All language subtitles for Solar.System.S01E03.Storm.Worlds.1080P.WEB-DL.x264-skorpion_track3_[eng]

It's midsummer.

A storm is breaking...

..unleashing torrents of rain...

..forming floods that drain into
raging rivers...

..and giant lakes.

This is the only world in our solar
system

where raindrops fall to the ground...

..apart from our own planet.

1.4 billion kilometres from the sun

lies Earth's strange, stormy twin.

Saturn's moon Titan is, in some ways,

more like a planet than a moon.

It is larger than Mercury,

and it is also, in some ways, more
like the Earth

than any other place in the solar
system.

I mean, I could stand on the surface
of Titan in a spacesuit

and look out over lakes.

And I could look into the sky,

and I could experience droplets of
rain landing on my visor.

But appearances can be deceptive.

Temperatures on Titan hover around
-180 degrees Celsius,

far too cold for liquid water.

Instead, these clouds are made of a
chemical that, on Earth,

is a flammable gas.

Methane.

Titan is a world sculpted by methane
storms.

Titan is the only moon in the solar
system

with a thick atmosphere.

And that atmosphere is the stage for
the methane cycle,

an arena within which liquid can
evaporate from lakes,

condense as clouds, and fall as rain.

But Titan is certainly not the only
storm world.

Among the most dynamic and violent
worlds in our solar system...

..are the handful that, like Titan,

have a thick atmosphere.

Planets where sulphuric acid storms
rage...

..giant dust vortices dance...

..and lighting ten times more powerful
than anything

found on Earth lights up the sky.

And worlds whose storms grow so large,

they are entirely engulfed.

On a perfectly still morning like
this,

as the sun rises above the high plains
of Utah,

it's easy to forget that we live in an
atmosphere.

But our atmosphere is central to our
existence,

and central to the character of our
planet.

Atmospheres behave like fluids,

and that's extremely important for a
planet like Earth.

Let me show you what I mean.

You can see that I'm a very
experienced camper.

Now, if I build a model of the Earth's
atmosphere -

which is coffee -

and then, if I put some milk in...

..which is a denser fluid than the
coffee,

and so it's sinking down to the bottom
of the pan.

And the reason I want to do that

is to show you something that happens
when I heat a fluid.

You think about a planet like the
Earth,

then it's heated from the sun.

That means that there are temperature
differences

naturally occurring in our atmosphere,
and it's what happens

in nature when there are temperature
differences that matters.

So what you see here is that that milk

at the bottom of the pan

is getting hotter than the coffee at
the top.

And that temperature difference is
trying to equalise.

So it's not that the temperature
difference

just equalises in a nice, uniform way.

But you can see it...there.

See? There are patterns developing,

tremendous amount of complexity.

And it's exactly the same in our
atmosphere.

But in our atmosphere, we call all
those patterns

and all that turbulence weather.

Wind, rain, and storms can almost be
thought of as side effects

of an atmosphere trying to move energy
between hot and cold.

If a world has an atmosphere, it will
have some form of weather.

But as the fleet of spacecraft

exploring our cosmic back yard have
revealed...

..atmospheres vary hugely by
temperature, pressure

and chemical make-up.

And that means that, while storms
might be common in our solar system,

on no two worlds are they ever the
same.

Journeying outwards from our shared
star,

searching for storm worlds...

..we dodge past a planet with no
atmosphere...

..and arrive at a world consumed by
one.

From a distance, Venus appears to be a
serene, pearlescent orb

floating in space.

But get a little closer...

..and the planet begins to reveal its
true nature.

All that can be seen are clouds.

Endless, thick, churning storm clouds

that conceal the entire surface from
view.

This is just the top of a cloud deck
that's 20km deep...

..and whipped up by hurricane-force
winds.

Venus is a true storm world.

Now, those clouds on Venus just look
like storm clouds here on Earth.

A bit foreboding, perhaps, but...

..maybe nothing too much to worry
about

if you were sat beneath them.

Well, they ARE actually something to
worry about.

They're not made of water.

They're made of this.

Concentrated sulphuric acid.

Now, even saying that sounds nasty,

but just wait till you see what this
stuff does

to the stuff that I'm made of, the
stuff that you're made of,

just organic material - in this case,
sugar.

