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IRA FLATOW, host:

This is SCIENCE FRIDAY from NPR News. I'm Ira Flatow, here in Tempe, Arizona, reporting from Arizona State University. I'm sure most of you have heard of the Crocodile Hunter - very, very famous person on television. But what about microbe hunters? These microbiologists trekked the weirdest, most hellish places on earth, wondering if they'll find anything living there. Take the folks who hike to one hot destination, the rust-stained river in Spain called the Rio Tinto, where water is more acidic than vinegar, it's loaded with heavy metals, and you might think that life has a really hard time surviving in these conditions.

But scientists were surprised to find a microbial zoo of amoebas and algae and fungi and yeast and bacteria all just chugging away, doing their thing there. And other microbe hunters have found hearty microbes thriving in the frigid, dry valleys of Antarctica, living in poor, salty soil with only a rare drop of water, topped off by a healthy dose of ultraviolet light. These discoveries are exciting for astrobiologists because they reason - and it sounds like it's pretty reasonable - if life persists in these inhospitable places on earth, why not some sort of slush beneath the surface of Mars, or maybe on Europa, a moon of Jupiter?

It's certainly a tantalizing possibility, especially with the recent discovery of methane in the Martian atmosphere. Was it from some tenacious bacterial colony hiding, hiding away somewhere? Well, that's what we're going to be talking about this hour. We've gathered some of the world's top astrobiologists to talk about what we know and don't know about life on earth, and where'd they place their bets for finding life elsewhere in our galaxy, if not in our solar system or our universe.

We're here at the campus of Arizona State University, broadcasting from the First Annual Origins Symposium. If you're here in the audience, you're welcome to step up to the microphone in front. And if you have your cell phone and you'd like to call in, our number is 1-800-989-8255. Also, on Second Life, you can go to SCIENCE FRIDAY Island. And our Twitter is @scifri. That's @scifri.

Let me introduce my guests this hour. Ariel Anbar is associate professor in the School of Earth and Space Exploration and the department of chemistry and biochemistry at Arizona State University in Tempe. He's also the principal investigator of the NASA Astrobiology Institute team here. Welcome to SCIENCE FRIDAY, Dr. Anbar.

Dr. ARIEL ANBAR (Professor, Arizona State University in Tempe; Investigator, NASA Astrobiology Institute): Thank you.

FLATOW: Sitting next to him is Dr. Barry Blumberg. He's the winner of the 1976 Nobel Prize in Medicine and the founding director of the NASA Astrobiology Institute. He's also a distinguished scientist at the NASA Lunar Science Institute and NASA Astrobiology Institute. Welcome to the show, Dr. Blumberg.

Peter Ward is professor for the department of biology and astrobiology program at the University of Washington in Seattle. Welcome back to SCIENCE FRIDAY, Dr. Ward.

Dr. PETER WARD (Department of Biology and Astrobiology, University of Washington in Seattle): All right. Nice to talk to you again.

FLATOW: Good to see, you, Peter.

And Paul Davies is a cosmologist, physicist and astrobiologist and director of the Beyond Center at Arizona State University here in Tempe. Welcome back to SCIENCE FRIDAY,

Dr. PAUL DAVIES (Cosmologist, Physicist and Astrobiologist; Director, Beyond Center, Arizona State University): Thank you.

FLATOW: Good to actually see you in person this time. I see so many people, and when we're not on the road, that it's good to meet them in person.

Let me start with you, Dr. Blumberg. You started this whole thing with an institute - working with NASA. Why did you think you needed to create this sort of niche area?

Dr. BARRY BLUMBERG (Founding Director, NASA Astrobiology Institute; Winner of Nobel Prize for Medicine): There was a growing interest in studying the origin of life and testing the hypothesis that life might exist elsewhere. And that was accelerated by the availability of instruments that would allow us to look at these things. The immediate causation, or near-immediate causation was the studies on a meteorite found in the Antarctic, ALH 84001, that initially was thought to contain some relics of bacterial - very small bacteria within it, and certain other characteristics that might be associated with life, a matter has been a subject of intense study in that particular rock.

And there was just forces coming together that made it an appropriate time to focus on that. And NASA took the initiative, since much of their research - one of the most interesting things is whether there's life on Mars or Europa or Titan or elsewhere in the universe.

