Original subtitles

NARRATOR: Flying through space,

a high-tech view from above

uncovers a strange expanse on the surface of Mars.

CYLITA GUY: This find is potentially huge for the future of space travel.

- (beep) NARRATOR: Cutting-edge technology

looking down from space

reveals a centuries-old legend in Earth's oceans.

TORRI YATES-ORR: Something weird is definitely going on here.

NARRATOR: NASA probes spot a vast hexagon

swirling around Saturn's north pole.

DAN RISKIN: This is honestly one of the weirdest things in the universe.

NARRATOR: And satellites capture a perfect doughnut-shaped lake

carved into the landscape.

GUY WALTERS: This is really weird. So what happened here?

- (boom)

NARRATOR: Everywhere we look on our planet,

there's evidence of the past.

In nature.

In buildings.

In relics.

Each holds a mystery

that technology now allows us to see from above.

- (dramatic music)

NARRATOR: What new secrets are revealed?

- (optimistic music)

NARRATOR: In the 21st century,

the view from above has reached ever greater heights...

..uncovering mysteries not just on Earth

but across our solar system.

As we search for clues on Earth to solve these cosmic enigmas,

technology reveals that outer space

holds answers to some of our own abiding secrets

and may even hold the key to the future of human space travel.

- (tense music)

NARRATOR: The Red Planet Mars

is Earth's most tempting neighbouring planet.

DAN RISKIN: Mars really does feel like

the next frontier in space exploration.

TORRI YATES-ORR: Since the 1960s,

we've sent probes and orbiters to explore the planet from above,

searching for clues about its history

and what it can reveal about planet Earth.

GEORGE KOUROUNIS: Today, there are even rovers on the surface,

and space scientists are looking forward to the day

humans can fly a mission to Mars.

PETER SOROYE: To chase that dream, scientists investigate

the Martian surface with the images and data captured from above

to find places where humans could land.

TORRI YATES-ORR: A landing site needs to be close

to major areas of interest,

including where signs of alien life could be found

and any resources that could support a human mission.

NARRATOR: And one team of researchers examining

a possible Martian landing site finds something astonishing.

- (tense music)

DAN RISKIN: It's amazing. I mean, you think of Mars,

you expect this boring desert of flat, orange nothing.

But this is stunning.

NARRATOR: Images captured of the Martian surface

reveal an unexpected bright area.

GEORGE KOUROUNIS: This is wild

because you just don't expect anything on Mars to look like this!

It's just completely the wrong shape and colour.

DAN RISKIN: It's not the jagged black of volcanic rock

and it's not the red waves of iron-rich sand dunes.

So what's happening on Mars to make these light tones?

PETER SOROYE: And this is pretty big.

It's around six kilometres long and four kilometres wide.

That's seven times bigger than Central Park.

NARRATOR: Millions of kilometres further away from the sun,

in the Kuiper Belt,

advanced space technology looking down from above

may uncover a clue.

- (intriguing music)

TORRI YATES-ORR: In the summer of 2015,

the New Horizons probe reached Pluto,

over nine years after it was launched from Earth.

CYLITA GUY: Until this major milestone,

the best view we had of Pluto was from the Hubble Space Telescope.

So when the first images of the dwarf planet finally reached us,

the difference was staggering.

DAN RISKIN: New Horizons captured

a huge bright feature on the side of the planet

that looks like a heart.

GEORGE KOUROUNIS: The size of this is staggering,

about 16-hundred kilometres across.

That's over three times longer than the Grand Canyon.

NARRATOR: But what is making this huge light-coloured shape on Pluto?

PETER SOROYE: Pluto is over three billion kilometres

from the sun on average, making it pretty chilly...

an unbelievably frigid

minus 232 degrees Celsius.

CYLITA GUY: It's so cold that nitrogen, methane

and carbon monoxide in its thin atmosphere can actually freeze.

DAN RISKIN: And this deep-space ice

collects on unique terrain.

Most of the heart is this massive basin

that's filled in with a thick layer of these weird kinds of ice.

NARRATOR: Could the bright area on Mars

be a vast ice field like Pluto's heart

and will these secrets bring humans closer to exploring Mars?

DAN RISKIN: Mars's atmosphere is more than 95% carbon dioxide.

So would it be possible for that

to solidify into an ice patch on the surface?

CYLITA GUY: Mars does sometimes have ice and frost made of CO2,

but it doesn't always stick around.

ROMA AGRAWAL: Mars isn't as cold as Pluto.

For carbon dioxide to stay solid as ice,

it needs to be pretty cold...

around negative 125 degrees Celsius.

GEORGE KOUROUNIS: At the poles or overnight...

no problem. Temperatures can drop to minus 130

or even minus 150 Celsius in winter at the poles.

But when the sun hits...

everything changes.

PETER SOROYE: On Earth, we know

frozen or solid carbon dioxide as dry ice.

And if you think about what happens to that

when it hits normal temperatures,

you can start to visualise what happens on Mars

every time the sun starts to warm up the surface.

DAN RISKIN: It's something called sublimation.