Now, you see that's already starting
to react -

it's turning brown, it's starting to
bubble.

The concentrated sulphuric acid -

and this is 90-odd percent
concentrated,

which is precisely what we find in the
clouds of Venus -

is ripping the water out of the sugar.

In fact, that dark material there is
carbon.

It's what's left over when you rip all
the water out of the sugar.

I can show you.

So C12H22O...11.

So that's the sugar we've got, and
then sulphuric acid,

which is H2SO4, and that goes to
carbon and water, and...

..I can smell it, actually, sulphur
dioxide.

That's it, and a lot of heat.

But just think -

that started off as sugar,

essentially organic material like this
stuff.

I mean, look at that!

So if you were to skydive through the
clouds of Venus,

for some reason, then that's what
you'd turn into.

So I suppose the moral of the story
is...don't.

But ignoring that advice

and taking the plunge down through
Venus's storm clouds...

..we reach a surface that's eerily
calm.

With air pressure so intense,

it's like being 1km beneath the ocean,

but with one key difference.

At 460 degrees Celsius,

Venus's surface is hotter than that of
any other planet...

..which is why one feature leaps
out...

..something that shouldn't be possible
on this roasting world...

..a mountain that seems to be covered
in snow.

Could it really be snowing on Venus?

Now, as well as being really nasty and
corrosive,

those sulphuric acid clouds are
extremely dense.

That's why, if you look at Venus
through a telescope

all you can see is clouds.

Until the 1950s, actually,

we imagined that Venus might be a
tropical paradise.

Now, Nasa's Magellan probe arrived in
the 1990s equipped with radar

that could peer through the clouds and
image the surface.

And it took pictures like this.

This is a vast mountain range called
Maxwell Montes.

And it's huge, it's much bigger than
the size of Wales,

to use the standard measure of area.

And there are points on here that are
11km in altitude.

Now, I think it's very difficult
using, as we do, our brains,

tuned to the landscapes of Earth, not
to look at that...and see that.

The material that coats Venus's
mountains reflects radar,

mimicking the appearance of snow.

But Venus's extreme atmosphere means
snow is...unlikely.

The atmospheric pressure on the
surface of Venus

is 90 times the pressure here on
Earth.

That's because its atmosphere is
extremely dense,

and 96% of it is carbon dioxide.

Now, carbon dioxide is a powerful
greenhouse gas.

That means that, although it lets the
visible light in from the sun,

which heats up the ground,

the heat radiation coming back out
again,

the infrared light, is trapped.

The result is a runaway greenhouse
effect.

Venus is so hot,

it's thought the ground might actually
glow,

like metal coming out of a forge.

It's a world far too hot for
snowstorms.

But the fact that this strange
material imitates snow,

by being found only on mountaintops,

is a clue.

The key is altitude.

As you go higher and higher in the
Earth's atmosphere,

then the atmospheric pressure falls.

And the reason for that is pretty easy
to understand,

if you think what pressure is.

It's just the weight of air pressing
down.

And so, imagine going up to 100km, for
example -

then you'd be in space -

there'd would be no atmosphere at all,
and the pressure would be zero.

As you increase altitude,

then it's not only the pressure that
falls,

it's the temperature as well.

Now, the explanation for that,
actually, is quite complicated.

It's what a physicist would call
slightly nontrivial.

There are a lot of things happening.

One is that, if you imagine a piece of
air,

a volume of air down at sea level,

and you lift it up higher and higher,
and the pressure falls,

and so that air expands,

and therefore it cools.

But there's another thing happening as
well, which is related to

the greenhouse effect.

So sunlight is coming down and heating
up the ground,

and then the ground is re-radiating
the heat up into the atmosphere,

which is trapping it.

And so the closer you are to the
ground, the hotter it is.

The point is, if you climb a mountain
on Earth,

then you can get to a point where the
temperature is so low

that water freezes out to form snow.

And that dividing line between the two
regions

is called the snow line, for obvious
reasons.

Now, on Venus, we also see something
that looks

for all the world like a snow line,
but water isn't involved.

So what is it?

Venus's snow line suggests that
something is freezing up there,

something that freezes at much higher
temperatures than water.

And that points us to chemicals that,
on much cooler Earth,

are only ever found as solids.

Now, one of the candidates for that
bright snowy stuff that coats

the mountaintops of Venus...

