Astronomy by microscope? | 91TV
Transcript
- Good evening everybody, and thank you very much for coming here. Thank you to those who
- are joining us online. It's a huge honour to be awarded this prize, I just want to give an
- aside here of the last time I did anything that was associated with Michael Faraday.
- This is again the Royal Institution, and it was the Christmas lectures given in 2016 by Saiful
- Islam, a chemist. He was talking about light and electricity, things that Faraday has… Well,
- certainly the electricity Faraday was associated with. So Saiful's for entertainment and the
- entertainment of the Christmas lectures audiences, I sat in a Faraday cage. Now,
- I don't know whether this was Faraday's original cage, but it was really ramshackle,
- so I think it could have been. So it's a wooden sort of hut thing, and it's covered in chicken
- wire. What happens is, when you put a great big voltage across it you don't get an electric shock,
- because the metal of the cage disperses the shock. So they had me sitting in this cage while God
- knows how many hundreds of thousands of volts was put through it. If you look at Saiful's lecture,
- you know, it shows me sort of cowering in this little cage. I did that for
- dramatic purposes because of course I knew that I wouldn't get hurt by the electricity,
- as long as I didn't touch the cage. Of course, Faraday cages or Faraday buckets are what we use
- in a lot of our instruments to collect and count the electrons or the ions that we're looking at
- for when we do things. So I work with Faraday on a daily basis. So first of all, my talk,
- Astronomy by Microscope. Let's start off with astronomy by telescope, which is the usual thing.
- This on the top there, that's the James Webb Space Telescope. It's been sending down some
- absolutely fantastic images. Just really, really wonderful. This on the right here is an image as
- far back in time as we can go. That image is about 400 billion light years across or something like
- that. It's huge. It's enormous. It's just big. Each of those little bright spots in there is
- a galaxy with 100000 million stars in it. There's just lots and lots of them. This at the bottom is
- also a telescope. This is a land-based telescope. This is one of our telescopes in Tenerife where we
- can… We can't take pictures quite as spectacular as this one of all the galaxies, but we can take
- amazing pictures of solar system objects, and it's part of our teaching things that we do.
- So, you know, astronomy then by microscope. These are the sort of things that I use instead of
- telescopes. Whereas before something was several hundreds of billions of light years across,
- this is now… Well, it's about two millimetres across there. So we're looking at something at
- a rather different scale. This is a microscope. This is an optical microscope and it produces
- images like this. These are two images, one in what we call plain polarised light, so that's
- just light going into the microscope, and this is what happens if you put a pair of sunglasses
- on it. So the light is polarised and you get those amazing colours there. So that's this.
- This is a scanning electron microscope. So this is using light. Okay? This is using electrons,
- and we get pictures like this which tells us the shape, the topography, the bumps in the sample.
- This is a map of aluminium, calcium and iron, and it shows that we've got different
- additions. If you add magnesium, iron and calcium in and you've got more magnesium
- you get this. If you've got more calcium, you get this. This tells us about mineral compositions.
- Then this thing… I use both of these. I'm allowed. I'm qualified to use these. This thing here is
- called the NanoSIMS, and instead of using a beam of light photons or a beam of electrons,
- it uses heavy ions, right. It uses something… It uses caesium usually,
- so that's a very heavy thing, and it bombards the sample. Instead of just bouncing back nicely, what
- it does is it drills holes in the sample. Although I beg my colleague Ian Frankie to let me use this,
- he says, 'No, no, no. It's beyond you. It's beyond you. Your students can use it, but you can't.'
- What it does is it produces… Well, it produces some maps like this, but it produces data
- on isotopes. We'll come back to what isotopes are. So there are three different types of microscope,
- and this is what I want to try and convince you this evening. There's a phrase here which I really
- don't like, and that's ground truth. Data from meteorites provide ground truth for astronomical
- observations and astrophysical models. What that means is, if you're an astronomer and you've taken
- a lovely picture of some of a galaxy or something, you can think, 'Oh, well it's this colour,
- it's this size, it's this age, it's probably doing this,' and then we can actually trace
- some of the things that have come from those processes, what's going on in the galaxies,
- and we can measure them. We can hold them in our hands. They're real. They're there. They're even
- more real there than an astrophysicist's model. Modellers, they can model anything. They can do
- whatever they want. They can say, 'Well, you know, given these parameters…' and it's like,
- 'Well, where did those parameters come from?' We put those parameters in there. We say,
- 'Well you've got to start with this because we have measured it. It's there.' So that's what I
- mean by ground truth, and we use these techniques. I've shown you the pictures of the optical and the
- electron microscopes. We also use microscopes that use x-rays and you get the structure. just
- like when you x-ray your hand. You can x-ray a rock and you can see the structure of the rock.
