In our Time Programme 98
ET

Melvyn Bragg : Hello.  The hunt for extraterrestrial life is 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 solar system and telescopes are being built that will enable us to look for water an 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 also been suggested that we might find life within in 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, and on 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 on 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 are Simon Goodwin a researcher in Astronomy at Cardiff University and co - author of XTL: Extraterrestrial life and how to find it, Heather Couper, space expert and 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?

Simon Goodwin :  It's quite possible that very complex molecules were formed in outer space.  We've found reasonably complex things.  When we look out in space, there are large clouds of gas and dust from which stars form, which we know as giant molecular clouds.  These things are very, very cold they sit around -250, -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 that you need to start life off with, and there's also lots of stuff out there that we really don't know what it is.  There are lots of ....(break in tape)...clouds - the Earth was seeded with a lot of these molecules. 

Melvyn Bragg : So the Earth - we got..something came in from outside onto Earth, so it didn't in itself carry the seeds of life?

Simon Goodwin :  Well we're really not sure.  It's quite possible that everything did start in Earth...on Earth itself, but it's quite possible that a lot of this...a lot of the material that was needed for life to start actually came from space. 

Melvyn Bragg : What are the further implications then if there are these molecules which seeded life on Earth - what are the further implications of that?

Simon Goodwin :  It could tell us that life is really quite common.  If space is a breeding ground for a lot of these complex molecules - then whenever a planet forms, it'll have rained down on it a lot of these complex molecules, and give life a sort of kick start.  The trouble is we're really not sure how you go from sort of quite complex molecules like - even possibly as complex as Amino Acids, and then go from that to life, that's the real sticking point, and so it's not at all clear that if you start off with lots of nice complex molecules in space, then that immediately leads you to life. 

Melvyn Bragg :  Okay, Heather Couper, you've a theory that we were seeded - we're going to keep to that word - from Mars.  Can you develop that?

Heather Couper : Absolutely, I mean Mars is further from the Sun, it's smaller than the Earth - and when you think of the role call of 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 going 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 a lot of asteroids an comets- these large chunks of left over 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 four of us in the studio are all Martian!

Melvyn Bragg :  Can you just explain to me why the Earth itself couldn't seed its own life, in all this maelstrom going on - this construction site and building site and things swirling around?

Heather Couper :  Indeed it could, 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.....

Melvyn Bragg :   But Simon just said that's questionable?

Heather Couper :  ...it's very questionable, but what actually constitutes the difference - if you like - between 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 sort of based on flexible Carbon compounds - what  constitutes the 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?

Melvyn Bragg :   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?

Ian Stewart : 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 a similar planet elsewhere" - that's the theory - I think it's wrong. 

Melvyn Bragg :   Well, just a second, can you just - before you tell us it's wrong - tell us what these - just list a few of the rarities that make us a Rare Earth. 

Ian Stewart : 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 Shomeaker-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 come....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 Bramley and they list 15 to 20 features of the solar system which they say are crucial to the way life developed here. 

Melvyn Bragg :   Our distance from the Sun - the Sun itself - the distance to the Moon - that sort of thing yeah. 

Ian Stewart : That's right, what sort of star have you got, what's sort of planet have you got, what sort of atmosphere have you got? etc etc. 

Melvyn Bragg :   And the odds against replicating this are massive?

Ian Stewart :  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. 

Melvyn Bragg :    Alright let's take it...why is it fallacious, and why isn't it interesting?

Ian Stewart :  Okay, the fallacy is the assumption that not only you need certain basic conditions like water, but that 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, you've got those cold atmosphere creatures, that you know, these vast lumbering sloth things, that can't tolerate boiling water, they need something much much colder.  Those are the extremophiles, we're normal. "

Melvyn Bragg :    Heather?

Heather Couper :  I think actually what Ian's touching on is one of the most important discoveries we've made about life in the last 5 or 10 years, that there are these things called extremophiles, which live in the most bizarre conditions, as Ian says you get them down the bottom of deep sea vents, with a....

Melvyn Bragg :   The white crabs. 

Heather Couper :   ....er yeah, and the bacteria that live around them, the white (bite?) crabs live around the vents themselves, but the actual bacteria live in the high pressure environment down there, it's incredibly dense. 

Melvyn Bragg :   Haven't they found bacteria inside nuclear plants as well?

