Instant Genius - Meteorites, with Dr Tim Gregory

Episode Date: July 3, 2022

Cosmochemist Dr Tim Gregory tells us about the exciting science of space rocks. Once you’ve mastered the basics with Instant Genius, dive deeper with Instant Genius Extra, where you’ll find longer, richer discussions about the most exciting ideas in the world of science and technology. Only available on Apple Podcasts. Produced by the team behind BBC Science Focus Magazine. Visit our website: sciencefocus.com Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

You said this place was steps from the water. We just haven't found the steps yet. How much did we save? Enough. Enough to get lost. Or you could book a stay with Hilton. Welcome to your ocean front room. Just steps from the water.

The Hilton sale is on now. Book on Hilton.com or the Hilton app and save up to 20% to get the stay you expected. When you want savings, not surprises. It matters where you stay. Hilton, for the stay. It's peak pollination season, and my business is scaling fast. To keep the nectar flowing, I need a phone plan with top priority data speed.

That's why I chose GoogleFi Wireless. My connections stay strong even when the hive is buzzing. Plus, unlimited plans started $35 a month. Now, that's a deal that doesn't stay. Explore Google Fi Wireless plans today. Plus taxes and government fees. GoogleFi Wireless is not subject to data traffic deprioritization during times of high network usage. No one goes to Hank's for his spreadsheets.

They go for a darn good pizza. Lately, though, the shop's been quiet. So Hank decides to bring back the $1 slice. He asks Copilot in Microsoft Excel to look at his sales and costs. Help him see if he can afford it. Co-pilot shows Hank where the money's going and which little extras make the dollar slice work. Now, Hanks has a line out the door.

Hank makes the pizza. Co-Pilot handles the spreadsheets. Learn more at M365Copilot.com slash work. This podcast is sponsored by name, audio and focal. Streaming has made music more accessible than ever, but true listening is about more than ease. It's about quality. British audio experts name audio,

alongside French acoustic specialist focal, combine handcrafted tradition with cutting-edge innovation and high-end materials, delivering digital precision with analogue warmth. So you can experience exceptional sound at home. Music just as the artist intended. Visit name audio.com to learn more. Hello and welcome to Instant Genius, a bite-sized master class in podcast form. I'm Jason Goodyear, commissioning editor at BBC Science Focus magazine.

In this episode, I talk to Tim Gregory, cosmochemist and author of the book Meteorites. About meteorites. So we're talking about all things that are space rocks, and this is very, very confusing. There are lots of different terms, and this is something that trips people a lot. So I think the best way to start is for us to go through a series of definitions. So what is a meteorite? What is a meteoroid? What is a meteor?

What is an asteroid? And what is a comet? Oh gosh, we've got all these words. I guess it wouldn't be science if there wasn't a load of jargon that came along with it. But to try and simplify things. So we have meteorids. They are loosely defined as objects in space. and so they encompass asteroids and comets.

And asteroids and comets, they're in orbit around the sun along with the planets. And we mostly find the asteroids between Mars and Jupiter in the asteroid belt, although there are quite a few in the outer solar system as well. Comets, they generally follow much more elliptical orbits. They don't orbit in nice circles like the planets and the asteroids do. They orbit in ellipses. They're sometimes really close to the sun and sometimes fire. away. Now, I guess one of the strange things about asteroids and comets is that there's no really

clear distinction between these two types of bodies. It's one of the things that we've learned over the last couple of decades about these objects is that they're not really that distinct from each other. Rather than having comets and asteroids as two separate classes, they sort of merge into each other. You get some asteroids that are very comet-like and some comets that are very asteroid-like. We used to have this view where comets were these dirty snowballs that were incredibly ice-rich and rich in volatile elements like nitrogen-ices and things like that. But we actually find asteroids that are like that as well. And so the distinction between comets and asteroids is blurred, but they all fall into this great category of meteorids. Now, meteors,

they are pieces of debris that fall to the Earth. And as they fall through the atmosphere, they get incredibly hot, and so they start to glow incandescence. And so the comets and the asteroids, they fall together in this grand category of meteoroid's objects in space. Now, meteors, that's the light phenomena that's associated with debris falling from outer space to the Earth's surface. And as this debris, which is generally quite rocky, falls through the atmosphere, it's travelling incredibly quickly.

You know, we're talking about, you know, tens of miles per second. of velocities as they fall through the atmosphere. And that generates quite a lot of heat. And that heat causes them to glow. And that light that we see, they are the meteors. And it's where the name Meteor shower comes from. These are events in the night sky where you get more than you you normally get on a normal night. You get them all the time.

