All language subtitles for BBC.The.Sky.at.Night.2025.Secrets.of.the.Red.Planet.1080p.HDTV.x264.AAC.MVGroup.org

Lift-off.

On July 1965, almost 60 years ago,

the Mariner 4 spacecraft

sent back these images -
the first close-up shots of

another planet ever taken
from space.

One pass, a single chance
for everything to work.

That planet was Mars,

and these fuzzy images made
this distant object,

millions of miles away,

feel close enough to touch.

Today, breathtaking images, like
these from Nasa's Curiosity rover,

make it easy to imagine being on
the Red Planet's surface.

I can plan my expedition across
the Martian desert

as easily as a hike on Earth.

And as we've traversed
across the planet,

we've discovered incredible wonders.

A labyrinth of deep, steep valleys.

A canyon almost ten times longer
and five times deeper

than our own Grand Canyon.

Spectacular craters, including one
of the largest in the solar system.

Desert sand whipped up to form
monster dust devils.

And we're even getting
closer and closer

to the question of life on Mars.

Just last month, Curiosity was
reported to have found

the longest organic compounds
ever found on Mars.

The ingredients for life
might be right there,

just beneath the surface.

And there's so much more
to be discovered.

Tonight, we're uncovering
the secrets of the Red Planet.

Welcome to The Sky At Night.

Walking about
this amazing environment,

with its lush vegetation
and free-flowing water,

it's hard to imagine that Mars
was ever like this.

Mars is our neighbour,
fourth planet out from the sun,

smaller than Earth,
about half the diameter.

And on Mars, you experience 38% of
the gravity we get here on Earth.

Which sounds like
a lot of fun to me!

SHE CHUCKLES
It's an alien world,

but one of the things
we're realising is,

the more we find out about it,

the more we realise
we have a shared history.

Mars was once covered in water,
just like Earth,

and had a core so active,

it created the largest volcano
in our solar system,

Olympus Mons.

All that activity died out
billions of years ago,

leaving a planet
that appears dry and barren.

But hidden in those rocks are
the answers to secrets

not just about Mars,
but about other planets,

including our own.

Secrets about climate change,

planetary evolution,

and even how life began.

Over the decades,

helped by some of the toughest space
explorers in the solar system,

we've been unlocking
some of these answers.

Chris is in London to find out
what we've been discovering.

In 1976, the Viking 1 lander

touched down on the Martian surface,
providing us with our first

clear images from the planet.

Technology since then has moved on
in leaps and bounds,

thanks particularly to
my favourite amongst our fleet

of planetary spacecraft,
the Mars rovers.

Perseverance is the newest
addition to the fleet.

Landing on Mars back in 2021,

it's equipped with
an array of instruments,

including several cameras
capable of sending back images

that transport you to the surface.

I'm meeting geologist Sanjeev Gupta,

a member of the team
running the rover,

to take a trip across
the Red Planet.

Sanjeev, this is astonishing.

I feel like I'm actually on Mars.
We kind of are.

These are images from
the Perseverance rover,

in Jezero Crater.

What was it like seeing this
landscape for the first time?

Oh, sort of, kind of
surreal and extraordinary,

because it actually looks like
an Earth-like landscape.

We could be in the desert
in Nevada, Utah.

And yet, we're on Mars,
hundreds of millions of miles away.

It's really quite weird.
HE CHUCKLES

Situated in Mars's
northern hemisphere,

Jezero Crater was formed when an
asteroid struck the surface of Mars

about four billion years ago.

The early images sent back
by the rover showed

a rock-strewn landscape,

containing clues of what
early Mars must have been like.

So, you're the geologist.

Tell me what you see
when we look round this site.

Oh, so this is...

This panorama was taken
early on after we landed.

And this is sort of
within the crater.

And we're looking out
towards the west,

and we can see, we're actually
stood on rocks that...

We actually had no idea what
they were before we landed.

