In Our Time - Extra Terrestrials

Episode Date: April 4, 2002

Melvyn Bragg examines Extra Terrestrials. New planets have been observed far beyond our solar system and telescopes are being built that will enable us to look for water and oxygen on these distant planets. If water and oxygen are present, there is every reason to suppose that some form of life might also exist there. It has even been suggested that we might find life within our own solar system. One of Jupiter’s moons, Europa, appears to be covered in an ice-crusted ocean and there is evidence that water once flowed on Mars. On our own planet, there are forms of life that don’t need the sun, living instead on energy from volcanic vents on the ocean floor. This discovery has changed our concept of what life needs in order to survive. Could life only exist on another planet like ours and what are our chances of ever discovering such a planet? If we find life, will it be intelligent, or little more than green slime? And if intelligent aliens exist, why aren’t they here? With Simon Goodwin, Researcher in Astronomy, Cardiff University; Heather Couper Space expert; Ian Stewart, Professor of Mathematics, Warwick University.

This BBC podcast is supported by ads outside the UK. Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.com.uk forward slash radio four. I hope you enjoy the programme. Hello, the hunt for extraterrestrial life is no longer confined to the pages of science fiction, but occupies astronomers, geologists, mathematicians, and new schools of scientists, astrobiologists and xenobiologists.

New planets have been observed far beyond our socialists. solar system, and telescopes are being built that will enable us to look for water and oxygen on these distant planets. If water and oxygen are present, there's every reason to suppose that some form of life might also exist there. It's even been suggested that we might find life within our own solar system. One of Jupiter's moons, Europa, appears to be covered in an ice-crusted ocean, and there's evidence that water once flowed on Mars. Under our own planet, we've found forms of life, extremophiles, that don't need the sun, living instead on energy from volcanic vents on the ocean floor. This discovery has changed our concept of what life needs in order to

survive. Could life only exist in another planet like ours and what are the chances of ever discovering such a planet? If we find life, will it be intelligent or a simple bacteria-like entity? And if super-intelligent aliens exist, why aren't they here? With me to discuss the possibility of extraterrestrial life as Simon Goodwin, a researcher in astronomy at Cardiff University, and co-author of XTL, Extraterrestrial Life and How to Find It. Heather Cooper, space expert, an author of Mars, the inside story of the red planet, and Ian Stewart, Professor of Mathematics at Warwick University, and co-author of the forthcoming book, Evolving the Alien.

Simon Goodwin, to start with you, astronomers say they've detected complex molecules floating in the atmosphere of the solar system. Is it possible that these molecules out there were the origins of life on Earth, and if so, how did they settle here? It's quite possible that very complex molecules have formed in outer space. found reasonably complex things. When we look out in space, there are large clouds of gas and dust

from which stars form, as you know as giant molecular clouds. These things are very, very cold. They sit around minus 250, minus 260 degrees centigrade. And in terms of interstellar space, they're very, very dense. There's hundreds or even thousands of molecules per cubic centimetre.

And astronomers have detected in these things like methane and long complex molecules of carbon. and these are the sort of things that we think you need to start life off with and there's also lots of stuff out there we really don't know what it is there are lots of molecules that we haven't actually determined

exactly what they are but we think there could be things possibly as complex as amino acids and the sort of thing you need for life out there in space and presumably when the solar system formed from one of these giant clouds the earth was ceded with a lot of these molecules

so the earth we got something came in from outside onto Earth. It didn't in itself carry the seeds of life? Well, we're really not sure. It's quite possible that everything did start on Earth itself, but it's quite possible that a lot of this a lot of material that was needed for life to start actually came from space.

