WIND BLOWS Listen carefully.
What you're hearing is the sound of wind
blowing across the Martian surface.
It was picked up by InSight, NASA's eighth spacecraft
to successfully reach Mars.
And it's on a mission like no other.
We're used to seeing Rover missions trundling over the surface of Mars,
capturing dramatic images of the alien landscape.
But InSight, on the other hand, has parked itself on a quiet corner
of the planet, where it will sit completely still,
listening to the Martian interior.
InSight is on the search for Marsquakes,
seismic tremors which reveal the interior structure of the planet,
from its core right up to the crust.
It's the first mission of its kind that will take the pulse
of the Martian interior, telling us whether it's dead or alive.
Tonight, we follow NASA's latest mission, as it unfolds.
Pete's also here to show us how Mars is not the only captivating colour
in the night sky.
And finally, we say a heartfelt farewell to the Opportunity Rover,
which transformed our view of Mars.
Welcome to The Sky At Night.
I've come to the University of Bristol, where they're communicating
directly with the InSight lander,
as it searches for Marsquakes.
What you can see here is the latest data,
beamed back to Earth just this morning.
It's a nearly live glimpse at the surface of another world.
You'd see data like this if you were looking for earthquakes
here on Earth,
but this is telling us about the seismic activity on Mars.
These readings and the data that InSight is going to send us
over the coming months and years represent our best chance
to really understand what makes the planet tick.
Is Mars a dead world,
or is there activity beneath its surface?
We see Mars today as a cold, desert, dusty place.
Its surface is scorched by radiation because it gets little protection
from its thin tenuous atmosphere. It's a hostile place,
but all evidence shows us that, a long time ago,
Mars was very different.
On its surface, we see huge volcanoes, towering giants
now long dormant, but still some of the largest in our solar system.
There's a canyon labyrinth so vast
it completely dwarfs the United States.
These suggest that Mars was once a geologically active planet.
And when missions like the Spirit and Opportunity Rovers
started exploring, they revealed that Mars was once a wet world,
a world not unlike our own.
But somewhere along the line, things went very badly for Mars.
To find out more about this titanic transformation,
I'm meeting with planetary scientist Neil Bowles.
So, Neil, we're here to talk about Mars,
which today is a very different place from the Earth.
Yeah, I mean, this is what's so intriguing about Mars,
is that when you look at the surface of Mars from images
both on the ground and also from orbiting spacecraft,
you see all sorts of evidence for a very much more complicated history.
And we'd really like to understand why that is.
Why is Mars today so different than it was in the past?
To understand the conflicting fates of Earth and Mars,
we need to look at the differences between the planets today.
One of the most obvious is that Mars has lost its magnetic field.
The thing to think about is on the Earth, we have a pretty strong
magnetic field, and that magnetic field has to come from somewhere,
and our best estimates of where it comes from are essentially
inside the core. Molten core, lots of metal churning around,
and that generates the magnetic field for the planet.
So, the magnetic field produces essentially a shield
that protects the upper atmosphere of the Earth from the sun.
So the sun, as well as streaming out heat,
it also streams out particles and things
called the solar wind, and they are essentially
blowing out from the sun, and they can strip away
a planet's atmosphere, if it doesn't have this protective
magnetic shield, so what's inside a planet,
the core of the planet, is a very important part
of what they're preserving, so the atmosphere,
and it might seem kind of a weird connection to think of
how the very deep interior is connected to what happens up here.
The atmosphere, yeah,
and we don't know how Mars lost its magnetic field.
No. We know it had one because we've flown magnetometers in orbit
around the planet, and they can measure residual hot spots of
magnetism, and understanding what changed in the planet to prevent
that magnetic field being present today is a really interesting
and important question.
So I'm not an expert in this stuff, but to me, the first answer
is that I know Mars is smaller, so does that make a difference?
It's smaller than the Earth, I mean. It does, and we think it should.
I mean, so as everybody is familiar, you know, smaller things
lose their heat more quickly, so we expect that Mars and the Earth
must have had similar evolutions at various points,
but because Mars is smaller, it probably lost its heat quicker.
So if Mars' magnetic field failed after it lost so much heat
that its core solidified, then investigating the planet's interior
should provide answers.
So, how will InSight help? So, InSight's a very different kind of
mission to the ones that we've seen recently.
