Original subtitles

This year, two missions will attempt one of the most daring feats

in space exploration.

They will gather rock samples from another world.

The spacecraft have been launched to two different asteroids,

they'll gather samples, and they will bring them back to Earth.

So, why the sudden interest in asteroids,

and what can we learn from these extraordinary missions?

Welcome to The Sky At Night.

When we think of the solar system, we usually think of the planets,

moons and the sun.

But there's more to our cosmic neighbourhood than that.

Gathered in a vast doughnut-shaped ring between Mars and Jupiter are

millions of asteroids.

Some are up to 300 miles across.

Until now, we've only been able to study asteroids - like this one -

when they've fallen to earth.

Or meteorites, to give them their proper name.

But now, missions have been launched to bring pieces of two different

asteroids back to Earth.

These samples could unlock secrets

about the origins of the solar system...

..and could even help save Earth from a catastrophic collision.

And so tonight, we're here at the Natural History Museum in London,

home to the world's largest collection of meteorites.

Coming up...

We'll see the alarming number of asteroids

orbiting close to our planet.

The impact energy if that thing entered the atmosphere would be

larger, 20 times larger than the largest atomic device

built during the Cold War.

We'll talk to the scientists attempting to bring pieces

of an asteroid back to Earth.

We have yet to have material brought back to Earth from such a primitive

body that will give us answers to possible origins of life on Earth.

And we'll meet the man who wants to catch a shooting star.

But first, we need to know a little more about asteroids.

Tim Gregory is here to explain

why they can tell us so much about our solar system.

TIM: Here at the Natural History Museum are thousands of samples

of rocks from across the earth.

Each one has a story to tell

about the geological forces that shaped our planet.

But there is a limit to what these rocks can tell us.

The rocks on the earth are always changing.

They are being made and unmade and remade by geological processes,

so there's only so far back in time that these rocks can take us.

To look back to the very earliest days of the Earth,

or even further back to before the Earth formed, you need

something that's unchanged since the beginning of the solar system.

And that's where asteroids come in.

The problem is getting our hands on one.

But, fortunately, we do have some fragments here on earth.

This one fell to the Earth on Christmas Eve in 1965 in Barwell,

a village in Leicestershire.

It's a piece of an asteroid.

And when a piece of an asteroid falls through the Earth's atmosphere

and lands on the ground, we call it a meteorite.

Pieces of this rock showered the streets.

Some fell through living room windows and even damaged cars.

Bet it was quite a shock for the residents

when this fell out the sky!

Slice open a meteorite and they start to reveal their secrets.

Take a look at this one.

These white, fluffy objects

are called calcium aluminium rich inclusions, or CAIs, and they

are some of the oldest material that you can get your hands on

in our solar system today.

The CAIs were the first solid material to condense out of

the solar nebula -

the disc of gas and dust that gave birth to our solar system.

You cannot touch anything older than this.

And it's by dating CAIs just like this one that we know the age of our

solar system to be 4.6 billion years old.

Surrounding them are these small, pale beads.

They're all round and that's because they were once molten droplets of

rock that cooled and crystallised under zero gravity.

They're called chondrules,

and they're a major building block of asteroids.

And the black stuff holding it all together?

That's called the matrix, and it was once free-floating dust

that coalesced to help form the asteroids.

And amazingly, the matrix contains water.

For some rocks, like this one,

that's as far as their evolution went.

It carried on orbiting the sun for billions of years unchanged.

But some asteroids grew bigger and bigger and bigger, until eventually,

they formed the planets.

Exactly how you go from specks of dust to something

the size of a planet is still not fully understood,

but we do know that it was a violent process.

Written in some of these rocks is evidence that asteroids were

colliding and breaking up

and melting and reforming early on in the history of the solar system.

This meteorite originated from an asteroid that got so big it melted

beyond all recognition.

This one probably formed when a rocky asteroid and a metal asteroid

collided and mixed together.

This shows how one rocky asteroid has fragmented on impact

with another metallic asteroid.

Bits of rock have embedded themselves

within a molten, metal matrix.

Contained within meteorites are most of the ingredients and some of the

instructions for how you build a solar system,

but there are still many unanswered questions,

and meteorites cannot help us answer all of them.