So, what did these white rocks,
these light rocks turn out to be?

So, we argued about it for ages.

And then, it's when we applied
some of our detailed chemistry

instruments that we were able
to work out that these

are actually volcanic rocks.

And what was the giveaway? What was
the kind of evidence that you got?

So, we could actually map
in detail the grains,

the particular grains of
a mineral called olivine.

And it was very, very clearly
of volcanic origin.

It's volcanic rocks like these
that could one day tell us

about the inner workings of Mars.

But the landscape itself also
has clues that tell us

how this part of Mars once looked.

So, the gap you can see there,
in the mountain side,

that's actually
a former river valley,

with the river coming from
outside the crater,

entering the crater, and building
a lake within the crater.

How long would it have taken for
something like that to form?

What we do know, by looking
closely at these rocks,

the sedimentary rocks
that form the delta,

is that it requires sustained water.

Most of the delta rocks appear
to suggest that there were regular,

continuous river flows
building this delta.

So, I think that's quite a
big finding, actually,

sustained water
3.7 billion years ago on Mars.

It was a watery, wet place.

Once we know water flowed
across this surface,

it's easy to think of ancient Mars
as a bit Earth-like.

About a year after landing,

the rover had moved on to
the foot of the delta,

where the water flowed in.

And it was the rock seen in
this natural-colour image

that provided a more
detailed picture of how

this ancient water flowed.

What's very exciting
is these light-coloured rocks

that you can see here.

You can see, they're really flaky.
Mm.

They're really, really thin,
breaking up.

And these are mudstones -

those are really, really
fine-grained rocks.

And they've really formed
by very fine particles

settling out a suspension, in
a standing body of water,

in a lake deposit.

So, that's one of the reasons
we know it was

a standing body of water,
it was a lake.

It wasn't just water that flooded
over the landscape. Exactly.

This required a quiet
water environment,

so there was water standing
there for tens, hundreds,

maybe thousands of years.

And they're really good places
to search for evidence for life,

because this is a quiet water
environment where life

is likely to have evolved in.

The picture we're getting is of
the kind of watery conditions

where life could have evolved.

But to find out if it did,

we need a closer look
at those rocks.

And so, Perseverance
has been collecting samples

in the hope that one day,

they'll be returned to Earth
for analysis.

In the meantime,
the rover has moved on,

and, having travelled about
20 miles since it landed,

it's reached the crater's edge,

sending back this wonderful image
just a few months ago.

Wow, this is just beautiful.

Where are we?
So, we're on the crater rim.

And this is an enhanced colour image

to bring out these
beautiful details,

all the different colours
of the rocks,

and the different
varieties of rocks.

And what are the rocks like up here?
Are they the same as in the delta?

Oh, no,
they're completely different.

This is the ancient, what we call,
the basement rocks, the oldest rocks

that the crater was formed in.

So, the rocks that you can see here
on the rim was what the asteroid,

or meteorite impacted into,
deformed and formed the crater.

And these are now preserved here.

And these are very old, this is...
These are very, very old.

So, these are like
3.9 billion years old,

something like that.

And we have really no idea
what they are.

And we're just trying
to reconstruct that at the moment.

And the nice thing, I think,
is that this landscape is older

than anything we have on Earth.
That's right, yeah.

Some of these rocks - and if you
look beyond in the distance,

those rocks, those are older
than anything we really have.

And so, we really get a deep
understanding of the early history

of rocky planets here.

In this beautiful place.
Thank you so much for showing us it.

It's a pleasure.

Our existing rovers are building up

our understanding of
the Red Planet's past.

But soon, future missions
could do even more,

maybe even answer
the ultimate secret -

was there life on Mars?

Esa's ExoMars project is hoping
to answer just that.

The mission includes the UK-built
Rosalind Franklin rover.

Due to launch in 2028,

it's equipped with next-generation
instrumentation,

and it's on the hunt for
well-preserved organic biomarkers

hidden beneath the surface.

