In Our Time - Extremophiles

Episode Date: June 25, 2015

In 1977, scientists in the submersible "Alvin" were exploring the deep ocean bed off the Galapagos Islands. In the dark, they discovered hydrothermal vents, like chimneys, from which superheated water flowed. Around the vents there was an extraordinary variety of life, feeding on microbes which were thriving in the acidity and extreme temperature of the vents. While it was already known that some microbes are extremophiles, thriving in extreme conditions, such as the springs and geysers of Yellowstone Park (pictured), that had not prepared scientists for what they now found. Since the "Alvin" discovery, the increased study of extremophile microbes has revealed much about what is and is not needed to sustain life on Earth and given rise to new theories about how and where life began. It has also suggested forms and places in which life might be found elsewhere in the Universe. With Monica Grady Professor of Planetary and Space Sciences at the Open UniversityIan Crawford Professor of Planetary Science and Astrobiology at Birkbeck University of LondonAndNick Lane Reader in Evolutionary Biochemistry at University College LondonProducer: Simon Tillotson.

Thank you for downloading this episode of In Our Time. For more details about In Our Time, and for our terms of use, please go to BBC.co.com. UK slash Radio 4. I hope you enjoy the program. Hello. In 1977, scientists made a discovery deep under the oceans that gave clues to life we might find in deepest space. The explorers were inside the submersible Alvin, near the Galapagos Islands, visited by Darwin the century before. They found hydrothermal vents like chimneys on the seabed.

with superheated water flowing out. There was no sunlight, but around the vents there was an abundance of life, feeding on microbes that were thriving in the vents in the vents' extreme conditions. These microbes were termed extremophiles, and a greater understanding of what they need and do not need, to survive as spawned theories about the origins of life here on Earth, and the conditions in which life might be found across the universe. They also helped establish astrobiology,

the science of our search for life outside our planet. to discuss extremophiles and astrobiology are Monica Grady, Professor of Planetary and Space Sciences at the Open University. Ian Crawford, Professor of Planetary Science and Astrobiology at Birkbeck University of London, and Nick Lane, reader in evolutionary biochemistry at University College London. Ian Crawford, what are extremophiles? Extremophiles are organisms, almost all microorganisms, which have adapted to live in environments that we consider to be very extreme. So there'd be very high temperatures or very low temperatures

or very acidic environments or very alkaline environments or environments with a high radiation level. And they're environments which until the last few decades, biologists would have thought were quite inimicable to life and yet suddenly we found living things have adapted to them. Of course, it's quite an anthropocentric point of view because for the organisms that have adapted to live in these extreme environments,

That's their normal environment and it's ours in this studio who are the extremophiles from their point of view. How significant was the role of Alvin in this? And can you tell us a bit about Alvin and what happened there? Well Alvin is a deep sea submersible, a submarine basically. It carried three people and again it can go down to depths of many kilometres below the surface of the sea. So in 1977 yes the Alvin crew dived to the ridge of submarine volcanoes close to the the Galapagos Islands at a depth of about 2,000 metres. And they discovered these hydrothermal vents where hot water is coming out of the earth's crust.

And sustained by the chemical energy in the fluids coming out of the vent was this amazing ecosystem of many microorganisms, extremophile microorganisms living at very high temperature and high pressure and no sunlight. And in fact, sustaining a whole ecosystem built on these microsystems. essentially isolated from the Earth's surface environment. So from an astrobiology point of view, it's hugely significant because of a sudden realisation here is this place where we didn't expect life, and yet life is teeming,

and we can look around the universe or the solar system and find, well, we can certainly imagine hydrothermal vents on other planets, which might sustain life also. It's fascinating that it went down that deep. I didn't know things would go that deep for the ocean bed in the Pacific. How did they see what they saw when they got there? That's a very good question. I mean, I think this is why it's something beauty of having humans exploring, actually,

and I think we might make the analogy with space exploration later on. Humans in a submarine, just as humans in a spaceship, can be on the alert to look out of the window and suddenly see things and see that this is something really quite unexpected. So I think it was a genuine discovery. The hydrothermal vent was known to be there, but the discovery that was life based around these vents was just an observational discovery.

And like much in science, you'd make a new observational discovery and the whole perspective suddenly changes. Was this a joint venture, different nationalities, different nations? I believe Alvin was a US, it's an American submarine and the nationality of the expedition.

