0:00:02 > 0:00:04Tonight is one of the most spectacular meteor showers
0:00:04 > 0:00:07- of the year, the Perseids. - If it's clear, despite the moon,
0:00:07 > 0:00:10you should be able to see a number of shooting stars streaking across
0:00:10 > 0:00:13the night sky. And just think about this -
0:00:13 > 0:00:16every time one vaporises in the atmosphere,
0:00:16 > 0:00:19a small part of that meteor can fall to Earth as dust.
0:00:19 > 0:00:24In fact, this all adds to the 40,000 tonnes of space debris and dust
0:00:24 > 0:00:29that falls onto our planet every year. 40,000 tonnes!
0:00:29 > 0:00:33And so tonight, from here at the Norman Lockyer Observatory in Devon,
0:00:33 > 0:00:35we're going to investigate the strange stuff
0:00:35 > 0:00:38that comes from outer space.
0:01:04 > 0:01:08Just think about that 40,000 tonnes for a moment.
0:01:08 > 0:01:13That means around 50 times more stuff falls from the sky every year
0:01:13 > 0:01:15than fell from the cliff in this landslide
0:01:15 > 0:01:17just down the road in Sidmouth.
0:01:19 > 0:01:23That sounds alarming, but most of this space debris is nothing more
0:01:23 > 0:01:28than dust, tiny particles that waft gently through the atmosphere,
0:01:28 > 0:01:30each no larger than a sand grain.
0:01:30 > 0:01:33Slightly larger particles burn up on the way in,
0:01:33 > 0:01:38producing spectacular shooting stars, or meteors.
0:01:38 > 0:01:42Tonight we'll find out how Earth's history has been shaped by
0:01:42 > 0:01:45this space debris in surprising ways,
0:01:45 > 0:01:49and how some of it can be found on every rooftop in the land.
0:01:49 > 0:01:53One of the remarkable things about cosmic dust is, these tiny little
0:01:53 > 0:01:58particles have the same composition as the solar system as a whole.
0:01:58 > 0:02:02We'll see how scientists are working to make sure that we're prepared for
0:02:02 > 0:02:05the threat of a rogue meteorite hitting the Earth.
0:02:07 > 0:02:09Pete explains the best ways to see the Perseids,
0:02:09 > 0:02:13and he meets an astronomer who's found a way to see these meteors
0:02:13 > 0:02:15in the daytime.
0:02:17 > 0:02:20Fortunately, large objects that make it down to the ground,
0:02:20 > 0:02:22meteorites, are pretty rare.
0:02:22 > 0:02:25There've only been a few recorded falls in British history.
0:02:25 > 0:02:29But smaller objects are falling around us all the time,
0:02:29 > 0:02:32bringing with them new and surprising information
0:02:32 > 0:02:35about our solar system's past.
0:02:35 > 0:02:37These are micrometeorites.
0:02:37 > 0:02:39Nothing more than cosmic dust.
0:02:39 > 0:02:42And this stuff is all around us all the time, in the air,
0:02:42 > 0:02:47settling onto the ground, landing in our gardens and on our roads.
0:02:49 > 0:02:51In search of this valuable dust,
0:02:51 > 0:02:55Maggie climbed up onto the roof here at the Norman Lockyer Observatory
0:02:55 > 0:02:59along with micrometeorite expert Matt Genge.
0:02:59 > 0:03:02Matt, I do have to ask, what are we doing up here on the roof?
0:03:02 > 0:03:05Well, we are up here to look for something quite incredible.
0:03:05 > 0:03:07We're looking for cosmic dust.
0:03:07 > 0:03:11And usually, I have to go to the Antarctic,
0:03:11 > 0:03:15but we've actually discovered that because it falls all the time
0:03:15 > 0:03:18everywhere, about one particle per square metre,
0:03:18 > 0:03:21that roofs like this are perfect
0:03:21 > 0:03:26little collection plates for cosmic dust, because they fall on the roof
0:03:26 > 0:03:30and then they get concentrated by the rains in gutters.
0:03:30 > 0:03:33- So should we see if you can find some?- We'll give it a go.
0:03:36 > 0:03:39So there's a nice little gutter here.
0:03:40 > 0:03:42- This is going to be highly technical.- Right, OK.
0:03:42 > 0:03:45So I'm going to start off by using a spoon.
0:03:47 > 0:03:50So it just looks like the sort of things you do find in the gutter.
0:03:50 > 0:03:52Yeah, it's nothing special. A lot of it is going to be algae.
0:03:52 > 0:03:57- Ah, yes.- There's going to be a lot of terrestrial, wind-blown dust.
0:03:57 > 0:04:01Some of that will be natural. So, for example, you end up with
0:04:01 > 0:04:05dust from the Sahara on the roofs in the UK.
0:04:05 > 0:04:07But a lot of it's also going to be artificial.