But it's rocks much closer to home

that are helping it prepare
for its mission.

Maggie's headed north to find out.

Exposed slabs of rock,
found all over Scotland,

were formed millions,
if not billions of years ago.

Layer upon layer of sediment and
dead material compacted together,

trapping evidence of early life.

But the question is,
could the same be found on Mars?

To find out what rocks on Mars
could reveal about possible

former life on the planet,
we first need to understand

where to look here on Earth.

And so, a team of scientists are
analysing samples from

the north-west of Scotland

to reveal the chemical signatures
of ancient life.

I'm joining Claire Cousins,

of the University of St Andrews,
to find out more.

So, Claire, you've been
collecting samples.

Can you tell me more about them?
Yes, absolutely, Maggie.

So, we've been looking at some rocks
in the north-west of Scotland.

So this is one of them here.

And these rocks are amazing because
they're about a billion years old,

but they're incredibly pristine.

Yes, so, can you talk me through
the rock? Yeah, absolutely.

So, if you look really carefully,
just at the very surface,

you can see this kind of
spider web sort of structure.

This is left behind by
microorganisms that were living

kind of their best lives.

They've left behind this
beautiful sort of network of,

sort of, trace structures
in this rock.

And it's by analysing the rocks,
using an electron microscope,

that the geochemical signature of
this previous life can be found.

This rock was made from muds,

these really fine-grained sediments
in this wet environment.

And these are all just laying down,

they produce these
really beautiful layers.

And you can see the striations,
the layers are very distinct.

Yes, absolutely. And it's those very
layers which actually then trap

and capture that microbial material.

So, every time you get new sediment
being washed into the environment,

it's then trapping
those microorganisms.

So, what's this telling us?

So, this is telling us that we have
localised elevation of potassium.

So, where you see all these
sort of red, kind of blotchy areas,

that's where we have locally
high potassium levels

trapped here within the rocks.

Potassium is really interesting
because it's sort of locally

scavenged by the action
of microorganisms.

Around three-and-a-half
to four billion years ago,

both Earth and Mars had
similar climates,

with plenty of liquid water.

This is also the sort of time when
life first started here on Earth.

If life also started out on Mars

and left behind similar chemical
indicators in the rocks,

then it's hoped that the
ExoMars Rosalind Franklin rover

will discover it.

The really unique thing about
ExoMars, compared to other rovers,

is that it can get samples
from about two metres down

into the subsurface.

The instrument that this then
is tying into, it's called Enfys.

Enfys means "rainbow" in Welsh,
it's a Welsh-led instrument. Ah.

And it's an infrared spectrometer,
so that means it looks at

the wavelengths of light in
the infrared that are bouncing off

the rocks that we're exploring.

So this is one of the few
instruments that actually

will analyse the rocks before
the rover is drilling. Oh.

So, this helps us then target
those rocks and say,

"This is where we should do,
you know, the incredibly

"time-intensive task of actually
drilling into the Martian surface".

Yes. And it's going to be
a completely different picture

down there, because it's going to be
samples of rocks which have

not been affected by the
surface environment of Mars,

which is, you know, a very
high-radiation environment,

it's destroyed a lot of
organic matter, for example.

So, I have to ask the question,

do you think we'll find
life on Mars?

THEY LAUGH

It's a really tricky question.
Or evidence of life?

There's probably not life
on Mars today.

Erm, but certainly in Mars's past,

all the geological evidence
on the surface of Mars

really shows us that, actually,
in the sort of first billion years,

it really wasn't so different
to Earth's environments.

And, of course, we know that life
arose here on Earth, you know,

this is why we're here today.

And so, the real big question
is whether or not

this also happened on Mars.

And, of course, if it didn't,

that's also an interesting question,
as well. Yes, why not?

You know, why didn't it? And that
makes us actually really special.

And I think it's not something
that's going to be achieved

with just one particular mission.

Well, thank you. It's fascinating.