I think it was a US expedition. Is it significant that it was near the Galapagos? Well, the Galapagos Islands of volcanic islands on the East Pacific rise, which is part of the spreading centres where two of the Earth's tectonic plates are moving apart, and so submarine volcanism is present there. So it's not a surprise the hot water and the hydrothermal vents are in the vicinity of the Galapagos Islands.

No, so the geology, this is where hydrothermal vents occur. But it's nice insofar as the Galapagos Islands have this place in the history of biology, where Darwin had some of his key insights, and then offshore there are these fantastic hydrothermal vents. Nick Lane, these discoveries coincided with discoveries by Carl Woz in 1970s. What was he doing? So Carl Woz started in the late 1960s trying to build a tree of life. And he needed to find a protein which all cells use in essentially the same way.

and then he could compare the structure of these proteins really to build a tree of relatedness. So the more differences there are between the protein than the more distantly related they are. So he used RNA, ribosomal acid, and he compared these sequences from all kinds of bacteria and also more complex organisms. He discovered an entirely new group that nobody had really come across before, which were called the archaea.

And they looked like, the reason we hadn't come across them before is they look the same as bacteria. If you look at them down, even an electron microscope, you really couldn't tell the difference between them. There had been some work in the 1970s as well, suggesting that there were chemical differences in the cell membranes and the cell wall, that these were an unusual group. But what Carl Woz showed was that there was an entire domain of life called the archaea. he named them the archaea, which are as important as the bacteria or our own type of cell, which is the eukaryotic cell,

which is basically all large and complex life, so algae and fungi and animals and plants and so on. But all cells are remarkably the same, aren't they? In certain ways, in the genetic code, for example, in some basic metabolism, but then there's huge differences. So eukaryotic cells are enormously large and complex, Again, we have lots of things in common, but the basic bacterial cell, they're shockingly different, actually.

Bacteria and archaea, their cell membranes are very different. Their cell walls are very different. Even things like DNA replication are done using different enzymes in the bacteria and the archaea. Why did this difference matter with the archaea? That really depends on when they diverged from the bacteria, and we don't exactly know that. There's disagreements about whether the archaea. Archaia adapted to extreme environments because that's where they were discovered. And so the samples that Carl Woz used for his sequencing were taken from these hydrothermal vents.

It depends on whether they adapted as a group to these kind of extreme conditions, but now we know there's all kinds of archaic which are also found in the open oceans, for example, in our own intestines, all kinds of relatively mild environments. and they still have this same cell wall structure, same cell membrane structure and so on. So it's not clear if it's an adaptation to an extreme environment or it just happened anyway for other reasons. But one thing it does do is it does fit them particularly well to very high temperatures in vents. I'm not quite sure still, though,

why it's so important to this new tree, the tree of life idea. Well, the old tree of life idea basically talked about empires, if you like, of plants and animals. and the things that we can see essentially, and it put a great deal of emphasis on large organisms and the traditional distinction in biology between botany and zoology. What it really did was say, that's all wrong. There's really only three major groups in life.

There's the archaea, the bacteria, and the eukaryotes, which is all of these complex life. And so it kind of put humans into a small corner of the tree of life next to plants and whatever else. It kind of squashes us again out of being the center of the universe. and instead we see massive variation, massive amounts of adaptation and evolution in these big groups that nobody had heard of

before nobody was aware of before 1978. Monica Grady, what implications does all this have for life on Earth? Well, the implications are that the idea that all life is based on the need for sunlight to actually exercise. You know, that has gone completely out of the window, as it were. And we can see that there are many, many environments now where things can exist in the dark and use a different type of energy transformation mechanism. And once you've accepted that for the earth, then you can look at many other environments

within the solar system where there is not sufficient energy from sunlight to allow photosynthesis and a food chain to exist. You can start looking for places in the dark. for underneath surfaces, which is really, really significant. Anything else is that the sunlight won the main difference? Well, then you start looking at places that are very acid, high temperatures, where are there likely to be any high temperature vents. Where is it going to be very cold and very dry?

All these extreme environments that we've found on Earth, there are places within the solar system. these extreme environments exist, which are perhaps even more extreme. And now we think, well, there is a chance that they could be inhabited. So to use that phrase, is it life but not as we know it? Would you see a connection between the four of us around the table and these things coming out of vents? I would certainly see a connection. And that connection is through the element carbon, because all life on earth requires carbon.

And as far as we understand things, carbon is so special that it needs that. if we start talking about things that aren't based on carbon, you get very rapidly into science fiction. And so it could be, yes, it's life, not quite as we know it, but has very, very many similarities. This quite quickly, because we're only talking about in science, we're only talking about 40 years ago or so, quite quickly, the application of this discovery was sent into space.