For one thing, they fall through the atmosphere at 30,000 miles an hour,

and develop this burned and charred crust on their surface as they fall.

And once they've landed, they quickly become contaminated.

To truly understand how our solar system formed,

what we'd like are some rocks from an asteroid out there in space,

pristine and unspoiled.

And we may not have long to wait...

There are currently two missions attempting the seemingly impossible.

To chase down an asteroid in space, land on it,

collect a sample and return that sample to Earth.

First in the race - a Japanese mission called Hayabusa2.

It recently arrived at asteroid Ryugu, 190 million miles from Earth,

and it sent back these images.

The Hayabusa2 mission aims to bring back a piece of Ryugu to help us

learn more about the history of our solar system.

I spoke to Shogo Tachibana about the plan now that the spacecraft

has arrived at its destination.

He's leading the team responsible for collecting the samples.

Hello, Shogo. Yes, can you hear me?

I can hear you, we can't see you... Oh, there you are.

Hello! Nice to talk to you. Yeah, good to see you.

Thank you for talking to us today.

What's the spacecraft doing now?

OK, so Hayabusa2 recently arrived at asteroid Ryugu on June 27.

The spacecraft has been remaining

at distance of about 20km

to observe the asteroid,

so we hope to very soon have a date for our first sampling.

And how will that sampling be done?

We'll touch down on the surface of the asteroid

and as soon as this happens,

a small projectile will be shot

at the surface of the asteroid

and ejected material will be

collected in a capture.

What are the challenges involved with taking samples in this way?

So, we will need to be very cautious.

The images of Ryugu have shown us

it's a very rough and bumpy surface.

A bumpy surface is a very dangerous environment for the spacecraft,

because the rocks may damage the probe.

So our engineering team is now working hard to find a way

to make a safe touchdown.

Can you tell us how you're feeling, and how the team are feeling?

Are people excited, or are you nervous?

Excited and nervous.

And especially... So I am in charge of sampling,

so we really need sample.

Good. Well, look, we all wish you the very best of luck.

I hope it goes well. Thank you so much.

I hope we'll get to talk to you about the science from the mission

once you get your samples back.

Thank you very much.

Hayabusa2 is due to collect its sample any day now.

It promises to answer questions about our solar system's origins.

But there's another reason why studying asteroids is so important.

There's an awful lot of them flying out there in space,

but we know from Earth's history that every now and then,

one of them will collide with us.

Were that to happen tomorrow, the results could be cataclysmic.

To find out how likely this is, and what we can do about it,

I met Alan Fitzsimmons.

So, Alan, how do we check asteroids that we don't know about?

Well, we find asteroids the same way

that the ancient Greek astronomers found or identified the planets.

Both planets and asteroids are in orbit about our sun,

and so that means

over an hour or a few hours,

you will see it moving against the background stars and galaxies.

And that's how we survey for asteroids out there

in our solar system.

So, we can actually beam live to Hawaii and find out what's happening

with the telescope at the moment?

That's right. What we're seeing here are the data coming back from the

ATLAS Project in Hawaii.

That's two half-metre telescopes surveying the night sky,

looking for near-Earth asteroids.

Although, tonight it's not looking too good, unfortunately.

Because we can see from the weather map we've got a very large storm

system, actually a hurricane, south of the Hawaiian Islands.

But we can have a look at what the telescopes found last night.

Oh, yes. And what we found during the night,

it found a lot of objects moving across the sky.

So, if we zoom in here we can actually see

in this part of the sky, over an hour this object has moved

from here down to here in the night sky.

And this is a real near-Earth object.

So, this is very important data

because this will allow us to refine the orbit and the trajectory of this

asteroid, and it will give us a little bit more insight into

where it's going over the next 100, 200 years.

So, you're detecting these asteroids virtually every night,

but do we have a feel of how many of them are out there?

I think we do now.

This shows the inner solar system

as we knew it 20 years ago in the year 1998.

And what we see here are the orbits of the planets,

the sun in the centre of the solar system,

and every one of these blue dots is one of the few hundred near-Earth

asteroids that were known then.

