.

And I'm going to use
Newton's picture,

not Einstein's,
cos we don't need

the additional accuracy
delivered by relativity.

Gravity is a force
of attraction between objects -

and it only attracts,

so that means that it tends
to clump things together.

And it's a force that only
depends on the distance

between objects, not the angle,

and so it tends
to make spheres.

It's this property
of gravity...

... that shaped the moons
and planets.

But beyond
the near-perfect spheres

that dominate
our solar system...

...out past the giant orbs...

...Of gas and ice...

.../n a distant realm
of the solar system...

...we found something strange.

Only one craft has been sent
to explore the worlds

of this distant region.

And on its epic,
ongoing journey,

the probe caught a glimpse
of something truly bizarre

moving in the dark.

Not a sphere like Earth,
or even Pluto...

...but a giant,
2,000-km-long egg-shaped world.

Orbiting around it,

two glittering moons.

Mountains of icy rock
and a faint ring.

If you were standing
on Haumea's surface,

the stars would wheel above you

six times faster
than here on Earth.

Haumea Is a truly unexpected
and bizarre-shaped object.

The first like it
ever discovered.

Leaving the question...

...what created

such a seemingly
gravity-defying world?

Now, for rocky worlds,

the force resisting
the inward pull of gravity

is created by this -

the rigidity of the rock.

And the thing about pressure is

that it acts equally outwards
in all directions,

so if you have a force

that's squashing
everything inwards equally

in all directions,
and a force that's resisting

that squashing equally
in all directions,

then the shape that's naturally
produced is a sphere.

And you might say,

well, why is something
like that not a sphere, then?

| mean, it's made of rock,

it's got a gravitational pull,

but it's a very weak
gravitational pull

because it's not very massive.

And that's the point.

So the gravitational forces
on the surface here

trying to squash it down
are nowhere near big enough

to overcome
the strength of the rock.

So, how big
does a thing have to be

such that the gravitational
force is strong enough

to overcome
the strength of the rock

and allow it
to deform into a sphere?

And you find, if you wave
your hands around a bit,

that that size, the radius,
is something like

200, 300km.

It's called the potato radius.

And indeed, you find that,

if you look out
into the solar system,

anything that's smaller

than about a couple of hundred
kilometres in radius

looks like that.

And anything that's bigger

than a couple of hundred
kilometres in radius

looks like the Earth.

From what we observe,
it seems that the potato radius

is a pretty strictly followed
rule.

The larger worlds are,

the more spherical they become.

Yet it's a rule Haumea breaks.

Way over the potato radius,

Haumea should be a round world.

So, if its egg shape is not
down to its size,

then what is it?

There is a clue,

found by looking at our world
in a Slightly unusual way.

This is a photograph of us
working on the beach today.

| use the term loosely.

And what we did is
we took a time-lapse.

But it's an interesting
time-lapse.

We used an astronomical mount,

and so we fixed the camera
at a single point in the sky -

the sun.

And then,
can you see what happens?

So, it's holding its position.

It doesn't look right

because the whole ground is
rotating around.

So, usually, our experience
on the surface of the Earth

is watching the sky and the sun
and the moon and the stars

rotate around us.

But if you take that motion
out,

then what you're seeing here
is the Earth

rotating beneath the sky.

This unusual view
really brings home the fact

that we live on a spinning ball
of rock.

And there are consequences
for sitting on the surface

of something that's spinning.

New forces are introduced,

forces that are so-called
fictitious forces -

but there's nothing fictitious
about them.

Actually, you'll know that
if you've tried to hang on

to a spinning roundabout.

If you let go,
you go flying off.

That's not a fiction.

And that force is called
the centrifugal force.

Like the Earth, all worlds
in the solar system spin.

But Haumea is spinning
incredibly quickly.

The entire
2,000-km-long world...

...Whips around once
every four hours.

And that makes the centrifugal
force very powerful indeed.

And | can show you...

...by taking a small thing...

...let's say that's Haumea...

...and spinning it really fast.