- We use spectroscopy. So a rainbow is where the light, white light, has been broken down into
- different colours based on their wavelength. Well, we can use all sorts of wavelengths much wider,
- much broader than just the visible wavelengths. We can also divide samples in terms of what their
- mass is. So if you've got a whole chunk of organic stuff and you can put it into a mass spectrometer
- through a column which teases out things depending on how fast the molecules can move
- along that column, and the little ones move ever so fast and the big ones are really much slower,
- so you can tease them out like that. Then this here is what our NanoSIMS would come under.
- So we can analyse all sorts of astrophysically significant materials, which is what I'll come
- to and talk about those. Then you've probably all read this already. Astronomers often have
- to go out to telescopes where it's cold. Sometimes if it's cloudy, you know, if they're looking for
- visible light or infrared or something, it's cloudy, they can't see anything, it's tough.
- In a lab it's never cloudy. We're not allowed coffee in the labs anymore,
- which is the drawback, but there you go. You don't have to worry about clouds.
- So this is the cycle, the star formation cycle, and yes, I'm still talking about
- images that we've had from telescopes here. Where should we start? I mean, this is the
- problem because it's a cycle, and we're not exactly sure where we start. Do we start with
- stellar evolution? So we've got a star like the sun. It goes through its life cycle.
- It's going to become a red giant and then it's going to become a white dwarf. Some different
- types of stars explode to become a supernova, and when the star explodes as a supernova all the
- material, all the matter that made up that star, gets thrown back out again. It gets thrown back
- out again into the interstellar medium, which isn't just the space between the stars, but
- that's the easiest way of thinking about it, the interstellar medium, space between the stars, the
- space between the galaxies and so on and so forth. There are parts of our galaxy which have got
- concentrations of gas and dust. The gas is mainly hydrogen. There's silicate dust there.
- Dark clouds. If a dark cloud collapses - and it might be triggered to collapse by the
- explosion of a supernova - as it collapses star formation happens. So you get stars.
- The stars might form a disk from the dust around the star, and then the star evolves and eventually
- might explode as a supernova. At each one of these stages material is coming and going through
- the interstellar medium. So what we can do with meteorites is meteorites as we can say, 'Stop.
- We're going to look at some of these processes that have been going on
- and find out the information about them.' Now, is this going to work?
- Do I have to do it again? Maybe I do it again. Yes. So this is a simulation of
- planetary formation, and it's terribly slow so we'll probably only watch a little bit of it.
- What you can see here is a cloud of gas and dust, and it's turbulent. It's rotating, and
- gradually the central mass gets bigger and bigger and bigger, and it gets big enough eventually so
- the mass causes it to switch on. It's a star. It's undergoing nuclear fusion. It's burning hydrogen,
- and then it can attract dust to it which can spin around and be clumped together as planets.
- I'm sorry. You know, we're still doing astronomy by telescope here. I just get so
- moved and excited by some of the pictures that you can see. This for me is one of the
- most exciting pictures I have ever seen. You might say, 'Get a life. Get out a bit more,' but just…
- It's amazing. It was taken by the ALMA telescope. Now, the ALMA is the Atacama Large Millimetre
- Array. I have no idea what a large millimetre is. I thought they were all the same size,
- but I think it's a large array of telescopes which measure things at millimetre wavelengths.
- So, it took this picture of this star in the centre and the protoplanetary disk forming.
- It's a real picture. It's not a simulation, it's a real picture. For us to get things
- like this, ah, just so wonderful. Here's another one. Again in the centre there what you've got is,
- you've got a protoplanetary disk. It's a real picture. I just get
- so excited by them. I get excited by chocolate as well, but there you go.
- So what's happened then is, once you've had your protoplanetary disk and it started to collapse,
- and it clumps into different things at different places, so we've now got our sun, we've got the
- inner planets, we've got the outer planets and then we've got something called the asteroid belt
- which is a mixture of small bodies, the biggest of which is about 1000 kilometres across,
- which are mainly rocky or stony and some metallic ones. We've got another belt out here
- called the Kuiper Belt. The objects there are much darker. We know a lot less about them than
- we do about the asteroids, but they're mainly rock and ice. This could be where a lot of our comets
- actually come from, our short-lived comets. Pluto has been promoted. It's no longer a
- planet. It's no longer the smallest planet in the solar system. It's now one of the biggest Kuiper
- Belt objects. So it's gone through… It's been upgraded. So anybody who says to you,
- 'I think Pluto should be a planet,' say, 'No, it's been promoted. It's no longer the smallest,
- most distant, most not-interesting planet in the solar system. It's a really, really, really
- interesting Kuiper Belt object.' So most of the stuff that I study comes from the asteroid belt.