OK. And over the past 20 years, the technology we have,

in terms of telescopes and detectors,

have really allowed us to detect many, many more objects.

I can illustrate the growth in our knowledge of the near-Earth object

population by playing this animation.

So here, we can see the asteroids all rotating.

Yeah, and you can see them moving.

So you're tracking... Whoa, OK!

That's suddenly quite a massive increase.

And again... That side.

What we're seeing here is the effect of the increase in the power of our

survey telescopes, which, every clear night, are trying to look for

these moving objects.

That looks like thousands, and it looks quite scary.

Well, there are thousands.

In fact, right now we've gone from just a few hundred up to over 18,000

near-Earth objects,

and we find another 40 new ones every month on average.

So, looking at this, we know where these asteroids come from,

but how many near-Earth objects

are actually dangerous to us, on Planet Earth?

Out of those 18,000, less than 2,000 are what we class as

potentially hazardous objects,

which come very close to the Earth's orbit and are 140 metres across

or so, or larger.

So, what sort of impact with something that size have?

Oh, it would be pretty, pretty disastrous for that local region.

And, of course, the larger the asteroid,

the more impact it would have.

Out of that 18,000, there's only 2,000 potentially hazardous?

Yes. So that's 2,000 potentially ticking time bombs?

And a case in point would be the asteroid Bennu.

This is a 500 metre,

half a kilometre diameter,

near-Earth asteroid that isn't

going to approach us in the next 100

years or so, but towards the end of

the next century has about a

one in 2,700 chance of hitting the Earth.

Sort of low probability,

but the impact, I guess, would be devastating? Absolutely.

The impact energy if that thing entered the atmosphere would

be larger, 20 times larger,

than the largest atomic device built during the Cold War.

And you'd really want to know, for example, exactly how big it is.

What is its mass? What is its density?

How is it constructed, exactly what is it made of?

Because all of that kind of information would allow us to plan

a deflection mission should the need arise.

Asteroid Bennu is a potential threat.

So, to discover all they can about it,

Nasa have sent the second of our

two asteroid missions, known as OSIRIS-REx,

to intercept and to collect a sample from it.

Right now, it's making its final approach to the asteroid.

I spoke to Kerri Donaldson Hanna from the OSIRIS-REx team.

She's got the difficult task of helping to select which bit of

the asteroid to bring back to Earth.

Where is the spacecraft now, and what's it doing?

OSIRIS-REx is on its way to Bennu,

so it started its approach phase in mid August.

And it's now about 2 million miles away from Bennu,

and roughly 60 million miles away from Earth.

And so what it means is we're starting to get the first

initial images of Bennu and start resolving what Bennu looks like.

It seems strange that you'd launch a spacecraft somewhere without knowing

what your target looks like.

What do we know about asteroid Bennu?

We do kind of have a basic idea of Bennu's shape.

I mean, it just looks like a blob... Yeah, yeah. ..to me.

But you can see that while we have the basic shape information,

we still are missing a lot of information about its surface,

including whether it's big boulders,

you know, where there's lots of dust.

And you need to pick somewhere to land,

which seems impossible with this sort of information?

In early December, we start doing our preliminary survey,

which means we start going into orbit and we start mapping

its surface properties.

So all of this work is to identify a single landing site

which OSIRIS-REx will then go to take samples from.

How does that work? How do you get a piece of an asteroid?

So, the spacecraft is going to

slowly make its way towards the asteroid.

The sample head will just touch

the surface of the asteroid for five seconds.

That's it? Yeah, just for five seconds.

And in that five seconds, a burst of nitrogen gas will be released,

which will loosen all the surface material.

And it'll flush all the material up into the sample head.

And how much material do you get, if you're lucky?

We are hoping to get a minimum of 60g of sample.

It's not very much. But up to two kilograms...

Oh, OK. ..of sample. A couple of bags of sugar?

Yeah, yeah. On Earth.

What will your role and the role of laboratories like this be?

They want to make sure they can go somewhere where they know

they can actually touch down, they will want to go somewhere safe,

so that's, you know, worries about the spacecraft itself.

But then they also want to go somewhere where they can actually

sample as much material as possible.

And they know that to get the maximum amount of sample,

they need a fairly flat surface,

and they also need a fairly boulder-free surface.