Can you tell us how and why that? happened? Well the idea then was to try and test and see whether microorganisms could exist in space with an idea of well you know could they have been transferred from one place to another I thought that well maybe life got going on Mars say for instance before it got going on Earth and actually was transferred to Earth from Mars this idea of things being able to survive inside rocks and to be protected from a radiation environment and things like that. It's right, okay, let's test it. Let's put microorganisms in space on the International Space Station.

How do they get on coping with the radiation up there? How do they get on coping with ultraviolet levels? How do they get on coping with space, the hard vacuum, things like that? So a whole series of experiments have been done on the International Space Station, including putting them on the outside of, returning spacecraft to see how they can actually survive re-entry heats. And how did they survive? Some died, but some survived because they were inside rocks.

They weren't on the outside. So am I right in saying that this is a whole new, a revelation for people thinking about life in space? Yes. The revelation in a sense of a whole new field of investigation has opened up. Yes. I mean, Ian on my left here is Professor of Astrosy. I mean, you know, 30 years ago, 40 years ago, anyone calling themselves a professor of astrobiology would have been run out of town as being some form of charlatan. But astrobiology now, the science has become an accepted discipline, which encompasses many, many different aspects of science.

Can I cut to or move to our prehistor astrobiology to ask him to justify his existence in this new strange world that Monika's... make quite clear it's just short of Charleston or just come out of this age of Charleston. So, I mean, it would have been 50 years ago. I think astrobiology is the, it is a relatively new science, and it's the name given to the science that searches for life in the universe, because we haven't found any life anywhere yet. So we can't have any actual exobiologies until we find any exo life. But we can search for life in the universe, and we can ask ourselves, where would we look, what environmental conditions are most suitable? And this is really what astrobiology is as a discipline. But it brings together many of the more traditional

disciplines of science. So it means astronomers have to talk to biologists and geologists and planetary scientists. I mean they've never talked to each other before. Well, no, you see, there was a tendency in the 20th century building on the 19th really to specialise. And science got a lot of benefits from specialisms, but also it tended to lose the big picture. Now, I think one of the great strengths of astrobiology is it brings these different disciplines together. It makes them go to the same conferences and read the same journals and actually has been really helpful, even though we haven't found any life anywhere.

Even if we never do, the astrobiology is a discipline that's helping us bring these different subjects together and see the big picture is intellectually very, very rewarding. Monica. And that's what you've got around the table today. You've got a biochemist, an astronomer and a geochemist.

And we talk the same language when we're talking about astrobiology. We use the same words we understand each other and we've got the same goals as Ian said to explore the possibilities of life beyond the earth and in different places in the earth and it's been really exciting to be part of the birth of a new science which has come you know into existence during my scientific lifetime Nick Lane can you please how do you want to say that yes no I mean the other thing from my point of view is it forces us to question why life on earth is the way it is what kind of adaptations do you have to these extreme environments? Why is it that way? As Monica said, why is it carbon-based?

We have a very good idea why it's carbon-based. Does it necessarily need water? Well, it's simply that carbon is particularly good at forming very strong bonds and four bonds between different atoms. So you can make very large, complex structures, proteins, DNA and so on. Nothing else, not even silicon, can do that in the same way. And carbon is also very abundant throughout the universe. So the combination of the two, the abundance, and it's really good at what it does, that life is overwhelmingly likely to be carbon-based, probably overwhelmingly likely to require water as well, again, just because it's so common.

How have these extremophiles, the investigation into them, changed the idea of what constitute extreme conditions for life? Can I ask you first and then go around? Yeah, I think, from my own point of view, I'd almost turn it on its head. As Ian said earlier on, we are the extremophiles here. This is an environment which was concocted by life on Earth.

And, you know, animals arose 500 million years ago. Oxygen levels in the atmosphere rose around that same time, go back 2 billion years. There were signs of oxygen then in the Great Oxidation event. But the first 2 billion years of life on Earth was in what we would consider to be extreme environments. Very little, if no oxygen. Yes, basically zero oxygen.

very often in hydrothermal systems at the bottom of the sea, we can tell what was going on roughly from the fractionation of isotopes of different elements. So we can see that sulfur, for example, different isotopes of sulfur are used by bacteria. We can see they were doing that three and a half billion years ago. So we have an insight into what we would consider extreme forms of metabolism, but that was the norm back then and it's still going on now.