- Here's two asteroids. These were the focus of NASA's Dawn mission a few years ago. This is
- Vesta, which is about… I think it's about 500 kilometres across, and this is Ceres, which is
- about 1000 kilometres across. Ceres is big enough actually to be known as a minor planet because
- it's pulled itself into this spherical shape. Vesta is the classic potato-shaped asteroid,
- potato or peanut. Depends whether which side of the Atlantic you are on whether you classify
- asteroids as potatoes or peanuts. Anyway, this is potato-shaped,
- but you can see they've both got lots and lots and lots of craters on them, which shows they've
- been bombarded throughout the whole of their history. So things have come and hit them,
- and when things hit something else, bits shatter off. Most of the bits will fall back down, but
- some of them go off, wander off and some of them eventually fall to the Earth as meteorites. Now,
- these are made of very different… They're very different types. They're both made of stone,
- but you can see this one, the craters are quite sharp. This one, they're more blurred. It's
- because this is actually more like a ball of mud, frozen mud. It's got quite a lot of water in it,
- and in fact these very bright spots here are thought to be evaporites like we get
- maybe in a rock pool at the seaside. So although there's no water on the surface,
- the minerals it's made of have got a lot of water in it, and it's like a sort of clod of
- mud rather than a rock, whereas this one is a good solid rock. They tell us about different things.
- So now I'm going to teach you all how to classify meteorites, okay?
- The traditional classification is, we've got iron ones which are made of iron,
- stony ones made of stone, and stony irons which are a which are a mixture of stone
- and iron. Have you got it? Stones, irons and stony irons, can't go wrong.
- However, a more modern classification, the way we do it these days - which is much more interesting
- and tells us a lot more about the meteorites - is we think of them as being primitive or processed.
- Primitive here means they're undifferentiated. That means they've never been hot enough to melt
- so that they can separate out inside themselves. So these primitive ones have been very,
- very little-changed. They might have been altered a little bit by water. There might
- have been a little bit of thermal metamorphism, but they've never got hot enough to totally melt.
- We call these ones chondrites. I'll come back to what this odd word is in a minute.
- Then the other type are the processed ones. These are ones that we call achondrites because
- they haven't got any of the classic things that chondrites have. These have been heated. They've
- been melted. Some of them have been melted completely so that the metal has separated
- from the rock, just like on the earth, because we've got a core. Our earth is differentiated. We
- can learn different things that have been going on in the solar system from these different objects.
- Now, this is a classification of all the meteorites. Would you like me to go through
- it box by box? We'll start off with the CIs over at this end and work our way gradually
- across to these. It'll only take, oh, about five or six hours. Maybe we'll skate through that and
- we'll just stick with some of the primitive ones. So this is a hand specimen. It's a chunk about the
- size of my fist, and it's from an asteroid which has got some carbon in it, not a huge amount. It's
- a meteorite which is called Allende. Now, what we do with meteorites when we want to look at
- them with a microscope is, the first thing we do is we saw a bit of them. Now a geologist - which
- at heart is what I am, a geologist - they look at a rock. The first thing they do is whack it
- with a hammer, and then the next thing they do is they spit on it. Now a meteoriticist,
- we are not encouraged to do that. It's not done, and I'm sure I've never done it ever.
- So what we do here is, we would take a section and we would saw it, polish it until it was very thin,
- until it was so thin that you could actually shine light through it - and that's about
- 30 microns - or we might embed it in a chunk of resin and just polish the top.
- When we do that you can look in greater detail at the objects that are in these meteorites.
- These round things are what we call chondrules, and that's from a Greek word,
- chondros, which means droplet or little seed. That's what the first person to identify them
- or to see them in through a microscope. He looked at them and he thought that they
- were like droplets of a fiery rain, and that's a really, really great description because, well,
- we still don't entirely know how these formed, but they must involve melting in some way.
- Now what you can see on this one here, the hand specimen, you can see all these very irregular
- features including this bit on top which is not a bird dropping. It's a very irregular feature.
- These things are called CAIs. CAI for calcium and aluminium-rich inclusions. Guess what elements
- these inclusions are rich in. Yes, they've got lots of calcium and aluminium in them.