So we're going to be making spectral maps based on visible

and near infrared reflected light,

as well as thermal infrared radiation emitted from the surface.

So they'll pull all of these different maps and try to pick

the best science value place on the surface.

Hayabusa2 is due to return its samples in 2020,

followed by OSIRIS-REx in 2023.

Now, that's a bit of a time to wait.

So in the meanwhile,

I want to find out what makes these samples so special,

and what we hope to learn about them.

I met with Ashley King, a geologist

working with the rock collection at the Natural History Museum.

So, the samples you get will be returned from an asteroid.

What makes them so special?

They'll be special because we're getting them from an asteroid,

but also we'll have context.

So we'll know which asteroid they come from and

whereabouts on the asteroid.

So, nearly all of the meteorites that we have,

we're pretty sure they come from asteroids but we don't know exactly

whereabouts, or which asteroids they come from.

So, I'm a geologist, so what I do here on Earth is when you go out,

you collect a sample, you're actually...

I have something here I can show you.

One you happen to have in your back pocket.

I have in my back pocket, like all good geologists!

This is a rock that was brought back by Scott from Antarctica.

Oh, wow. So this is... Can I hold it? Absolutely, yeah.

This is a piece of granite, and so what we have here on Earth

is that you can go to the outcrop, you can see the rocks, you can,

you know how that rock fits into the bigger picture of that area.

Then you can bring that sample back and study it in the laboratory.

Meteorites are brilliant because we have the samples and we

can study them in the lab. But we don't have that original context.

Where did they come from on the asteroid?

What were the other rocks... What did they look like?

How did they relate to each other?

For these rocks that come back from Hayabusa2 and OSIRIS-REx,

we'll have that information

which as a geologist, is completely invaluable.

What will be samples tell us that we don't already know?

One of the big questions in planetary science is where

did the Earth get its water from?

We know from the meteorite record that they look like meteorites

that have water in them.

This isn't liquid water,

it's water that's locked up within the minerals.

When we go there, we'll be able to get samples and study the water

that's in these things and compare it to what we see on the Earth.

Yeah, we don't really know where the Earth's water came from.

We think maybe comets was one option.

It turns out from missions like Rosetta, have kind of shown

that the comets aren't the perfect match for the water that we see

here on the Earth, so hopefully asteroids,

or these asteroids, might give us some clues to that.

How about life? Yeah.

The other interesting thing that we're going to these asteroids,

to Bennu and to Ryugu, because they are dark.

They are really black surfaces.

One of the reasons we think these things are so dark is that they

probably got organic molecules

and the kind of building blocks for life are in there.

These samples will be pristine,

so they won't have been altered in the terrestrial atmosphere.

It'll be really exciting to see whether asteroids like this are

one of the ways that we can bring the starting materials for life.

But as well as life,

asteroids threaten to deliver death and destruction to our planet.

Some of these near-Earth asteroids are actually potentially hazardous.

There's a possibility, a very small possibility,

that they could collide with the Earth at some point in the future.

So, one of the reasons we want to go and study these things is to

understand the composition, the structure.

Hopefully, if something was going to hit the Earth,

we can plan a bit about

how we would deal with that kind of problem.

So, if we detect dangerous asteroid, what can we do about it?

I mean, Bruce Willis blew it up. Is that a good idea?

So, that's one thing that's discussed.

There's ideas, particularly for these dark ones,

there's this idea that we could go and paint one side white

and the solar radiation would just nudge it off of its course

ever so slightly.

It's all about trying to change the orbital path just enough

so that it won't hit the Earth.

I suppose, the more we know about them,

the more effective that will be. Yes. Thank you.

Whilst we wait for samples from the two different missions,

technology is giving us new ways to understand more about asteroids

from here on Earth.

Pete Lawrence shows how you can get involved.

PETE: When small pieces of rock pass-through Earth's atmosphere,

they leave a bright light in the sky called a meteor or a fireball.

I've been fascinated by meteors

and indeed fireballs for the past 40 years or so.

And over that time, I've taken tens of thousands of images.

And I've been lucky enough

to capture several hundred meteor trails.

But tonight, I'm going to try something different.

