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.