..is this.

This is lead sulphide.

So the idea is that the lead and
sulphur that are becoming vapour

because it's so hot, and heading up
into the atmosphere,

cool and condense out onto the
mountaintops,

and react to coat them in this bright
silver.

I mean, we don't really know for sure,

and part of the reason for that is
it's so difficult to explore Venus.

It would be wonderful to drop a
spacecraft onto those mountains,

but we haven't landed a spacecraft
successfully on the surface of Venus

since the Russian probes in the 1980s,

and they didn't last very long.

But just imagine if that's right.

I mean, what a sight that would be.

Instead of water, it's thought that,
on Venus,

it's lead and sulphur that vaporise.

In vapour form, they're carried on air
currents,

from lower altitudes...

..up into mountain ranges...

..where, because of the altitude, the
temperature drops just enough...

..to allow them to crystallise out of
the air...

..coating Venus's mountaintops in
glittering metallic frost...

..creating snowy peaks on a hellish
world.

Leaving Venus's crushing atmosphere
behind...

..we head out in search of a world

that could almost be Venus's opposite.

Bypassing our own planet...

..and dodging two potato-shaped
moons...

..we arrive at the farthest rocky
planet from the sun.

We've sent more spacecraft to explore
Mars

than any other world in the solar
system.

And thanks to this robotic army
beaming back photographs...

..we know that, in the deep past...

..Earth-like rainstorms carved the
Martian surface.

But around four billion years ago,

Mars began to lose its atmosphere,

transforming it into a planet where
you wouldn't expect

to see any storms at all.

Modern Mars's wisp of an atmosphere

is just 1% the density of Earth's...

..and it's so dusty, the sunrise is
tinted blue.

Temperatures on the surface average
-60 degrees Celsius.

Mars might appear to be a frozen
world...

..but all is not what it seems.

Strange lines, often tens of metres
wide,

are etched on the surface.

Unlike Mars's dry rivers, these are
not relics.

We see them appear and disappear...

..almost as if they're being
deliberately drawn,

and then wiped away.

What, on dry, freezing Mars,

could be behind these bizarre,
shapeshifting patterns?

Oh, look at that. This is...

Moab is just a fascinating place, the
Uranium building.

This was known as one of the wildest
places in the Wild West.

And then, in the 1950s, they
discovered uranium,

so there was a boom, it was like the
Gold Rush.

But it was a uranium rush,

and there's all these echoes of the..

The Atomic Hair Salon over there,

and there's Nuclear Coffee.

HE CHUCKLES

Nuclear coffee - I'm having some of
that.

Clues to solving the mystery of the
Martian lines...

..come from a pair of trailblazing
Mars rovers.

Spirit and Opportunity were small
rovers.

And unlike the big nuclear-powered
rovers of today,

they were purely solar-powered.

And the solar panels were very small,
only about this big.

And those rovers were only designed to
last around three months,

because Mars is a dry, dusty desert
world,

and all the engineers thought that,
over time, those solar panels

would be covered with dust, and the
power would drop.

And that's indeed what happened... for
a while.

Thanks to Mars's dusty atmosphere,

at first, the solar panels' energy
output dropped.

But then, suddenly...

..their power started leaping up.

Something was sweeping dust from the
solar panels,

keeping the rovers alive much longer
than expected.

Before long, images started to arrive
at Earth...

..that hinted at what was going on.

On Mars, as on Earth, the sunlight
passes through the atmosphere

pretty much unhindered, and hits the
ground and heats it up.

But on Mars, because the atmosphere is
much lower pressure,

much more tenuous,

then the temperature gradients you get
closer to the ground

can be far greater.

So I could stand on the equator of
Mars,

and the ground can be at 20 degrees
Celsius,

but my head can be in air that's at
-10 degrees Celsius.

And that temperature gradient has
powerful effects,

it has consequences, because the
gradient wants to equalise.

So the air, in contact with the
ground, will heat up,

and that means that it will rise.

Hot air rises.

Under the right conditions, that
rising air creates

a lower pressure into which colder air
can fall,

and so you can get a system where air
rises, air falls,

the whole thing spins, and that can
form a stable structure,

a dust devil.

So this is, again, a beautiful example
of a gradient, an imbalance,

creating temporary structure -

in this case, a spinning storm of
dust.