It's when something goes from a frozen solid to a gas

so fast that it just skips the liquid stage altogether.

CYLITA GUY: And this weird light area on Mars

is right by the equator.

While it can get down to below minus 70 degrees Celsius at night,

this isn't quite cold enough for CO2 ice.

DAN RISKIN: And at noon, It can get up to a balmy 20 degrees Celsius

at the surface.

But even then, because of the thin atmosphere,

if you go up just one-and-a-half metres above the ground,

you're already down to zero degrees Celsius.

- That's far too warm for any CO2 ice to really stick around.

GEORGE KOUROUNIS: So what else could be going on?

What other clues can we find?

NARRATOR: A closer look at the NASA images

suggests something surprising.

- (intriguing music)

TORRI YATES-ORR: This bright area on Mars is full of geographic features

that look shockingly familiar.

NARRATOR: There may be a clue closer to home

here on Earth in Iceland.

GEORGE KOUROUNIS: Iceland is known as the land of fire and ice -

and for good reason. It has some of the world's most active volcanoes

and some of the largest glaciers.

NARRATOR: This is Vatnajokull,

one of the largest ice caps in Europe.

DAN RISKIN: This massive chunk of slow-flowing ice

covers over 75-hundred square kilometres.

CYLITA GUY: There is more to this chilling beauty

than meets the eye.

Active volcanoes are hiding under the ice.

TORRI YATES-ORR: But it's the glaciers that hold the clue

to the strange bright region on Mars...

particularly the dramatic Svínafellsjokull glacial tongue.

DAN RISKIN: If you look at the glacier tongue,

where it hits the sea,

you can see some cracks in the ice that are starting to spread outward.

And if you look at the shapes,

they look an awful lot like the ones on Mars.

CYLITA GUY: There are also bands of

earth and rock in these really long wavy piles.

These are called moraines -

material that's either been picked up

by the sides of the glacier or pushed together by the front.

ROMA AGRAWAL: And they create shapes

nearly identical to the strange area on Mars.

GEORGE KOUROUNIS: And this wasn't the only icy clue in Europe.

NARRATOR: Around 26-hundred kilometres to the southeast

is another stunning ice form,

high in the Austrian Alps.

- (tense music)

NARRATOR: This is the Pasterze Glacier.

PETER SOROYE: Climate change is chasing

this epic glacier into the past.

It's been receding since the 1850s.

100 years ago, it was over 11 kilometres long.

Today, it's less than eight kilometres long,

and it's dropped in mass by over 50%.

- (dramatic music)

DAN RISKIN: But for now it still holds clues to the Martian mystery.

NARRATOR: Its stunning crevasse-like shapes

reveal signs of the flow of water and ice over the terrain.

DAN RISKIN: Circular crevasses

with these concentric rings of cracks

can happen when there's water flowing under

or on top of or even within the glacier.

These wear away at the ice,

and then the ice gets weak spots,

and when it gets unstable enough, it collapses.

- And these cracks that look like hash marks

are called tic-tac-toe crevasses.

They occur when the glacier ice

flows on top of a higher area in the landscape,

which stresses it in different directions,

creating this unique crack pattern.

TORRI YATES-ORR: And when you look at them side by side,

these look uncannily like the fracture shapes

on the Martian surface.

GEORGE KOUROUNIS: The weird shape on Mars

has the hallmark features of a glacier.

NARRATOR: Could a glacier be the secret

to this unexpected feature on the Martian surface?

GEORGE KOUROUNIS: If we're able

to find a source of water, even if it's frozen ice,

that would make further explorations of Mars,

especially by humans, so much easier.

It could change everything.

DAN RISKIN: Water could be used for everything,

from drinking to feeding plants.

It could even be converted into rocket fuel.

NARRATOR: But there's a problem.

ROMA AGRAWAL: The satellites and probes that look at Mars from above

have found signs of water ice glaciers.

But there's a key difference.

DAN RISKIN: Any glaciers at the surface

are nowhere near the equator,

and that is because of sublimation.

CYLITA GUY: Water is really unstable on Mars,

and that's because of its thin atmosphere.

The atmospheric pressure is more than 100 times less

than here on Earth.

PETER SOROYE: Because of the low atmospheric pressure on Mars,

instead of liquid water boiling at 100 degrees Celsius,

like it does on Earth,

it actually turns into gas at around ten degrees Celsius.

Basically, if it's not frozen, it's boiling or evaporating away.

TORRI YATES-ORR: So if it can't be a surface water glacier,

what's going on?

NARRATOR: What clues can be found

by the advanced probes searching Mars from above?

TORRI YATES-ORR: The Mars Reconnaissance Orbiter, or MRO,

has been flying high above the Red Planet for over 17 years.

Packed with high-tech equipment, it offers a crucial clue.

ROMA AGRAWAL: When the researchers looked at the data from the MRO,

they found that the light area

was actually a kind of salt.

- (dramatic music)

NARRATOR: But how did this salt appear?

- And how can salt on Mars

make shapes just like those we see in glaciers here on Earth?