I'm excited to find out
what future rovers will reveal.

But, in all our Mars
exploration so far,

no spacecraft has ever made
a return trip from the Red Planet.

And the time and
the cost of space flight

is one of the major hurdles.

But imagine how much more
we could discover

if we could bring Mars samples
back to Earth.

Guest presenter Dr Mekhi Dhesi
is at Bletchley,

to find out about
an exciting new approach

that could one day help
make that a reality.

MEKHI: Since the first rockets were
launched almost 100 years ago,

the fundamentals have actually
changed very little.

Sure, there have been some
improvements in efficiency

and in fuel type,
but chemical liquid fuel

remains one of the most widely-used
methods of propulsion.

And here we go.

These traditional engines are
still the only way

to get a spacecraft past
Earth's gravity and atmosphere.

But attempts are being made to
truly revolutionise space travel.

Some are looking at solar sails,

others at theoretical warp drives,

and one UK company is going nuclear.

I'm meeting James Lambert,
from Pulsar Fusion,

to find out more...

..starting with the
electric plasma engines

they are already building.

Wow. So, what do we have here?

So, this is one of our
electric propulsion engines,

and it works by taking an inert gas,

and using an electric current
to push it out of the engine.

That's how we get these really
high-exhaust velocities.

Amazing. I love the design.

I feel like,
if I had one on each hand,

I could be like Iron Man.
Exactly like Iron Man.

Yeah, yeah, yeah.
And are there different sizes?

Is this the only one?

So, this is one of our
500-watt engines, quite small.

But we also have, over here,
a five-kilowatt engine.

Much larger, but really just
a scaled-up version of

what I was just holding in my hands.

Engines like these are
commonly used for satellites,

and even small spacecraft.

But it's by turning the
electric plasma engine nuclear

that they hope to change the future.

The goal is to build
our Sunbird project,

and this is all about maintaining
these really high efficiencies,

but increasing the thrust
of the engine,

so that you can fly
more ambitious projects.

So, I'm talking about interplanetary
missions out to the outer planets,

or big science missions.

So, what kind of propulsion is that?

So, this is our fusion
propulsion concept.

It uses nuclear fusion to actually
drive a plasma out of the back

of the spacecraft, and that's
its source of propulsion.

So, what are the fuel savings
between using traditional

chemical liquid rockets,
versus nuclear fusion?

Right. It's a huge trade-off.

Because the fusion engine is
so much more efficient,

it's anything from 100
to 1,000 times more effective.

So, we can carry 100 to
1,000 times less fuel.

The concept that they are developing

would see a bank of engines
docked in space,

fuelled by nuclear fusion.

They will then connect with
a launch spacecraft

and power it through
the solar system at high speeds.

So, at the moment,
with our traditional methods,

we're looking at a round trip to
Mars for about two to three years.

But with this, you're saying...?

Down to a year or better.
Amazing. Yeah.

So, this kind of technology could
help us make bringing sample

returns back from Mars a reality,

and, hopefully, eventually getting
humans to Mars a reality?

Absolutely, the works putting
a new space station in orbit

around Mars suddenly
becomes much easier, as well.

What stage is it currently at?

So, at the moment,
we're deeply embedded in all of

the computer simulation of
the reactor, and how it work.

The next step is all about building
the chamber to actually test it in.

That is so exciting.
Good luck, guys.

Thank you, Mekhi.

It's early days
for the Sunbird project,

but it's big dreams like these
that could change the way

we travel through space.

Until then, we continue
to observe from a distance -

but that doesn't stop
big discoveries being made.

One of the biggest mysteries
of Mars is its water -

which once flowed over the planet,

but today, it's barren and dry.

And yet, there are things moving
on the surface of Mars,

just as we'd expect
if water were present.

Maggie's in Scotland, meeting
planetary geologist Lonneke Roelofs,

who has been trying to solve
part of this puzzle.