Heather Couper :  Yes, they've them in nuclear plants, they've found them down deep bore holes.  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 experiments done that show they can live in a sort of sandstone cavity maybe a centimetre 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 nobody had taken cognisance of before. 

Melvyn Bragg :    So where does that leave you Ian Stewart?

Ian Stewart : Well I was 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, now 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. 

Melvyn Bragg :    So what's the significance of that?

Ian Stewart : It means that we have to be very careful saying 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 his 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 there waste products, it was building up in the atmosphere, it was stopping things going, and then  live developed - evolved a trick - a trick to use that waste product and turn it into something that was a source of energy and then....

Melvyn Bragg :   How did that happen? D'you know?

Ian Stewart :  ...that made it possible for complex life to get going. 

Melvyn Bragg :   How did that trick...how did we turn Oxygen into an asset?

Ian Stewart :  We had to learn to metabolise 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 generate it to power your metabolism, then you've got a new trick that you can build on. 

Melvyn Bragg :   Simon, before we leave Earth, the  - can you tell us what the Sun gives to the Earth that might fit in with the Rare Earth theory, and why that particular combination of Sun and us might be hard to repeat?

Simon Goodwin :  The Sun's a particular unusual star.  I think - I agree that a lot of the ideas in the Rare Earth Hypothesis are 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 it's age it's incredibly rich in these heavy elements. 

Melvyn Bragg :   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?

Simon Goodwin :  Yeah, that...the Sun is exactly the right sort of size, and stars come in all sorts of sizes- from about a tenth of the mass of the Sun, up to about a hundred times the mass of the Sun.  The bigger a star is the shorter it's lifetime is.  Anything that's bigger than about 3 or 4 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...er 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 doesn't really do anything nasty. 

Melvyn Bragg :    Heather, can I ask you, Europa, Mars and Titan have been identified as having similar-ish environments to Earth, what are the important features of all these three, and why do we think life might be found there?

Heather Couper :  Water - that's the basic thing.  Ian mentioned earlier on about bacteria needing this and that and the other, and the one thing....

Melvyn Bragg :    The assumption being in all this, that once we've got bacteria we've got the beginnings of life, that's the sort of.....?

Heather Couper :  Yes, I mean, well we're being very anthropomorphic, or bacteriamorphic here I guess in a way.....

Melvyn Bragg :     We've got no other way to be have we?

Heather Couper :  We've got - this is our only test tube - the test tube called planet Earth. 

Melvyn Bragg :     Are they like us is the only way we can go about it....

Heather Couper :  Exactly. 

Melvyn Bragg :     ..well Ian doesn't think that, so when you don't do you think we've got to use...are they unlike....yeah?

Ian Stewart : No I think we can use our imaginations as well as experiments, and experience. 

Heather Couper :  Well Ian's a science fiction writer , and I think we should give him his head. 

Ian Stewart :  That's...!!

Melvyn Bragg :   Science fiction has got it right in a way a lot earlier than science I think. 

Ian Stewart :  The best science fiction has and the rubbish has got it hopelessly wrong as always! 

Melvyn Bragg :   We were on Europa, before you were rudely interrupted. 

Heather Couper :  Yeah, going back to the three worlds we 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. 

Melvyn Bragg :  But what sort of life are we talking about Ian, if there is this sort of life up there?

Ian Stewart : 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 data base to build on where we can be pretty sure of what we're talking about, and the other aspect of this is - yes but it's the nature of life, that once one kind of it gets going, it sort of takes over the whole environment. 

Heather Couper : Exactly. 

Ian Stewart :  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 Earth's 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....(Mel makes a comment in hushed tones).... well I, 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? 

Melvyn Bragg :   I'd like to bring you in here Simon, elsewhere in the galaxy, earth like plants 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?

Simon Goodwin :  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, and....

Melvyn Bragg :   A bit of glass he bought at Stourbridge fair didn't he? Yes. 

Simon Goodwin : ...yes and he produced a rainbow and he showed that white light was made up of the different colours that make up a rainbow and later on towards the beginning of the 19th century,  a German physicist Fraunhoffer, inspected the spectrum produced using a microscope and he found an awful lot of dark bands in it, hundreds of little dark bands where it seemed as though the light was missing, and later in the 19th century, Bunsen and Kirchoff -Bunsen of Bunsen burner fame - discovered that the lines were produced by different elements, and if you shine a light through a gas of some element, say Hydrogen or Carbon or whatever, then it absorbs light of certain frequencies and each element absorbs light at different frequencies, and...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. 