0:04:07 > 0:04:11So how will you be able to identify the cosmic dust out of all these
0:04:11 > 0:04:15- different materials?- Well, the cosmic dust is heated as it comes
0:04:15 > 0:04:18through the atmosphere, so it burns up as it comes through...
0:04:18 > 0:04:20Like a shooting star. It sort of burns up in the atmosphere.
0:04:20 > 0:04:24Absolutely. And they end up as tiny little magma droplets.
0:04:24 > 0:04:26So they're perfect little spheres,
0:04:26 > 0:04:28so we're going to be looking for that shape.
0:04:28 > 0:04:32But more importantly, they contain magnetic minerals.
0:04:32 > 0:04:34And that means we can use a magnet
0:04:34 > 0:04:37to separate them from all the terrestrial debris.
0:04:37 > 0:04:42- Fantastic. Well, let's get started. - Yep.
0:04:42 > 0:04:46We'll return to Matt's experiment later when he's had time to process
0:04:46 > 0:04:48his potential cosmic dust.
0:04:55 > 0:05:01Meanwhile, more on the highlight of this week's night sky, the Perseids.
0:05:01 > 0:05:04And Pete's here to show you how to get the most out of this glorious
0:05:04 > 0:05:07meteor shower, and how to see it even in the daytime.
0:05:09 > 0:05:12The Perseid meteor shower is one of the astronomical highlights
0:05:12 > 0:05:16of the year. Activity starts about mid July, but reaches its peak
0:05:16 > 0:05:20on the nights around the 12th, 13th of August.
0:05:20 > 0:05:22This year we've got a bit of a moon,
0:05:22 > 0:05:25which is going to mess up some of the display, and it'll knock out
0:05:25 > 0:05:27some of the fainter meteors.
0:05:27 > 0:05:29But if you go outside and it's nice and clear,
0:05:29 > 0:05:32you should still be able to see the brighter ones -
0:05:32 > 0:05:33and they can be pretty magnificent.
0:05:35 > 0:05:40The Perseids all appear to emanate from a small area which starts south
0:05:40 > 0:05:42of the constellation Cassiopeia
0:05:42 > 0:05:46and shifts eastward over a few weeks into Camelopardalis.
0:05:49 > 0:05:53Make sure you're in darkness for at least 20 to 30 minutes so your eyes
0:05:53 > 0:05:56can properly dark adapt. Now, if you intend to use a torch,
0:05:56 > 0:06:00a good tip is to use some red gel over it so that it looks red and it
0:06:00 > 0:06:02doesn't destroy your dark adaption.
0:06:02 > 0:06:06The best time to view is after 1:00am BST,
0:06:06 > 0:06:09because after that time, the Earth will have turned,
0:06:09 > 0:06:11so we're hitting the meteors head on,
0:06:11 > 0:06:15the energy of impact is increased, and the meteors appear brighter.
0:06:17 > 0:06:22The Perseids are actually the remnants of Comet 109P/Swift-Tuttle.
0:06:22 > 0:06:26Each flash is caused by a tiny piece of rock called a meteoroid,
0:06:26 > 0:06:29typically between the size of a grain of sand
0:06:29 > 0:06:31up to about the size of a golf ball.
0:06:32 > 0:06:36A meteoroid trail is actually the site of some interesting science,
0:06:36 > 0:06:41because a meteoroid doesn't burn up in the atmosphere, it vaporises.
0:06:41 > 0:06:43Now, as the meteoroid passes through the atmosphere,
0:06:43 > 0:06:47it compresses the air ahead of it, and that creates a huge amount
0:06:47 > 0:06:51of heat, which vaporises the front surface of the meteoroid.
0:06:51 > 0:06:55You can see how this happens with this glass piston.
0:06:55 > 0:06:59There's a little bit of lint in the bottom and the piston is sealed.
0:06:59 > 0:07:01When I press the plunger down...
0:07:03 > 0:07:05..we get a flame.
0:07:05 > 0:07:08By compressing the air in the piston fast,
0:07:08 > 0:07:11I've raised its temperature hundreds of degrees,
0:07:11 > 0:07:15so hot that the lint spontaneously combusts.
0:07:18 > 0:07:20As the meteor vaporises,
0:07:20 > 0:07:24it sometimes leaves a trail of colour in its trail.
0:07:24 > 0:07:26The colours depend on the make-up
0:07:26 > 0:07:29of the meteoroid and the gases in the atmosphere.
0:07:32 > 0:07:35Sometimes, when you get a really bright meteor trail streaking across
0:07:35 > 0:07:39the sky, you get what looks like a smoke trail left behind it.
0:07:39 > 0:07:41And that's known as the meteor train.
0:07:41 > 0:07:45Now, it's not a smoke trail at all, it's a column of ionised gas.
0:07:45 > 0:07:47And if it's there for long enough,
0:07:47 > 0:07:50the high altitude atmospheric winds can blow it about.