- If you think, minerals which have got these, the calcium and aluminium in them, they are really,
- really refractory. You can heat them to really high temperatures. So the lining of an oven for
- instance will be made of ceramics, these things which are what these what these mineral grains
- are. So what you've got here is something that's fluffy. It's not a regular shape,
- and it's made of calcium and aluminium-rich inclusions. These formed at a very high
- temperature, some of the highest temperatures, as the gas and dust of the protoplanetary disk
- was cooling and minerals were forming. These probably… I mean, there are several different
- minerals in there, but these were probably the first-formed things that go into meteorites.
- The second lot are these things called chondrules. You've got the same picture.
- You can see the rounded shape, and here's a close-up view of one. These are not made of
- calcium and aluminium. These are made of iron and magnesium and silicon, and you can see they're
- very rounded. So they've got a different shape, a different texture, different composition, but
- formed from the same cloud of gas and dust that formed the whole of the solar system. So, what is
- the process that has caused these two things, the CAIs and the chondrules, to be formed differently?
- Well, what's happening is you're getting this protoplanetary disk, the presolar nebula is
- cooling, and you're getting changes in turbulence, in the dust-to-gas ratio, in the amount of oxygen
- that may or may not be there. You can see this. There are at least eight, or there were nine,
- processes that have been thought to produce chondrules. My favourite quotation
- is from a very old colleague - who is actually in the audience at the moment,
- so I'd better say a dear and esteemed colleague rather than an old colleague - when she said,
- 'Chondrules are formed by the chondrule formation process, whatever that might be.' She is an
- international expert on chondrules and chondrule formation, and that's about as good as we can get.
- The chondrule formation process, whatever that might be. So it could be that bolts of lightning
- went through the dust and fused some of the dust grains together. It could be the shock wave from
- a supernova, or the shock wave from something else, or as our protoplanetary disk was travelling
- through the nebula and it was it was scooping up stuff. There's all sorts of different ways.
- Now, when we look at this grain, though, you can see it's got an extra bit on the side,
- so it must have been tumbling and it's accumulated other bits towards it. So it's helping to actually
- look at the processes that have been going on as the star, the sun, was forming. Now this is very
- technical, but don't worry too much. I'm not going to go through all the radioactive decay equations
- stage by stage, promise. All I'm going to say is that there are some isotopes that are
- radioactive and they decay. Uranium decays to lead. I think we're quite familiar with that,
- but there are lots and lots and lots of decay systems, lots and lots of different
- isotopes which decay. So we've got ones that decay over periods of billions of years, or ones
- which decay over thousands or a million years, and depending on the decay system you choose,
- you can learn different things. So what actually happens is you have a parent
- which decays to a daughter. Now, if you've got uranium and it's decaying to lead,
- what actually happens is sometimes the remaining uranium stays in one bit and the daughter isotope,
- the lead, likes to go into another bit, or aluminium decaying to magnesium. You've got one
- bit going into another bit. So you can actually start looking at the ages of formation things. So
- this is where we go back to the chondrules and the CAIs. We're using a very short-lived system. We
- don't need to know that too much. So if you've got something and you've got aluminium, which decays
- to magnesium, and if you've got something and you can find the particular type of magnesium in that
- mineral that has come from… That magnesium's come from the decay of the aluminium. You can say that
- that mineral must have been around. It must have been forming when the aluminium was still present
- to be decaying to magnesium. Because the aluminium has such a short
- half-life it's gone after a few tens of short lives, hundreds of half-lives. So you can say,
- oh, right, actually this particular mineral has got that brand of magnesium in so it must have
- been formed very early on. This mineral hasn't got that brand of magnesium in. It can't have been
- formed until after all the aluminium was gone. So this is what we're doing here. We're looking and
- we can say right, actually - and this is a very simplistic picture. It's more complicated, but
- simplistically - these that have got the aluminium in, they also have some minerals that have got…
- They've got these minerals with aluminium in. So you can look for those aluminium-rich minerals and
- look to see if they've got any magnesium in, and if they've got the magnesium in then yes,
- they were formed really, really early on. Now, another aside. I take every opportunity
- to get astronomers because it's fun. If you ask an astronomer, 'How old is the solar system?
- they might say 5 billion years, 4.5 billion years, something like that. We can say
- that the solar system is 4567.2 million plus or minus 0.6 million years old. All right?
- That is very precise. 4567.2 million plus or minus 0.6 million years. That is precise and accurate,
- as we all know the difference. The age of chondrules is this, 4564.7 million years.