So, can you see
what's happening is

it was a sphere,
and now it's bulging out.

And it's bulging out
along its equator.

Look at that. That's
cos the centrifugal force

tends to flatten things.

Oh-h-h!

(LAUGHS)

See?!

You see that?

| mean, there it is, right?

Those are fictitious forces
at work.

And that's essentially,
actually, what happened

to some bits of Haumea,
we think.

We think
it was spinning so fast

that some bits got thrown off.

And, um...

In fact, there it is.

So what you just saw there
was a demonstration

of how we think this system
was created.

This is the best photo we have
of that system.

And these bits are essentially

that bit that's now over there
somewhere!

There we are. See, look.

Haumea.

The battle between spin
and gravity has created

a truly strange world.

Gravity shapes everything
in the solar system,

and our next destination
has the scars to prove it.

Let the pull from our star
draw us inwards...

... past Neptune...

..Uuntil we reach
the innermost ice giant.

Uranus Is pretty odd
to begin with.

The entire planet
is knocked over on its side,

likely by a giant impact
in the past.

But it's not only the planet
that's strange.

Voyager 2 is the only
spacecraft to have visited

the moon Miranda.

As it flew past
the south pole...

..ItS cameras saw a truly
weird patchwork landscape.

A jumble of towering mountains
the height of Everest

and plunging chasms
deeper than the Grand Canyon.

One of the most astonishing
surfaces

in all the solar system...

... where strange cliffs rise
to unimaginable heights...

..UNlike anything seen
on Earth.

So, what created the truly
bizarre face of Miranda?

The geology of our world
is awe-inspiring,

even though
we're really familiar with it.

| mean, this island rises
two-and-a-half kilometres

from the surface
of the Atlantic Ocean.

But just imagine
what it would be like

standing on the surface
of Miranda.

| mean,
there's a slope not unlike this

that stretches for something
like 10,000 metres.

And | remember
when Voyager 2 arrived

at Miranda in 1986,

and sent back images like this.

That slope is up here.

But one of the scientists
at the time said

that this world is exotic.

And you can see why.

One of the explanations
for why it's like this

was that it must have been hit
by something

and then reassembled.

It's like a Frankenstein world.

But we now know the explanation
for this strange geology is,

if anything, even more exotic.

We're pretty sure

that Miranda must receive
the occasional impact.

The result would look like it
was playing out in slow motion.

Debris taking the best part
of ten minutes

to slowly tumble to the bottom
of those great slopes.

On Earth, it would take
only 50 seconds

to fall the same distance.

Because on this moon -

smaller than the width
of the UK -

the pull of gravity
is much weaker.

One hundredth
of the strength on our world.

Now, the basic explanation
for Miranda's strange surface

really is just basic physics.

Miranda's very small.

It's only
about 470km in diameter -

not too far away
from the potato radius.

And so its gravity is
just not quite strong enough

to squash it down
into a sphere.

But there's more
to the geology,

to the surface of a world,

than just basic
physical principles.

There's also the history
of the world.

Miranda's weak gravity is what
makes this landscape possible,

but it's not alone
responsible for sculpting it.

Something must have happened
to Miranda

to create its battered
and scarred surface.

All we have to go on
are the glimpses of this world

captured
as Voyager 2 flew by...

...Which suggest this moon
had a troubled past.

The key to unlocking
the mystery of Miranda

is to notice that this surface
is not as chaotic as it looks.

It's not entirely random.

There are
these three distinct regions,

which are known as corona.

And, at least
on these two external regions,

there are ridges, fault lines
that surround them -

and to a geologist
that's a smoking gun.

What it suggests
is that this surface

was not created
by external forces,

by impacts from the outside -

it was created from within.

And it's similar
to this landscape here.

This is new land.

These are volcanoes.

They were created by a hot spot

deep underneath
the surface of the Earth -

and by buoyant hot material
rising up

through the surface
of the Atlantic Ocean.

And we think
that's what's happened here.

Buoyant, less-dense material
rising to the surface,

creating these features.