0:07:50 > 0:07:54So you can see it distort in the sky as you watch it.
0:07:55 > 0:07:58There is another technique which can be used to see these incredible
0:07:58 > 0:08:03events, a technique which amateurs can use to see hundreds more meteors
0:08:03 > 0:08:06than they would normally, even during the day.
0:08:10 > 0:08:15Amateur Mike Dennis is able to spot meteors from indoors.
0:08:17 > 0:08:19He uses radio waves.
0:08:20 > 0:08:22So this looks interesting. What's going on here?
0:08:22 > 0:08:26- Well, we have a VHF signal that goes up into the sky.- Right.
0:08:26 > 0:08:30And when a meteoroid enters the Earth atmosphere,
0:08:30 > 0:08:34and as it's burning up, it generates an ionization
0:08:34 > 0:08:37that we can reflect radio waves off of.
0:08:37 > 0:08:40Right, OK. So you're detecting the trail left.
0:08:40 > 0:08:43Yes. These are very short little pips.
0:08:43 > 0:08:45So each one of these peaks is actually a meteor...
0:08:45 > 0:08:48- Tiny specks of dust. You wouldn't see them visually.- Oh, there's one.
0:08:48 > 0:08:51Oh, look at that! Yes! So that's, that's quite...
0:08:51 > 0:08:54I guess you're going to say... You're going to bring me down now
0:08:54 > 0:08:56- and say that's quite a small one. - That is quite a small one.
0:08:56 > 0:09:02You wouldn't even see it, but that is a larger speck. About the size
0:09:02 > 0:09:05of a grain of sand, probably even smaller.
0:09:05 > 0:09:07That's a big one going off there.
0:09:07 > 0:09:10Yeah. You can see now that this one was faster when it...
0:09:10 > 0:09:13- Right.- Although it produced less energy, it actually came in faster.
0:09:13 > 0:09:15OK. So when you get an event at night,
0:09:15 > 0:09:18can you tie that up to what you see visually?
0:09:18 > 0:09:21We certainly can, and I've got an example here.
0:09:21 > 0:09:26And you can see, this is the meteor that's happening on this building.
0:09:26 > 0:09:29That's first from our north camera, then from the east.
0:09:29 > 0:09:33- And this is the radar screen event that happened.- Oh, I see.
0:09:33 > 0:09:36This is the actual event that you just saw.
0:09:36 > 0:09:38- This is another meteor that came after it.- OK.
0:09:38 > 0:09:42So, with a shower like the Perseids, what would that actually look like?
0:09:42 > 0:09:46The peak of the Perseids... This is last year's.
0:09:46 > 0:09:50- Wow, OK.- It can get very, very busy.
0:09:50 > 0:09:53So, if people wanted to set this up themselves, is it difficult to do?
0:09:53 > 0:09:57To set this up as we've done it, it would be very difficult.
0:09:57 > 0:10:02But if you just want to experiment with listening to meteors,
0:10:02 > 0:10:07you can use even as something as simple as an FM broadcast radio,
0:10:07 > 0:10:09during a busy meteor shower.
0:10:09 > 0:10:13So long as there is an out of range radio station on that frequency,
0:10:13 > 0:10:15when a meteor happens,
0:10:15 > 0:10:17the radio wave will bounce off the meteor...
0:10:17 > 0:10:20- Oh, right, OK. So you can hear it? - You'll hear for a brief moment,
0:10:20 > 0:10:23you'll hear that for about half a second to a second.
0:10:23 > 0:10:27- Sometimes longer.- That's actually brilliant because, I mean,
0:10:27 > 0:10:30the thing which clobbers us all the time in the UK, of course,
0:10:30 > 0:10:31is the cloud cover. So with that,
0:10:31 > 0:10:36you can actually effectively hear a meteor shower throughout the day?
0:10:36 > 0:10:40- Yes.- Fantastic! Well, thank you very much for your time.- Thank you.
0:10:42 > 0:10:45We learn a lot about meteors from watching them in the sky.
0:10:45 > 0:10:48But even more when they land on Earth.
0:10:48 > 0:10:53Objects which do that are known not as meteors, but as meteorites.
0:10:58 > 0:11:01Earlier this year, we had the chance to see one of the largest
0:11:01 > 0:11:04collections of meteorites in the world.
0:11:04 > 0:11:06Perhaps surprisingly,
0:11:06 > 0:11:10that collection belongs to the Vatican Observatory.
0:11:10 > 0:11:14Maggie saw some of the highlights guided by the collection's curator,
0:11:14 > 0:11:16Brother Bob Macke.
0:11:16 > 0:11:19So, Brother Macke, how big is the collection?
0:11:19 > 0:11:22We have 1,200 specimens here, representing all of the different
0:11:22 > 0:11:24meteorite types. The vast majority
0:11:24 > 0:11:28of our collection are ordinary chondrites.