It's not a Rover that's driving around on the surface
of Mars, and it isn't scooping up soil and putting it into
chemistry laboratories on board, or anything like that.
It's actually designed to go and land on the most boring place
on the planet, is kind of what we'd like... Deliberately.
Deliberately, because we want it to be quiet and calm so that we can run
a series of geophysics experiments from the lander. On Earth, the way
we understand the interior of a planet is by placing
seismometers, which are effectively very sensitive microphones, and we
can listen to the shaking of the Earth, things like earthquakes.
We use the energy that's released in an earthquake, it reverberates
inside the planet, and from that, we can work out inside the planet,
so if we can do that for Mars, that's a really great way for us
to understand what the inside of the planet is doing.
That then ties into things like how the core... Is the core...?
What's the state of the core today? Is there a mantle?
How does all that structure fit together?
And then we can work out how we got to where we are today,
based on four billion years of history. Exactly.
So how is that different from the evolution that we saw for the Earth?
Exciting stuff. Thanks a lot. Thank you very much.
Five, four, three, two...
..zero.
On the 5th of May last year, InSight blasted off from the
Vandenberg Air Force Base in California.
Six and a half months and nearly 500 million kilometres later,
it arrived above the Red Planet.
As the $800 million lander entered Mars' thin atmosphere,
tension grew at Mission Control.
Descent is where 50% of spacecraft suffer a catastrophic failure,
in what is known as the Seven Minutes Of Terror.
That's the time it takes for a probe plummeting towards the surface
at hypersonic speeds
to shed enough velocity that it can touch down without harm.
Touchdown confirmed!
CHEERING AND APPLAUSE
The lander is about the size of an SUV,
and it contains a suite of instruments,
tasked with understanding the interior of Mars,
and giving it a health check.
To test Mars' reflexes,
there's a radio science experiment to see if the planet wobbles
on its axis, an indicator that it might have a liquid metal core,
just like Earth.
Next, a package of seismometers was carefully deployed
to listen to the planet's pulse.
A wind and thermal shield protects its readings.
Finally, to take Mars' temperature, a heat probe, nicknamed the Mole,
is burrowing down to see just how much heat
is still inside the planet.
The seismometers were partly built here in the UK.
It's these seismometers that will measure the Marsquakes.
It's like a stethoscope measuring the heartbeat of a planet,
but with a whole world to monitor,
they've really got their work cut out for them.
At Imperial College London
is the man behind the UK seismometer, Tom Pike.
Tom, the light in here is so yellow! It's like being on another planet!
Why this colour?
This is what we need to do to protect our devices.
They're insensitive to yellow,
so we put a filter over all of the lights.
So it's like a red light in a dark room?
Absolutely. Just the same.
This is a seismometer. Yes.
How excited are you that they are on the surface of Mars?
Well, it's an incredible feeling. The brothers and sisters
of this sensor are at the moment on Mars,
trying to pick up the first Marsquakes and illuminating
for the first time, helping to illuminate,
what is inside another planet.
And they started off in this lab, and that's quite a feeling.
So, in basic terms, what is a seismometer?
It's a mass on a spring, which is very, very sensitive to vibrations.
So, we've got some tiny little silicon springs, they're about
half the width of a human hair here. This is very, very sensitive.
This is going to react to the smallest motion.
In fact, a subatomic displacement is going to be picked up
by the electronics that we have on board. How sensitive is this?
So, the testing of this mostly happened in the basement
of the physics building in Oxford.
And, on some days, we detected a very particular signature,
which, after a little bit of analysis, we were able to
tie down to the ringing of the bells,
not the sound of the bells themselves, but...
The vibrations the bells cause.
Yes. So, I was emailing round the bell ringers to say,
"Were you ringing the changes at 11 o'clock on Sunday?"
In this tower. And they said, "How did you know?"
And we said, "Well, we picked it up on the sensor
"we're going to fly to Mars," which, I must admit, surprised them.
On Mars, these seismometers aren't listening for bells,
but for seismic vibrations.
It's the time that these vibrations take to pass through Mars
to incite seismometers that will help scientists better understand
the planet's interior.
With this technique, you can get an understanding of
what's happening inside Mars?
Exactly. We want to look way below the surface.
We really want to get, from this mission, a cross section
all the way from the surface, right to the centre of the planet.
So, we're in place, you're ready.