Lonneke, lovely to meet you.

Now, we talk about water on Mars,
cos, when we look at Mars today,

it is dry, it is barren,
it is red -

and very unlike this.

But I guess we believe
that there used to be water

flowing on the Martian surface.

Yeah, so we have quite
a lot of evidence for that,

both from minerals that we observe,

but also actually from landforms.

And I can show you an example,
if you want. Love to, thank you.

This is a river delta
somewhere on Earth.

And this is a similar river delta,

but then, fossilised on
the Martian surface. I see.

So, I guess this gives us
the evidence that

there was water on Mars -
where's it gone?

Yeah, so that's actually
a big mystery.

So, part of the water on Mars
is still present in its ice caps.

So, Mars has polar caps.

Part of it is ice in the ground.

And, very, very deep underground,

there might be a trickle
of liquid water left,

but there's no liquid water on
the surface any more.

While a fraction of the water
may still remain on Mars,

the vast majority was lost to space.

And yet, something very eerie
has been spotted happening

on the Martian surface.

So, from afar, Mars seems like
a cold desert right now.

But if we zoom in, we actually
see movement of material

on the surface.

Now, I have an example for you here.

So, this is a channel system
on a hill slope,

like we also have in Scotland,
in many places. OK, yes.

And you see that big boulder
in the middle?

It's like a metre-sized rock.
It's quite a big rock. Yeah.

And then, we see that, that rock...

Yeah, it's moved further down.

..it moved further down. Ahh.

On Earth, the same process -
called a debris flow -

is created when a landslide is
so saturated with water,

that the loose rock and soil
flow like a liquid.

But Mars has very little water left,

so what could be at work here?

So, have you got an idea?
So, what we see on Mars -

Mars has seasons,
just like on Earth.

So, in winter, on Mars,
it becomes so cold

that the CO2 that is present in
the very thin Martian atmosphere

becomes frost on the surface.

And then, in spring,
the planet heats up, and then,

this frost becomes gas again.

We're talking about carbon dioxide,
which is effectively dry ice.

Yes, it is.

So, why does it differ on Mars
than on Earth?

So, on Mars, it forms naturally.

It becomes so cold on the surface,
-120 degrees Celsius,

that it actually forms naturally -

whereas on Earth, we can only
form it in industrial processes.

Yes, but the sublimation process
happens here on Earth

because you have dry ice,
and then, there's no liquid.

It just sort of vaporises. Exactly.

So, that happens on Mars, as well.

But the difference is,
is that on Earth,

when the CO2 ice becomes a gas,
it expands a little bit.

But the atmosphere is quite thick,
so it pushes back on the gas.

But on Mars,
the atmosphere is very thin.

So, if it goes from an ice to a gas,

it's much more explosive.

Yes, but a much bigger
volume of gas... Yes.

..which can cause the flow. Exactly.

OK, so that is a nice theory,

but have you got any evidence
to support this theory?

Yeah, so we have remote sensing data
that shows that the time of activity

in these systems is the same
as the moment in time

in the Martian year
when the CO2 ice sublimates.

But that's only indirect, right?

We don't have a rover
there filming it,

because you don't want
your multimillion rover...

Just sitting there, watching.
..end up under this debris flow.

Oh, yes! So, what I have done
is I've recreated the

Martian environment in the lab.

What does that involve?

Yeah, so this Mars chamber
is an old diving chamber,

in which we can lower
the atmospheric pressure

to mimic the low atmospheric
pressure that we have on Mars.

Oh, yes. And we can then make
these debris flows driven

by the sublimation of CO2 ice.

So, did it work?
What were the results?

It worked! It actually did work.

So, this CO2 can actually make
this sandy material

behave like a liquid.

So, that's really, really exciting.

But it must be wonderful for you,
cos this is your research.

Yeah, it is. This is your theory.
Yeah, I was jumping up and down

in the lab when this, for the
first time, happened, of course.

Oh. It's a new geologic process.