0:11:28 > 0:11:31These form the majority of the meteorites that fall to the Earth.
0:11:31 > 0:11:35These are primitive meteorites that are 1,000 million years old.
0:11:35 > 0:11:40And so, they still contain tracers of the origin of our solar system.
0:11:40 > 0:11:43They are older than any rock you'll find on the Earth.
0:11:43 > 0:11:46This is an important historical sample right here.
0:11:46 > 0:11:51This is a specimen of L'Aigle, which fell in 1803.
0:11:51 > 0:11:54It fell in France. This was the first meteorite fall that was
0:11:54 > 0:11:58well-documented by scientists of the era.
0:11:58 > 0:12:04So, it represents the recognition among the scientific community
0:12:04 > 0:12:07that meteorites actually are rocks that fall from space,
0:12:07 > 0:12:09that they have an extra-terrestrial origin.
0:12:09 > 0:12:12Oh, wow! And so you've got the chondrites,
0:12:12 > 0:12:14these are the common chondrites,
0:12:14 > 0:12:17- what other types do you have? - There are carbonaceous chondrites,
0:12:17 > 0:12:19which are also very primitive
0:12:19 > 0:12:23but formed in a different part of the solar system. This is a very
0:12:23 > 0:12:27rare type of carbonaceous chondrite called Orgueil,
0:12:27 > 0:12:29also fell in France in 1864.
0:12:29 > 0:12:32And these have been very precisely dated
0:12:32 > 0:12:38to 4.568 thousand million years in age. And this gives us the best
0:12:38 > 0:12:42estimate we have for the age of our solar system.
0:12:42 > 0:12:45This is an iron meteorite.
0:12:45 > 0:12:49- Oh, yeah.- It is made of solid iron nickel.
0:12:49 > 0:12:52You can see all the crystal structure. It's amazing.
0:12:52 > 0:12:54Yes, it's called the Widmanstatten pattern.
0:12:54 > 0:12:58And it's because there's two different alloys of iron and nickel,
0:12:58 > 0:13:00one with a little more nickel, one with a little less nickel.
0:13:00 > 0:13:02And they formed together.
0:13:02 > 0:13:06- And they form this pattern. - Yes. Beautiful.
0:13:06 > 0:13:10- What else have you got? - This is a specimen of Chelyabinsk.
0:13:10 > 0:13:13- Oh!- Which fell over Russia in 2013.
0:13:13 > 0:13:16When it exploded, it exploded into hundreds and hundreds of pieces.
0:13:16 > 0:13:20So the original object would have been possibly perhaps as large as
0:13:20 > 0:13:23this small room here. This closet.
0:13:23 > 0:13:26So you have this amazing collection, what science do you do with them?
0:13:26 > 0:13:30Here, we study meteorite physical properties -
0:13:30 > 0:13:32density, porosity, which is the amount of pore space,
0:13:32 > 0:13:37and heat capacity, which is the amount of energy it takes to change
0:13:37 > 0:13:38the temperature of the meteorite.
0:13:38 > 0:13:42It's a very important property for understanding the asteroids
0:13:42 > 0:13:46that they came from, how they behave when they interact with each other
0:13:46 > 0:13:47or interact with the sun.
0:13:47 > 0:13:51For instance, an important effect is called the Yarkovsky effect,
0:13:51 > 0:13:56which as the sunlight heats one side as that energy re-radiates,
0:13:56 > 0:13:58as the asteroid rotates,
0:13:58 > 0:14:04it can actually change the orbit, or the spin rate, of the asteroid.
0:14:04 > 0:14:07Many people study that specific effect. But to understand it better,
0:14:07 > 0:14:09they need to know what the heat capacity is.
0:14:09 > 0:14:12- And that's what you measure here? - That's what we measure here.
0:14:12 > 0:14:13Thank you.
0:14:19 > 0:14:23Studying meteorites can tell us about the solar system.
0:14:24 > 0:14:28But some scientists believe they can also tell us a lot about the Earth.
0:14:30 > 0:14:34Scientists now believe that this steady rain of stuff from space
0:14:34 > 0:14:38may have influenced our atmosphere, our geology and even our weather.
0:14:38 > 0:14:41And possibly life itself.
0:14:41 > 0:14:46Dr Penny Wozniakiewicz is at the heart of this new research into
0:14:46 > 0:14:49the role larger meteorites have played in Earth's evolution.
0:14:51 > 0:14:55Her team at the University of Kent have built a massive gun
0:14:55 > 0:14:58and are using to model how meteorites could produce unique
0:14:58 > 0:15:01compounds as they smash into the Earth itself.