Now spotted frequently by spacecraft
on the surface...

..it's thought that dust devils
passing over the rovers

sucked dust off the solar panels like
a vacuum...

..keeping Spirit roving for six years,

and making Opportunity seem
unstoppable.

But the cleaning power of dust devils
doesn't just work on rovers.

Thanks to Mars's thin atmosphere,

Martian dust devils can grow up to
20km tall and 1km wide.

And as they travel,

these spinning vortices suck up dust
from Mars's surface,

exposing the darker bedrock beneath...

..leaving trails so large,

we can see them clearly from our
orbiting spacecraft.

There are no Martians behind the
lines.

The culprits are spinning Martian wind
storms.

But dust devils are just one half of
the puzzle.

They might create the tracks...

..but it's something else that wipes
them away.

Just like the Earth, Mars has a tilt
that gives it seasons.

Summer in one hemisphere means winter
in the other,

and a planetary temperature gradient
that wants to equalise.

But Mars has no oceans or thick
atmosphere

to help move heat around the globe.

The one thing it does have, however...

..is dust.

As summer progresses,

a huge amount of dust is lifted into
the air by the sun's heat.

The dust absorbs sunlight, heating up
the air around it...

..causing updraughts, and more dust to
be lifted...

..until a storm is formed...

..that wipes away any dust devil
trails in its path.

And every few years, these storms grow
so large...

..they encircle the entire planet.

In 2018, a monster dust storm darkened
Mars's skies

for months on end...

..and for solar-powered Opportunity,
it was catastrophic.

This is the last of over 200,000
photographs

that Opportunity sent back from the
surface of Mars to Earth.

And it's certainly not the most
beautiful photograph by any means,

but it is, I think, remarkably
poignant,

because these speckles, they're not
stars in the sky.

They're camera noise,

because it was so dark when this
photograph was taken.

And this dark area here, it's not the
Martian surface -

it's actually nothing at all, because
Opportunity ran out of power

just before it finished transmitting
this photograph back to Earth.

So, after 14.5 years,

this is the final thing that
Opportunity saw,

defeated by the Martian atmosphere
that kept it alive for so long.

But the darkness plays an important
role for Mars.

With less sunlight hitting the
surface,

the temperature difference between the
hemispheres is reduced.

And when the storms recede...

..they leave a slate wiped clean...

..ready for dust devils to start
etching the surface again.

Leaving Mars and its dust cycle
behind...

..we head out in search of a
completely different

kind of atmosphere.

But first, we must traverse the
asteroid belt...

..ruled by the dwarf planet Ceres...

..until, three times further from the
sun than Mars,

we enter the realm of giants.

Twice as massive as all the other
planets of

the solar system combined...

..this is a storm world on the
grandest scale.

Made mostly of hydrogen and helium,

Jupiter is a gas giant...

..on which storms can grow bigger than
planet Earth.

Since 2016, Nasa's Juno spacecraft

has been exploring this gargantuan
planet...

..and found that the violence of its
weather matches its scale.

Lightning strikes here in abundance,

with bolts ten times more powerful
than those found on Earth.

Most flashes are trapped under
Jupiter's thick outer layer

of ammonia ice clouds.

But the most powerful storms break
free...

..allowing us to get a proper look at
the fireworks.

It's not really fully understood in
precise detail

how lightning forms on Earth.

You need ice crystals rising and
hailstones falling,

and they collide, and in that process,
electrons are exchanged,

and so electric charges separate.

The top of the cloud and the bottom of
the cloud

become electrically charged.

THUNDER ROLLS

I mean, it's just like walking around
on the wrong kind of carpet,

and then grabbing a door knob and
getting electrocuted,

but the spark is much bigger.

But what we do know is that, in the
same region of the atmosphere

for lightning to form,

you need all three phases of water to
be present -

as a vapour, ice and liquid.

Lightning is common on our planet
because of Earth's water cycle.

But Jupiter is a very different kind
of world,

five times further from the sun.

Thanks to Juno, we know that its
atmosphere

does contain a trace of water,

around a quarter of 1%.

But could this water really be the
cause of Jupiter's lighting?

We all learn about the water cycle at
school.

The sun shines down on the oceans and
lakes, water evaporates,

the water vapour rises and cools,

condenses back to form clouds,

and then falls down to the ground
again as rain.