- So the difference between these two phases that you find in intimate contact within a meteorite,
- the age differs by 2.5 million years. 'What's 2.5 million years between planetary scientists?' you
- might say. Well, it's actually quite a lot to keep things separated in a very active and turbulent
- solar nebula, and so that's why we're still trying to explore this and find out how this
- has actually happened. This is something that's very important to understand for nebula evolution.
- Okay. So I skated over uranium lead and radioactive dating. Now let's
- delve much more deeply into nucleosynthetic processes. That's a good one, isn't it?
- So, nucleosynthesis. What's nucleosynthesis? Well, it's when things happen with elements,
- when you've got neutrons around. Some elements can absorb a neutron slowly,
- and this happens when you've not got very many of them. What happens is, an isotope captures a
- neutron, and it sits there and says, 'I'm waiting for another one. Oh, but there aren't much. I'm
- going to decay,' and so that's what happens. It decays before it can capture a second neutron
- where you've got a lot of neutrons you've got this. That's S for slow,
- R for rapid. We do like to keep things simple. So here you've got a lot of neutrons. So you've got a
- nucleus atom. It captures a neutron, and then before anything else can happen to it,
- it captures another one and maybe another one. So you've got different types of nucleosynthesis
- process processes going on, and they leave their signature in the elements.
- They leave them very particularly in presolar grains. So when we look at stars, a star isn't
- a thing that's there and it doesn't change. A star evolves in the same way as we evolve. So
- this diagram here is a complicated picture of what happens to a star. It can start off big,
- burn fast, die, or it can become out somewhere along here. We've got a lifetime of about 10
- billion years, and we're about halfway through it. This is us. What's going to happen to us is,
- we're burning hydrogen - well, the sun's burning hydrogen - into helium. Then it'll burn helium,
- and then it'll puff up enormously into a red giant, and then it'll burn all its fuel
- and it'll shrivel down into a white dwarf and it'll die. It's not big enough to do something
- dramatic like exploding as a supernova. So what we can do is, we find products
- of these processes that have gone on in other stars. We find them in meteorites.
- Sorry, this is a very busy slide, but I tried to reduce the number of slides I've got by putting
- more on each slide, which is very bad. So, presolar grains. They're a minor constituent
- of chondrites, up to two per cent max. They were recognised on the basis of their unusual noble gas
- isotopic compositions. Xenon has got what, nine stable isotopes. It's got a ridiculous number
- of isotopes. Sometimes one particular isotope is enhanced over another isotope. So in this one here
- the signature, if you've got some gas, some xenon and you look at it and you say, 'Oh, it's got a
- lot of xenon 128 and a lot of xenon 132 relative to xenon 130, but hardly any 129 or 131,' that
- is caused by S process xenon. S process xenon is produced in stars which are going through helium
- burning and various other processes, and they also have very unusual carbon and nitrogen in them.
- So this is a picture of carbon and nitrogen, and this, at last, some of my data. This is
- what I do for a hobby. I burn rocks and when I burn the rocks, the meteorites, I look at
- the carbon dioxide that comes off and I can say, 'Oh, if carbon dioxide has come off at about 1000
- degrees C, so I've heated my sample up to 1000 and it's got carbon which has got a very low… It's
- got a high delta-13, so you don't need to worry about that, but it would be plotting down here.'
- So it's something which has probably come from an AGB star, an asymptotic giant branch star,
- a big star. It's not come from the sun. These are examples of these types of
- materials. Silicon carbide. Graphite. Aluminium oxide. I've put for dramatic purposes diamonds,
- emeralds and rubies. Emeralds and rubies are just aluminium oxide by any other name.
- So the other type of material that we've got are these nanodiamonds. There are
- only three nanometres in size, and they're produced… They've got xenon associated them,
- which is got a lot of the light isotopes down here and a lot of the heavy isotopes. There is no
- known astrophysical process which can produce a pattern like this. Now astronomers,
- when they can't explain an astrophysical process, they either say it's a black
- hole or it's a supernova. One or the other. Black hole or supernova. Here we've gone for
- supernova. So we've produced a huge number of neutrons in the explosion of the supernova and
- they've produced little diamonds. Now again, it's not terribly certain that this is the
- right answer for the diamonds. There's some thought that they might be produced
- somewhere else, but we don't really know. Now then, I'm going to have to move quickly.