What are the repercussions of seeing that life can dwell in such extreme conditions in corporate? Well, I think from an astrobiology point of view, they're profound. Because what we've got is now we've got a much wider spectrum of environmental limits. So go from minus 20 degrees Celsius to 120 degrees Celsius. And acidities, pH levels from zero to 11. And we now know that life can exist in this whole range of environments. And what that means is it means that biology has natural selection. has found solutions to the problem of living in these extreme environments.

So it means we can go to a place on Mars where it's minus 20 degrees Celsius or speculate about hydrothermal vents in oceans and Jupiter's moon Europa, for example, which very likely does have hydrothermal vents. And we know that these conditions are in principle habitable. We don't know they're inhabited, but we know they're in principle habitable by carbon-based life because life on Earth has found a solution to living in those environments. So this really changes everything.

It means we can go out into the universe looking for places that we know to be habitable and seeing whether they are in fact inhabited or not. And so I think, yeah, this wider perspective has... I mean, this is the rationale for astrobiology existing as a discipline. Can you continue with that, Monica Grady, please? Europe has been mentioned, around Jupiter and Mars has been mentioned, as it always is. Can you tell us more about what space people are finding out that's new to them and exciting and what they can build on because of this development.

Well, starting with Europa, and we should also add to that Enceladus, which is one of Saturn's moons, they have an icy crust, and below that is an ocean. We can tell that from the results from space probes travelling in those systems. Now, the fact that an ocean means something is keeping that water liquid, and that something has got to be heat in Europa. It's produced in the core of Europa by being close to Jupiter, which sort of stretches and pushes Europa.

That heat has to get out from the centre somewhere, and the idea is it comes out at hydrothermal vents on the bottom of Europa's ocean, which must be really dark, very dark down there, long way from the sun, icy crust, so no sunlight. Now we know that on the Earth, on oceans floors where it's dark and no sunlight penetrates, There are not just microbes there. There's a whole ecosystem of tube worms and spider crabs, advanced organisms, eukaryotes. And so it's possible that those sort of things could be present on Europa. So finding the hydrothermal vents and the ecosystem there really opened people's eyes to the possibilities of quite advanced life forms on Europa, which would be fantastic.

Turning to Mars, you're looking at something different. Mars is very dry. very, very cold. Where do we have on earth that's very dry and very cold? We have Antarctica. Now there is a huge natural biomass in Antarctica, which people, you know, are not necessarily aware of, and these are things which live inside the rocks. So, you know, for those people who, you know, like to pick apart words, they're cryptoendoliths, crypto-hidden, endo-inside, lith. So these are microorganisms hidden inside a rock, they're an ecosystem of their own, they might be inside rocks on Mars, they might be in caves on Mars, protected from radiation, feeding from

earth's sunlight and drawing nutrients also from the rock. How are you going to get at this stuff on Mars and Europa? That is a very interesting question. I'm glad you asked me that, and it's one which is very difficult to answer without a lot of money for. space expeditions. Obviously there's a rover on Mars at the moment called Curiosity, which is doing fantastic work looking at the rocks, but you're looking for trace fossils. It's not going to be easy. Going to Europa, you need to penetrate the icy crust. You need some sort of remote mission to get down through the ice to the bottom of the floor. So it's going to have to be robotic exploration. Ian Crawford? Well, I was just, I mean, it certainly has to be exploration. I mean,

and this is the way we found the hydrothermal vents on the earth. It's how we know there are crypto endoliths in Antarctica because we've had expeditions to... We wouldn't know these things and if we didn't get out into the world and explore. And Darwin wouldn't have had his insights if he hadn't, you know, chance to visit the Galapagos Islands. So exploration is the key.

Certainly there are places in the solar system where the exploration certainly does have to be robotic. If you want to build a submarine to go to look at the bottom of Europa's ocean, then this has to be robotic exploration. I mean, I do think, though, that in the context of our places like Mars, where, you know, we have good reasons to think humans certainly could go, then having human expeditions to places like Mars probably will make more discoveries than robotic explorations. So I don't think, I think it would be wrong to sort of over-emphasise this. I mean, this is a big deal in space exploration circles, whether we explore with robots or humans. The answer is we need to explore with both. But exploration is the key. Unless we get out into the universe, we won't know what's the thing.

there. Yeah, I completely agree with that. But we also need to think seriously about how they got there, what they're doing there. So in the case that Monica mentioned of these large organisms down in black smoke events at the bottom of the ocean,

they're actually using oxygen. This entire ecosystem down there is using oxygen. And the oxygen came from photosynthesis. And so it does in a sense depend on the sun. Excuse me, sorry, I'm interrupted. If they're using oxygen, You said oxygen didn't turn up until about two and a half billion years in.