0:15:07 > 0:15:09So in the lab, we take an object that we know really well,
0:15:09 > 0:15:11we accelerate it to high velocities
0:15:11 > 0:15:14into any target that we are interested in. So, for example,
0:15:14 > 0:15:16here we have an aluminium plate
0:15:16 > 0:15:20that's been impacted by something only a few millimetres across.
0:15:20 > 0:15:23- Wow!- But at 7km/s. And so you can see that
0:15:23 > 0:15:26the impact crater that it's produced is much bigger.
0:15:26 > 0:15:28And that's down to the sheer energy of the impact process.
0:15:28 > 0:15:31It really does look like a crater. It looks like something you might
0:15:31 > 0:15:34- see on the moon, with the rough edge to the crater there.- Yeah.
0:15:34 > 0:15:36So what's going on with these impacts? What are the results?
0:15:36 > 0:15:40After we impacted, we found that we had produced impact melt.
0:15:40 > 0:15:44So, stuff that had solidified and, well, it quenched as a glass.
0:15:44 > 0:15:45But we also found within that,
0:15:45 > 0:15:51that we had crystals that seem to have kept the original composition,
0:15:51 > 0:15:54but changed their structure. So their atomic form had changed under
0:15:54 > 0:15:58- the pressure and temperature of the impact.- So these are quite profound,
0:15:58 > 0:16:02detailed changes to the composition of these bodies.
0:16:02 > 0:16:06Yeah, so you get the production of what we would see as exotic
0:16:06 > 0:16:08materials during these impact events.
0:16:08 > 0:16:13And so, if we think about what meteorites might bring to a planet,
0:16:13 > 0:16:16particularly in the earlier days, it's not just about what's in the
0:16:16 > 0:16:18- meteorite, it's about what can be produced when it hits.- Absolutely.
0:16:18 > 0:16:21And there's been some very interesting research done recently
0:16:21 > 0:16:25looking at whether you can actually produce more interesting organics.
0:16:25 > 0:16:28So things that might be interesting for life.
0:16:28 > 0:16:30- So, quite complex molecules? - Complex molecules, yes.
0:16:30 > 0:16:34So, if that's the case, and these things happen on impact, we know
0:16:34 > 0:16:37there was a time when Earth was hit by lots of these small bodies.
0:16:37 > 0:16:40So could some of the stuff we see around us on Earth
0:16:40 > 0:16:43- come from impacts?- Yeah, I think something could have been generated
0:16:43 > 0:16:45by the impact event itself.
0:16:45 > 0:16:48And some of it could have been brought by the impacting object.
0:16:49 > 0:16:53It's a fascinating idea. Four billion years ago,
0:16:53 > 0:16:57basic organic materials, the very stuff of life,
0:16:57 > 0:17:01might have been created by the impacts of meteorites.
0:17:01 > 0:17:04And those meteorites might have changed Earth's destiny
0:17:04 > 0:17:06in other ways, too.
0:17:08 > 0:17:12There are theories that some of the water on Earth actually accreted
0:17:12 > 0:17:14as part of the original Earth.
0:17:14 > 0:17:18Another thought is that water was also brought in at a later time
0:17:18 > 0:17:21by comets and meteorites - sorry, asteroids.
0:17:21 > 0:17:24You would have had to have had a lot of impacts, though, surely,
0:17:24 > 0:17:28- to create enough water on the Earth. - Yeah, and there were a lot of
0:17:28 > 0:17:32impacts in the early history of the solar system. So, yeah.
0:17:32 > 0:17:34The water could've come from these objects.
0:17:34 > 0:17:37So Earth's water might have come at least partly from asteroids
0:17:37 > 0:17:41and comets. But what else might meteorites bring down to Earth?
0:17:41 > 0:17:43So, meteorites can also bring things
0:17:43 > 0:17:46like organics to the Earth's surface. So, a particular example
0:17:46 > 0:17:50would be the carbonaceous-type chondrite meteorites.
0:17:50 > 0:17:55These have quite a large proportion of organic materials within them.
0:17:55 > 0:17:57A very notable example is the meteorite Murchison.
0:17:57 > 0:18:01This one is often referred to as, if you smell it, you can smell
0:18:01 > 0:18:04a solvent smell, because of the organics that it contains.
0:18:04 > 0:18:06- You get smelly meteorites? - Smelly meteorites, yes.
0:18:06 > 0:18:09And that's because of the complex chemistry that's inside?
0:18:09 > 0:18:13Exactly. These can be a whole range of organic molecules within them.
0:18:13 > 0:18:18So, including carboxylic acid, amino acids, amines, alcohol, sugars.
0:18:18 > 0:18:21A whole range. So these are, I mean, you don't want to jump to this,
0:18:21 > 0:18:23but they're the building blocks of life.
0:18:23 > 0:18:26- They're the kind of things that biology uses.- Exactly, yeah.
0:18:26 > 0:18:31They are the precursor chemistry that you need for life to thrive.