NARRATOR: A mystery whose answer

may still hold the key to human missions to Mars.

- (dramatic music)

- There's a clue on Earth that provides

the final piece of the puzzle.

- (intriguing music)

NARRATOR: Hiding only a few decades in the past,

in the bright red waters of Bolivia's Laguna Colorada

is a staggering secret.

GEORGE KOUROUNIS: The lakes of this region,

in the high plateau known as the Altiplano,

are extremely salt and form

large and dramatic salt islands in the brilliant waters.

ROMA AGRAWAL: But in the 1980s

scientists discovered something incredible

hiding in these salty shells.

Ancient ice.

CYLITA GUY: The researchers believed that this ice was formed

during the Little Ice Age, which started in the Middle Ages.

DAN RISKIN: This thick layer of salt insulated this ice against melting,

so it could stick around for decades or even centuries, even though

in the bright sunlight the summer temperatures

get to, like, 16 degrees Celsius.

PETER SOROYE: And these aren't just little ice cubes.

These ice-cored salt islands were as large as 1.5 kilometres across

and seven metres high.

TORRI YATES-ORR: It's unknown if the ice persists to this day,

but the hidden ice implies

something staggering about the shape on Mars.

NARRATOR: Could the salt and the glacial-looking terrain

at this strange bright area on Mars be a sign of ice hiding below?

DAN RISKIN: Experts believe there is a way this could happen.

First, a long time ago, a Martian volcano could have erupted

right next to a water ice glacier.

GEORGE KOUROUNIS: The hot ash would have instantly melted

the top of the ice, and - as it evaporated away -

it would have left a layer of salt behind, hidden by the dark ash.

CYLITA GUY: Eventually, Martian winds would have blown the ash away,

leaving behind the bright salt layer,

which would hold the shape of the glacier beneath.

GEORGE KOUROUNIS: Even though this isn't 100% confirmation,

it's really important because, if it is there on the surface,

that changes everything.

- (tense music)

ROMA AGRAWAL: Glaciers have been found on Mars before,

but in the unfriendly and extreme environments at the Martian poles,

where the icy temperatures and long winter nights

would wreak havoc on humans and electronics alike.

PETER SOROYE: And at such cold temperatures,

simply turning that ice into liquid water

could be a near-impossible task.

CYLITA GUY: But this glacier is at the much more accessible

warm and sunny equator.

And digging through a crust of salt is going to be far easier

than trying to break up polar ice in negative 50-degree Celsius weather.

GEORGE KOUROUNIS: If there really is ice hiding under this salt,

it'll be a total game changer.

- (tense music)

NARRATOR: This shocking discovery on Mars is just the beginning.

CYLITA GUY: This find is potentially

huge for the future of space travel.

The possibility of accessible frozen water

makes the logistics of a mission to the Red Planet a little simpler.

Mind you, not simple,

but just a little bit easier.

GEORGE KOUROUNIS: What we're seeing here in this view from above,

even though it's on another planet,

could change the direction of human history.

NARRATOR: Advanced satellite technology in space,

looking down from above,

captures planet Earth like never before.

- (dramatic music)

DAN RISKIN: The US has all kinds of cutting-edge equipment in space,

and a couple of satellites have something called

the Visible Infrared Imaging Radiometer Suite, or VIIRS.

CYLITA GUY: It's amazing.

Sensors collect visible and infrared images,

which can be used to do everything from predicting the weather

to tracking fires and even sensing changes in the ocean colour.

ROMA AGRAWAL: And crucially, it has something called

the Day Night Band Sensor,

which can see in very low light conditions

to capture things at night that we can't see with the naked eye.

NARRATOR: And this new view from above

captures a long-hidden secret in the nighttime darkness

of Earth's oceans.

In the summer of 2019, off the coast of Java,

this technology reveals an eerie shape

emerging from the black ocean waters.

- (tense music)

TORRI YATES-ORR: Something weird is definitely going on here.

PETER SOROYE: From the satellite, it looks

so otherworldly and ethereal.

CYLITA GUY: This looks like an abstract work of art.

I see this glowing cloud floating in the black.

DAN RISKIN: It's paler than the city lights on the island of Java,

but it's definitely brighter than the nighttime ocean should be.

GEORGE KOUROUNIS: It's hard to tell exactly what's going on here,

but it's huge.

CYLITA GUY: This shape covers a massive area,

100,000 square kilometres.

That's like the size of Iceland.

- (eerie music)

NARRATOR: This strange vast shape

moves over time and raises countless questions.

TORRI YATES-ORR: What is causing

this enormous glow-in-the-dark spectre?

PETER SOROYE: Is this some kind of weird natural phenomenon

or is it caused by humans?

CYLITA GUY: How long has it been here?

DAN RISKIN: Is there any other technology in space

that could offer a hint as to what we're seeing here?

NARRATOR: Over 8,000 kilometres to the northeast,

off the coast of Siberia,

satellites looking down from space

capture a possible clue...

in the Sea of Okhotsk.

Familiar-looking shapes swirling in the water.