Yes. And I thought they got cracking at the very beginning, four billion years ago. Yes, but they didn't get cracking in the same way that they are doing now. So today they're dependent on oxygen. So all this astonishing density of life down there, it's like a tropical rainforest in terms of its density. It depends on the gases which are coming out of the vents, gases like hydrogen sulfide or hydrogen. And the bacteria are reacting those gases with oxygen. And that oxygen is just dissolved in the water.

and it comes ultimately from photosynthetic organisms further up. So if we go back to before there was any oxygen, we need to reconstruct, well, what kind of life would you expect to find in those vents then? And that would give us probably a better guide to what we should be looking for in places like Europa. Well, going back even further, Ian Crawford, there's a theory about the distribution of life in the universe, Panspermia. Can you tell us about that? Yes, so Panspermia is originally a 19th century idea.

I mean, the word means seeds everywhere. and the idea was that the space is permeated by seeds of life and the reason there's life on Earth is because it settled on the Earth and took root here. These days the term is used slightly differently. It's used to denote the possibility that life might travel between planets, usually encased in meteorites that we know are exchanged between planets, and we know that because we've got bits of Mars found on the Earth, bits of Moon found on the Earth, and there'll be bits of the Earth found on Mars.

and so the experiments that Monika was referring to earlier on the space station, they have shown that microorganisms, particularly microorganisms that have shut themselves down and are sort of hibernating, can survive the space environment surprisingly well. And so this does raise the possibility that life might be transferred between planets on meteorites, which have been knocked off surfaces by bigger meteorite impacts. So if we look for life on Mars, would be a big question if we find it tremendously exciting. But the next question would be,

is it earth life that's been transferred to Mars or vice versa? Or is it an independent origin of life? And a lot hinges on that question. Monica, I know you want to come in, but just before you do, Fred Hoyle got hooted out of the community of people like yourselves, because he suggested something not entirely unlike this. Yes, and he was much more on the original pansepermia,

you know, idea in terms of transfer of, life into the solar system and coming from from beyond. And to my way of thinking, okay, but you're just putting back the problem of the issue of where did life come from to start with. It doesn't solve anything to say, oh, it came from out there. You know, if you want to try and understand life's origins, you know, you've got to understand it whether it was on Mars or on a planet around another star. And so coming back to the idea of interplanetary transfer of microorganisms brings us to the idea that when the planets first were formed,

Mars and the Earth were formed at the same time from the same materials. They were bombarded by asteroids and comets. They've got the same, you know, volatiles there. We know from pictures of Mars that there was a lot of water on the surface at one time. It had a thicker atmosphere. because Mars cooled quicker than the Earth, because it's smaller, it's possible that actually the conditions for life to get going were more amenable on Mars earlier on than they were on Earth.

So Mars could have hosted life before Earth did. Nick Lane, you seem to hold to the idea that the extremophiles and the archaea tell us, or indeed began the story. of the origin of life on us? Well, if we trace back this tree of life that Carl Woz initially developed, that's changed somewhat

since Woz's time, but the last common ancestor of all life on Earth seems to have been the common ancestor of the bacteria and the archaea. And if we compare their properties, I mentioned several of them are strikingly different, we can try to reconstruct

what that common ancestor looked like, what kind of environment it might have lived in. And we're talking about billion years ago, genes are very cloudy over that kind of distance. It's difficult to be specific and people argue about it. But it points really to a hydrothermal environment. It points to what's called an autotroaf, so cells that produce their own organic molecules from inorganic things like carbon dioxide and hydrogen reacting them together to produce organic molecules. That's what the tree of life says is the kind of environment that life started in. Did Darwin's origin of the species

actually pinpoint the origin? No. He did talk in a letter to hook about the origin of life as speculation and he talked about a warm little pond with phosphorus salts and proteins as he called

them but he would have been thinking about amino acids this century at least. That is the primordial soup idea which is probably not true in my view though it's still debated. I'm sorry to use vernacular shortcuts but he didn't nail it, did he? And you think that this, you're all shaking your head.