But in order to understand that, one had to understand how life started here, because the model we have for life is the only model we have. That is the one that's here. And we use that model with the full expectation that it can be rejected. One often puts up a model, in a way, hope it's rejected in the sense you'll be discovering something quite new if you reject the old vision of the image, the old model of it.

And it was also recognized that we had to have a multi-disciplinary program. So NASA decided to set up a virtual institute, with an administrative center at one of their bases in California, NASA Ames Research Center, and then to select teams from academia, from other sites, and to provide them long-term funding - well, five-year funding - because the projects in astrobiology are long-term. In fact, they're generational.

(Soundbite of laughter)

FLATOW: Take a while to find these things. Ariel, you've read the long list of - and Dr. Blumberg talked about this has to be a multidisciplinary setup, because you just don't know what you're going to be needing…

Dr. ANBAR: Right, right.

FLATOW: …what kind of knowledge you're going bring to the table on this.

Dr. ANBAR: Right. You need to bring together geologists, biologists, chemists, astronomers, astrophysicists.

FLATOW: And you have to also believe that there is life out there, right?

Dr. ANBAR: Well, no. You don't have to believe that.

FLATOW: You don't have to believe that.

Dr. ANBAR: I mean, that's a common misconception about astrobiology, that, yes, we are searching for evidence of life out there, but whether you find it or not - from a scientific standpoint - is equally compelling. You can even make the case that if you don't find that stuff, that's a more profound discovery than if you find life elsewhere. And the idea for that is - you know, if you step back and ask why are we engaged in this search, you know, what astrobiology is really all about is trying to determine are we unique? Is life on earth an unusual, freak thing? And are we, by inference, an unusual, freak thing beneath the cosmos? Or is life a typical, common manifestation of the physical laws of the universe? And by inference, is intelligence, perhaps, also?

And so answering that question - I mean, that's a hypothesis - that's a question you can frame a hypothesis from that life is common. So you go and test that hypothesis. And either way, it's profoundly interesting.

FLATOW: Peter Ward, you just got back from Antarctica, and one colleagues - you and one of your colleagues were looking at snow algae down there, right? Why?

(Soundbite of laughter)

Dr. WARD: Well, Mars is going to be a nasty, cold place, and we're looking for analogues, any sort of model to give us an idea of what type of life could be present on Mars. We were also looking not just at snow algae. We were looking at past mass extinctions, because much of what our discipline - paleontology and geology - can do is try to identify the threats that face us in the future based on what saw in the past. So we were looking at Mars, but we were also looking at our feet and trying to figure how much danger and threat is there to our civilization, our species from outer space and from dear, old planet Earth itself.

FLATOW: Could we bringing stuff to other planets that we don't want to be bringing to them? You know, like, they talked about if go to Mars, don't we have to make sure we're not bringing our own life forms there?

Dr. WARD: Over-contamination is a huge problem. We cannot sterilize a spaceship. We are just beginning to look at the various types of microbes on earth. Could these survive in space? Which could? Which couldn't? And are we producing a second sort of formation of life on Mars just from Earth life itself?

FLATOW: Paul Davies, you have an interesting take on this, because you think we might be missing, not seeing life that might exist on earth in a different form. Would that be correct in assuming?

Dr. DAVIES: That's correct. So Ariel summed up very well that astrobiologists are open-minded about whether life is some unique freak - maybe restricted to earth, maybe splashed around the solar system a bit in rocks. But the alternative is that it emerges as a natural and automatic part of intrinsically bio-friendly laws of the universe, and we don't know.

And the question is, how can we test that? Now, one way is to go to an Earth-like planet somewhere else and discover that life has arisen there from scratch, independently of life on Earth. That's difficult because of the cross-contamination of the planets in the solar system by rocks.

But it turns out that all we really need to answer is, did life happen more than once? And if it did, no planet is more Earth-like than Earth itself. So if life does form easily in Earth-like conditions, surely it formed many times over right here on our home planet.

Then the next question is, how do we know it didn't? Has anybody actually looked? And to my astonishment, when I began getting interested in this a few years ago, it seemed that nobody really had taken the trouble to look for microbial life - obviously we're not talking, you know, elephants and oak trees - but microbial life as we don't know it.

