It Came From Outer Space The Sky at Night

Tonight is one of the most spectacular meteor showers

-of the year, the Perseids.

-If it's clear, despite the moon,

you should be able to see a number of shooting stars streaking across

the night sky. And just think about this -

every time one vaporises in the atmosphere,

a small part of that meteor can fall to Earth as dust.

In fact, this all adds to the 40,000 tonnes of space debris and dust

that falls onto our planet every year. 40,000 tonnes!

And so tonight, from here at the Norman Lockyer Observatory in Devon,

we're going to investigate the strange stuff

that comes from outer space.

Just think about that 40,000 tonnes for a moment.

That means around 50 times more stuff falls from the sky every year

than fell from the cliff in this landslide

just down the road in Sidmouth.

That sounds alarming, but most of this space debris is nothing more

than dust, tiny particles that waft gently through the atmosphere,

each no larger than a sand grain.

Slightly larger particles burn up on the way in,

producing spectacular shooting stars, or meteors.

Tonight we'll find out how Earth's history has been shaped by

this space debris in surprising ways,

and how some of it can be found on every rooftop in the land.

One of the remarkable things about cosmic dust is, these tiny little

particles have the same composition as the solar system as a whole.

We'll see how scientists are working to make sure that we're prepared for

the threat of a rogue meteorite hitting the Earth.

Pete explains the best ways to see the Perseids,

and he meets an astronomer who's found a way to see these meteors

in the daytime.

Fortunately, large objects that make it down to the ground,

meteorites, are pretty rare.

There've only been a few recorded falls in British history.

But smaller objects are falling around us all the time,

bringing with them new and surprising information

about our solar system's past.

These are micrometeorites.

Nothing more than cosmic dust.

And this stuff is all around us all the time, in the air,

settling onto the ground, landing in our gardens and on our roads.

In search of this valuable dust,

Maggie climbed up onto the roof here at the Norman Lockyer Observatory

along with micrometeorite expert Matt Genge.

Matt, I do have to ask, what are we doing up here on the roof?

Well, we are up here to look for something quite incredible.

We're looking for cosmic dust.

And usually, I have to go to the Antarctic,

but we've actually discovered that because it falls all the time

everywhere, about one particle per square metre,

that roofs like this are perfect

little collection plates for cosmic dust, because they fall on the roof

and then they get concentrated by the rains in gutters.

-So should we see if you can find some?

-We'll give it a go.

So there's a nice little gutter here.

-This is going to be highly technical.

-Right, OK.

So I'm going to start off by using a spoon.

So it just looks like the sort of things you do find in the gutter.

Yeah, it's nothing special. A lot of it is going to be algae.

-Ah, yes.

-There's going to be a lot of terrestrial, wind-blown dust.

Some of that will be natural. So, for example, you end up with

dust from the Sahara on the roofs in the UK.

But a lot of it's also going to be artificial.

So how will you be able to identify the cosmic dust out of all these

-different materials?

-Well, the cosmic dust is heated as it comes

through the atmosphere, so it burns up as it comes through...

Like a shooting star. It sort of burns up in the atmosphere.

Absolutely. And they end up as tiny little magma droplets.

So they're perfect little spheres,

so we're going to be looking for that shape.

But more importantly, they contain magnetic minerals.

And that means we can use a magnet

to separate them from all the terrestrial debris.

-Fantastic. Well, let's get started.

-Yep.

We'll return to Matt's experiment later when he's had time to process

his potential cosmic dust.

Meanwhile, more on the highlight of this week's night sky, the Perseids.

And Pete's here to show you how to get the most out of this glorious

meteor shower, and how to see it even in the daytime.

The Perseid meteor shower is one of the astronomical highlights

of the year. Activity starts about mid July, but reaches its peak

on the nights around the 12th, 13th of August.

This year we've got a bit of a moon,

which is going to mess up some of the display, and it'll knock out

some of the fainter meteors.

But if you go outside and it's nice and clear,

you should still be able to see the brighter ones -

and they can be pretty magnificent.

The Perseids all appear to emanate from a small area which starts south

of the constellation Cassiopeia

and shifts eastward over a few weeks into Camelopardalis.

Make sure you're in darkness for at least 20 to 30 minutes so your eyes

can properly dark adapt. Now, if you intend to use a torch,

a good tip is to use some red gel over it so that it looks red and it

doesn't destroy your dark adaption.

The best time to view is after 1:00am BST,

because after that time, the Earth will have turned,

so we're hitting the meteors head on,

the energy of impact is increased, and the meteors appear brighter.