But meteor showers, you get a higher rate than normal. And another name for meteors are shooting stars. They're exactly the same thing. Shooting stars are meteors. Now, because they're travelling so fast and there's so much heat generated, most of them get destroyed before they reach the Earth's surface, they just sort of fizzle out into dust and never quite make it. But the lucky few that do make it to the Earth's surface, these are the meteorites.

And so just to sum up, we've got meteorites, their objects in space, meteoros, that's the light that's associated with these rocky debris falling through the atmosphere, and meteorites are the bits that land. I was reading your book earlier, and it called, Funnily Enough Meteorite, you tracked through the fascinating history. So they've always sort of been prized by human beings. And there are several really famous meteorites discovered throughout the ages that you mentioned. And could you just talk us through a couple of those, a couple of your favorites? Oh, gosh, there are so many.

You know, one of the things that I learned while researching the topics that, ultimately made it into meteorite my book, was the history of meteoritics is actually just about as fascinating as the science as the stones themselves. There's a really famous example of ancient people encountering meteoritic material.

So King Tutankamun, who is perhaps one of the most famous ancient people to ever have lived, in his linen that his mummified body was wrapped in when his tomb was discovered. In his linen was this beautiful, handsome dagger. This dagger was a dagger was about a foot long and it was sheathed in this beautiful, beautiful sheath made of gold

with a sort of mother-of-pearl hilt on it. And the blade from which that dagger was forged was actually made from an iron meteorite. If you look at the chemistry of the dagger that belonged to King Tutankhamun, the blade of that dagger, it actually matches perfectly the chemistry of iron meteorites. Now, this iron blade predates the Iron Age by thousands of years, and so a natural question for archaeologists was, where in earth did the ancient Egyptians get the iron to make King Tutankham Coon's dagger from? And it turns out that the iron came from the sky. It fell to the earth as a meteorite. And the ancient Egyptians used it to make this sacred object. And so, you know, we've been encountering meteorites for thousands of years and probably

way into prehistory as well. And it's really only the last few hundred years that we've been studying them with a sort of scientific perspective. In fact, it was only in the early 1800s that The modern minds of science really accepted that meteorites were real and that they did in fact come from space. And so it's a fairly new science. Yeah, that is just an amazing thing to think of. And another thing, like now we're in the state of knowledge that we are in. So considering, I mean, God, no, I mean, do we even know how many of these are hurtling through space? Thankfully, there are agencies around the world that track asteroids as the orbit around the sun.

But the real answer is that they're countless in number because there's no real lower limit to how big one of these objects in space can get. We have a pretty good idea of where all the big ones are and where all the medium ones are. But it depends how small you go. There are millions of these things orbiting the sun. And in fact, it's tens of thousands of tons of extraterrestrial rock fall to the Earth's surface every year, which is just a number that is kind of beyond comprehension, really. that amount of material falling from the sky. So say I want to find one, how do we go about finding them? You know, obviously people have found them over the years and studied them.

How do you do that? And how do you know this is a bit of rock, that's a meteorite? That's a really good question. So it sounds like an alarming number, 40,000 tonnes or so of extraterrestrial rock falling to the Earth's surface every year. But the thing about meteorites is that they fall roughly evenly. all over the surface of the planet. There's a slight tendency towards the equator, but they fall roughly evenly,

which means that most of the material that falls from space actually ends up in the oceans because Earth is about 70% covered in water. So most of it's completely lost. And as for the 30% or so of the Earth's surface that isn't covered in water, it's almost entirely uninhabited. We humans, although it feels like we have entire planetary domination,

we actually only occupy a very, very tiny fraction of the Earth's surface. And so most meteorites fall unnoticed, and they just simply weather and become unrecognizable parts of the Earth. However, there are places on the Earth, which are really, really good places to look for meteorites. And the best place is actually Antarctica. About two-thirds of all-known meteorites were collected in Antarctica. There are a couple of reasons why Antarctica is so good for looking for meteorites.

And one of them is simply that by the time meteorites have passed through the Earth's atmosphere and undergone all that heating, they're generally quite dark when they fall. And so they stand out atop the ice. They just stick out like a sore thumb. And another thing about Antarctica is on the ice sheet, if you find a rock sat on top of the ice sheet, it can't really have come from anywhere else but the sky. It's not like a mountainous region. There are no rivers or cliffs or anything where rocks can fall down.