- (tense music)

CYLITA GUY: In 2023, NASA captured this,

as thinning ice breaks up

and starts to flow with the spinning ocean currents.

DAN RISKIN: As sea ice melts,

swirls of white spin off into the ocean.

Here it covers hundreds of kilometres.

PETER SOROYE: These happen here every year,

and sometimes last for months.

It's even appearing earlier and earlier

as sea ice breaks up sooner, thanks to climate change.

- This swirling ice, seen from space,

looks a lot like the shape we see in the images from around Java.

CYLITA GUY: Does that mean that forming or melting sea ice

could be behind the mysterious swirl in the Indian Ocean?

NARRATOR: Further investigation from above

uncovers some shocking clues.

This isn't the only place this strange phenomenon appears.

ROMA AGRAWAL: The VIIRS equipment finds several more instances

of these strange glowing patches of sea.

NARRATION: These weird phenomena are spotted

off the coast of East Africa

and in the waters of Southeast Asia.

DAN RISKIN: And there's something all of those sites have in common.

They're all in warm tropical waters.

PETER SOROYE: That means there's no way

these could be caused by melting or forming sea ice.

So what else could cause huge areas of the ocean to get so bright?

NARRATOR: Perhaps a record-breaking event in Spain

can reveal a clue.

In January of 2020,

the Mediterranean is hit by a major storm.

- Winter storm Gloria batters Spain

with unparalleled heavy rain,

high winds and blizzards.

NARRATOR: And the quiet seaside town of Tossa de Mar

faces something staggering.

DAN RISKIN: Storms can cause something called a storm surge,

where the sea level rises up higher than normal

and then floods coastal areas.

CYLITA GUY: And Gloria's storm surge poured more than just water

into the streets of Tossa de Mar.

The town suddenly flooded with a staggering amount of foam.

- (wind whistles) PETER SOROYE: Sea foam occurs

all the time, and all around the globe.

It's made when the agitation of wind and waves

stirs up the organic material, pollutants, surfactants

and general bits and bobs that are found in seawater.

DAN RISKIN: To get sea foam in these large quantities,

there has to be a lot of dissolved organic material,

like a big algal bloom, getting broken down.

And you have to pair that with choppy ocean waters,

like a big cyclonic storm.

NARRATOR: Could the churning ocean waves

make a giant island of sea foam visible from space

or is there something else hiding in the ocean depths?

TORRI YATES-ORR: Maybe it's not a sign

of organic material breaking down.

Maybe there's something alive down there.

- (tense music)

NARRATOR: There may be a clue

in an old maritime legend.

TORRI YATES-ORR: Over centuries, there have been reports from sailors

of a very weird phenomenon...

something they called "milky seas".

GEORGE KOUROUNIS: Researchers poring over

ships logs and other historical records found over 200 reports

of vast stretches of ocean

emitting a starling white or green glow.

- When those are mapped alongside the 12 instances

captured by modern satellites,

you can see that it continues a pattern.

CYLITA GUY: These rare glowing ocean waters are most often found

in the Arabian Sea and Indian Ocean.

TORRI YATES-ORR: So are these ocean hazes seen on satellite

the milky seas of maritime legend

and are there any contemporary

on-the-ground sightings that could back this up?

- (tense music)

NARRATOR: In an unbelievable moment of luck,

the vessel Ganesha happened to pass through

the tail of ocean haze captured by satellite.

And what they record from the ocean surface is astonishing.

- The crew described a vast and steady glow

coming from beneath the ocean surface.

GEORGE KOUROUNIS: Even more amazing...

they catch it on camera.

And that gives another huge clue to what's happening.

CYLITA GUY: The crew see the ocean glow as a pale white or green

because their perception of colour is affected

by the dark and moonless night.

The human eye contains two types of receptor cells - rods and cones.

Cones help us to see colour,

while rods work in low light to help us see in grayscale.

Cone cells need lots and lots of light to work,

which is why colour vision decreases at night

or in other dark conditions.

DAN RISKIN: But the cameras on the ship

aren't affected the same way human eyes are.

So they capture the truth.

A glowing, greenish-blue haze

that spreads out for miles.

NARRATOR: It's a critical revelation and raises the question...

what on Earth can make the ocean glow from below?

GEORGE KOUROUNIS: There are some other glowing ocean phenomena

that can give us a clue.

PETER SOROYE: There are parts of the world

where the impact of the waves on the shore

can make a magical blue sparkle.

Even the motion of fish or dolphins swimming in the water

can create the same kind of glow.

- These stunning phenomena are caused by a type of plankton.

Tiny living things are producing light with their bodies

through chemical reaction.

They give off light when they're moved around.

DAN RISKIN: But these creatures only emit little flashes of light,

so it looks like it sparkles.

That's not what we're seeing off the island of Java.

So could it be another form of hidden life

that's making the sea glow?

NARRATOR: There may be a clue in Northern Iran

where the salty Lake Urmia

makes a statement visible from space.

PETER SOROYE: In these satellite images,

you can see that this lake actually changes colour.

There is nothing subtle about it.