What are the further implications then if there are these molecules which seeded life on Earth? What are the further implications of that? It could tell us that life is really quite common. If space is a breeding ground for a lot of these, these complex molecules, then whenever a planet forms, it will have rain down on it to a lot of these complex molecules and give life a sort of a kickstart. The trouble is we're really not sure how you go from sort of quite complex molecules, even possibly as complex amino acids, and then go

from that to life. That's the real sticking point. And so it's not so clear that if you start off with lots of nice complex molecules in space, then that immediately leads you to life. Okay. Heather Coup, are you with here that we were seated, we're going to keep to that one, Mars, can you develop that? Absolutely. I mean, Mars is further from the sun. It's smaller than the Earth. And when you think of the role called the solar system, it probably actually got settled down first when the planets were being born. The Earth was hot, turbulent, closer to the sun. If life was going to get started, possibly by stuff raining down from space, it may have started on Mars first of all. And the amazing thing about the early solar system, it was a cross between a construction site and a demolition. site, and you had stuff flying around actually making the planets and breaking them up. In fact, the way the moon was formed, it sounds bizarre to say this now, something the size of Mars collided with the Earth, splashed out material from the Earth, and that in a very, very short

space of time formed the Moon. So you've got the measure of just how much activity there was. And it seems that a lot of asteroids and comets, these large chunks of leftover debris from the construction site, splashed into planets like Mars and the Earth. And if there had been very primitive life on Mars, then the rocks that were ejected from Mars would have swirled around the inner solar system and then later collided with planets like the Earth

and indeed Venus, which is too hot for life. So I think it's perfectly probable that life started on Mars, seeded the Earth, in which case the forest in the studio are all Martians. Can you just explain to me why the Earth itself couldn't seed its own life in all this mails from going on, this construction site and building site Indeed, it could indeed have started its own life. It just seems that outside in space you have all the raw materials ready to start life. The big question mark is what actually...

Well, Simon just said that's questionable. It's very questionable, but what actually constitutes the difference between, if you like, inanimate organic compounds, even as complex as amino acids. Things made up of loads and loads of chains of carbon. I mean, you and I are all based on carbon proteins, which are based on sort of flexible carbon compounds. What constitutes a difference between these organic compounds which you can make in the lab and sentient conscious life?

That is the really big question. You've got the raw materials out there, but then how does the spark ignite it into life? Ian Stewart, can you explain the rare earth theory that the earth is uniquely suited to life? First of all, can you tell us what it is and then tell us whether you agree with it? Okay, what it is is essentially that you should look at the only form of life that we really know about, which is ours, it could be the only form of life in the whole galaxy for all we are currently aware. Understand the conditions under which life arose, understand what's necessary for life. And then the rare earth theory boils down to when you put all that stuff together and say,

where else could this happen? The answer is it's going to be very unusual. There's such a strange combination of circumstances in the history of life on this planet. And if you do your sums, you will find it's incredibly unlikely that you will find that you will find a similar planet elsewhere. That's the theory. I think it's wrong. Oh, just a second. Before you tell us it's wrong, tell us what these, just list a few of the rarities

that make us a rare earth. Okay, liquid water, which is certainly important for our kind of life. Oxygen atmosphere, we didn't have it until about 2.5 billion years ago when the bacteria produced it. So they were bacterial life, but nothing more interesting.

A planet like Jupiter to shield us from comets, Jupiter sucked up Shoemaker Levy, 9 recently. That could have hit us. Jupiter protects us against comets. On the other hand, a certain number of near disasters to keep evolution ticking over and get the diversity going. The rare earth hypothesis, the name comes, it's a pun. It's a pun on the rare earth elements. There was a book written a few years ago with that title by Peter Ward and Donald Brownlee. and they list 15 to 20 features of the solar system,

which they say are crucial to the way life developed here. I'm distance from the sun, the sun itself, the existence of the moon, what sort of star have you got, what sort of planet have you got, etc., etc. And you're against replicating this, I'm massive. This is what they argue. Firstly, I think that actually that argument is probably fallacious, but secondly, I don't think that's really the interesting question. All right, let's take it.