It's thought that it was
this internal turmoil

that left
ruler-straight canyons

running
for hundreds of kilometres

across the face of the moon.

Formed when warm material,

pushing up from the interior,

caused the surface to crack
along fault lines.

Part of the active geology
that, over millions of years,

created
this Frankenstein world.

But that raises
another mystery,

because Earth's geology
is driven by the heat

stored away from its formation

four and a half billion years
ago,

along with the energy released
by radioactive decay.

But Miranda is far too small
to have retained

any of the heat
from its formation.

So, where did all that energy
come from?

For the answer,

you have to look
at Miranda's relationship

with its parent planet,

and another quirk of gravity.

Probably several times
in its history,

Miranda was in a more
elliptical orbit around Uranus.

That meant that it went close
to the planet,

far away, close and far away.

And the changing
gravitational forces

injected the heat
into the moon,

and that's
what drove its geology.

Gravity...sculpting one
of the most tortured landscapes

in the solar system.

| think
the story of Miranda reveals

something quite deep, actually,

about the way that the laws
of nature sculpted

the strange worlds
in our solar system,

and actually
the way that they sculpt

everything in the universe.

Because the basic shape,
in this case a sphere,

reflects the simplicity
and beauty and symmetry

of the laws of nature
that created it -

in this case, gravity.

But the detail of the surface,

the complexity reflects

a turbulent
and often chaotic past.

So you're seeing history
frozen in time.

And it is this interaction
between simplicity

and symmetry and complexity

that truly makes our universe
beautiful.

Beautiful and strange.

Travel further
into the solar system,

and we enter the realm
of the outer gas giant.

Home to a sight unrivalled
in the solar system.

A structure of outrageous size
and shape.

Rings of rock and ice.

Split into hundreds of ordered,
repeating tracks and gaps...

... almost engineered
in their precision...

..and looping
for thousands of kilometres

through the void.

So how did nature create
the intricate, ordered beauty,

the spiralling gaps and tracks
of Saturn's rings?

One of the most obvious things
you can say about our universe

is that, at first sight,
it is very complicated indeed.

But one of the deepest things
you can say about it

is that complexity emerges from
the action of very simple laws.

If you just think
about this desert landscape -

there's all these beautiful
sand dunes and ripples.

But if you look more closely,

there's regularity
in the ripples.

And if you look
at the sand dunes,

this angle that they fall away
at is always the same.

So there's regularity
and beauty and structure

emerging
from the action of simple laws.

In this case, it's just
the wind blowing sand grains

and gravity pulling them down
to the ground.

And | think the best

and certainly the most
evocative example of that

in the solar system has to be
the rings of Saturn.

Yet at first sight,

there's nothing simple
about Saturn's rings.

We think they formed
when an icy moon

strayed too close to Saturn...

..and was pulled apart
by its gravity...

...creating a jumble

of trillions
of individual fragments of ice.

So, what turned such chaos

into the ordered beauty
of Saturn's rings?

NASA's Cassini probe captured
the rings in stunning detail.

And orbiting within them,

it saw one of the most
Startling objects

in the entire Saturnian system.

Pan is the most wonderful,
bizarre object. | mean,

look at these photographs
taken by Cassini.

| mean, this is...

It looks like a cross between
a UFO and a piece of pasta.

And it's really small!

It's less than 30km
in diameter.

But its impact on the rings
is profound.

The shape, actually, is the key
to understanding how it is

that Saturn's rings are
so wonderfully complex.

And you can see
the basic idea...

... here.

So, there's Pan.

And the moon is orbiting
inside the ring.

And so that means
that ring particles

can...can essentially hit them.

They fall onto the surface.

And because Pan has got

a very weak
gravitational field -

it's too small,
way below the potato radius -

they don't get squashed
into a sphere.

They stay there,
sort of a ridge.

So part of the explanation
for the gaps

is that the rings are slowly
being eaten.

For millions of years,
Pan has been nibbling away,

clearing icy particles
out of its orbit.

And yet,

Pan is only 28km across...

...but it sits within a track
that is over 300km wide.