0:18:31 > 0:18:34It's an amazing thought that the ingredients that produced life on
0:18:34 > 0:18:37- Earth might have come from space. - Yeah. It's mind-blowing, really.
0:18:37 > 0:18:41- It's fascinating stuff.- Yeah. - Thank you very much.- Thanks.
0:18:44 > 0:18:46Meanwhile, in our makeshift laboratory,
0:18:46 > 0:18:49Matt Genge has been preparing his sample from the rooftop.
0:18:51 > 0:18:53Having dried it in an oven,
0:18:53 > 0:18:55he sieves it and then passes a magnet over it,
0:18:55 > 0:18:57pulling out anything magnetic.
0:18:59 > 0:19:00He then places this material
0:19:00 > 0:19:04on a slide and puts it into an electron microscope.
0:19:06 > 0:19:10So we can see actually all these really dark things on here.
0:19:10 > 0:19:14They're probably bits of algae with some windblown dust in.
0:19:14 > 0:19:17What we're really interested in is the really bright stuff.
0:19:17 > 0:19:20- Because that probably contains lots of iron.- There's one there.
0:19:20 > 0:19:22But I guess that's a bit too irregular.
0:19:22 > 0:19:25Yeah, this one's very angular. So, that's not melted.
0:19:25 > 0:19:29I suspect if we look at some of these little bright spots.
0:19:29 > 0:19:32Yeah. What's the probability of finding a cosmic particle?
0:19:32 > 0:19:34- I'm afraid it's actually quite low. - So the odds are against us?
0:19:34 > 0:19:37The odds are against us. But we will do our best.
0:19:37 > 0:19:40- It does look as if we've got a few candidates.- There's a nice one here,
0:19:40 > 0:19:44just below the middle. Let's try and get that one right into the middle.
0:19:44 > 0:19:47And then I can increase the magnification.
0:19:47 > 0:19:50- OK, so we are going up to sort of 150 times magnification now.- Yeah.
0:19:50 > 0:19:53- 200.- So, actually, it's not looking too bad. It's certainly...
0:19:53 > 0:19:55Actually, it does look quite spherical.
0:19:55 > 0:19:56It does look pretty spherical.
0:19:56 > 0:20:00- Let's go right in. - OK, 1,000 times magnification now.
0:20:00 > 0:20:04- This is amazing.- Actually, it's looking surprisingly good.
0:20:04 > 0:20:06But it is a perfect little sphere.
0:20:06 > 0:20:10- It is. Yeah, with sort of a small nodule on top.- Yeah. Actually,
0:20:10 > 0:20:13the nodule's good, because many of the micrometeorites like this have
0:20:13 > 0:20:16these little protrusions from the sides.
0:20:16 > 0:20:18So... Actually, that's looking really good.
0:20:18 > 0:20:22It's definitely a potential. We've got to be slightly careful because
0:20:22 > 0:20:26there are molten droplets that we produce - artificial droplets.
0:20:26 > 0:20:28So, how can we tell the difference?
0:20:28 > 0:20:30Well, there's these wonderful little crystals on it.
0:20:30 > 0:20:33Can you see these lines on the surface?
0:20:33 > 0:20:36- Yes, like striations or something. - We called them dendrites.
0:20:36 > 0:20:39And they tell us that this was molten.
0:20:39 > 0:20:43So this was maybe a temperature of 1,500 degrees C.
0:20:43 > 0:20:45And then cooled very rapidly.
0:20:45 > 0:20:49And that's what happens to meteors during atmospheric entry.
0:20:49 > 0:20:52- I see.- They burn up, and then they cool down really quickly.
0:20:52 > 0:20:55So that all fits quite nicely. To be sure, though,
0:20:55 > 0:20:58we'll do a chemical analysis on that.
0:20:58 > 0:21:01- And we can do that...? - We can do that with this machine.
0:21:01 > 0:21:06So what we're seeing here is there's lots of iron in the particle.
0:21:06 > 0:21:09- Yes.- There's lots of oxygen over here.
0:21:09 > 0:21:11So that means it's an iron oxide mineral.
0:21:11 > 0:21:15There's some silicon and aluminium, but these particles tend to absorb
0:21:15 > 0:21:18that when they're sitting around in all of this water and algae and...
0:21:18 > 0:21:22- Yes, on the roof up there. - On the roof for a long time.
0:21:22 > 0:21:25So, it's mainly iron oxide. And that's actually really good,
0:21:25 > 0:21:27cos this isn't prepared at all, really.
0:21:27 > 0:21:30It just comes straight off the roof, into an oven and then straight into
0:21:30 > 0:21:34the microscope. So to have such an incredible image as this...
0:21:34 > 0:21:36- It is.- ..is actually really exciting.
0:21:36 > 0:21:39I'm really quite sure that this...
0:21:39 > 0:21:42This is a really good possible micrometeorite.