The Perseids are actually the remnants of Comet 109P/Swift-Tuttle.

Each flash is caused by a tiny piece of rock called a meteoroid,

typically between the size of a grain of sand

up to about the size of a golf ball.

A meteoroid trail is actually the site of some interesting science,

because a meteoroid doesn't burn up in the atmosphere, it vaporises.

Now, as the meteoroid passes through the atmosphere,

it compresses the air ahead of it, and that creates a huge amount

of heat, which vaporises the front surface of the meteoroid.

You can see how this happens with this glass piston.

There's a little bit of lint in the bottom and the piston is sealed.

When I press the plunger down...

..we get a flame.

By compressing the air in the piston fast,

I've raised its temperature hundreds of degrees,

so hot that the lint spontaneously combusts.

As the meteor vaporises,

it sometimes leaves a trail of colour in its trail.

The colours depend on the make-up

of the meteoroid and the gases in the atmosphere.

Sometimes, when you get a really bright meteor trail streaking across

the sky, you get what looks like a smoke trail left behind it.

And that's known as the meteor train.

Now, it's not a smoke trail at all, it's a column of ionised gas.

And if it's there for long enough,

the high altitude atmospheric winds can blow it about.

So you can see it distort in the sky as you watch it.

There is another technique which can be used to see these incredible

events, a technique which amateurs can use to see hundreds more meteors

than they would normally, even during the day.

Amateur Mike Dennis is able to spot meteors from indoors.

He uses radio waves.

So this looks interesting. What's going on here?

-Well, we have a VHF signal that goes up into the sky.

-Right.

And when a meteoroid enters the Earth atmosphere,

and as it's burning up, it generates an ionization

that we can reflect radio waves off of.

Right, OK. So you're detecting the trail left.

Yes. These are very short little pips.

So each one of these peaks is actually a meteor...

-Tiny specks of dust. You wouldn't see them visually.

-Oh, there's one.

Oh, look at that! Yes! So that's, that's quite...

I guess you're going to say... You're going to bring me down now

-and say that's quite a small one.

-That is quite a small one.

You wouldn't even see it, but that is a larger speck. About the size

of a grain of sand, probably even smaller.

That's a big one going off there.

Yeah. You can see now that this one was faster when it...

-Right.

-Although it produced less energy, it actually came in faster.

OK. So when you get an event at night,

can you tie that up to what you see visually?

We certainly can, and I've got an example here.

And you can see, this is the meteor that's happening on this building.

That's first from our north camera, then from the east.

-And this is the radar screen event that happened.

-Oh, I see.

This is the actual event that you just saw.

-This is another meteor that came after it.

-OK.

So, with a shower like the Perseids, what would that actually look like?

The peak of the Perseids... This is last year's.

-Wow, OK.

-It can get very, very busy.

So, if people wanted to set this up themselves, is it difficult to do?

To set this up as we've done it, it would be very difficult.

But if you just want to experiment with listening to meteors,

you can use even as something as simple as an FM broadcast radio,

during a busy meteor shower.

So long as there is an out of range radio station on that frequency,

when a meteor happens,

the radio wave will bounce off the meteor...

-Oh, right, OK. So you can hear it?

-You'll hear for a brief moment,

you'll hear that for about half a second to a second.

-Sometimes longer.

-That's actually brilliant because, I mean,

the thing which clobbers us all the time in the UK, of course,

is the cloud cover. So with that,

you can actually effectively hear a meteor shower throughout the day?

-Yes.

-Fantastic! Well, thank you very much for your time.

-Thank you.

We learn a lot about meteors from watching them in the sky.

But even more when they land on Earth.

Objects which do that are known not as meteors, but as meteorites.

Earlier this year, we had the chance to see one of the largest

collections of meteorites in the world.

Perhaps surprisingly,

that collection belongs to the Vatican Observatory.

Maggie saw some of the highlights guided by the collection's curator,

Brother Bob Macke.

So, Brother Macke, how big is the collection?

We have 1,200 specimens here, representing all of the different

meteorite types. The vast majority

of our collection are ordinary chondrites.

These form the majority of the meteorites that fall to the Earth.

These are primitive meteorites that are 1,000 million years old.

And so, they still contain tracers of the origin of our solar system.

They are older than any rock you'll find on the Earth.

This is an important historical sample right here.

This is a specimen of L'Aigle, which fell in 1803.

It fell in France. This was the first meteorite fall that was

well-documented by scientists of the era.

So, it represents the recognition among the scientific community

that meteorites actually are rocks that fall from space,

that they have an extra-terrestrial origin.