Geology often feels
as if we know it all.

And so, coming up with a whole new
process must be exciting for you

and your team.
It's extremely exciting.

Yeah. Fantastic.
SHE CHUCKLES

This new discovery
has big implications,

as it may suggest that
there was less water on Mars

in the past five billion years
than was previously thought.

While many mysteries
still remain about Mars,

for astrophotographers here
on Earth,

spending time observing
the Red Planet

can reveal some of its secrets.

Pete is in Bletchley,

taking us through
his own mission to Mars.

PETE: I will admit, I have found
Mars frustrating over the years.

I first saw Mars in the '70s
through a home-made

222mm reflecting telescope,

and I couldn't really see
much detail on it at all,

and I wondered what all
the fuss was about.

You get a good view of it for
a few months around opposition

when it's closest to the Earth,

and then, it takes 2.1 years before
it gets to the next opposition.

But as you do study it,
and you keep with it,

you will notice
that there is detail there,

and those details get
sharper and sharper.

The first thing that became apparent
was the bright polar cap.

And then, I could pick out
the subtle markings on the surface,

which are basically exposed rock.

The rest of the surface,
the sort of orange-pinky hues,

are down to the sands of Mars,
the deserts of Mars.

It's a wonderful planet to measure
your improvement in astronomy.

So, if you want to start your own
Mars journey, here's how.

Mars is an easy spot when
it's in view and bright,

thanks to its
distinctive orange hue.

And now is a good time
to try and catch it

before it gets compromised by
the bright summer skies.

To locate it in mid-May,

just look to the western horizon,

about a third of the way up
from the horizon

as the sky is getting dark.

It then moves east and,
by mid-June,

can be spotted next to
the bright star Regulus.

But the window to see Mars

will be getting narrower
all the time.

Look for the pairing around 11.30pm,

low above the western horizon.

As Mars moves away from
its opposition

at the start of this year,

telescopically seeing it
at its best

will need to wait until early 2027,

as it approaches opposition again.

But a naked-eye spot of
our red neighbour

is always a beautiful sight.

As we move into June,
the nights get shorter and brighter,

and that makes stargazing
that bit harder to do.

But it also brings
the possibility of one of

my favourite summer sights,
noctilucent clouds - or NLCs.

And, if visible, these are
typically seen from late May

through to early August
in the Northern Hemisphere.

These high-altitude ice-sheet clouds

form in a narrow layer
about 50 miles up,

high enough to reflect the light
from the sun after it has set.

They appear to shine
in the deep twilight,

giving them their name noctilucent,
meaning "night shining".

NLCs are easy to recognise because
they're quite unlike regular clouds,

glowing against the deep
summer twilight.

They typically show
an electric blue colour

and often have fine structures,
such as herringbone patterns.

Irregular clouds are present -

these appear dark and silhouetted

against NLCs because they're too low

to be illuminated by the sun.

NLCs can typically be seen somewhere
across the northerly horizon,

depending on the time of day.

Looking around 90 to
120 minutes after sunset,

they can appear low above
the north-west horizon,

or a similar time before sunrise
can find them low

above the north-east horizon.

A big display may persist
all night long,

moving from above the north-west
horizon through north,

and ending low above
the north-east horizon before dawn.

Bright NLC displays can be
so dramatic that they sometimes

get incorrectly reported
as the Aurora.

NLCs are a great target
to capture with a phone,

so if you're new to
snapping the skies

or a more advanced astroimager,

do share any results you get
with us on our Flickr account.

And you can find details
of this at...

Meanwhile, here are some images from

the Milton Keynes
Astronomical Society,

as well as our Flickr account.

CHRIS: Since humanity first
looked up at the night sky,

we've been fascinated by Mars,

that pale red dot in the night sky.

But now, year by year,
mission by mission,

decade by decade,

we're finally beginning
to unravel its story,

turning that pale red dot
into a world.

Goodnight.