- Where are we? Organic interstellar material. Right. So I've talked about the non-organic stuff,
- the silicon carbide and things like that, but we've got in some meteorites… and this is a
- picture of a meteorite called Murchison which is very rich in carbon. It's got about eight per cent
- carbon in, which is buckets for a meteorite. Most of that carbon is a sort of entangled
- mass of sort of gunge, really. It's a mixture of all sorts of different carbonaceous components,
- some of which have got a lot of… Oops, sorry. Some of which have got a lot of deuterium in them,
- and again these heavier isotopes of carbon and nitrogen. What's thought is happening is,
- in the interstellar medium, in things like the dark molecular cloud where you've got grains
- of silicate and they're coated with ice, what's happening is they're being bombarded by radiation.
- It might be UV radiation, but it might not necessarily get into the molecular clouds,
- or cosmic rays, and what's actually happening is you get a whole a whole suite of reactions
- called ion molecule reactions, which leave the solid stuff behind to be enriched in
- these isotopes. So what we can actually do is, we can use this as a tracer for astrochemistry
- and look at the evolution of molecular clouds when we look in meteorites for these things,
- which is quite interesting. Now, origin of life. Some asteroids are rich in water and
- organic molecules. This is asteroid Ryugu, which was the target of Hayabusa 2, and this is Bennu,
- which is the target of OSIRIS-REx. This is comet 67P/Churyumov-Gerasimenko, which was the target of
- the Rosetta mission. Now this has brought some material back, and it seems to be sort of… One
- of my colleagues, Dr Verkhovsky, has analysed some of the grains from Ryugu and he has found
- that they're medium enriched in carbon, but they seem to have quite a lot of water in them.
- This is my bit. Can you see? Six or seven little black specks there. Yes. They're
- mine. Mine, which I've been looking at the reflectance spectrum from, and then I'll burn
- them. Okay. So they're sitting there, and so we've had these from this particular asteroid. We'll be
- getting some back from Bennu in September. They arrived back in September. The Open University is
- one of three laboratories outside the NASA system which are getting these materials. We're one,
- the Natural History Museum is one, and I think there's one in Switzerland. So I think we're
- the three European partners which are going to get some of the material from Bennu. Now
- it's possible… These both look as if they're like the types of asteroid that Murchison came from.
- We've got a handful, about five meteorites, that aren't like Murchison, that aren't like anything
- else, and possibly come from a comet. Now, the Rosetta mission
- produced a… There was an instrument called Ptolemy which was built at the Open University,
- and it produced a spectrum you can see here. This is the molecular mass of some of the samples that
- came from… Some of the data that came from the mass spectrometer on board Ptolemy, on the Philae
- lander. Some of these are signals of alkanes, alcohols, things like that. The types of material,
- the types of molecules, which make up the building blocks of life. So it could be that when the earth
- first formed it was bombarded by this sort of material, so the water came from… A portion of
- it came from extraterrestrial samples. Right. I'm going to have to go really fast now. Sorry.
- Processed meteorites. These are the opposite of the primitive ones. Some of them,
- like the ones that come from Vesta, which is like this, they're the solidified remnants of the solar
- system's earliest magmatic activity. So we've got really old volcanoes on some of these asteroids.
- Iron meteorites. These are the ones that have actually completely separated out. So if you think
- about how stainless steel is made, or how steel is made, you take the iron ore, you heat it up with
- a catalyst, and what happens is all the iron goes to the bottom of the furnace and you get a scummy
- bit on top, the slag. Now, the iron in the core of the earth, that's been through the same sort of
- process. So the core of the earth is the pure iron with some nickel and other bits and pieces in it,
- and the bits that we're standing on, we're the slag. So we're the slag on the crust of the earth.
- I won't go into the Widmanstatten pattern. This is the closest we can get to the core of the earth,
- because of course we can't dig down that far. So going back to our radiogenic nuclides, using
- different half-lives we can look and see when an asteroid has differentiated, when the metal core
- is produced. We've got the mantle which is rich in a mineral called olivine, and you've got the crust
- which is rich in a mineral called plagioclase. You can look at the time scales of when that happened
- and when that happened by looking at these different systems. We can bring up this diagram
- again. We've got the CAIs here, the chondrules. We've got the chondrite formation where they all
- came together to make the solid bodies. We've got the Earth forming here and then differentiating,
- and the moon forming, and it all happened in a very, very short period of time. Really rapidly.
- We've got meteorites from the moon. I'm going to try and finish by 7:45. So we've
- got some meteorites from the moon. We know they're from the moon because we can compare them with the
- Apollo samples. We've got meteorites from Mars. How do we know they're from Mars? We haven't got
- any samples that have been brought directly back from Mars. However, this is a meteorite which was
- collected in Antarctica in 1979, and it's got these pockets of glass in. When you take out,
- dig out a pocket of that glass and melt it, gas comes out, and the composition of that gas is
- identical to the composition of Mars's atmosphere. Now this was taking place in 1984 when people were
- just recognising that we got meteorites from Mars. That's mine. That's my data point. So we analysed
- this. This is when we were still over in Cambridge actually, before we came to the Open University.