CYLITA GUY: Scientists believe this stunning colour shift

is caused by microscopic organisms...

either algae or bacteria.

In very bright and salty conditions,

the algae, Dunaliella salina,

turns from green to red as it makes these protective chemicals.

DAN RISKIN: The bacteria, Halobacteriaceae,

actually produce a red pigment that converts light into energy.

So when they appear in large enough numbers,

they make the water look red.

PETER SOROYE: Lake Urmia shows us that there are microscopic creatures

that can change the colour of water for extended periods.

So could invisible bacteria

be behind the glowing milky seas as well?

CYLITA GUY: The latest research suggests

that a bioluminescent bacteria known as Vibrio harveyi could be

the secret ingredient behind these milky seas.

DAN RISKIN: The bacteria can thrive under certain rare conditions,

and when they grow to huge numbers,

they collectively begin to glow.

PETER SOROYE: Glowing is an adaptation that

in other ocean creatures can be anything from

a lure for food to a warning to a means of burning off UV radiation.

NARRATOR: But what's driving these glowing bacteria

is still a mystery.

CYLITA GUY: Milky seas are rare enough

that spotting them and getting to them quickly enough

to test the waters for bacteria is tricky.

So we won't know for sure

if Vibrio harveyi is the culprit

until more research is done.

NARRATOR: And this maritime legend

may hold hints of something even more staggering.

TORRI YATES-ORR: Glowing bacteria may hold a clue

not simply to Earth's milky seas mysteries

but to life on other planets.

DAN RISKIN: A lot of people think that

since bioluminescence works so well

and it's evolved so many times independently,

it's one of the key things we should be looking for

when we look for life on other worlds.

GEORGE KOUROUNIS: With tools like VIIRS pointed toward outer space,

could we uncover a milky sea on another planet?

Only time will tell, but it's a tantalising possibility.

- (dramatic music)

LAUNCH ANNOUNCER: Three, two...

NARRATOR: In 1997, the Cassini Orbiter

launches into the skies... - (boom)

..beginning a 3.4-billion-kilometre journey through space.

- (electronic hiss) GEORGE KOUROUNIS: Its mission?

An in-depth examination of Saturn...

from above.

DAN RISKIN: As Cassini comes down over the north pole,

it sees something truly incredible.

CYLITA GUY: This is amazing.

There's what looks like a perfect hexagon

right at the top of the planet.

DAN RISKIN: This is honestly one of the weirdest things in the universe.

GEORGE KOUROUNIS: It seems too geometrically perfect to be real.

And this thing is unbelievably massive.

Each side is 13,800 kilometres long,

and it's almost 25,000 kilometres across.

- You could fit almost four Earths in there.

GEORGE KOUROUNIS: How is it possible to have

what looks to be a near perfect hexagon

at the north pole of Saturn?

TORRI YATES-ORR: I mean, what is going on here?

What is this thing made of?

- Why is it there?

GEORGE KOUROUNIS: Saturn is over a billion kilometres

away from Earth. So how can we investigate such a distant mystery?

DAN RISKIN: When it comes to solving mysteries like this,

sometimes you have to start a little closer to home.

NARRATOR: Could clues to this strange phenomenon

be found on Earth?

CYLITA GUY: It seems odd to think about,

but there are actually naturally occurring hexagons

all over our planet.

PETER SOROYE: From beehives to snowflakes,

ancient rock formations to the pinpoint-lenses of dragonfly eyes.

- But why does nature love this shape so much?

NARRATOR: Perhaps a clue can be found

in the heights of Bolivia's Altiplano,

where a vast plain of white can be seen from space.

- This is the Salar de Uyuni.

It covers over 10,000 square kilometres,

making it the largest salt flat in the world.

It's about the same size as the Big Island of Hawaii.

NARRATOR: And viewed from above,

stunning patterns in these ancient salts form a familiar shape.

CYLITA GUY: There are hexagonal formations all across the surface,

around one or two metres across.

TORRI YATES-ORR: But what drives the salt into the hexagon shapes?

PETER SOROYE: For years, scientists believed

that the salt was forming hexagonal ridges

from cracking under the pressure of contracting.

ROMA AGRAWAL: This is something that can happen in cooling lava,

and we can see the results in impressive rock formations

like the Devils Tower in Wyoming

and the Giant's Causeway in Ireland.

CYLITA GUY: These kinds of shapes form because,

as the lava cools, it contracts.

These contractions stress the cooling rock,

which cracks, forming these very efficient shapes.

DAN RISKIN: And that just happens to be at 120-degree angles,

and those are the angles that make a hexagon.

- (dramatic music)

PETER SOROYE: The latest research reveals

the secret behind the salt flat hexagons

is actually in the movement of water.

DAN RISKIN: What's happening at the salt flats

is really happening in the water underneath the crust

in a phenomenon called convection.

PETER SOROYE: Technically, convection is just the transfer

of heat across a space by the movement of a fluid.

CYLITA GUY: The warmer, less dense parts will rise,

while the cooler, more dense material will sink down.