0:21:42 > 0:21:46I'm 95% sure that this is a micrometeorite.
0:21:46 > 0:21:49- And that's really against the odds. - It is really against the odds.
0:21:49 > 0:21:51I am actually really excited by this.
0:21:51 > 0:21:54Because I wasn't expecting to find anything on this roof at all.
0:21:54 > 0:21:57Well, that's fantastic! So, what does this particle tell us
0:21:57 > 0:21:59about the early solar system?
0:21:59 > 0:22:03Grains like this, if this was one of those primordial grains,
0:22:03 > 0:22:06they actually form in stars.
0:22:06 > 0:22:08- Yes.- In the outflows from stars.
0:22:08 > 0:22:13So we could be looking at, you know, a stellar dust particle
0:22:13 > 0:22:16that has survived four and a half billion years
0:22:16 > 0:22:18to be collected on a roof.
0:22:19 > 0:22:21- In Devon.- In Devon.
0:22:21 > 0:22:24Well, it's an amazing find and a wonderful story.
0:22:24 > 0:22:27I wasn't expecting to see anything, so it's brilliant to find one.
0:22:30 > 0:22:32It really is a remarkable find.
0:22:32 > 0:22:37A genuine micrometeorite, possibly older than the solar system itself,
0:22:37 > 0:22:39from the mud found on a rooftop.
0:22:41 > 0:22:43And all the more amazing because of its size,
0:22:43 > 0:22:46less than the width of a human hair.
0:22:46 > 0:22:49Of course, space debris of this size is generally harmless.
0:22:49 > 0:22:51It floats gently to the Earth.
0:22:53 > 0:22:57But when the debris is larger, the outcome can be much more alarming.
0:23:00 > 0:23:04To understand why, we need to think of the energy involved.
0:23:04 > 0:23:07Your average Perseid is an object about this size
0:23:07 > 0:23:10travelling at 30km/s -
0:23:10 > 0:23:12far faster than a speeding bullet.
0:23:12 > 0:23:15And if we scale it up to something the size of a brick,
0:23:15 > 0:23:17when something this size hits the atmosphere,
0:23:17 > 0:23:21it releases the equivalent of one tonne of TNT.
0:23:23 > 0:23:26And many are much, much larger than bricks.
0:23:28 > 0:23:342013. A 300kg meteor explodes over Chelyabinsk in Russia.
0:23:35 > 0:23:39The blast it produced was so powerful that it shattered windows
0:23:39 > 0:23:42over several thousand square kilometres.
0:23:42 > 0:23:45And there's plenty of evidence of even larger strikes, too.
0:23:45 > 0:23:50In Siberia, trees were flattened for hundreds of square kilometres
0:23:50 > 0:23:53after a meteor airburst in 1908.
0:23:53 > 0:23:55This is the famous kilometre-wide
0:23:55 > 0:23:58Barringer Meteorite Crater in Arizona.
0:23:59 > 0:24:02And in the Yucatan Peninsula 66 million years ago,
0:24:02 > 0:24:06scientists believed there was a super massive impact.
0:24:06 > 0:24:08This radar image shows evidence of
0:24:08 > 0:24:12a huge crater edge now buried deep underground.
0:24:12 > 0:24:15This, of course, was the K-T impact.
0:24:15 > 0:24:18The dinosaur killer.
0:24:18 > 0:24:21Chris met asteroid expert Professor Alan Fitzsimmons
0:24:21 > 0:24:25to gauge the real risks of a large meteorite impact.
0:24:27 > 0:24:30How big a threat are asteroids to life on Earth?
0:24:30 > 0:24:35Well, they're a threat, certainly. If we go back millions of years ago,
0:24:35 > 0:24:36we know that mass extinctions
0:24:36 > 0:24:39on Earth have been caused by asteroid impact,
0:24:39 > 0:24:42and the famous one being the K-T impact, which helped at least
0:24:42 > 0:24:44wipe out the dinosaurs.
0:24:44 > 0:24:47So, how are we doing? Could there be a dinosaur killer out there?
0:24:47 > 0:24:50Well, the good news is because the dinosaur killers, as we called them,
0:24:50 > 0:24:54are so big, you're talking objects that are 10km across.
0:24:54 > 0:24:58We can see those from a long way away and we believe
0:24:58 > 0:25:00we've catalogued all of them. There are only a handful.
0:25:00 > 0:25:01We know where they are.
0:25:01 > 0:25:04They're not going to come anywhere near the Earth any time soon.
0:25:04 > 0:25:08- OK, so any dinosaurs, they can relax.- They're fine.- Right.
0:25:08 > 0:25:11- But we've seen you can get damaged from smaller objects.- Absolutely.
0:25:11 > 0:25:14In fact, even if you go down to a 1km-diameter asteroid,
0:25:14 > 0:25:18there's models that suggest that could still set off
0:25:18 > 0:25:20significant casualties around the world
0:25:20 > 0:25:22because of the environmental effects from the impact.