Melvyn Bragg :    That's extraordinary.  So you just look at this and you can say "That star contains, or is made up of the following elements"?

Simon Goodwin : 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. 

Melvyn Bragg :    So can you give us an example of what this might mean -because we're still on the track of might there be 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?

Simon Goodwin :  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. 

Melvyn Bragg :     Is this the way  that you would go about it, Ian Stewart, or... because you've said in xenobiology we ought to imagine something entirely outside ourselves?

Ian Stewart : I mean what Simon is getting at 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 that we're right on, but what are the other possibilities that are reasonable?

For example, 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. You can...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 a 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 the...you've got to bet your money on Earth-like planets as the most likely ones. 

Melvyn Bragg :   How could we tell though? As I understand it, if somebody had looked at the Earth 4 billion years ago they wouldn't have given it much chance as a place on which to find life?

Ian Stewart : That's right, and again there are two points here.  There is 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 that actually happen?
 And if we're going to look for life on distant planets, we've got  to find one's that have got it now, not ones that will have it in 4 billion years time, or did have it.  I mean Mars may have had life in the past - I mean for all we know it it's still got a bit now...

Heather Couper :  I'm sure it has. 

Ian Stewart :  Yeah...no it may have had really thriving life in the past, and indeed that's where we may have come from. 

Simon Goodwin :  One thing that should be said about sort of this search using spectroscopy for alien life is that Oxygen is a dead give away for life.  If we find Oxygen on another planet we know it's...

Melvyn Bragg :   A live give away?

Heather Couper :  I live give away it certainly is! (laughter breaks out)

Ian Stewart :  Simon's saying something which is 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 sure fire sign of life, and you've got to have enough Oxygen, but that's pretty good point.  But Oxygen's not the only thing that could do that. 

Heather Couper :  But Oxygen's 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 sounds like a sort of touchy-feely wooly greeny thing, but it's not - he's made a very strong point that there are 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 look for a planet which has its atmosphere in what's called - as we discussed - chemical disequilibrium" - that plants produce the Oxygen, and we're the ones who actually the use that Oxygen, and in fact we've come now closer to actually finding the composition of the atmosphere of a planet around another star.  If the planet actually goes in front of the star, you can use spectroscopy to actually analyse 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. 

Melvyn Bragg :    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 very primitive, bacteria like entity, that's the implication.  D'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". 

Ian Stewart :  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 happened by accident and probably wouldn't happen again if you re-ran 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 maybe 100 intelligent races in the galaxy, and if there,  are we'll never see any sign of them, they're all too far away. 

Melvyn Bragg :    What's your view on this Simon Goodwin? D'you think there's any evidence so far from where you sit, that there could be intelligent life out there?

Simon Goodwin : 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 civilisations would have destroyed 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 ten million years to explore the entire galaxy.  said that 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 that we can colonise? What d'you make of that? Is there any...?

Ian Stewart :  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 let's be selfish about this, we seem...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...

Heather Couper :  I hope so! ( A clamour of voices and laughter rises up)

Ian Stewart :  I mean it is actually....

Melvyn Bragg : Why is everything...?   Nothing you've said...nothing you three of you have said on this programme says that it's certainly nonsense.  I think there hasn't been a real argument that there are...

Ian Stewart :  Well...

Melvyn Bragg :  ....a substantially intelligent forms out there.  You haven't denied it, but you're very, very guarded about it. 

Ian Stewart :  Well...okay now let me...well yeah, let me put it more positively.  The Fermi paradox is why aren't the aliens here. 

Melvyn Bragg :  If they brighter than us whey aren't hey here? Yeah. 

Ian Stewart :  If..yeah...if they're...so maybe there's only us - in which case, the 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 conditions all over the place at all sorts of time. 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...that the conditions are very, very special is like saying an animals legs have to be long enough to meet the ground. It...it's you know - 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. 

Melvyn Bragg :  Well thankyou very much Ian Stewart, Heather Couper, Simon Goodwin.  Next week we'll be talking about Bohemia - the place in the middle ages, with Norman Davies, Karen Friedrich, and Robert Pinsent, and thankyou very much for listening.