If you find a rock on top of the ice, it probably came from the sky. But the other cool thing about Antarctica is that over thousands of years, the Antarctic ice sheet flows. If you watched it in fast motion, if you sped time up, you'd see the ice flowing a bit like a river. And you get these particular zones in Antarctica where the ice flows together and then gets blasted away by polar winds. And the ice, as it flows, it carries meteorites like a natural conveyor belt and

dumps them in these places called accumulation zones. And every year people go through these accumulation zones and hunt meteorites there. And we found tens of thousands over the last few decades. So that's the best place to go. But say, you know, we're UK based. Say I want it to go on a meteorite hunt. Is that a possibility or is, am I just clutching its straws? So here in the UK, where I guess fortunate enough to live in a place where it, firstly, it rains quite a lot. And secondly, it's very green. You know, there are lots of fields, lots of forests, that kind of thing.

So really, you know, I wouldn't personally recommend going out with the specific aim of looking for a meteorite because chances are you would never find one. Although it has been done. People do occasionally go out with metal detectors, and once or twice people have found meteorites doing that, but you're really looking for a needle in a thousand hair stacks. The only really reliable way of finding a meteorite in somewhere like the UK is to very patiently wait for one.

And if you see a particularly bright one and you happen to see where it lands, it's not unheard of of people finding the debris from those events. In fact, there was one at the beginning of last year in Winchcombe where a really bright shooting star was captured on CCTV cameras and dedicated hunters went out and found pieces of it. so it does happen. That's amazing. So say if I do see one of these, you know, shooting stars, these meteors near me and I want to go look for it, what do I look for? So when meteorites have fallen through the atmosphere, they're generally quite dark. And so, you know, if you do fancy going out to look for a fallen shooting star, you're

looking for dark rocks on the ground. That's the telltale sign. It's one of the only ways, actually, that you can often tell that it's a meteor. that you're looking at until you sort of take it into a laboratory and get a specialist eye. Most meteorites, when they fall, they have this. It almost looks like a varnish on the exterior of the stone that we call a fusion crust. And this varnish is the once molten surface of the stone that quickly quenches shortly before landing. And it's thought of this lovely black varnish that you get surrounding the stone called a fusion crust.

So that's one of the telltale signs that you've just found a meteorite. That's amazing. I do, if I'm lucky enough to go out and see a shooting star falling and I find one, would I be quids then? So some meteorites are incredibly valuable actually. Most of them are not that expensive. You can actually go on eBay and buy meteorites for just a couple of quid often. In fact, funnily enough, the meteorite that I studied for my PhD at the University of Bristol, I actually bought that off eBay. No way. Yeah, I did. I bought it from eBay, which apparently raised quite a lot.

a few eyebrows in the procurement department at the university when we tried to get the expenses back. So I bought this. It was about an apple-sized meteorite for a few hundred quid off eBay, and it ended up being the subject of my PhD. And I actually withheld the review on eBay until I'd finished my PhD and verified the age of the meteorite. And it turned out to be 4.6 billion years old, which is older than the Earth itself, which I guess definitively proved it's meteoritic origin, so that particular set, I got a five-star rating from me. But anybody can go on to eBay and buy a meteorite. They're not that expensive, but there are different types of meteorites, and some types of

meteorites are incredibly expensive, and I guess probably the most expensive meteorites are the Martian meteorites, and as the name suggests, these come from the planet Mars. And so you can imagine that scientifically they're incredibly valuable because they're the only way that we can get pieces of the red planet in laboratories here on the Earth to learn about it. And secondly, they're prized among collectors as well for obvious reasons. There's something quite exciting and captivating about a rock that comes from Mars. And so they're probably the most expensive meteorites. That's like really fascinating.

So my next question, obvious question that everyone's going to want to answer this, how does a piece of Martian rock end up on Earth? Oh, it's a great question. So all meteorites pretty much start life the same way. They exist on a planetary body somewhere else in the solar system. Usually an asteroid, sometimes Mars and sometimes the moon. And the first thing that has to happen for it to become a meteorite is it has to be ejected from its parent body. And they're ejected by impact on the surface. And this is beautifully demonstrated by our closest celestial neighbor, the moon. Even with the naked eye, you can look up at the surface. You can look up at the surface. the moon and you can you can you can you can see the impact creators on the surface of it it's absolutely covered in these impact craters and these impact creators therefore when impactors strike the surface of the moon at hypersonic velocities and the amount of energy that's released we're talking about you know thousands of nuclear weapons worth of energy released in a couple of seconds in many of these impact events and that amount of energy ejects rock off the surface of these

bodies and into space and most of this debris actually falls into the sun, but some of it makes it to the earth, and some of that material becomes meteorites. And so it's exactly the same with Mars. If we look on the surface of Mars, it's covered in impact craters, and it's these impact craters that are the source of the Martian meteorites. That's mind-blane to think they make their all the way here to Earth. It's, wow. So how do we know they come from Mars? Another good question. So, So first of all, we have the lunar meteorites, and they're called the lunar meteorites because they come from the moon.