But there's something else to the
water cycle

that's extremely important,

because it is a very efficient energy
transport mechanism.

If I take some water from the river

and pour it into the hot frying pan on
the camping stove...

..then the water boils, turns into
vapour

and disappears off into the
atmosphere.

Let's think what's happening here at a
deeper level.

So water molecules, H2O, are bonded
together in the liquid.

Now, I have to put energy in from the
flame to break those bonds

and turn the liquid into vapour.

The reverse must also be true,

so the vapour, the steam, turns back
into liquid again,

the bonds reform, and all that energy
is released.

And that's why steam...burns.

Now, what's happening is the vapour is
touching my cooler hand,

turning back into liquid, and, as the
bonds reform,

a tremendous amount of energy is
released.

The water cycle acts like a battery.

On Earth, when water evaporates,

it absorbs the sun's energy and stores
it...

..until re-releasing it into the
atmosphere,

when it condenses into clouds.

In a typical cloud, the energy
release,

when the vapour turns to liquid,

is hundreds of tonnes of TNT.

Just in a cloud like that.

If you think of a big storm system,
like a hurricane,

and over its lifetime, the energy
release is more like

thousands of atomic bombs.

By funnelling the sun's energy into
the atmosphere,

the water cycle powers Earth's
electrical storms.

But the same can't be true on Jupiter.

The planet receives just 4% of the
sunlight

that we do here on Earth.

And the surface we see, the ammonia
ice clouds,

is at -100 degrees Celsius.

But looking at the planet in the
infrared

provides a clue as to what's going on.

Jupiter is radiating heat...

..double the amount of energy it
receives from the sun.

Jupiter is basically a giant ball of
gas,

and there's nowhere, really, as you
descend into the planet,

where the atmosphere ends, just that
the pressure increases.

And ultimately, those gases become
liquids,

and actually, at the core, are strange
sorts of metallic solids.

Now, Jupiter is collapsing under its
own gravity -

it's been doing that since it formed
about 4.5 billion years ago.

And even now, it's collapsing by about
one millimetre per year.

But that releases a tremendous amount
of this.

It's gravitational potential energy.

That release is heating Jupiter up.

At the core, it's 24,000 degrees
Celsius -

a huge temperature gradient -

and it's that that powers the storms
on Jupiter.

This internal heat allows water to
drive storms on Jupiter,

just as it does here on Earth.

And that's why Jupiter has so much
lighting.

In vapour form, water ascends,

carrying energy from deep inside the
planet...

..until it reaches a place under the
ammonia ice clouds...

..where it's cool enough for it to
condense

into droplets and ice crystals.

The energy released as the water
condenses

powers the growth of violent
thunderstorms.

In places, so much energy is
released...

..that ice crystals are swept upwards
into the ammonia ice clouds.

Here, ammonia acts as antifreeze...

..allowing liquid water to grow
thunder clouds 60km tall...

..even though it's
-100 degrees Celsius.

Jupiter's about as different from the
Earth as you can possibly get.

Now, it's a gas giant, extremes of
temperature and pressure,

really different chemical composition.

But there is a water cycle.

There's a region in the atmosphere
where the temperature and pressure

is just right for water to exist in
all of its three phases.

And it's that region that plays the
dominant role in allowing

the energy from deep inside the planet
to escape

into the upper atmosphere, drive the
storm systems that we see,

and ultimately allow energy to flow
from inside the planet

and out into space.

Heading out from Jupiter...

..we cross 700 million kilometres of
empty space...

..before we encounter the solar
system's other gas giant.

Taking the crown for the planet with
most moons,

Saturn is orbited by at least 146...

..that we know of.

But one stands out amongst the crowd.

More than 20 times the mass of all
Saturn's other moons combined.

The only moon in the solar system to
have a thick atmosphere.

But what makes Titan really special

is it's the only place we know of,
other than Earth...

..where you could see a sight like
this.

Thanks to Titan's thick nitrogen
atmosphere

and temperatures of
-180 degrees Celsius...

..methane, naturally found as a gas
here on Earth,

can exist as a liquid.

It forms clouds in the sky, falls as
rain,

and pools in giant lakes.

But lakes like these are not found
everywhere on Titan.

They're only located at the poles.