A lot of attention given by astrobiologists to life as we don't know it on other planets. But what about life as we don't know it here on Earth? We could simply have overlooked it.

FLATOW: Do we know how to look for life as we don't know it?

Dr. DAVIES: Well, there are two…

FLATOW: We only know it, you know, what do you know what to look for?

Dr. DAVIES: That is the difficulty.

FLATOW: Small problem.

Dr. DAVIES: Well, it's a problem that is not insuperable. So one is to guess that weird life, which is the preferred designation, it's alien life in a sense, this weird life might occupy regions of the planet which are beyond the reach of regular life, life that we know.

And you mentioned at the beginning about all these sort of horrible places where life as we know it struggles. There will be outer limits to that. And so we can look beyond those outer limits in some sort of multi-dimensional parameter space, to use the technical term. We can look outside those limits to see if there's some seriously weird form of life.

But much harder will be if weird life and regular life are just intermingled. So there could literally be aliens under our noses or even in our noses.

(Soundbite of laughter)

Dr. DAVIES: Right there, and so…

FLATOW: A lot of room in my nose for life to…

Dr. DAVIES: If you take a cubic centimeter of soil, it's teeming with microbes. Almost all of them have not been characterized, let alone cultured and sequenced. We don't know what they are. So there could be weird life among that.

So you make an educated guess. What might weird life do? What form might it take? And then you look for those features. So you might guess - there's a whole branch of biology called synthetic biology. So these are the guys who beaver away in labs trying to make their own life in the lab. And so they're very good. They have good intuition about what works, what would an alternative biology be.

So you go look for that stuff, or you might guess that one of the elements that life is, is not carbon because we think that all life is going to be carbon, but one of the other elements. Say, the one that is a favorite, Ariel and I and some collaborators worked on is that phosphorous might be replaced by arsenic. Arsenic could do the job for phosphorous.

FLATOW: A poison…

Dr. DAVIES: Poisonous to us, but if there's arsenic-based life, phosphorous would be poisonous to them. So let's look in arsenic-rich, phosphorous-poor environments. So these are the sort of strategies we have in mind.

FLATOW: All right. We're going to - very fast, and we're going to come back and talk lots more about astrobiology with Paul Davies, Peter Ward, Barry Blumberg and Ariel Anbar.

Our number, 1-800 - we have to change that today because we're having trouble with it. The number is 202-513-2530, 202-513-2530. Stay with us. We'll be right back after this break.

(Soundbite of music)

FLATOW: You're listening to SCIENCE FRIDAY from NPR News. I'm Ira Flatow at Arizona State University in Tempe, talking about astrobiology and the origins of life with my guests: Ariel Anbar, Barry Blumberg, Peter ward and Paul Davies.

Our number, our new number - write it down because it's not the usual one - is 202-513-2530, 202-513-2530. Let me ask you, Ariel, about this Martian methane story. Kind of intriguing, is it not?

Dr. ANBAR: It's very intriguing.

FLATOW: Where - review for us what was found.

Dr. ANBAR: What was found is small amounts of methane in the Martian atmosphere. There have been tantalizing reports, tantalizing hints of this over the years, but now the evidence has gotten to the point that it's widely accepted down the scientific community.

The reports are that the methane varies, and it's variable in its geographic distribution over the Martian surface. And one of the exciting possibilities is that methane could be produced by so-called methanogenic bacteria, which we think may have been on Earth, may have been ancestral bacteria that existed early in Earth history.

It's also possible that this is non-biologically produced methane. We know of ways to produce methane without biology. So it's by no means proof of life, but it's the sort of thing that gets people excited and wanting to explore.

FLATOW: Are you saying that it's ancient methane?

Dr. ANBAR: No, no, there's methane in the current atmosphere of Mars today.

FLATOW: But it was made by current…

Dr. ANBAR: So the excitement is the possibility there could be microbes today somewhere on Mars, possibly in the sub-surface, metabolizing right now as we speak.

FLATOW: But it's going away very rapidly, is it not? It's disappearing?