Oh, wow! And so you've got the chondrites,

these are the common chondrites,

-what other types do you have?

-There are carbonaceous chondrites,

which are also very primitive

but formed in a different part of the solar system. This is a very

rare type of carbonaceous chondrite called Orgueil,

also fell in France in 1864.

And these have been very precisely dated

to 4.568 thousand million years in age. And this gives us the best

estimate we have for the age of our solar system.

This is an iron meteorite.

-Oh, yeah.

-It is made of solid iron nickel.

You can see all the crystal structure. It's amazing.

Yes, it's called the Widmanstatten pattern.

And it's because there's two different alloys of iron and nickel,

one with a little more nickel, one with a little less nickel.

And they formed together.

-And they form this pattern.

-Yes. Beautiful.

-What else have you got?

-This is a specimen of Chelyabinsk.

-Oh!

-Which fell over Russia in 2013.

When it exploded, it exploded into hundreds and hundreds of pieces.

So the original object would have been possibly perhaps as large as

this small room here. This closet.

So you have this amazing collection, what science do you do with them?

Here, we study meteorite physical properties -

density, porosity, which is the amount of pore space,

and heat capacity, which is the amount of energy it takes to change

the temperature of the meteorite.

It's a very important property for understanding the asteroids

that they came from, how they behave when they interact with each other

or interact with the sun.

For instance, an important effect is called the Yarkovsky effect,

which as the sunlight heats one side as that energy re-radiates,

as the asteroid rotates,

it can actually change the orbit, or the spin rate, of the asteroid.

Many people study that specific effect. But to understand it better,

they need to know what the heat capacity is.

-And that's what you measure here?

-That's what we measure here.

Thank you.

Studying meteorites can tell us about the solar system.

But some scientists believe they can also tell us a lot about the Earth.

Scientists now believe that this steady rain of stuff from space

may have influenced our atmosphere, our geology and even our weather.

And possibly life itself.

Dr Penny Wozniakiewicz is at the heart of this new research into

the role larger meteorites have played in Earth's evolution.

Her team at the University of Kent have built a massive gun

and are using to model how meteorites could produce unique

compounds as they smash into the Earth itself.

So in the lab, we take an object that we know really well,

we accelerate it to high velocities

into any target that we are interested in. So, for example,

here we have an aluminium plate

that's been impacted by something only a few millimetres across.

-Wow!

-But at 7km/s. And so you can see that

the impact crater that it's produced is much bigger.

And that's down to the sheer energy of the impact process.

It really does look like a crater. It looks like something you might

-see on the moon, with the rough edge to the crater there.

-Yeah.

So what's going on with these impacts? What are the results?

After we impacted, we found that we had produced impact melt.

So, stuff that had solidified and, well, it quenched as a glass.

But we also found within that,

that we had crystals that seem to have kept the original composition,

but changed their structure. So their atomic form had changed under

-the pressure and temperature of the impact.

-So these are quite profound,

detailed changes to the composition of these bodies.

Yeah, so you get the production of what we would see as exotic

materials during these impact events.

And so, if we think about what meteorites might bring to a planet,

particularly in the earlier days, it's not just about what's in the

-meteorite, it's about what can be produced when it hits.

-Absolutely.

And there's been some very interesting research done recently

looking at whether you can actually produce more interesting organics.

So things that might be interesting for life.

-So, quite complex molecules?

-Complex molecules, yes.

So, if that's the case, and these things happen on impact, we know

there was a time when Earth was hit by lots of these small bodies.

So could some of the stuff we see around us on Earth

-come from impacts?

-Yeah, I think something could have been generated

by the impact event itself.

And some of it could have been brought by the impacting object.

It's a fascinating idea. Four billion years ago,

basic organic materials, the very stuff of life,

might have been created by the impacts of meteorites.

And those meteorites might have changed Earth's destiny

in other ways, too.

There are theories that some of the water on Earth actually accreted

as part of the original Earth.

Another thought is that water was also brought in at a later time

by comets and meteorites - sorry, asteroids.

You would have had to have had a lot of impacts, though, surely,

-to create enough water on the Earth.

-Yeah, and there were a lot of

impacts in the early history of the solar system. So, yeah.

The water could've come from these objects.

So Earth's water might have come at least partly from asteroids

and comets. But what else might meteorites bring down to Earth?

So, meteorites can also bring things

like organics to the Earth's surface. So, a particular example

would be the carbonaceous-type chondrite meteorites.

These have quite a large proportion of organic materials within them.