- That showed you've got the identical composition, and the only way that you could get that gas
- in those glass clasts is, those clasts had to be molten. So it's probably when something hit the
- surface of Mars, blasted material off, and in that instant some of the atmosphere was
- trapped. Now, knowing that we've got meteorites from Mars, we can then go on and say, 'Let's
- look at them and see what we can learn about Mars from these meteorites.' I hope my good
- friend Everett is listening online. He said he was going to be. Here you are, Ev. This is our
- meteorite. This is Allan Hills 84001. Everett Gibson and his colleagues produced an image in
- 1996 where they showed this, which is a couple of hundred nanometres… Sorry, micrometres long.
- What they said was that it's possible that this is actually a fossilised bacterium, and the substrate
- is these, which are rosettes of carbonates, which are produced in warmish sparkling water.
- So they had… It was a long detective story, a long chain of evidence, and not everybody believes that
- this is actually a fossilised bacterium. What it did was it really literally and figuratively put
- a rocket up the Mars program and now, exploring Mars like there's no tomorrow. So at the moment
- Perseverance is at Jezero Crater. I'm sorry. I've got some more telescope images, or at least from
- camera images. Just look at that. That puts me in mind of Brimham Rocks in Yorkshire. Just look
- at that. Look at the way it's balanced. Isn't that amazing? It's just amazing! I can't get
- over these pictures. They're so gorgeous. It's just like, wow. They could be seals basking
- but they're not, obv. Anyway, so there's a Mars sample return mission coming back in about 2033
- when I'll be 75, God willing. If I'm still here I'll be in the lab, pestering the head of school.
- This here is about 20 centimetres long. This is one of the samples they've produced… A
- depot is what they're calling it, a depot of ten samples. Now, to me, a depot is you've got ten
- samples all gathered together. Now, these are between 5 metres and 15 metres apart so that
- they can be readily collected. I don't call that a depot. I call that a string. Anyway,
- so these are the things. These are cores which another mission will go to collect.
- Where do they come from? Where do we get them? We get them from deserts. Look. Antarctica.
- Desert. Ice. Meteorite. Dead easy. Sometimes, though, they come without us knowing about
- it. This is a fireball from the Winchcombe meteorite which fell a couple of years ago now,
- which is beautiful. This is another beautiful thing. Isn't that beautiful? Isn't that beautiful?
- To you, it might look like a barbecue briquette, but to me it's got the secrets of the solar system
- locked up in it. Mr and Mrs Wilcock and their daughter woke up on the morning of the 29th and
- found that somebody had been throwing things at their drive. If you if you look online you can
- see through the Natural History Museum, some people went and they've dug up the drive and
- they've taken all this away, and it's now going to be on display in the Natural History Museum. My
- colleague, the one who doesn't know how chondrules are formed, she went with a toothbrush on her
- knees to get all the bits from that drive. Isn't that dedication? Or stupidity. Who knows? Anyway.
- Right, where are we? So this is my almost-last slide. What can you learn from meteorites?
- Well, the different populations and ages. I didn't go into the age of the presolar grains,
- but some of them are maybe 2 billion years older than actually our solar system.
- We can learn about molecular cloud evolution. I've talked about that with the organic molecules. We
- can learn about stellar evolution, the presolar grains, the hydrogen burning, the helium burning
- or the supernova. The CAIs and the chondrules tell us how our protoplanetary disk has evolved,
- which is not just the origin and evolution of the solar system, but the origin and evolution
- of planetary systems and exoplanets, which is fantastic. We've also got planetary melting from
- the achondrites, the core formation from the iron meteorites. We've got the formation and evolution
- of the moon, the formation and evolution of Mars, and the history and fate of water and
- possibly life on Mars. We've got the origin of life itself all from those little poxy rocks.
- I hope I've persuaded you that we can do astronomy by microscope.
- I've just got two final slides. I want to thank my friends and colleagues, especially my family,
- especially my husband Ian. Caroline, this is for you. We went to Houston as colleagues
- and came back as lovers. Caroline really hates that. No, no.