Travel beyond, and we find a very
different world.

Great plains...

..rolling dune fields...

..these are Titan's deserts.

But get down closer...

..and a familiar shape comes into
view.

The reason we know so much about Titan

is because of the iconic spacecraft
Cassini.

It arrived in the Saturnian system in
2004,

and spent over a decade exploring the
planet and its moons.

And it discovered not only that Titan
is a desert world

with methane lakes around the poles,
but also...

..it saw features like this,
meandering across the deserts.

And this...is one of those.

Titan's desert regions are
crisscrossed with dry river beds...

..some 3,000 kilometres away from the
methane lakes at Titan's poles.

So we're faced with a mystery.

What is carving these rivers?

The southwestern United States is just
covered in canyons like this,

and they're very similar to the
canyons that Cassini saw

on the surface of Titan.

Now, here they're caused by flash
flooding.

So in the summer months, the North
American monsoon

sweeps across this landscape.

So a huge amount of moist air that's
risen up from the Gulf

of California, and dumps rain onto
this otherwise parched desert,

and it flows down and cuts these
canyons.

If Earth's dry rivers have a seasonal
origin,

could the same also be true for Titan?

Just like Earth, Saturn is tilted on
its axis.

And that means that, just like Earth,
Saturn has seasons.

But Saturn's year is 29 Earth years,

and so that means that each season is
something like seven years long.

Now, Titan shares Saturn's tilt.

In Titan's southern hemisphere summer,

the southern hemisphere points towards
the sun.

And even though it's a billion miles
away,

so there isn't much energy falling on
the southern hemisphere,

there is enough for those seven years

for methane to evaporate from the
lakes

and up into the atmosphere.

Cassini saw this happening.

It flew by Titan during southern
summer,

and saw methane clouds swirling around
the south pole.

All that methane condensing out in
Titan's atmosphere releases

a tremendous amount of energy,

just like water condensing out in our
atmosphere releases energy,

and that energy release seeds the
formation of storms.

But the clouds didn't stay at the
south pole.

In 2010, Cassini took this image of
Titan,

and I think it's just remarkable,

because this is a storm around Titan's
equator.

It's worthwhile sometimes just sitting
back

and realising what this is.

It's a photograph of a storm in the
atmosphere

of a moon orbiting Saturn.

In Titan's deserts, autumn brings
change to the air.

Storms like the one seen by Cassini
arrive from the pole...

..unleashing torrents of methane rain.

But because the gravity on Titan is
even less than that of our moon,

the raindrops fall at one-sixth of
their speed on Earth.

Storms in slow motion, the most
powerful

thought to drop 30cm of methane rain a
day.

Forming flash floods...

..that, over millennia, carve canyons
into the desert landscape...

..before they spill out into vast
flood plains.

Now, Cassini also took these images.

This one is an image of the surface,

and these dark areas here have been
interpreted as liquid methane,

a flood of liquid methane.

It's a few tens of centimetres deep,
but the area of this flood

is something like the area of Utah and
Arizona combined.

And then, just a few months later,

this image was taken of the same
region on Titan.

And now you see that the flooding has
disappeared.

All that methane has evaporated back
up into the atmosphere again

over the period of just a few months,

and the storm had moved on.

In 2022, five years after the Cassini
mission had ended...

..the James Webb Space Telescope
turned its infrared gaze

towards Saturn's distant moon.

By now, it was late summer in Titan's
northern hemisphere,

and the telescope spotted something
magical.

Giant clouds over the north pole.

The travelling storms had reached
their destination.

It's now believed that Titan's storms
go on

an epic 29-year migration...

..from one pole to the other and back
again.

As they travel, they unleash methane
floods that, over millennia,

carve canyons into Titan's deserts...

..seasonal rivers on a moon 1.2
billion kilometres from Earth.

Titan is a fascinating world,

and although it lives in permanent
twilight -

and so we might expect it to be frigid
and frozen solid -

it has a tremendously dynamic
atmosphere.

It has storms and seasonal monsoons
that sweep across the surface -

not unlike the monsoons that sweep
across Utah and Arizona.

It's just that, because of those
temperatures,

it's not water that carries energy
around the atmosphere.

All of the chemistry is shifted,

and it's methane that takes centre
stage.

This, then, is the story of the storm
worlds of our solar system.

