Original subtitles

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)