Clearly far broader
than Pan could clear

through snacking alone.

This moon doesn't just create
a tiny gap in the rings.

It creates a very big gap
indeed.

It's so big, in fact -
it's called the Encke Gap -

that that gap was discovered
using 19th-century telescopes.

It's about ten times
the diameter of the moon.

And the way it does that is
really key to understanding

the complexity
of Saturn's rings.

So...

...| have to tell you
one thing,

a very important thing
about orbits.

Here's Saturn...

...and here is Pan,
orbiting around.

Now, it's a property of orbits

that the further away
from the planet you are,

the slower you move.

That's actually traced back
all the way

to the beautiful simplicity

of Newton's law
of universal gravitation.

So that means
that ring particles

on the inside of Pan

are orbiting faster.

They're overtaking the moon.

These particles get
a gravitational tug

that tends to slow them down.

They are pulled back
by Pan's gravity.

And ring particles further out

are moving slower.

Now Pan is overtaking them.

And that tends to give them
a gravitational kick

which speeds them up.

And the effect of that

is that
Pan's gravitational pull

on the particles
that are overtaking it

tends to cause them to fall
down towards the planet

and its gravitational pull
on the particles outside

that it's overtaking

tend to get raised to a higher
orbit around the planet.

And so Pan clears
a much bigger gap in the rings

than you might
otherwise expect.

And Pan is not alone.

Daphnis,
a moon a mere 8km across,

clears its own track.

Tiny worlds

creating structures
on a staggering scale.

What's more puzzling
is that so far,

these are
the only moons we've seen

directly clearing a track
like this.

But there are thousands
of looping spirals and gaps

seemingly created
by nothing at all.

Including one of the biggest -

the Cassini Division -

over 3,000km wide.

So, what's creating
these other structures?

Surprisingly, the answer lies
not within the rings,

but out beyond
the discs of ice.

There really is
tremendous complexity

and structure
in Saturn's rings.

Not only gaps,
but also sort of structures -

density waves
that wrap round the planet,

often several times,
like the grooves on a record.

And all those structures
ultimately

are Caused
by hundreds of moons.

Actually, over 140 largish
moons at the last count,

and countless smaller ones.

And all those have
a gravitational influence

on the particles in the rings.

One of the key culprits
or drivers of complexity

is this moon,

which looks like
a space station,

but it's not a space station.

It's a moon. It's called Mimas.

Another truly odd,
almost science-fiction world...

...With its dominant
impact crater.

Yet it's not obvious

why this moon should influence
the rings,

as it's about 40,000km away.

So, Mimas, it's orbiting
outside the rings,

such that it goes round Saturn
once

for every two orbits

of particles that would be
inside the Cassini Division.

So that means
that those particles

would regularly meet Mimas
on its orbit.

There's
a gravitational interaction

that disrupts the orbits
of these particles

and moves them
out of the division.

Each time the moon
and the ice particles align,

Mimas's gravity tugs at
the fragments of ice and rock

like an invisible hand.

Over millions of years
opening up the giant gap.

And Mimas is just one
of over 140 known moons...

...each capable of creating

their own resonances
with the rings.

Look at this picture.

This is an image
from the Cassini spacecraft.

And you see the complexity here
Is mind-boggling.

This is a resonance
with a moon called Prometheus

that orbits 14 times
around Saturn

for every 15 orbits
of the particles in there.

And that causes
this disruption,

this structure in the rings.

Here's a moon called Janus.

That creates a recognisable
structure in the rings,

and so on.

And these are just the
structures that we've observed.

The orbital dance
of Saturn's moons

recorded in the rings...

... creating a pattern
we're lucky to see.

Imagine how complicated
the gravitational field is

around Saturn,
and that's what you're seeing.

It's very beautiful.

It's as if Someone had
sprinkled ice crystals

over the gravitational field
so that we can see it.

And | suppose that
a vinyl record really is

a bit like Saturn's rings.

There's a structure here,
a physical structure,

which can give rise
to something

that we can perceive now -
sound made solid, in a sense.