Why is it fallacious and why isn't it interesting? Okay, the fallacy is the assumption. that not only you need certain basic conditions like water, but the way we got water is the only way you can get water, the way we got oxygen is the only way you can get oxygen. We now know, and furthermore, that oxygen is necessary at all. We now know that down at the bottom of the ocean, the black smokers, the volcanic vents,

in those areas there are these extremophiles, these creatures that live in what we consider to be very extreme environments. and you can't help thinking about that from their point of view and saying, my God, look at those cold atmosphere creatures, these vast lumbering slow things that can't tolerate boiling water, they need something much, much colder. Those are the extremophiles. We're normal.

I think actually what Ian's touched on one of the most important discoveries we've made about life in the last five or ten years, that there are these things called extremifiers which live in the most bizarre conditions. As Ian says, you get them down the bottom of deep sea vents. These white crabs. Yeah, and the bacteria that live around them. I mean, the white crabs live around the vents themselves.

But the actual bacteria live in the high-pressure environment down there. It's incredibly dense. Haven't they found bacteria in nuclear plants? Yes, they found them in nuclear plants. They found them down deep boreholes. They can't quite survive in space without, in the vacuum of space. But if you actually protect them inside a coating, in fact, there's been experience.

done that show they can actually live in a sort of sandstone cavity, maybe a centimeter across, so it proves that life could have got from Mars to the Earth in that way. But they can live in the most amazing environments. And that's something that nobody had taken cognizance of before. So why does that leave you in, Sien? Well, I'm just going to add to what Heather was saying there, that a few years ago, there was bacteria were discovered in salt crystals. And these experiments were done very, very carefully to avoid contamination.

the bacteria were 250 million years old. These were dried up bacterial spores. They opened up the salt crystal, took them out, put them into the right culture medium, and they came to life again. And they've looked at their DNA, and they are not the same as modern bacteria. They are a credible precursor to various modern strains of bacteria.

So bacteria can survive as spores for probably forever. So what's the significance of that? It means that we have to be very careful, you've got to have temperatures that can sustain liquid water. The one that really is attackable is you've got to have oxygen. Oxygen for this planet, when it first appeared, was essentially pollution. It was poisonous, living creatures could not survive in it. They were all anaerobic bacteria.

It was their waste products. It was building up in the atmosphere. It was stopping things going. And then life developed, evolved a trick, a trick to use that waste product and turned into something that was a source of energy. And then that made it possible for complex life to get going here. How did that trick? How do we turn oxygen into an asset?

We have to learn to metabolize it. I mean, oxygen is corrosive. Things burn in oxygen. But burning is a source of energy. It's a chemical reaction. So if you can find a way to protect your cells against the bad effects of the oxygen while using it to extract energy and generally to power your metabolism,

then you've got a new trick that you can build on. Simon, before we leave Earth, can you tell us what the sun gives to Earth that might fit in with the rare earth theory and why that particular combination of sun and us might be hard to repeat? The Sun's particularly unusual star. I think, I agree that a lot of the ideas in the rare earth hypothesis and things that could be fairly easily replicated, The one really strange thing about the sun

is that it's very, very rich in heavy elements. When the universe first started after the Big Bang, there was nothing in it except hydrogen and helium. And that's pretty useless. Most of what makes up humans and makes up any sort of life form are things like carbon, oxygen and nitrogen. Most of our weight is made up of those. And when the sun formed about four and a half billion years ago,

for its age, it is incredibly rich in these heavy elements. So there's a combination of time we're talking about here as well. You have to be a certain age. It takes about a billion years for life to grow on a planet and some stars like the sun are too big to... Can you just explain that? Yeah, the sun is exactly the right sort of size. Stars come in all sorts of sizes

from about a tenth of the mass of the sun up to about 100 times the mass of the sun. The bigger a star is the shorter its lifetime is. anything that's bigger than about three or four times the mass of the sun goes through its entire life cycle and dies within about 500 million years but any star that goes through its entire life cycle in that amount of time there's probably not enough time for life to start anything that's a lot smaller than our own sun

is very faint and they tend to do nasty things like flare up and put out lots of nasty radiation which is not particularly good for life something like the sun will live for about 10 million years 10 billion years, not really doing very much. The great thing about the sun is it just sits there. It does very, very little. It's great for life on Earth because it pumps out radiation and heats us up, but it doesn't really do anything nasty.