I'm going to try and capture meteor trails using a video camera.

Now, the camera I'm going to use is a bog-standard security CCTV camera,

and this is powered so that it comes on as the sun sets,

and the power's taken off via a timer when the sun rises.

Now, I'm going to set this up permanently

so it's looking for fireballs all year round.

And to do that, I need to use a weatherproof housing,

and this is a fairly bog-standard bit of kit as well.

The camera needs to point at a clear patch of sky,

so I'm mounting mine onto the side of my garden shed.

The camera is connected to an ordinary computer with software

that will identify and record any fireballs that occur.

Now, I've only had my camera set-up for the past couple of nights,

but rather excitingly,

I have managed to capture a number of meteor trails over that period.

I've got a very nice one here that's running down the sky beautifully

against the stars of Pegasus.

They are not particularly bright meteors,

but they have recorded really well

with this actually quite simple set-up.

The great thing is that, with it,

I can join the UK Meteor Observation Network, or UKMON, as they're known.

This is a group of amateur astronomers

that have set up cameras all over the UK.

And if you do so and you catch a meteor trail passing through the

field of view of your camera, the

likelihood is that another camera will have picked it up as well.

If that happens, then you can work out the height of the meteor,

its speed, and also,

you can track it back to work out the particle's orbit that created

the meteor in the first place.

So, you're doing real meteor science.

Tracking where meteors come from is important work.

But there's a bigger prize.

Most meteors are nothing more than tiny sand-sized particles

that burn up in the atmosphere.

But some are big enough to make it to the ground.

Like this one that was filmed over Perth fewer than two weeks ago.

Luke Daly is helping to set up a global network of cameras

to not only track, but to recover meteorites that have hit the Earth.

One of his cameras is on the roof of a stately home in North Yorkshire.

We're setting up a network of ten cameras here in the UK.

Basically, like this one.

It's got a nice fish-eye lens,

so we see the entire night sky all the time.

It takes 30-second-long exposures.

And so, if a fireball comes through our images,

we see it on this camera, and hopefully we see it

on another camera and we can start sort of seeing what's

flying around up in the atmosphere at all times across in the UK.

The camera's been down for the last few nights,

and so Luke has come to carry out some vital maintenance.

Getting to the camera's very easy,

it's just these three Phillips head screws - we just wind them off.

Then this top just pops off like so.

As I suspected, we've got this card read error.

Now we just need to see if it'll take a picture for us.

Once all of the cameras are up and running,

Luke and his team will be able to see all of the meteorites

that land anywhere within the UK.

He hasn't found any yet, but the concept has been proven.

He helped set up a similar network under the clear skies of Australia,

which has seen success.

So, when multiple cameras see the same event,

we are able to quite precisely mapped that trajectory.

In Australia, three of our stations so the same event,

and we were able to get that trajectory,

triangulate it down to the ground,

figure out very precisely where it landed.

In 2016, these images of the same fireball

led one of Luke's colleagues to a remote location

in the Australian desert.

Buried half a metre into thick mud

was a two-kilo meteorite.

It's an iron meteorite, mate. Oh, my gosh!

Phil, how does it feel to find your first DFN meteorite?

Splendid!

LUKE LAUGHS

So, as well as getting the full position of these rocks,

we can also track it back into our solar system

and get its orbit really precisely.

And from that, we can start to figure out where these rocks

are coming from, and even what asteroid or asteroid family

they're originating from.

Luke's team are working on a method to calculate the precise journey

that each rock has taken before landing here on Earth.

So, understanding where meteorites come from as the sort of oldest

material, and understanding how that has evolved over time,

and how our solar system has evolved, gives us a...

Sort of enhances our understanding of how the planets form,

how our planet formed, what's special about our planet

that it developed life when others didn't.

Much of what we know about the early solar system comes from studying

asteroids and meteorites.

Yes, cos these are time capsules, relics from the past,

and they tell us about our origins.

But there's still a lot to learn.

That's where Hayabusa2 and OSIRIS-REx come in.

The samples they return will give us an unprecedented window into the

history of the early solar system.

As to what they'll find, we'll just have to wait and see.

But we'll be here to tell you all about it.

Goodnight.