When you put a needle
on there...

A stylus, needle...
All right, Grandad!

But also there is, of course,
a sense of history

about a recording on a record.

It tells you something
about the past.

And so it is with the pattern
that we see in the rings.

(CRACKLES)

(ROCK MUSIC)

In Saturn's rings,
we can see gravity at work,

shaping our solar system.

Over half a billion kilometres
closer to the sun

is a planet
on a mind-boggling scale -

so huge you could fit all
the other planets inside it.

Jupiter's immense gravity
has helped shape

an astonishing world.

Since 2016,
NASA's Juno spacecraft

has been exploring Jupiter
and its moons...

...[ncluding the largest moon
in the solar system.

Ganymede is
a very strange world indeed.

A moon playing
at being a planet.

It's the only moon we know of

with an internally generated
magnetic field,

producing strange aurora.

And elsewhere on its surface,

Juno witnessed bizarre scars
gouged into its icy crust.

These phenomena suggest

Ganymede may be hiding
an extraordinary secret.

Ganymede is becoming,
| think it's fair to say,

one of the most fascinating
places in the solar system.

This is one of our best images
of Ganymede, taken by Juno.

It is a big moon.

This is the eighth-largest
object orbiting the sun,

bigger than Mercury
and not much smaller than Mars.

But it doesn't look
particularly different

from our moon.

But a series of observations
are beginning to suggest to us

that there may be something
extremely interesting indeed

going on below the surface.

One clue comes
from Ganymede's aurora.

Detailed observations
have shown

that it behaves
in an unexpected way.

To have an aurora,

then a planet or moon needs
two things, basically -

it needs a tenuous atmosphere

and it needs a magnetic field.

So, what's happening
on Ganymede is

that charged particles,
primarily from Jupiter,

are being funnelled down
the magnetic field lines

to the poles,

and there they hit particles
in the atmosphere,

they excite them and cause them
to emit light, to glow.

And that's the same process
that we see here on Earth

in the northern
and southern lights.

However, Jupiter also has
a magnetic field,

and that will affect
the aurora on Ganymede.

And so what was done is
some computer modelling.

You get Ganymede
with its field and its aurora,

and you get Jupiter
with its magnetic field

and you put it all
into the computer

and you see what happens,

and you find
there is a prediction

that the aurora on Ganymede
should kind of wobble around,

wander in the vicinity
of the pole.

And we observed that.

But we observed
that the aurora wanders

far less than it should,

so that implies there's
something else going on.

If Ganymede had an additional,
second magnetic field,

it would interfere
with the aurora,

causing it to wander less.

But the only way
to generate that extra field

would be if another layer
within the moon

conducts electricity.

| really was never very good
in the lab.

No, it doesn't work! (CHUCKLES)

- Have we got another battery?
- WOMAN: Yeah.

Let's plug another battery in.

Here's an electrical circuit.

There's a battery and a bulb.

And if | connect it,

the electrons flow
and the bulb lights up.

But now look what happens
if | take these two wires,

but connect it by dipping
the wires into saltwater.

Very cool, isn't it?

So, in here,
the circuit is being completed.

Saltwater is a conductor
of electricity.

An electrical current flows

and that can produce
a magnetic field.

So, we think that is the origin
of that third magnetic field

that's making the aurora wander
far less than it should.

The implication is that,

beneath the surface
of Ganymede,

there's a saltwater ocean.

Welcome to the largest ocean
of water in the solar system.

It's estimated
that there's a layer of water

over 100km deep
wrapped around the moon.

One that never sees
the light of day,

hidden beneath
150km of rock-hard ice.

But how can liquid water exist
in such enormous quantities

beneath the frozen surface?

One fascinating theory involves

those strange gouges
in the surface.

These are impact craters.

Not single craters, like those
found on other worlds...

...but long chains.

You know, quite a lot
of the answer actually

of how it came to be
that Ganymede has an ocean is

the presence of Jupiter.

Yeah, | can see clouds
on the surface of Jupiter

through
this pretty small telescope,

even though tonight it's about
600 million kilometres away.