NARRATOR: At the surface,

water evaporates leaving behind ridges of salt

that mirror the patterns of movement hidden under the surface.

ROMA AGRAWAL: This movement tends to form polygonal shapes -

and in perfect conditions,

where there's nothing to interrupt the flow,

convection loves to make hexagonal patterns.

DAN RISKIN: So, could the same forces that make hexagons on Earth

be what's happening on Saturn?

CYLITA GUY: But Saturn's skies aren't made of water.

DAN RISKIN: There isn't even land on Saturn. It's a gas giant.

CYLITA GUY: Gas giants are huge planets

made mainly of gases like helium and hydrogen,

which surround a comparatively smaller solid core.

TORRI YATES-ORR: So you've got to wonder

if the same kind of motion in water on Earth

can happen in gas...

on a much larger scale.

NARRATOR: Perhaps images from the Cassini Orbiter

can provide a clue.

To the naked eye, Saturn's hexagon

appears pale yellow and blue.

But the bright shades of the false colour images

taken right above the pole

uncovers depth and details inside this vast alien shape.

DAN RISKIN: Those different colours

indicate how deep you are in the hexagon.

The redder colours are lower down,

the blue is higher up.

PETER SOROYE: So we can see that this isn't just right

at the very top of the atmosphere. This has some real depth to it.

DAN RISKIN: And crucially, looking straight down from above like this,

Cassini also shows you that the hexagon is rotating.

TORRI YATES-ORR: So how can a perfect shape like this

hold together in the swirling gaseous atmosphere?

NARRATOR: There may be a clue hidden in Earth's skies.

DAN RISKIN: Just like in the water underneath the salt flats,

convection also happens in the atmosphere.

NARRATOR: Convection is behind

the creation of clouds and thunderstorms.

- (thunder cracks)

- And it's the key driver of one of the most powerful

phenomena on Earth...

Hurricanes. - (wind howls)

NARRATOR: Could an epic cyclonic storm

be responsible for Saturn's hexagon?

CYLITA GUY: But there's a problem.

This hexagon isn't like Earth storms.

NARRATOR: In 1981, the Voyager II space probe

approaches Saturn,

and this historic view from above

reveals something shocking when it sees Saturn's north pole.

GEORGE KOUROUNIS: And what did they find? A hexagon.

CYLITA GUY: And since that first finding,

when Saturn's tilted just right,

we've even been able to spot it from Earth.

- This strange shape has been sitting right here

at Saturn's north pole for decades.

PETER SOROYE: But how could a cyclone

last for such a long time?

- (dramatic music)

NARRATOR: A clue lies over 600 million kilometres away,

where a space landmark

on another gas giant stands out...

Jupiter's famous red spot.

DAN RISKIN: The red spot on Jupiter is iconic.

TORRI YATES-ORR: There have been records of a red spot on Jupiter

since the 1600s.

And while we can't be totally sure it's the same one,

it sure looks similar.

- From more modern records,

we know that Jupiter's red spot

is at least 150 years old.

Now, if those 17th century images are of the same spot,

it could be over 350 years old.

TORRI YATES-ORR: So is there something about

a gas-planet atmosphere that can make

these enormous storms live for decades or even centuries?

PETER SOROYE: Unlike Earth and other rocky planets,

gas-planet atmospheres can stretch for thousands of kilometres

before you reach the core.

DAN RISKIN: Basically, gas giants just don't experience

the same kinds of factors we have here on Earth

that make our atmosphere so changeable from day to day.

So if something gets going,

chances are its gonna keep going.

CYLITA GUY: It's an important clue.

But is Saturn's hexagon a cyclonic storm like Jupiter's red spot

or is there something more going on?

NARRATOR: A closer look at Saturn's hexagon

reveals something staggering.

GEORGE KOUROUNIS: How crazy is this?

The centre looks like a hurricane.

- (tense music)

DAN RISKIN: This thing's huge.

The eye of this thing is 2,000 kilometres across.

That's 50 times bigger than the eye of a hurricane on Earth.

NARRATOR: But this stunning whirlwind

is only a small piece of the giant hexagon.

What other hidden forces could be behind this colossal mystery?

GEORGE KOUROUNIS: With a shape like this right at the centre,

it sure seems like there's some potent convection

happening in the atmosphere here.

But could that have any connection to the whole hexagon?

- (ominous music)

NARRATOR: In 2020, Harvard scientists investigate,

running a simulation on NASA supercomputers to test their theory.

CYLITA GUY: One that focused on

the sheer size of Saturn's atmosphere.

DAN RISKIN: Their model imagined clouds and winds

going down to 10% of the planet's radius...

So like 6,000 kilometres deep.

Then they started looking at the kinds of wind patterns that happen

when you combine the planet's rotation

and that really, really deep convection.

- (optimistic music)

CYLITA: Let's remember convection -

hot goes up, cold goes down -

is behind the hexagons in our salt flats on Earth

and the power behind hurricanes.

- Their 3D model showed something really amazing.

The thermal convection spontaneously

makes exactly the right kinds of patterns all over the planet,

including at the pole.