0:25:22 > 0:25:27Up to perhaps 25% of the world's population dying from
0:25:27 > 0:25:31starvation due to the failure of crops in farming around the world.
0:25:31 > 0:25:34I hope the next line is, "I know where they all are."
0:25:34 > 0:25:37We know where 90% of them are.
0:25:37 > 0:25:39So we think there's roughly 1,000 of them,
0:25:39 > 0:25:44and over 900 have been found. And, as the surveys continue,
0:25:44 > 0:25:47we should sweep up most of the rest of those in the next
0:25:47 > 0:25:5010 or 20 years. But we have a class of near-Earth asteroids we call
0:25:50 > 0:25:54potentially hazardous asteroids. And these are asteroids that can
0:25:54 > 0:25:58pass within seven 7.5 million km of the Earth's orbit.
0:25:58 > 0:26:01So they come as close as that, or closer.
0:26:01 > 0:26:05And we believe initially that they could be up to 140 metres
0:26:05 > 0:26:09across or larger. And we have that size limit because we know that
0:26:09 > 0:26:13no matter what the asteroid is, calculations show that if it enters
0:26:13 > 0:26:16the Earth's atmosphere, it's going to make it to the ground.
0:26:16 > 0:26:20OK, so that's the difference between a spectacular shooting star
0:26:20 > 0:26:22and something we should worry about.
0:26:22 > 0:26:24Absolutely, 140 metres across is when you worry, because you know,
0:26:24 > 0:26:27no matter what it's made of, it's going to reach ground level
0:26:27 > 0:26:30and it's going to make a crater and the effects will be multiplied.
0:26:30 > 0:26:33So, what's next? We've found a potentially hazardous asteroid.
0:26:33 > 0:26:36We think it's pretty big. We think it might be on a collision course.
0:26:36 > 0:26:38We've got an initial orbit.
0:26:38 > 0:26:41Does this get kept quiet, or do we announce immediately?
0:26:41 > 0:26:44Well, the important thing to realise is that everything is public.
0:26:44 > 0:26:47Everything is announced. And we need that because when you discover
0:26:47 > 0:26:49a potentially hazardous asteroid,
0:26:49 > 0:26:54you need everybody that can observe it to observe it, so we can pin down
0:26:54 > 0:26:57the orbit better. And so everything is public.
0:26:57 > 0:26:59And so, are you worried?
0:26:59 > 0:27:02Are there objects that you know about that might hit us?
0:27:02 > 0:27:06There are no significant worries at the moment.
0:27:06 > 0:27:10But we've got to remember that if we go to the size range of potentially
0:27:10 > 0:27:15hazardous objects - anything 140 metres across or larger -
0:27:15 > 0:27:18then there's probably about 20-30,000 of those that exist
0:27:18 > 0:27:21at the moment. We've only found 8,000 of them.
0:27:21 > 0:27:26So, we've only got about 30% of that population.
0:27:26 > 0:27:28And even when we do find them,
0:27:28 > 0:27:31quite often, the orbits are uncertain.
0:27:31 > 0:27:33If we go down to smaller sizes
0:27:33 > 0:27:36such as the Chelyabinsk or Tunguska impacts, all bets are off.
0:27:36 > 0:27:38These things are random.
0:27:38 > 0:27:41They're like buses. Sometimes they won't turn up.
0:27:41 > 0:27:45Sometimes, you can get two very closely arriving at the same time.
0:27:45 > 0:27:48So, who knows?
0:27:48 > 0:27:51We could be hit by one as people are watching this programme.
0:27:51 > 0:27:53Well, there's a cheerful thought!
0:27:53 > 0:27:56Alan, thank you very much. I hope you make it home safely.
0:27:57 > 0:27:59Well, don't let that thought deter you -
0:27:59 > 0:28:04do go out right now and try and see tonight's Perseid meteor shower.
0:28:04 > 0:28:07It really is one of the astronomical highlights of the year.
0:28:09 > 0:28:12Don't forget to watch us again next month, when we'll be
0:28:12 > 0:28:15telling the incredible story of Cassini,
0:28:15 > 0:28:18one of the most successful space explorations ever.
0:28:18 > 0:28:20And as it reaches the end of its mission,
0:28:20 > 0:28:23we'll be asking, what questions has it sent us for the future?
0:28:23 > 0:28:26Meanwhile, don't forget to check out our website for more content
0:28:26 > 0:28:30from this month's packed show, and for our star guide,
0:28:30 > 0:28:33which includes information on how to spot asteroid Florence
0:28:33 > 0:28:36as it skims past the Earth in September.
0:28:36 > 0:28:40And, of course, get outside and get looking up.
0:28:40 > 0:28:44- Especially if it's clear. Check out those Perseids.- Goodnight.