And we know that they come from the moon because we have Apollo rocks, the Apollo astronauts brought pieces of the moon back to the earth, and we can look at these meteorites side by side with the Apollo rocks, and they're very, very similar. So we're pretty sure that the lunar meteorites come from the moon. With the Martian meteorites, we're not so lucky because, of course, we've never been there ourselves. We've only ever sent robots to the surface of Mars. A good question is how do we know that the Martian meteorites come from Mars?

Well, it turns out that in these Martian meteorites, there are tiny little bubbles of gas, and if you very, very carefully measure the chemistry and the isotope composition of the gas that's trapped in these bubbles, well, first of all, it's unlike anything that you would ever measure on the earth. It really is truly alien, this gas. But it is just like the gas that was measured elsewhere. Specifically, the chemistry of the bubbles trapped inside the Martian meteorite is exactly the same as the composition of the Martian atmosphere measured by the rovers that land on the surface of the red planet.

And so this gas, this chemical and isotopic fingerprint that we find inside the Martian meteorites is a perfect match for the Martian atmosphere, which I guess is indisputable evidence that these meteorites actually originate from Mars, which is just amazing to think that we actually have peace. of the red planet here on the Earth already that fell as meteorites. That's fantastic. So you mentioned then the one that you were studying was incredibly old. So how do we date things that are that old? Yes. My particular area of research during my PhD was the chronology of the early solar system, the evolution and one of the cornerstones of looking at the evolution

and the formation of the early solar system is by dating meteorites. And we date meteorites using radioactive decay. So some elements are naturally radioactive. And as they undergo radioactive decay, they become new elements. And so a really good example of a radioactive element is uranium. Over time, uranium naturally radioactively decays, and it ultimately ends up turning into lead. And so if you measure the amount of radioactive decay that the uranium and a meteorite

has undergone since it formed by measuring the amount of uranium that's decayed and the amount of lead that has grown into the meteorite throughout that decay. It's actually a relatively simple calculation to date the meteorite itself. And it's one of the really sort of distinctive things about meteorites of their antiquity. They're about 4.6 billion years old, which predates planet Earth. In fact, it predates all of the planets. They were among the first rocket material to form right at the beginning of the solar system's history. And a lot of what we understand about the formation of not just our solar system, but solar systems in general come from the chronology of meteorites and dating them. So they're so old, as you say, older than the planets

in the solar system. So what role did they play in the formation of planets and things like that? So once upon a time, our solar system, it didn't look anything like it looks today. It used to exist in interstellar space as a giant cloud of gas and dust called a nebula. And you've probably seen pictures of nebula. They're these beautiful, beautiful structures that sort of span the distance between the stars, these giant clouds that hang in interstellar space. The Orion Nebula is a really lovely example of this. And these nebulae that they're incredibly thin and wispy,

but every now and again, tiny pockets of these nebula begin to collapse in on themselves gravitationally. And at the center of this gravitational collapse, you eventually attain temperatures and pressures high enough to ignite fusion reactions, and a star is born. This is how our sun was formed. And around these early stars,

around these young stars that form in these collapsing nebula, some of the gas goes into orbit around these early stars, and eventually this gas begins to condense and turn into minute moats of rocky dust. And this is what happened in our solar system. So the sun formed and gas went into orbit around our young sun and eventually condensed into tiny motes of rocky dust. And it's these moats of rocky dust from which the asteroids were formed.

And it's these moats of rocky dust that ultimately the planets are formed as well. And so the meteorites, they preserve this earliest history of the solar. solar system, by preserving these moats of rocky dust, they record the sort of the earliest history of the solar system, this process from gasey nebula to rock and ultimately, I guess, the building blocks of planets. So that's why by studying these meteorites, we can learn more about the evolution of the solar system? Absolutely. One of the cornerstones of natural sciences is understanding the history of the Earth. And, you know, the best way of understanding the history of the Earth is by using the rocks. But there is a limit to how far back in time