You can fit over 1,000 Earths
inside it.

It's massive.

And being massive,

it means it's got
a strong gravitational pull.

And Jupiter tends to attract
things, suck things in

that come within its vicinity
and rip them apart.

And we've seen that.

This is a great image.

It's one of the most famous
images in astronomy

in recent times, actually.

And you see that?

So, that is
comet Shoemaker-Levy 9.

This is a comet
that came too close to Jupiter,

it was drawn in
by its gravitational field,

ripped to bits
by its gravitational field,

and then
ultimately hit Jupiter.

And it hit Jupiter
with such ferocity

that we saw the impact
in the clouds.

And some of them
were bigger than the Earth.

Now, you look at that...

...and then look at that -

the surface of Ganymede.

Being so close to Jupiter puts
Ganymede in the firing line.

(LOUD CRASH)

Ferocious impacts...

...that create
the chain craters.

These scars are just a fraction
of what Ganymede has suffered

living so close to Jupiter.

And that's the key
to understanding

how it may have got
its hidden ocean.

(THUNDER)

The early solar system was
a much more chaotic place

than it is today.

Impacts were common.

Everything got hit.

Jupiter's immense gravity
drew in

countless asteroids
and comets...

..and Ganymede was caught
in the crossfire.

Impacts delivered enough energy
to heat the moon...

..and kick-start a process

that caused it to melt
and separate into layers.

Dense heavy metals
at the core...

...and an outer shell
made of water and ice.

And we think Ganymede has
retained enough of that heat

to produce a saltwater ocean,

with more water, actually,

than all the oceans
of the Earth combined

below the frozen surface
of Ganymede.

A strange giant moon
with an ocean and aurora

nearly a billion kilometres
away from the sun.

We're talking about
potentially a habitat for life.

This is a big world,
a planet-sized moon,

which has a magnetic field
and a saltwater ocean

and a ready source of energy,
it seems.

All the things
that we think are necessary

for the origin of life.

And it's important

because we used to think of
what's called a habitable zone

around a star, which
is where the Earth orbits,

and indeed Mars and Venus,
just about, which is the zone

where you could potentially
have liquid water on the world,

on the surface of the world
in that case.

But now,
looking at places like this,

we understand that
there might be habitable zones

far away from stars,

in this case a habitable zone
around a gas giant.

And that habitability here
is delivered by gravity.

Leaving this distant ocean moon
behind,

we head inwards on
the final leg of our journey...

... Passing through
the asteroid belt,

rubble left over

from when gravity failed
to pull a planet together...

..Uuntil we reach
the inner rocky planets.

The worlds here
are home to phenomena

and landscapes
that are mesmerising.

So strange and alien.

But amongst all these wonders

lurks perhaps
the strangest world of all.

Welcome to Earth.

It is the biggest rocky world.

Radius about 6,370km or so.

It's a bit unusual
in that it's got a single moon,

but the thing that makes it
very unusual indeed

is the presence of that -
liquid water on the surface.

You might not think of Earth
as Strange,

because we live on it,

but it is, in fact,
a very rare world.

You know,
this is a really wonderful

and unusual thing to be able
to do in our solar system,

because there is no other world

where the conditions

of temperature and pressure
on the surface

allow liquid water to exist.

It's a very narrow range.

And that range is set

by the details
of our atmosphere.

There are tonnes...

... tonnes of atmosphere

pressing down on this rock pool

to stop it
from boiling away.

The nature of our atmosphere
is defined by the history

of our world,
our place in the solar system

and gravity.

Now, if you imagine
that you'd reduced

the mass of the planet
just a bit,

then the pressure would fall

and this would boil away.

If | carried on doing that

and reduced the gravitational
pull some more,

the whole atmosphere would
disappear off into space.

All the myriad properties
of our planet have combined

to allow liquid water
to persist here

for over four billion years...

... leading to planet Earth's
most unique feature.

Life.

As we explore the solar system,

we're discovering
ever-stranger places...