We haven't, we haven't nailed it yet. You haven't nailed it yet. But he coined a note and the notes of one or two or three of you. It only happened once and it was very rare and it hasn't happened since. The origin of life. Yeah, well, we don't know that. Well, the origin, I mean, the origin of life itself, we know for a fact that all life shares a common ancestor. But as soon as, and Darwin said this himself, that as soon as you have a cell which is capable,

of hoovering up essentially all the raw materials around, then proto forms of life are not going to have a chance. So as soon as you've got cells that can reproduce themselves, you're not going to see. And that is the warm little... In Darwin's letter to Hooker, that really is the point he's making. Because the question was, why don't we still see life? How are it formed? Why don't we see it forming today?

And Darwin's answer was, yes, he imagined the warm little pond, and that implies implicitly that's the environment. he imagined life would appear in. But the actual point he was making was if you had a warm little pond today and this chemistry tried to get going, then it wouldn't get very far because the pre-existing life would consume it. And so once life appeared first and took root, then it has taken over the planet and essentially precluded another origin of life.

But that's why we have to look else. This is the importance of looking elsewhere on life on other planets. I'll come to you in one second, molecule. But what do you mean when you say life? Ah, so there is no universally agreed definition of life amongst biologists Nick might correct me I mean I read an article with a title like 101 definitions for life There is a

That isn't helping us at the moment No, no so there is a rather a rather Prezac working definition that tends to be used in astrobiology And it's along the lines of a self-replicating molecular system capable of undergoing natural selection So make of that what you will clear actually so if that is the yes it is isn't it

Monica you're going to build on that the different dictionary definition of life is the period between birth and death which gets it's even less further forward but it's the idea of being self-sustaining and the transfer of information and knowledge and replication

but coming back to the idea of you know life getting going Nick was talking about the last common ancestor now that's not the first ancestor. This is the last one. So life might have got going lots and lots of

times but then be knocked out by adverse circumstances, you know, meteorite impact, whatever. And it wasn't until the last one took root and flourish. That's why we call it the last common ancestor, not the first common ancestor or the common

ancestor. So we could have had life starting in loads of places. But we haven't got any evidence. No, no evidence. Nick, Nick, I, Humans were eukaryotes with the nucleus in each cell and our cell structure. What's our cell structure? Does it tell us anything about the origin of life?

Nothing at all. What it tells us is that we are actually chimeric. We are formed from part bacteria and part archaean. So there was what's called an endosymbiosis, but essentially one cell got inside another cell. Population of bacteria got inside archaeal cells. And that was apparently a singular event. Again, we know it really happened once in four billion years.

Because everything shares a common ancestor. How do you know it happened once? Well, we don't know for sure it happened once, but we know for sure that all complex life shares this common ancestor, which is very, very different to a bacterium or an archaeon. So there's a lot of evolution went on there. There's no evidence to suggest that it happened on lots of occasions, but it got wiped out.

There's actually evidence against that. But that means we are a derived domain, and we have large complex cells that aren't really very good at dealing. with the kind of extreme conditions that you find in vents or in ice deserts or whatever it may be. So when we're talking about extremophiles, we're really talking about archaea and bacteria

and the eukaryotes have almost nothing to do with it. Monica Grady, what about the leap from microbial life and microbial life here and in space and the possibility of intelligent life? Is that a leap or is it just an evolution? I think that's an absolutely massive leap to go from something, you know, if you look at what's happened on the earth and the leap between microbial life and us, well, you know, we are very close to some

quite primitive forms of life, you know, mould and fungi and stuff like that. We are very close to bananas and mold, you know. Bananas, okay, mould's a bit worrying, isn't it? Well, I know, we're still, we're still there. But you have to think then that. the jump from just an evolved organism you carry out into something which is capable of civilization and communication and technological advance, which is what extraterrestrial intelligence is searching for. Because to have something which is intelligent, it's got to be intelligent and capable of communicating and wanting to communicate.

and communicating in a very specific manner so that people can hear it. And so the search for that is very, very different from the search for more primitive forms of life. So Ian Crawford, do you find any, just as more or less the same question, really? It's fascinating. Do you find any link between what Monica's been talking about and the stuff coming out of vents in the Pacific Ocean? Well, yes, if I backtrack a little bit, though.

So the jump between microbial life and extremophiles are we talking about and intelligent life, yes, it's enormous, but then it's taken a very long time. It's taken 3,000 million years. And I think one of the key insights that is useful here is that life seems to have been present. Microbial life, probably extremophiles, was present on this planet almost as soon as the Earth's surface environment was habitable.