I guess it's fingers crossed for that first event.
Absolutely. I think it's going to be worth it after all of the time,
first to fabricate the sensors here, to get them onto the surface,
and now that first clear signal is going to tell us
that the planet is ready to reveal what is in its interior.
What lies beneath. Exactly. That's right.
Thank you very much. Thank you.
While we wait for the first Marsquake,
Pete's already been out on the hunt for our fourth planet.
Mars is visible at present, but it's moving to a far part
of its orbit, relative to Earth,
and is consequently rather small to see.
However, one characteristic of Mars which always stands out,
even without a telescope, is its red colour.
Now, in astronomy, colour can be quite misleading.
Despite being called the Red Planet, Mars often looks more salmon pink
than deep red.
This trend continues out to the stars as well.
For most of us, when we look up at the night sky, they look
like tiny white pinpricks of light, but, with a little bit of know-how,
there are a medley of hues which can be teased
out of the night sky.
One great example appears in the top left corner in the constellation
of Orion the Hunter.
Here, you'll find the red super giant Betelgeuse,
one of the brightest stars in the sky.
And here it is.
Now, Betelgeuse has got a definite orange colour to it,
but this can be tricky to see But one sure-fire way of seeing it
is to compare it to another star of a different colour.
Stay in Orion, and look to the bottom right corner,
and here you'll find the blue super giant Rigel.
Now, if you flip your view between red super giant Betelgeuse and
blue super giant Rigel, the colour difference should be fairly obvious.
You might not realise,
but a star's colour tells you a lot about its temperature.
We normally consider red to be hot and blue to be cold,
but red Betelgeuse is three times cooler than blue Rigel.
Now, if you want to test out your skills, draw an
imaginary line between Rigel in the bottom right corner of Orion
through Betelgeuse in the upper left corner, and keep it going
for almost two times that distance.
You'll come to a pair of reasonably bright stars,
known as Castor and Pollux, the two brightest stars in Gemini the Twins.
And there they are.
At first, you'll note they're almost identical in appearance,
but if you take some time, their true colour should be revealed,
although it can be quite tricky.
If you've got a camera, there's a really neat trick you can employ
to bring star colours out, and that's simply to set the camera up,
point it at the stars, and do an extended exposure.
So the stars trail through the field of view. That really brings out
the amazing colour of many of the stars you can see
in the night sky.
If you manage to get a photo which shows the star's true colours,
why don't you upload it to our Flickr page?
We'd love to see it.
InSight has been collecting data since arriving on Mars
nearly five months ago.
One of its key objectives is to find out whether Mars' interior
is still geologically active,
whether there's anything going on inside the planet.
On Earth, one of the major signs of geological activity
is the presence of earthquakes.
On Mars, they're called Marsquakes and these tremors,
originating within the planet, would be a key sign that it's still alive.
Back in Bristol, planetary seismologist Anna Horleston is
sifting through InSight's findings, looking for seismic activity.
It's been a few months now since you landed on Mars.
How's InSight doing?
Well, for the most part, it's doing really, really well.
You might have heard in the last few weeks that we had the Mole,
the heat flow probe, drilling, and then it's got a little bit stuck.
So we're working around that anomaly.
But other than that, everything is running perfectly.
What does that mean that it's got stuck? So this is the probe
that's supposed to drill down under the surface.
Yes. So, it's got a target depth of about five metres,
and it was expected that it would drill down about 70 centimetres
in the first hammering session, but we've only got
to about 30 centimetres. So, we may have hit a rock.
We may have just snagged on something, and hopefully,
the probe will be able to work its way around that,
and the team are working on that.
But it wasn't unexpected completely, but it's a little disappointing.
Your particular piece of the puzzle is the seismometer,
looking for Marsquakes. What's that been doing since landing?
Well, I can show you on here. Yeah. OK.
So this is data from Mars? Yes. This is data from Mars.
That's still pretty cool.
Every day, when we get new data from Mars, I'm like,
"Yes! It's data from Mars!" So I am like a five-year-old.
In fact, more excited than my own...
A five-year-old who is particularly interested in seismometers and Mars!
That's good. Come on. Yeah.
So, a lot of what we see is just very small vibrations.
We also see some really prominent signals in the seismic data. Wow!
Yeah. Even I can see that.
Yes! There's a big dip. Yes, exactly. There's a massive dip.