The beautiful and complex structures
we call weather

emerge from each atmosphere trying to
do the same thing...

..move energy to balance out hot and
cold.

But what makes these worlds so
dazzlingly different...

..is which chemicals play the leading
role

in carrying that energy.

Chemistry is what happens between the
heat of the stars

and the cold of space,

and it plays out on the surface of
planets and moons.

The arena is the atmosphere.

Storms sculpt the surface of worlds.

On Venus, the mountains might be
coated in metal,

and methane falls as rain on Saturn's
moon Titan.

Here on Earth, the atmosphere has
allowed life to emerge.

But our solar system is only one of
hundreds of billions

of solar systems out there in the
Milky Way galaxy alone.

So just imagine what nature - that
great tinkering chemist -

might have created out there.

- Navigation has confirmed that the
parachute has deployed.

Packing manoeuvre has started.

About 20 metres off the surface.

- For decades, NASA has used rovers to
explore the Martian surface.

But because Mars is a storm world...

..a world with an atmosphere...

..there is another way.

- Ingenuity is a helicopter.

It's our first spacecraft that we've
built to fly on another world.

- In 2021, after hitching a ride to
Mars

with Nasa's latest rover,
Perseverance...

..Ingenuity made history.

- It is now reporting spin up, take
off, climb.

Altimeter data confirmed that
Ingenuity has performed

its first flight of a powered aircraft
on another planet!

- Ingenuity's first flight was so
cool!

It was one of these, "Oh, my God, it
worked," moments.

You know, you test and you test,

and you do your best to design
something,

but to actually see it work on the
surface of Mars -

we called it the Wright brothers
moment,

but for another planet.

- APPLAUSE

The helicopter was designed at Nasa's
Jet Propulsion Laboratory,

a test vehicle to prove that
extraterrestrial flight is possible.

But the major challenge for engineers
was Mars's atmosphere.

- Mars does not have a lot of
atmosphere to speak of.

It's not like here on the Earth. It's
much thinner.

A couple of molecules bouncing into
each other

every once in a while is not a lot of
stuff to push against

to generate lift.

- So you have to have a helicopter
that's very, very, very, very light,

and you have to have rotors that spin
very, very, very, very, fast.

- Only designed to fly five short test
flights,

Ingenuity surpassed all expectations.

- The light looks great.

We're right in the vicinity of where
we wanted to be.

- Its mission was finally brought to
an end

when it sustained rotor damage on its
72nd flight.

But during its active three years on
Mars,

the helicopter pioneered a new
approach

to exploring the storm worlds of our
solar system.

- Helicopters like Ingenuity open up a
new dimension

to exploration on the surface of a
planet.

And I mean dimension literally.

- You can cover so much more ground.

Instead of driving for metres every
day,

you can drive kilometres.

You're also going to get this
bird's-eye view of the planet

that's going to be very different.

- A rover on the surface has got to
climb over boulders, climb up hills.

With a helicopter like Ingenuity,

you just fly right over it, no big
deal.

- Which is why Nasa's future mission
to Titan

is going to be a flying one.

- Titan is a fabulous place to explore
by rotor craft.

It's smaller, so it has much lower
gravity than Mars...

..but it also has a much thicker
atmosphere.

- If you and I were sitting on the
surface of Titan,

and strapped some wings, and an oxygen
mask to our face,

we would be able to generate enough
lift to fly.

- So you can build something that's a
lot heavier,

that has a lot more complicated,
intense science instruments.

- In 20-30 minutes, Dragonfly will
cover several kilometres.

Compare this to the rovers on Mars,

which go about 100 metres over the
course of a day.

- This will allow the Dragonfly team
to visit many sites

with one spacecraft.

- Dragonfly's fundamental mission

is to give us an understanding of the
chemistry on Titan.

What is the surface of Titan actually
made of?

That question has huge implications
for our understanding

of how complex chemistry can become,

which means it's important for our
understanding of how

life may emerge elsewhere in the
universe.

- And it's, I think, going to be so
cool.

I can't even imagine what Dragonfly is
going to see,

and what we're going to learn.

I can't wait for that mission.

- Next time - the ice worlds...

..where mountains of ice float across
great frozen plains,

where strange aurora hang above an icy
giant...

..where a moon is torn apart by a
monster planet.