Deep under the surface there are these vortices, these cyclones,

that kind of pinch the jet stream into that hexagon shape.

Because those air movements are deep, they're stable.

So the forms they make stick around for decades.

GEORGE KOUROUNIS: But this is space

we're talking about. We can't close the case just yet.

DAN RISKIN: These are just computer models

based on what we can see from Cassini and a whole lot of guessing.

If we wanna learn more, we gotta send a probe right into the hexagon,

and that's probably at least a few years away.

Until we get to the ringed planet ourselves,

Earth is gonna be the only laboratory we have

to learn about how it all works.

- (contemplative music)

NARRATOR: Far above the Canadian landscape,

satellites looking down from space

spot something uncanny

among the lakes of Northern Saskatchewan.

PETER SOROYE: There are over 100,000

lakes and rivers in Saskatchewan,

mainly left behind by Ice Age glaciers.

- When seen from the skies, one of these lakes

really stands out.

SHEILA HOFFMAN: There's a body of water that looks almost like an eye.

It's almost perfectly round and has an island right in the centre.

CYLITA GUY: Which kind of makes

the whole thing look like a giant Cheerio.

GUY WALTER: Now, the lake isn't huge.

It's about four to five kilometres across

and the island itself is about two kilometres long,

but it doesn't look normal.

CYLITA GUY: If you think about the depth of the lake

along with its circular shape

it almost looks like a crater that's filled with water.

TORRI YATES-ORR: What could have created such a bizarre formation

and why does it look so different from the surrounding lakes?

PETER SOROYE: What forces are capable

of creating huge circles on the Earth's surface?

- (tense music)

NARRATOR: A potential clue could be hidden

around 6,000 kilometres away,

in the English village of Hanbury.

From above, among a patchwork of farm fields,

lies an unexpected circular crater filled with trees

concealing the heart of a disaster.

GUY WALTERS: About 80 years ago, in 1944,

the UK is in the home stretch of the Second World War.

- (artillery fire)

GUY WALTERS: That's the year that you have

the D-Day landings in Normandy and the liberation of Paris.

TORRI YATES-ORR: But in the rural countryside,

hundreds of kilometres from the front lines,

peace is about to be shattered.

GUY WALTER: On November the 27th,

at 11 o'clock in the morning, there's this sudden explosion

that shakes the entire village of Hanbury.

- (explosion)

GUY WALTER: You've got this double blast

shooting this mushroom cloud into the sky,

and it flattens everything in a 13-hundred-metre radius.

TORRI YATES-ORR: The blast leaves

a huge circular crater on the landscape.

It's around 250 metres across and about 30 metres deep.

NARRATOR: But what explosive power is behind this destruction?

Could the answer be concealed below the surface?

GUY WALTER: What you've got here is a highly secret

British bomb storage site,

known as RAF Fauld.

And this place stored absolutely huge amounts

of various explosive munitions.

I mean, this place was packed to the rafters.

TORRI YATES-ORR: That's a lot of power in one place,

and if anyone found out about it that would be a major target.

So did spies discover it and plan its destruction?

Was it sabotaged?

GUY WALTER: This is a part of England

that has long been targeted by Axis air raids,

and the Nazis very quickly claim

that it's one of their V-2 rockets that has caused this devastation.

- (explosion)

SHEILA HOFFMAN: But this time, it isn't the Germans.

The investigation revealed something shocking and tragic.

In the pressure of wartime,

a fatal mistake was made.

GUY WALTER: It's very likely that someone

mishandled a live bomb.

Now, the thick walls of the mine prevent an even worse catastrophe,

but what happened was bad enough.

TORRI YATES-ORR: About four million kilograms of explosives,

including a whopping 500 million rounds of rifle ammunition, blew up.

- (explosion)

TORRI YATES-ORR: It was one of the largest explosions ever in the UK.

SHEILA HOFFMAN: When you see it from above today,

the crater is filled with trees and plants

and looks quite peaceful and safe.

GUY WALTER: But the hole in the earth remains,

along with a number of explosives still buried in those tunnels below.

NARRATOR: Could the strange-shaped lake in Saskatchewan

be the result of a World War II era weapon?

GUY WALTER: While Japan lobbed shells

at a British Columbia lighthouse in 1942

and Axis forces hit the St Lawrence River

during the Battle of the Atlantic,

Saskatchewan was well out of reach.

TORRI YATES-ORR: So if this weird doughnut-shaped lake

isn't a sign of some kind of human-made explosion,

what else could be going on?

SHEILA HOFFMAN: What other forces can make

this kind of unique shape on the landscape?

Is a powerful natural force at play here?

CYLITA GUY: There's another out-of-this world possibility.

- (meteor cracks)

PETER SOROYE: There are a few known impact craters around Canada,

so it makes sense to think this could be among them.

NARRATOR: But when researchers venture

into the wilds of Saskatchewan to investigate,

they uncover something revealing.

TORRI YATES-ORR: When they examine the rock of the centre island,

they realise something strange is going on.

NARRATOR: This isn't like any impact crater they've ever seen on Earth.