Can I ask you, Europa, Mars and Titan have been identified as having similar environments to Earth. What are the important features of all these three? And why do we think life might be found there? Water. That's the basic thing. Ian mentioned earlier on about bacteria needing this and that and the other. The assumption being in all this is once you've got bacteria,

we've got the beginnings of life, that's a sort of... Yes, I mean, well, we're being very anthropomorphic or bacteriaomorphic here, I guess, in a way. We've got another way to be, have we? This is our only test tube. The test tube called planet Earth. Are they like us is the only way we can go about? Exactly.

Ian doesn't think that. So when you don't, do you think we've got to think... Are they imaginations as well as experiments and experiments and experience. Well, Ian's a science fiction writer about it. Actually, we should give him his head. Science fiction's got it right in a way

a lot earlier than science. The best science fiction has and the rubbish has got it hopelessly wrong, as always. We were on Europa before you were really interrupting. You're going back to the three worlds you talked about. Mars certainly did have water in the past. You can actually see the dried up river beds on Mars. Almost certainly it has water today,

literally running streams that have, you know, run recently, sort of gullies on Mars. So there appears to be water on Mars today and almost certainly erupting volcanoes, which again is something that we think on Earth might have actually kick-started life. But what sort of life are we talking about, Deanne? If there is this sort of life up there.

There's a tension here between two entirely reasonable things. One is we really only know a lot about our kind of life, and we don't know for sure there's anything else. So there's a really good database to build on where we're pretty sure of what we're talking about. And the other aspect of this is, Yes, but it's in the nature of life that once one kind of it gets going, it sort of takes over the whole environment.

What could have happened on a different planet if it started in a slightly different way? Would it really have to be like here? And my feeling is the biggest hole in the rare Earth hypothesis is not that Earths are rare, which I think is probably reasonably true, though not quite as much as is sometimes claimed, but that there are lots of alternatives. Life is very adaptable. That's the message of the extremophiles. Life does not need oxygen.

Some of these bacteria run on sulphur and iron. Two miles down in the ground. There's an ecology down in the rocks which has more mass of living creatures than the entire content of the Earth's oceans and we know nothing about it. And it's probably very, very primitive and not very interesting. But who knows?

So when you come to... It's not just a question of water on Europa. There are perhaps silly questions like, could you get life in Jupiter's atmosphere? Could you get some form of life on the surface of a star? I'd like to bring you in here, Simon. Elsewhere in the galaxy that Earth-like planets have been discovered using the technique of spectroscopy. Now, can you tell us about that? And can you tell us how spectroscopy works and what it's brought into play that wasn't there before?

Spectroscopy is wonderful. It's the most powerful tool astronomers have. Newton was one of the first people to split the light from the sun using a prism, and he got a rainbow. A bit of glass he bought a starbridge fair, didn't he? Yes, and he produced a rainbow, and he showed that white light was made up of the different colors that make up a rainbow. And later on, towards the beginning of the 19th century, a German physicist, Frannhofer, inspected this spectrum produced using a microscope, and he found an awful lot of dark bands in it. There were hundreds of little dark bands where it seemed as though the light was missing.

And later in the 19th century, Bunsen and Kirchhoff, two more German physicists, Bunsen of Bunsen Burm of fame, discovered that the lines were produced by different elements. And if you shine a light through a gas of some elements, say hydrogen or carbon or whatever, then it absorbs light of certain frequencies. And each element absorbs light at different frequencies. and a frequency just being colour. And so if you see what lines are missing from a spectrum, then you know what elements are actually in a star.