A very notable example is the meteorite Murchison.

This one is often referred to as, if you smell it, you can smell

a solvent smell, because of the organics that it contains.

-You get smelly meteorites?

-Smelly meteorites, yes.

And that's because of the complex chemistry that's inside?

Exactly. These can be a whole range of organic molecules within them.

So, including carboxylic acid, amino acids, amines, alcohol, sugars.

A whole range. So these are, I mean, you don't want to jump to this,

but they're the building blocks of life.

-They're the kind of things that biology uses.

-Exactly, yeah.

They are the precursor chemistry that you need for life to thrive.

It's an amazing thought that the ingredients that produced life on

-Earth might have come from space.

-Yeah. It's mind-blowing, really.

-It's fascinating stuff.

-Yeah.

-Thank you very much.

-Thanks.

Meanwhile, in our makeshift laboratory,

Matt Genge has been preparing his sample from the rooftop.

Having dried it in an oven,

he sieves it and then passes a magnet over it,

pulling out anything magnetic.

He then places this material

on a slide and puts it into an electron microscope.

So we can see actually all these really dark things on here.

They're probably bits of algae with some windblown dust in.

What we're really interested in is the really bright stuff.

-Because that probably contains lots of iron.

-There's one there.

But I guess that's a bit too irregular.

Yeah, this one's very angular. So, that's not melted.

I suspect if we look at some of these little bright spots.

Yeah. What's the probability of finding a cosmic particle?

-I'm afraid it's actually quite low.

-So the odds are against us?

The odds are against us. But we will do our best.

-It does look as if we've got a few candidates.

-There's a nice one here,

just below the middle. Let's try and get that one right into the middle.

And then I can increase the magnification.

-OK, so we are going up to sort of 150 times magnification now.

-Yeah.

-200.

-So, actually, it's not looking too bad. It's certainly...

Actually, it does look quite spherical.

It does look pretty spherical.

-Let's go right in.

-OK, 1,000 times magnification now.

-This is amazing.

-Actually, it's looking surprisingly good.

But it is a perfect little sphere.

-It is. Yeah, with sort of a small nodule on top.

-Yeah. Actually,

the nodule's good, because many of the micrometeorites like this have

these little protrusions from the sides.

So... Actually, that's looking really good.

It's definitely a potential. We've got to be slightly careful because

there are molten droplets that we produce - artificial droplets.

So, how can we tell the difference?

Well, there's these wonderful little crystals on it.

Can you see these lines on the surface?

-Yes, like striations or something.

-We called them dendrites.

And they tell us that this was molten.

So this was maybe a temperature of 1,500 degrees C.

And then cooled very rapidly.

And that's what happens to meteors during atmospheric entry.

-I see.

-They burn up, and then they cool down really quickly.

So that all fits quite nicely. To be sure, though,

we'll do a chemical analysis on that.

-And we can do that...?

-We can do that with this machine.

So what we're seeing here is there's lots of iron in the particle.

-Yes.

-There's lots of oxygen over here.

So that means it's an iron oxide mineral.

There's some silicon and aluminium, but these particles tend to absorb

that when they're sitting around in all of this water and algae and...

-Yes, on the roof up there.

-On the roof for a long time.

So, it's mainly iron oxide. And that's actually really good,

cos this isn't prepared at all, really.

It just comes straight off the roof, into an oven and then straight into

the microscope. So to have such an incredible image as this...

-It is.

-..is actually really exciting.

I'm really quite sure that this...

This is a really good possible micrometeorite.

I'm 95% sure that this is a micrometeorite.

-And that's really against the odds.

-It is really against the odds.

I am actually really excited by this.

Because I wasn't expecting to find anything on this roof at all.

Well, that's fantastic! So, what does this particle tell us

about the early solar system?

Grains like this, if this was one of those primordial grains,

they actually form in stars.

-Yes.

-In the outflows from stars.

So we could be looking at, you know, a stellar dust particle

that has survived four and a half billion years

to be collected on a roof.

-In Devon.

-In Devon.

Well, it's an amazing find and a wonderful story.

I wasn't expecting to see anything, so it's brilliant to find one.

It really is a remarkable find.

A genuine micrometeorite, possibly older than the solar system itself,

from the mud found on a rooftop.

And all the more amazing because of its size,

less than the width of a human hair.

Of course, space debris of this size is generally harmless.

It floats gently to the Earth.

But when the debris is larger, the outcome can be much more alarming.

To understand why, we need to think of the energy involved.