Now, one of the great things about InSight is that we have
lots of different sensors, and I've got access to all the data,
and we are seeing the pressure and seismic signal of dust devils
blowing past our landers.
This one was probably pretty close, because it's a really strong signal.
These have been seen before. Some of the rovers, Spirit and Opportunity,
recorded dust devils whipping across the planet. Yeah.
So that's fun, but we're here, really, for Marsquakes.
Have you found any yet?
Not yet, but it's early days.
We've only been fully commissioned with the wind and thermal shield
protecting us for about a month.
And we only expect to see a handful over the course
of the whole mission, so we've got time.
So, yeah, it would be lovely to see one.
And I'm really, really excited, looking forward to seeing one.
But as yet, we haven't seen one.
What would you see if a Marsquake happened? What signals
would you be looking for, and how would we interpret them?
Well, we'd hope that we'd see something very like we see on Earth.
And in fact, we could do a little demonstration. OK, yeah.
If you're up for a little demonstration.
Sure. All discussions on quakes have to involve...
Of course! Common Slinky.
Would you like to take one end of this Slinky? All right.
So, the first seismic wave we would see is called a
compressional wave, or a P-wave, and this moves with the motion...
With the motion as in, in the direction of travel of the wave. OK.
So... So this is the Martian sort of surface or rock.
Yeah. And the quake here would cause a signal that would propagate
directly in that direct path.
So the second way we see, called the secondary wave or S-wave,
is a shear wave, so it's side to side. So if I do that... OK.
And this is a slightly slower wave because you've got to make
that do all of this.
It can also only travel through a solid. Shear waves can't travel
through a liquid, which is how we know... Part of the reason
how we know that we have a liquid outer core in our Earth,
because we have what's called the shadow zone, where we can't see
the shear waves arriving.
So one of the open questions is whether Mars has anything
like that in its core. Exactly, yes. Or near its core. Yeah.
So if we can see shear waves and we have a shear wave shadow zone,
then we know we've got a liquid core.
On Earth, when you say an earthquake,
I start thinking about volcanoes and plate tectonics and so on,
but Mars doesn't have active volcanoes.
It doesn't have plate tectonics, so where are Marsquakes
expected to come from? Are you a baker, Chris? I have baked, yes.
Have you ever taken a cake out of the oven, and it's been beautifully
domed when it's hot, and then it's just gone...? Yes, many times.
OK. So just like that, the planets, all of them, they start out
really hot and obviously then, they cool, and they contract.
And so as they contract, they crush in and they then have to
move past themselves, so as the planet cools, it's contracting,
and that can cause a really exciting scientific result in itself,
but also it may not be a Marsquake that we see first,
we might see a meteorite impact.
So, Mars... We get hit by meteorites on Earth,
but our atmosphere protects us from a lot of them.
But Mars sees regular impacts, and an impact that would
form a crater of even 30 or 50 metres would be something
that we could detect within a few hundred kilometres.
And we've seen those craters appear, haven't we? Yes, we have.
So we know from the satellite images we get from the
Mars Reconnaissance Orbiter that there are impacts happening.
So we do expect to see, you know, maybe... Again, maybe a handful,
a dozen or something, over the next couple of years, impacts,
and the wonderful thing about impacts is, if we can see
the seismic signal, then we can ask those orbiting satellites to go
and take pictures for us. Cos you'll roughly where it's come from. Yes.
So we can work out a rough location and then they can give us
a precise location, which means that we can calibrate all our models.
Because you'll see the crater. Yes.
So you'll know how big the thing was that hit. Yes.
So in the same way that a lot of our best science that's been done
with seismology on the Earth has been from things like
bomb explosions and things where we have a known source
a known time, and a known location,
you know, you can just suddenly calibrate everything else.
So a meteorite impact would be...
I mean, even with Marsquakes, meteorite impacts would still
be really, really valuable because, yeah, they are
literally a calibration shot across the planet. OK.
Well, I hope you get a Marsquake soon,
all the meteorite impacts you need, and we'll come back and talk to you
as soon as InSight sees something. Thank you very much. Thank you.
Whereas InSight's mission is only just beginning,
this month, we say goodbye to the longest-serving Rover on Mars,
Opportunity.
Opportunity landed on Mars back in January 2004,
at the start of what was supposed to be a 90-day mission.