That's extraordinary. So you just look at this and you can say that star contains or is made up of the following elements. Yeah, it's quite amazing. It turned astronomy from being a science which was just interested in where points of light were on the sky to a science that could actually say something about those points of light. So can you give us an example of...

of what this might mean, because we're still on the track of, might there be a life elsewhere, and if so, what's it like? So we have this tool now, which I presume since the 19th century has been much, much more heavily developed, intensively developed.

What does it mean? What does it bring us? The huge advance it might bring us is we can go and look at other planets, and if we can actually detect the light from those planets, then we can tell what their atmosphere is made of. Is this the way that you would go about it in, ensured or because you've said your

xenobiology that we ought to imagine an entirely, ought to imagine something entirely outside ourselves? I mean what Simon's getting out here is that let's say if we think oxygen and water are important then at least in principle we could try and do some spectroscopy and

see if they're present I think we need to ask not just how are things that we the things that we can see the things that we can be sure we're right on, but ask, what are the other possibilities that are reasonable? For example, a biologists have done experiments over the last few years to show that virtually everything about DNA can be changed. You can change the genetic code. You can make different amino acids.

You can make different proteins. What seems to be the key to life on this planet is actually just one key out of many different kinds. And any question you ask about living creatures, the answer now seems to be, even on this planet, they could have been different. And we should be asking much more general question. What kind of environments can life exist in? And how could we pick up some of those? Let's go for the exotic possibilities as well.

Not as front-line research, because you've got to bet your money on Earth-like planets as the most likely ones. How can we tell that? As I understand it, if somebody looked at the Earth four billion years ago, they wouldn't have given it much chance as a place on which to find life. That's right. And again, there are two points here.

There's the general question of what sort of places can life come up and arise. But there's the other question of, yes, and at what stage during the life cycle of that environment does this actually happen? And if we're going to look for life on distant planets, we've got to find ones which have got it now. Not ones that will have it in four billion years' time or did have it. I mean, Mars may have had life in the past. I'm for all we know it's still got a bit now. I'm sure it has. Yeah.

But, you know, it may have had really thriving life in the past, and indeed that's where we may have come from. One thing that should be said about sort of this search using spectroscopy for alien life is that oxygen is a dead giveaway for life. If we find oxygen on another planet, we know it's you. A live giveaway. Certainly is. So I'm saying something that's actually quite important here,

which is if you find oxygen, what you've got is, unbalanced chemistry. You've got the sort of chemistry that wouldn't happen on a dead world. And that's a surefire sign of life. And you've got to have enough oxygen, but that's a pretty good point. But oxygen is not the only thing that could do that. But oxygen is produced by plants basically who take in carbon dioxide and excrete oxygen. And in fact, Jim Lovelock, who is one of these wonderful independent scientists who came up with the Gaia hypothesis, which sounds like a sort of touchy-feely, woolly greeny thing, but it's not. he's made a very strong point

that there are very, very small, subtle things on the earth like methane excreting bacteria which keep the balance which keeps life having the status quo that it has today. He says, look, you've got to have a look for a planet which has its atmosphere and what's called, as we discuss, chemical

disequilibrium, that plants produce the oxygen and we are the ones who actually then use that oxygen. And in fact, we've come now closer to actually finding the composition of an atmosphere of a planet around another star. If the planet actually goes in front of the star, you can use spectroscopy to actually analyze the atmosphere of the star and see if there's anything superimposed on that, which is weird, and that's now

been done for the first time. Let's move finally to what form might extraterrestrial life take? We seem to have been saying, well, if it's there at all, it's a very primitive, bacteria-like entity. That's to be implicated. Do you think there's any chance that we'll find intelligent life forms. One has to say something like human beings. I'll desist from saying us. Yeah, let me, there's an important distinction here, at least I think it's important,

between what's sometimes called parochial and universal features of life on this planet. Parochials are things that happen by accident and probably wouldn't happen again if you reran evolution. The fact that we've got five fingers, it could have been six, it could have been four, it's not quite clear why it's five,

it's probably an accident to do with the fish that first crawled out of the oceans. On the other hand, intelligence looks to me like a universal. Intelligence is being very good at analysing and predicting your environment. It has a lot of survival possibilities. So if intelligent life can evolve somewhere, then given enough time, it probably should. The question is, what's the chance that there's some within a reasonable distance of us now? And if you do the sums, you can either convince yourself those chances are reasonably good, or if you're pessimistic about these things, you can decide it's exceedingly unlikely.