Soon as the Earth is 4.5,000 million years old. And certainly by 3.5,000, there were, living things on it. But they were microbes and they were, by our definition, they would have been extremophiles. But it's then taken most of the history of the earth, another 3,000 million years to evolve anything as complicated as a jellyfish. I mean, things like that started to appear perhaps 500 million years ago. So we know it's a huge leap and it took natural selection a very long time. So the key thing is how often, if at all, has this been duplicated elsewhere in the universe. And to answer that question, we have to look beyond our own solar system.

We certainly know that no civilisations have evolved, no intelligent species have evolved elsewhere in our solar system. So we would have to look further afield to get an answer to that question. Nick Lane. There's a feeling sometimes that evolution, natural selection operates very slowly over enormously long periods of time, whereas in fact the world has been in stasis in effect for long periods. So the origin of the eukaryotic cell, I say it seems to have happened. It took about two billion years before that happened. Then there was a kind of great leap forward at the cellular level,

but another billion years went by before we see animals. And quite what led to the Cambrian explosion and the appearance of animals, there's arguments about it. But oxygen levels went up around that time. And so certain planetary conditions allow things to happen. It doesn't force them to happen. But when they do happen, they often happen very, very quickly. And we see an explosion of life.

And again, with humans, that seems to have happened once, another half a billion years later. So perhaps there's another kind of bottleneck there. You, Monica, then. Well, I mean, talking about evolution, it's not, as Nick was saying, it's not gradual and steady. It proceeds in leaps and bounds at some stages. And you have other things going on.

You know, you have asteroid strikes which did for the dinosaurs. So you have these haphazard events, chance events. And so even if we find all the conditions for life to have taken place in other parts of the solar system, in planets around other stars, evolution can take many, many pathways. So whatever we find, if and when we do find it, it will have been affected by other influences, other chance events, as well as steady Darwinian evolution or even punctuated evolution, if we can still call it that. and so the chances of finding something that we can communicate with I don't think not very high Just finally before we leave your vents What absolutely has to be there for things to get in?

Well very little I would say we need water We need rock and specifically minerals like olivine which are rich in iron And that's basically it they will react together to form specific types of hydrothermal vents We're called alkaline hydrothermal vents but any planet, any wet, rocky planet, is likely to have these kind of vents on. So they're likely to be ubiquitous. The only other thing you need is carbon dioxide,

because the vents provide you with hydrogen. That's technically the shopping list for life, rock water and carbon dioxide. That's why earlier when I said it was simple, and you said, no, it was very complicated. It was very complicated to get from there to replicating cells with proteins and DNA. But the basic raw materials, there's not many environments.

And then to get from something which is conscious and capable of making decisions. Or incapable of making decisions. That's another programme, you know. There's something called the Drake equation. Can you briskly tell us about that, Ian? Yes, yes, I can. So the Drake equation is an equation

formulated by the American radio astronomer Frank Drake in 1961. And it was an attempt, because he was radio astronomer, right? So he was actually trying to find civilizations that he might detect with a radio telegraph. So he was looking right at the extreme end of advancedness. But he formulated this equation to try and predict how many he might find. And the equation basically equates the number of radio-transmitting species in the galaxy

by multiplying together a whole string of numbers. So he took the rate at which stars form in the galaxy and multiplied this by the fraction of stars that have planets, and we now know that's probably 100%, multiplied by the fraction of these planets on which like, evolves about which we know nothing by the fraction of which life becomes intelligent we don't know that either by the fraction of which this intelligent life can communicate and then multiplies by the lifetime of a civilisation and we don't know that either but the thing is you

multiply all of these numbers together no no that's that's right so so so so so but the drake equation so it lacks predictive power because so many of the terms are currently unknown but it's nevertheless a useful exercise because it breaks the problem into bite-sized chunks that we can then start to address. So the astronomers have already addressed the question how common are planets. I mean, 40 years ago, we wouldn't know the answer to that term either, but now we do, and it's about 100%.

And questions are how common life is, which is the next term in the Drake equation, is addressable, and it's addressable by exploring Mars and Europa and planets around other stars. So you can see an experimental and observational, an exploration program that will gradually fill in terms in the Drake equation. so until eventually it might yield a useful answer. And, Glenn, how are we at the beginning of investigations

into this sort of life? Extrememophiles? I mean, you've sorted them all out and you can move on, or do you think there's a lot more than that? No, I think there's all kinds of very interesting questions remaining, but what really strikes me most about the extremophiles is how similar they all are. They're almost trivial adaptations that have a true.

tremendous power in terms of allowing things to survive in different environments. So, for example, there's a bacterium, dinococcus radiodurans. It's sometimes called con in the bacterium. It can survive massive doses of radiation. Why? Well, because it's basically adapted to very dry environments. And that produces breaks in the DNA. And the repair of those brakes is basically the same as repair of breaks from radiation.