Dr. ANBAR: Well, it's being produced and destroyed at a very rapid rate, and the fact that it's being destroyed at a rapid rate means it must be being produced at a rapid rate, as well.

FLATOW: Ah, so it's even better. Peter, you're shaking your head like you like this news.

Dr. WARD: I really like the news. I always thought that Mars, the best shot for Mars would be a paleontologist first on the surface looking for fossil life, but this is exciting. Any hope is a good reason for us to keep sending probes, and let's get a human space group there.

FLATOW: Dr. Blumberg, would Mars be a good place to go, or how about - I know that you're talking about going to the moons of Jupiter, like Europa. Which would you put higher on your list?

Dr. BLUMBERG: Well, Mars has always been considered the best candidate. It's more Earth-like. Its early life may have been very similar to that of Earth, and hence our interest in studying these extreme environments, which are more similar to early Earth and therefore more similar to Mars.

One of the issues that always comes up as you find methane, for example, or the question of the magnetite that was discovered in (unintelligible) 4001. To make this distinction, differentiation, about whether it's of biological origin or of, I suppose you'd call it physical or geological origin, and that question lingers, it always leaves us.

But I like what Ariel said about whether you believe there is life or not. Because of course, when you're testing a scientific hypothesis, you want to be unbiased in your interpretation of the data.

So if you believe something, there's no point to doing the research because you know it and believe it. So belief has a big role in other areas of our life but not so much in science.

But also, we have to consider, suppose we are alone. Suppose we're the only life here. That has some important consequences.

FLATOW: Paul Davies, what would that say to you if we were the only life here?

Dr. DAVIES: I often speculate that we are, perhaps, the only life in the universe or the only intelligent life in the universe. And that would place an awesome responsibility on us, I think, because it would be our cosmic duty to keep the flame of intelligence and culture alive and maybe to spread out into the universe.

It would be a terrible tragedy if, through mismanagement of our planet and our own species, we annihilated the one little corner of the universe where the flame of reason is alight.

FLATOW: But isn't - the scientists tell us that it's a higher probability that there are life forms.

Dr. DAVIES: They have no justification without (unintelligible). It's very curious. When I was a student, more decades ago than I care to say, it was generally assumed that life began as a freak chemical accident and that it would be restricted just to Earth.

And the idea there may be life anywhere else in the universe, which excited me, there was almost nobody to speak for it. It was considered almost a crackpot idea.

And over the last 30 years, the pendulum has swung the other way. And it's now fashionable to suppose that the universe is teeming with life and that there's probably intelligent life out there somewhere. And people say, oh, the universe is so vast, it must be the case that there's going to be life there somewhere.

None of this is true. The scientific facts haven't changed. All we know now that we didn't know when I was a student is that there are going to be other Earth-like planets out there. But we guessed that there probably were.

We have no idea how life began. We have no idea what the chemical steps were that preceded it and whether these steps are likely or exceedingly unlikely.

FLATOW: So you dispute that - Carl Sagan's big equation he used to put up on a blackboard about the probability.

Dr. DAVIES: That's right. The Drake Equation. It was actually named after Frank Drake.

FLATOW: His mentor.

Dr. DAVIES: There are two terms in that equation where the error bars are enormous. The first is the probability that life will emerge on an Earth-like planet, if you've got one. That's anywhere from zero to one, anywhere from certainty to it's a unique event.

And the other is that once life gets going, what is the probability that intelligence will evolve? We know that Darwinian evolution is blind. It's not directed anywhere. It's just groping around, and there's no guarantee that intelligence is going to emerge.

It might. It has some survival value, but so do other biological aspects. And so we have only one sample of life to work with. That's why it's so important if we had two samples of life, we could separate the general features from the special features. But at the moment, we just don't know.

So it's all wishful thinking. And the great thing about astrobiology is that we're doing something about it. We're actually trying to get the answers and reduce those error bars.

FLATOW: Ariel, you wanted to jump in.

Dr. ANBAR: Yeah. I don't want to disagree in general with what Paul's saying. I think he's exactly right, but there is a reason that the fashion changed.

And there was a change in our understanding of some of the science. Which is, in the last 30 years, we have come to realize just how diverse the different ways are that life can make a living and the diversity of environments in which life can survive.