You know, there may be 100 intelligent races in the galaxy, and if there are, we'll never see any sign of them. They're all too far away. What's your view on this, Simon Goodwin? Do you think there's any evidence so far from where you sit that there could be intelligent life out there? I'm very pessimistic. Sorry to put a downer on this.

but there's what's called the Fermi paradox. And it's the idea that if there is other intelligent life out there, why isn't it here already? It's possible that civilizations would to destroy themselves, but we're very, very close to being able to go out and explore the universe, well, explore the galaxy. And it would only take us about a million to 10 million years to explore the entire galaxy.

That sounds like an awfully long time, but the galaxy is 10 billion years old. so it's only a tiny fraction of the lifetime of the galaxy. So if there are intelligent aliens out there, and especially now, because we're very close to being able to build telescopes that will tell us if there's Earth-like planets out there, even if there's life on them. So aliens would know there is an interesting planet here.

They might not know there was intelligent life on it, but they'd look at Earth and they go, that's an interesting planet, let's go there. Then you can build a robotic spaceship and send it to a planet. And you could seed that planet and you could start settling it. And it wouldn't take you very long. It would take you a very, very small fraction of the lifetime of the galaxy to do this.

I know I insert that you're working towards finding other ways that life could be. But just to continue with this idea of maybe there's nothing out there much. and Sir Martin Rees, historian-reis, if that's the case, and given that we are so fragile on this planet, subject to meteorites and subject to blowing ourselves up, isn't it our duty, he used the word, to colonise, to let what we've got spread about a bit

and find places which we can colonise? What do you make of that? Is there any... I think that's, whether it's our duty or not, I think it's a natural feature of the human race that it likes to get itself spread around and colonise. And at the moment, we've got all our eggs in one basket. So, I mean, let's be selfish about this.

We have this feeling that we really would feel rather sad if we all disappeared. As far as we know, we're the highest life form in the universe. I think that's almost certainly nonsense, but nonetheless that's what we... I mean, it's actually... Nothing you three of you have said in this programme says that it's certainly nonsense. There hasn't been a real argument that there are substantially intelligent forms out there. You haven't denied it, but you were very, very guarded about it. Well, yeah, let me put it more positively.

The Fermi paradox is why aren't the aliens here. If they're bright and less why. Yeah, if they're, so maybe there's only us. In which case, the other question is, why are we here? How come there's this one thing on this one planet in an enormous great universe, which as far as we can tell, duplicates the same general kinds of, all over the place at all sorts of times. There's nothing special in general terms about this planet.

Yes, there are special features, but what we learn is that life is adaptable. The reason that life is so exquisitely, the conditions of this planet are so exquisitely tuned to life. That's not how it works. Life has adapted itself to fit the conditions on this planet. To say that we're exquisitely, the conditions are very, very special, is like saying an animal's legs have to be long after his life. meet the ground. It's getting the whole thing back to front. So there should be life out there because life is a very general, self-complicating, self-adapting process. Anywhere it can

find a niche, it does. Well, thank you very much, Ian Stewart, Heather Cooper, Simon Goodwin. Next week we'll be talking about Bohemia, the Place in the Middle Ages with Norman Davis, Karen Friedrich and Robert Pinsent. And thank you very much for listening. We hope you've enjoyed this Radio 4 podcast. You can find hundreds of other about history, science and philosophy at BBC.com.com.com.com.