And so, you know, all it does is it has multiple. copies of its genome and it recombines between them. It's basically doing a form of bacterial sex with itself and that allows it to withstand thousands of times the dose of radiation that would kill us. So it's a trivial adaptation at a molecular level with huge consequences

for ability to survive. Well that was such a comprehensive answer that we have time to ask it. By the time I've asked the next question our time will be up as indeed it's sort of it, which is our nuisance. But thank you Monica Grady in Crawford and Nicolaine. Next week we'll be talking about Frederick the Great

of pressure. Thank you for listening. And the In Our Time podcast gets some extra time now with a few minutes of bonus material from Melvin and his guests. Did we miss out something? What's significant? I was going to ask you, I was going to go on. My idea was to go on from what Nick said to how are you doing that microbial life in space at them?

What is actually happening? Well, there's a whole load of experiments still going on on the space station. you know, once you learn one set of things, then you, you know, change new experiments, add new experiments. But there's also, you know, to come back to the space exploration robotic versus human, one of their real worries about looking for life on Mars is that if we find, you know, to find any traces of life there is really difficult.

I always come back to the trace fossils in Australia. So some rocks have been found. in Australia, which have got these marks in them, which some people think are biological and some people think aren't. And you can go back to Australia and you can examine these with every single, you know, really, really complex bit of equipment you've got and people still don't know the answer. Yeah, I mean, there's a huge rouse about this about 10 and 12 years ago. Unfortunately, Martin Brazier is now sadly diseased. He died, yes. But so the idea, you know, on earth where we can go back and get more and look at it with sophisticated equipment and

we still can't tell the answer. But I think we have come a long way since that argument 12 years ago. They now do look like they probably were living cells, but the level of evidence required has gone up. So what are you going to do? How are you going to replicate that investigation on Mars if you get some funny marks in a rock? And, you know, that's where you've got to have humans. Yeah, well, I think so. But it's the start of a process. I mean, the first thing is to find the... Find the... The first tentative evidence and then that will stimulate a lot more exploration. Yeah.

This is the only way. As did finding the little microfossil in the meteorite in 1986, which was very, very controversial at the time. There's a little mark found in a meteorite from Mars and some people thought it was evidence of a fossilised bacterium and lots of people thought it wasn't. But it started off the conversation. It really pushed people into finding out, well, is this true? Is it not? What's the evidence? And then more missions to Mars and stuff like that.

You know, you need something controversial, really, to get people talking. Often at the end of these programmes about advanced sciences in the different areas, there's a kind of triumphal last five minutes of which goes something like, this started many, many years ago by people like U3, doing abstract work following their curiosity and this seemed to be very strange business all together and several decades or whatever was later

oh look it's turned into chips that are run in the world or it's turning into something it has a sort of terrestrial and immediate and practical legacy is there anything in this? Yes I mean we didn't get around to talking about it earlier but many of the enzymes that these microorganisms have had to develop to survive at very high temperatures

have turned out to be very useful for all sorts of applications. So actually, if it's applications that you're after, the study of... Gene sequencing, for example, it all depends on enzymes taken from extremophiles and all this genome sequencing and so on. Yeah, or genetic fingerprinting, all of this,

it wouldn't be possible without studying these high-temperature extremophiles. But it's become very difficult to... There's no possibility of genetic fingerprinting before we got to extremophiles. The key enzymes, which Nick knows more about me, the polymerase chain reaction, which you take a tiny bit of DNA and then it's got to be multiplied millions

of times until there's enough of it to sequence. So you have to melt it and then make copies from each thing. And so you go through sequences of melting and then annealing, but the enzyme that works at their high temperatures required are enzymes taken from extremifiers that work at 70, 80 degrees and discovered. And had we not discovered

them, we wouldn't have this technique. The trouble with, I mean, curiosity driven research and exploration, they You go hand in hand, really, is just curiosity about the world around you. And it's very hard to justify these days in terms of this is what we're going to discover. You don't know. That's the whole point about explorations. You don't know what you're going to discover.

30 years down the line, it's obvious. But, you know, you can't begin to predict. And so it's very hard to write a grant application or something that says. I'm going to discover. There are many more Radio 4 Arts and Discussion Programs to download for free. Find these on the website at BBC.com.com. Radio 4.