the rocks of the Earth can take us to get back into the prehistory, the prequel, if you like, to Earth's history, to its planetary history. You need meteorites because they're the only surviving bits of rock from that period of the solar system's history. We can't talk about space rocks without talking about the idea of panspermia. the idea that actually life didn't originate on Earth, but it came here on a space frog. Okay, so I don't want anybody listening to this to go away, thinking that there has been evidence of life found inside any meteorite

that's ever been discovered because it hasn't. There's never been any evidence for life discovered in a meteorite. But there is a rare group of meteorites called the carbonaceous chondrites, and as the name suggests, the carbonaceous chondrites are, or they can be incredibly rich in the element carbon. And some of these carbonaceous chondrites contain quite complex organic chemistry, carbon-based chemistry, so things like carboxylic acids and aromatic hydrocarbons. And some of them even contain amino acids, which kind of makes people, I don't know,

it makes their eyes light up when they hear that because amino acids, they're the molecular building blocks of proteins and life. on Earth is made of protein. Amino acids aptly named the molecules of life, because they're often called the building blocks of life amino acids, and we find them inside meteorites, which raises the really intriguing possibility of a link between life on Earth and meteorites. And it is possible that the material from which life on Earth originated from was delivered to the early Earth aboard meteorites like the carbonaceous chondrites. But it's really important to stress that the organic chemistry that we find inside meteorites is a biotic. It didn't

originate as a consequence of life. It originated in the absence of life. It's prebiotic, perhaps. But there could be a link between the organic chemistry on which life on Earth is based and the organic chemistry that we find inside these meteorites. Also inside carbonaceous condrites, we find copious amounts of water, some carbonaceous chondrites, when you pick them up, you know, 10 to 20% of the weight of the meteorite is actually water. Now, you can't ring them out like a wet dishcloth and water comes dripping out. The water is bound up in the mineral structure of these rocks. But the particular isotopic composition of the water that we find inside carbonaceous meteorites

is very, very similar to the isotopic composition of the water that we find here. on Earth, which leads to the quite intriguing hypothesis that Earth's water originated from meteorites like the Carbonaceous chondrites. And so at some level, there probably is a link between life on Earth and meteorites, but the idea that life originated elsewhere in the solar system and was delivered, sort of pre-cooked to the Earth aboard meteorites, there's no evidence at all that happened. And also, like another one, I bet you get asked this all the time. So obviously, when people talk about... about space rocks impacting Earth, the first thing most people are going to think about is

the dinosaur extinction. A bit back, we got the Cheleabinch impact. So what are the odds of that sort of thing happening again? Right. So yeah, perhaps, I guess one of the most famous impacts on the surface of the Earth happened 65 million years ago and caused the extinction of the dinosaurs, as well as many other species on the earth. As for the odds of such event, such an event happening again, it's essentially guaranteed. We live in a solar system that's absolutely full of rocky debris. And it's that old cheesy Hollywood line of it's not a matter of if, it's a matter of when. That really does apply to asteroid impacts on the surface of the earth. It will happen again. But being an intelligent species and being a space-faring species,

crucially, we actually could develop the technology to stop such an event happening again. And I really, really hope we do. I think that, you know, the long-term survival of humanity really does depend on understanding asteroid deflection tactics and what would we do if we found an asteroid that was on our collision course with the Earth, because it will happen again. As for whether or not we can prevent it from happening, that's only down to us, really. So it was studying for a PhD that led you to write your book on meteorites. So during my PhD, I learned an awful lot about meteorites and meteor showers and comets and asteroids and that kind of thing.

And I felt really lucky to be learning about such an interesting topic that had such a lovely history to it. And he's also kind of with us all the time with meteor showers and, you know, comets off to make the news and meteorites make the news. And I guess that was my main motivation behind writing my book. meteorite. And so I tried to include, well, the book is about the science of meteorites and the history of meteorites, but I also put a guide in for meteors showers. And I also compiled all of the meteorites that have fallen in Britain and gave a little bit about the history of them too. And so if anyone listening does see a British meteorite falling, please do let me know. And I might try and update the book for another edition. Thank you for listening to this episode of Instant Genius.

That was cosmochemist Tim Gregory. If you want to know more about meteorites, check out his book, Meteorite. Or to hear him talk more about meteor showers, head over to the Instant Genius Extra podcast. Pick up a copy of BBC Science Focus magazine in shops or visit sciencefocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist vocal, Name creates high-end audio systems,

combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at Name Audio.com. Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building. Fit for your ambition for Citizens Bank. Some follow the noise. Bloomberg follows the money, whether it's the funds fueling AI or crypto's trillion dollar swings.

There's a money side to every story. Get the money side of the story. Subscribe now at Bloomberg.com.