In fact, the Rover lasted more than 50 times longer than that,
travelling more than 45 kilometres across the Martian surface
in a little over 14 years,
and sending back a quarter of a million images.
But in June last year, Opportunity was engulfed in a storm
that covered the entire planet, and NASA lost contact.
By the 12th of February,
NASA had made nearly 1,000 unsuccessful attempts
to re-establish the link.
It is therefore that I declare the Opportunity mission as complete.
Well, Maggie, you're the engineer.
What do you think went wrong with Opportunity? Just looking
at this screen, that dust storm, was across the entire planet.
So it's not surprising that it had difficulty, because for any Rover,
it needs power. Solar panels charge up the batteries, and it keeps
it trundling, but with a dust storm that big,
sand on the solar panels means it can't charge up the batteries,
and it was dead in the water. It was the loss of power that did for it.
But we should remember it was an amazing technological achievement,
even starting with the landing. Oh, yes.
It's hard to slow down any spacecraft
in Mars' thin atmosphere,
and so, to ensure a soft landing,
NASA developed a novel method, bouncing Opportunity and its twin,
Spirit, onto the surface in a giant inflatable pyramid.
I love that landing method, because it sounds as if a child designed it.
I mean, inflatable balloons, and it bounces across the surface,
so it's potluck where you land, but it works.
And with Mars, working is good!
And so the fact that it landed, and Spirit as well, successfully
onto the surface... These two Rovers used a method that hadn't
been tried before, to get down on the surface
and trundle off to explore. It's really quite impressive. It is.
It wasn't all plain sailing for Opportunity.
At one point, it became trapped in soft sand.
Back home, NASA's best brains scrambled to try and save it.
After five stressful weeks, the Rover finally escaped
to continue its mission.
I was also fascinated, and it was the science.
I mean, as a scientist, what were your favourite highlights?
We didn't know before Spirit and Opportunity that Mars
used to be a wet world, that it had oceans and lakes and rivers.
We had hints. If you looked from orbit, you can see things
that look a bit like lake beds. But it was a theory.
Yeah. And so what you need to do is go and be a geologist.
You need to get there, touch the rocks, and actually
look at the minerals, and that's what Spirit and Opportunity did.
So Opportunity, pretty early on,
found gypsum, for example, which is a mineral that only forms
when you've got water. And then we were all kept busy
thinking about these things called blueberries that they found,
these sort of round blobs of mineral, if you like,
which were the sign that water had been involved
in the rock's formation.
So there's now real evidence that there was, in the past,
ancient water on Mars. So actually, we had a geologist on Mars.
A remote one, but a geologist. That's right. A hard-working one!
Yes!
I think what really impressed me was the distance
it was able to cover. I mean, it was huge.
Yes. And I think the science team got ambitious.
Once they realised that it was going to survive much longer than 90 days,
they set off across the Martian surface,
looking, really, for more history. If they could get to big craters,
they could see more rocks, and they could look further back in time.
Because a crater means you can dig deeper.
You actually see what's below. Exactly, and so Opportunity
reached first a crater called Victoria Crater.
And then they got really ambitious, and set off across the surface
to reach Endeavour Crater. Endeavour's the really big one.
That's right. Yeah.
Which no-one at landing ever thought they'd get anywhere near.
But that's where Opportunity ended up, and it sent back spectacular
images. To get there, though, it travelled more than 45 kilometres
across the surface.
That's further than a marathon, and it actually holds the record
for the furthest distance travelled on a body in outer space.
It's a record breaker!
It's a marathon, but it did take 14 years to do it!
To be fair, I'd take about that long to do a marathon.
So would I!
My favourite thing that Opportunity gave me was the images
of Mars, because the images were breathtaking.
There was something about it.
I think it's because the cameras were just at the right height,
cos it felt as if I was standing on the Martian surface, looking out,
and I could sort of step into the picture and just walk off into Mars.
Yeah, those last few panoramas in particular, taken from a spot
just at the crater rim of Endeavour, looking down,
and all of that Martian history laid out before us.
It just makes you want to go and wander off and explore, doesn't it?
Yes, definitely! I think I'm a Martian at heart!
I'm afraid that's all we've got time for this month.
But join us next month, when we're hoping to have the first
detailed images of the black hole at the centre of our galaxy.
Until then, goodnight. Goodnight.