.all born of the interplay

between beautifully simple
laws of nature...

..and the deep history
of each and every world...

... creating endless wonders
of the solar system...

... Including...

AUS.

Just look at these telescopes,

our eyes on the universe.

Now, | find it so remarkable

that on one strange world
in our solar system,

collections of atoms have
come together

that can do astronomy, because

there's nothing particularly
special about the Earth.

It is just
another lump of stuff

that has found a way to avoid
gravitational collapse.

But somewhere in between

the relentless inward pull
of gravity

and the sheer bloody-mindedness
of matter,

some of that stuff has found
a way to contemplate

its place in the universe.

NEW SPEAKER: No other planet

has rings quite like Saturn
does. They're beautiful,

but it's odd to think that they
might not be there for ever.

PROF COx: Far from
a permanent structure,

we now know that
these strange loops

of rock and ice
are constantly changing

and may one day
disappear completely.

NEW SPEAKER: We have big
questions about Saturn's rings.

How old are the rings?

How did they form and
what is their evolution like?

How long
are they going to last?

PROF COX: NASA's Cassini
spacecraft studied Saturn

and its rings for 13 years
in search of answers.

NEW SPEAKER: Cassini allowed us
to see Saturn from closer up

than ever before,
but also from

new vantage points

that we had never been able
to access from the Earth.

PROF COX: Cassini witnessed
a series of bizarre moons

clearing paths in the rings.

But one of the biggest insights
came from its encounter

with a strange kind of rain
falling onto Saturn.

It was Voyager
that gave us the first hints

that particles could be falling
into Saturn.

Towards the end
of the Cassini mission,

when we flew the spacecraft
between the rings

and the planet,
we were able to detect

small ring particles that
were falling into the planet,

so-called ring rain.

PROF COX: The immense gravity
of Saturn is pulling

on these particles,
eroding the rings.

DR O'DONOGHUE: Ring rain causes
the rings to slowly die.

But what we don't know is
the rate at which the rings

are perishing.
We just know that they are.

PROF COX:
Flying through the icy rain,

falling from ring to planet,

was one of Cassini's
last endeavours.

In 2017, the mission
came to an end

before Cassini could find out
how long the rings had left.

To get a definitive answer

on the lifespan
of Saturn's rings,

we needed a brand-new mission.

So, JWST isn't like
a normal telescope

that you would find on Earth.

It's not at the top
of a mountain,

like the big telescopes
that we have here.

Instead, it is 1.5 million
kilometres away, in space.

PROF COX: The space telescope
is designed

to peer into the depths
of the universe.

But its infrared cameras
are also showing us

our solar system
in a strange new light...

.llluminating the faint rings
around the outer planets

normally invisible to us.

It's extremely difficult to get
to the outer solar system,

and so an instrument like JWST

that can look at these distant
objects is invaluable.

PROF COX: Amongst its targets
is Saturn and its rings...

...where the hope is

that the telescope will be able
to help answer

how fast
the ring rain ts falling.

So the rings are made
of mostly water ice,

and some of the smallest pieces

flow up the magnetic field
and fall into the planet.

That happens
all the way around,

so in our observations,

we see
this kind of infrared glow

all the way around the planet,
at that location,

which indicates that there is
ring material flowing in.

PROF COX:
In the next few years,

JWST will measure the intensity

of the infrared glow
in that band,

revealing how fast the rings
are losing particles...

DR O'DONOGHUE: I'm very excited
to find out how quickly

Saturn's rings are eroding
today

because finding out
what's going on today

is really important
for mapping their past

and predicting their future.

PROF COX: ...bringing us
ever closer to understanding

exactly how long
Saturn's stunning rings of ice

are likely to last.

DR BROOKS: There's something
about seeing Saturn's rings.

You have this almost childlike
fascination

and a professional curiosity
that come together

In a very unique way.

DR ROWE-GURNEY: Knowing that
Saturn's rings won't be around

forever and that we're here
at the exact moment

when they are here
is really amazing.

| feel really lucky
that we get to experience them.

(ROCK MUSIC)