CYLITA GUY: On Earth, you expect

two main kinds of impact craters.

Smaller impacts make simple craters,

which are basically just these bowl-shaped holes.

Bigger impacts make something called complex craters.

PETER SOROYE: When these bigger meteors hit the ground,

it's so big and powerful, has so much energy,

that solid earth starts to act like a fluid

and rebounds or splashes up in the middle of the impact hole,

like when a stone is thrown into the water.

When that rebound of solid earth drops back down,

you're left with a central peak.

GEORGE KOUROUNIS: If you look at the shape of this lake doughnut,

it looks just like a complex crater filled with water.

That's what the researchers expected to find.

- (dramatic music)

NARRATOR: But what they uncover is out of this world.

CYLITA GUY: Basically, the rock here is the wrong kind of rock.

Whatever this central island is,

it wasn't made by the rebound you see of a complex crater.

DAN RISKIN: But it can't be a simple crater either

because the floor and the walls are too full of debris.

CYLITA GUY: The researchers realised

they'd seen something like this before

but not on Earth.

NARRATOR: The final clue to solve this mystery

can be found by looking down from above

at our planet's nearest neighbour...

the moon.

PETER SOROYE: Earth's moon is pockmarked

by countless thousands of craters

from the giant 25-hundred-kilometre South Pole-Aitken basin

to the microscopic dents found in moon rocks from the Apollo missions.

- Because of the lack of atmosphere and plate tectonics,

the moon's craters aren't subject to

the same changes we see here on Earth.

For example, they don't get hidden over time by things like water.

As a result, these craters can tell us

a lot about the history of the meteoroid strikes that form them.

NARRATOR: And one type of moon crater

could solve the mystery in Saskatchewan.

DAN RISKIN: When you look at sort of medium-size craters on the moon

from like 15 to 42 kilometres in diameter,

you see something pretty special.

PETER SOROYE: These aren't bowl-shaped, like simple craters,

but they don't have the central peak of complex craters either.

DAN RISKIN: Instead, they're kind of like this in-between stage

where they have some of the traits of each type of crater.

These are called transitional craters.

They have flat floors,

one or more terraces or rock slides,

like you'd see in a complex crater,

but with no central peak.

NARRATOR: But can this happen on Earth?

CYLITA GUY: Transitional craters form so easily on the moon

because of its lack of atmosphere and low gravity.

So it's easier for larger objects to hit more gently.

DAN RISKIN: But with Earth's atmosphere and gravity,

we don't expect quite so much of that middle ground.

Anything that would make a medium hit on the moon

would accelerate way more in Earth's gravity,

so it would end up being a big punch, not a medium one.

- (meteor hisses)

CYLITA: Science basically thought that finding that middle ground

here on Earth was essentially impossible.

But this discovery changes everything.

DAN RISKIN: To find something

that we can confirm is a transitional impact crater

and to see that it's in such good shape,

this is groundbreaking.

PETER SOROYE: But then you've got to ask...

how did the central island form

if not through the initial space rock impact?

- (dramatic music)

DAN RISKIN: The crater is about 200 million years old.

So it happened when the Earth looked very different

from the way it looks today.

CYLITA GUY: So it's hard to say for sure

what factors created the island.

DAN RISKIN: But the thinking is that, over millions of years,

wind and rain would have worn down

the edges of the crater until it was almost flat,

and that central dip would have filled with sediment.

CYLITA GUY: Then, experts think that

the movement of glaciers over the land during the last ice age

could have carved up the landscape,

including in this ancient crater.

DAN RISKIN: Thanks to the melting glaciers,

water would have filled these new scars in the landscape,

which merged with the crater to form the lake as we see it today.

NARRATOR: This astonishing discovery isn't just unprecedented.

CYLITA GUY: It's the chance to study

a phenomena we observe on the moon right here on Earth.

This is what makes this discovery even more exciting.

NARRATOR: Another Canadian impact crater in Labrador

is already hosting cutting-edge lunar research.

PETER SOROYE: The meteorite that made the Mistastin Lake crater

left behind rocks that are almost identical

to ones found all over the moon.

CYLITA GUY: So today NASA uses the site to train astronauts

for their new moon mission - Artemis.

DAN RISKIN: And this lake may hold

just as many lunar-style secrets.

CYLITA GUY: It's amazing to me

how much we can learn about our solar system and beyond

from studying features right here on Earth.

DAN RISKIN: I think this is cool because we use the moon

to solve this mystery here on Earth.

But as we do the research on the ground,

we uncover these secrets that are gonna help us understand the moon.

- (wind whistles)

- (dramatic music)

NARRATOR: From signs of ice on Mars

and stunning shapes on Saturn

to hidden impact craters and mysterious milky seas on Earth...

some of the grandest mysteries are discovered from space.

And with the latest technology looking down from above,

Earth's secrets can reveal the truth about space

and resolve longstanding riddles back home.

- (uplifting music)

- I love the fact that we're learning more and more

about our own backyard here in the vastness of space.

- And you just know that the next find is right around the corner.

Subtitles by Sky Access Services