- Okay. So, that's my family. I would also like to thank the institutions that have sheltered me,
- encouraged me, helped me, especially the ones that gave me money - that's these here - and also these
- missions. OSIRIS-REx is going to be fantastic when the stuff comes back in September. This,
- when it comes back next century. I owe such a lot to the Royal Society for allowing me to give this
- lecture, but I owe so much to the Open University. The Open University is just an amazing place
- to work because of its mission to be open to peoples, places, methods and ideas, which is just
- a dream, that we can help to educate people who haven't had the opportunity. I love being part
- of that. It's really, really important for me to say that to you. Thank you very much indeed.
- Well, thank you very much, Monica. Unfortunately, my notes on what I'm
- supposed to do next have been scribbled all over with comments from your talk.
- Oh, sorry.
- I know that people out there, if you've got questions, you want to send them by slido.com
- and enter… It doesn't say up there. Enter the code hashtag F6323. For questions in the hall
- here there is a microphone that will roll around. We've probably got about five minutes max. So
- a question from outside. Do you have a favourite meteorite and why?
- Oh gosh. Well, it depends what I'm working on. Sometimes my
- favourite meteorite is Allan Hills 84001, the one from Mars with the
- clusters of carbonates in. Sometimes it's Winchcombe, the one that fell recently.
- So, I'm really sorry. No, I haven't got a favourite meteorite. I love them all.
- Here's a great question how would you convince an eight-year-old to follow a career in
- planetary science? Which are the exciting and rewarding bits, and what are the challenges?
- Cool, right. Well, hold on a bit because my grandson's eight in a few weeks' time,
- and I'll ask him. I think really for more and more people to go out and talk, talk to schools,
- go and talk to Scouts and really go out, because if the younger children can get the interest and
- carry it on through those difficult teenage years, and then get on to university and carry
- on… I think people like Brian Cox have done a fantastic job of enthusing people, and try and
- make complex ideas understandable, and give people an idea of the excitement of things to come.
- Question in the second row.
- Thank you very much for those interesting insights. Would you compare what it's like
- for you waiting until the stuff arrives and for some of our colleagues who go out to fetch it?
- Ah, interesting because I've also been out to fetch it, and that's great. You go out
- in the field, you go to Antarctica and you see some of the rocks. I remember when I was there.
- the guy who was leading the expeditions, Professor Cassidy, he just looked at us. There were four
- newbs there, four newbies who'd never been before, and he just said, 'You're like fish in
- a feeding frenzy.' We were zapping backwards and forwards trying to pick up all these meteorites.
- It was amazing. You then have to let them go. They go to a curation facility and they're not
- your meteorites. It's not easy to compare what it's like waiting for a sample to come back,
- because things happen all the time. I mean, we're waiting for the samples to come back
- from Ryugu and from OSIRIS-REx, and Winchcombe falls right in the middle of lockdown. Oh,
- I know. Let's all go over to Cheltenham, and it's lockdown. Yes. Health and safety
- forms in the universities. I don't know. I can't answer that question, really. Sorry.
- We can probably squeeze in one more in the second row.
- Thanks. Monica, you explained about how we could tell those meteorites were from Mars
- because of the glass and the composition of different elements that came out of
- the gas that was in the glass. How do we know what Mars's atmosphere is made from?
- Oh, because this was going on in 1983, 1984, the acceptance that these came from Mars. There was
- the Viking orbiters and landers in 1977 which measured the composition of Mars,
- and they found out… Mariner 9 had also found that the atmosphere was mainly carbon dioxide,
- and it had a very, very particular carbon-12 to carbon-13 ratio, and that was mimicked,
- the relative abundances of the different molecules and their isotopic composition.
- Any last comments? Questions? Otherwise, I slide across here, because the real thing of
- the evening, apart from thanking Monica for an astonishing presentation that's taken us
- back 4567-point-something years - I love that - but really it's a great honour on behalf of
- the Royal Society to present Professor Monica Grady with the 2022 Michael Faraday Prize for
- her expertise in communicating science. I think we saw that tonight. Congratulations.
- Fortunately, I did not scribble across the thing that says,
- 'Remember to present Monica with the scroll and the medal.' Congratulations.
- Thank you very much indeed. Thank you.
It makes sense to use a telescope to look up at the heavens, but what can we learn from using a microscope instead?
Meteorites are natural objects that survive their fall to Earth from space. Almost all are fragments of ancient asteroids, formed at the birth of the Solar System, approx 4567 million years ago. Meteorites carry within them a record of the history of the solar system. Tiny grains within meteorites have come from other stars, giving information about the stellar neighbourhood in which the Sun was born. And some meteorites contain organic compounds – materials which might have helped life on Earth to get started!
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