Your average Perseid is an object about this size

travelling at 30km/s -

far faster than a speeding bullet.

And if we scale it up to something the size of a brick,

when something this size hits the atmosphere,

it releases the equivalent of one tonne of TNT.

And many are much, much larger than bricks.

2013. A 300kg meteor explodes over Chelyabinsk in Russia.

The blast it produced was so powerful that it shattered windows

over several thousand square kilometres.

And there's plenty of evidence of even larger strikes, too.

In Siberia, trees were flattened for hundreds of square kilometres

after a meteor airburst in 1908.

This is the famous kilometre-wide

Barringer Meteorite Crater in Arizona.

And in the Yucatan Peninsula 66 million years ago,

scientists believed there was a super massive impact.

This radar image shows evidence of

a huge crater edge now buried deep underground.

This, of course, was the K-T impact.

The dinosaur killer.

Chris met asteroid expert Professor Alan Fitzsimmons

to gauge the real risks of a large meteorite impact.

How big a threat are asteroids to life on Earth?

Well, they're a threat, certainly. If we go back millions of years ago,

we know that mass extinctions

on Earth have been caused by asteroid impact,

and the famous one being the K-T impact, which helped at least

wipe out the dinosaurs.

So, how are we doing? Could there be a dinosaur killer out there?

Well, the good news is because the dinosaur killers, as we called them,

are so big, you're talking objects that are 10km across.

We can see those from a long way away and we believe

we've catalogued all of them. There are only a handful.

We know where they are.

They're not going to come anywhere near the Earth any time soon.

-OK, so any dinosaurs, they can relax.

-They're fine.

-Right.

-But we've seen you can get damaged from smaller objects.

-Absolutely.

In fact, even if you go down to a 1km-diameter asteroid,

there's models that suggest that could still set off

significant casualties around the world

because of the environmental effects from the impact.

Up to perhaps 25% of the world's population dying from

starvation due to the failure of crops in farming around the world.

I hope the next line is, "I know where they all are."

We know where 90% of them are.

So we think there's roughly 1,000 of them,

and over 900 have been found. And, as the surveys continue,

we should sweep up most of the rest of those in the next

10 or 20 years. But we have a class of near-Earth asteroids we call

potentially hazardous asteroids. And these are asteroids that can

pass within seven 7.5 million km of the Earth's orbit.

So they come as close as that, or closer.

And we believe initially that they could be up to 140 metres

across or larger. And we have that size limit because we know that

no matter what the asteroid is, calculations show that if it enters

the Earth's atmosphere, it's going to make it to the ground.

OK, so that's the difference between a spectacular shooting star

and something we should worry about.

Absolutely, 140 metres across is when you worry, because you know,

no matter what it's made of, it's going to reach ground level

and it's going to make a crater and the effects will be multiplied.

So, what's next? We've found a potentially hazardous asteroid.

We think it's pretty big. We think it might be on a collision course.

We've got an initial orbit.

Does this get kept quiet, or do we announce immediately?

Well, the important thing to realise is that everything is public.

Everything is announced. And we need that because when you discover

a potentially hazardous asteroid,

you need everybody that can observe it to observe it, so we can pin down

the orbit better. And so everything is public.

And so, are you worried?

Are there objects that you know about that might hit us?

There are no significant worries at the moment.

But we've got to remember that if we go to the size range of potentially

hazardous objects - anything 140 metres across or larger -

then there's probably about 20-30,000 of those that exist

at the moment. We've only found 8,000 of them.

So, we've only got about 30% of that population.

And even when we do find them,

quite often, the orbits are uncertain.

If we go down to smaller sizes

such as the Chelyabinsk or Tunguska impacts, all bets are off.

These things are random.

They're like buses. Sometimes they won't turn up.

Sometimes, you can get two very closely arriving at the same time.

So, who knows?

We could be hit by one as people are watching this programme.

Well, there's a cheerful thought!

Alan, thank you very much. I hope you make it home safely.

Well, don't let that thought deter you -

do go out right now and try and see tonight's Perseid meteor shower.

It really is one of the astronomical highlights of the year.

Don't forget to watch us again next month, when we'll be

telling the incredible story of Cassini,

one of the most successful space explorations ever.

And as it reaches the end of its mission,

we'll be asking, what questions has it sent us for the future?

Meanwhile, don't forget to check out our website for more content

from this month's packed show, and for our star guide,

which includes information on how to spot asteroid Florence

as it skims past the Earth in September.

And, of course, get outside and get looking up.

-Especially if it's clear. Check out those Perseids.

-Goodnight.