And I think that is what has changed the fashion, that now we know, as you alluded to in your introduction, life can exist in very strange environments, environments nobody would've thought life could exist in 30 years. And so naturally, that leads people to think well maybe it's a lot more probable.

FLATOW: And what's wrong with that thinking?

Dr. ANBAR: It's fine thinking, but it leads to a hypothesis that needs a test.

FLATOW: Right, it's just a hypothesis.

Dr. DAVIES: But it's all the same life, you see. It's just one sample of life. It's spread to places we didn't think it could survive in, but it doesn't tell us anything about how probable it is that life gets going in the first place.

What is the chance that some chemical mix will transform itself into life? It could be something that happens readily and easily, all around the universe, which I hope. I mean, I'd love to believe that the universe is teeming with life, but we don't know.

FLATOW: We don't have any evidence.

Dr. DAVIES: We have no evidence because we don't know what happened.

FLATOW: Barry? What do you think about this?

Dr. BLUMBERG: Well, the importance of these extreme (unintelligible) seen pretty early on in the formation of the astrobiology program and at the institute. And we funded a great deal of the early work on it, and that was mostly - the reason we funded it is that's what the scientists wanted to do.

And I think it's just led to all these intriguing possibilities, as well, by the way, as potential commercial applications. Because you're dealing with organisms that are operating under near-industrial conditions.

Again, the - Paul's point is very well taken. This switch from inorganic material into having long-chain biological information, functional containing biological particles, pieces, molecules, and that is the - a crucial part of the origins issue.

FLATOW: So you almost sound like when you talk to physicists saying about, well, this string theory, it's a great theory, but there's no way really to test it out now. That the theory that there might be intelligent life in the universe is a great theory, but we haven't been able to test it out.

Unidentified Man #1: We can test it.

Dr. DAVIES: We can test it with SETI, the Search for Extraterrestrial Intelligence, and that's 50 years old next year. And these courageous astronomers have been scouring the skies with radio telescopes hoping to stumble across a message…

FLATOW: Well, let me throw your own argument back at you. You're one who believes that we might find other forms of life on the planet here that we don't recognize. Might SETI be looking for signals for forms of life that are sending out different kinds of signals that we don't recognize?

Dr. DAVIES: Yeah, it's entirely likely. We naturally think of radio. The usual argument is that E.T. will be smarter than we are, so surely they will adapt their technology to what they know we can cope with. And radio is a pretty good way to do it.

So I think that's a good strategy, but I think that we need to think outside the box a bit more on this subject after 50 years and only an eerie silence out there.

FLATOW: 1-800-989-8255. Let's go to the phones here. Also, you can Twitter us at scifri. That's @scifri, if you'd like to send us a Twitter. Sharon in Iowa City. Hi, welcome to SCIENCE FRIDAY.

SHARON (Caller): How's it going?

FLATOW: Go ahead.

SHARON: Yeah, just had a question about - I once read about the possibility of silicon forms where the carbon's basically replaced with long chains of silicon. Is there any research on that?

FLATOW: Yeah, that's a staple of Star Trek, I think, right?

Dr. WARD: Let me butt in there.

FLATOW: Go ahead, Peter Ward.

Dr. WARD: Steve Benner(ph) from the University of Florida has suggested that if we go to Titan, and personally, I once sent in to Seed Magazine an editorial that we should skip Mars and Europa and go straight to Titan. It's an easier landing, you got an atmosphere. It's the only place where you really could get major alien life, non-carbon life.

And you replace silica into - in those temperatures, silica makes the equivalent of long-chains. These are called silanes. There's a whole of chemistry of silane. And silane chemistry, that Benner and others suggests that the life there would be as alien as anything you could imagine. And that under the conditions where methane comes out as snow, where you have giant lakes of gasoline, you're really looking at alien conditions, cooler than any place closer.

FLATOW: Hmm. So go to Saturn not to Jupiter.

Dr. WARD: Go to Titan. Titan, Titan, Titan.

FLATOW: Titan. Our number is 202-513-2530. If you have question here, please come on up to the microphone and ask your question.

That's interesting. Go Titan.

Dr. WARD: Yeah.

Mr. LYLE BERKEY (Audience Member): Thank you for taking my question. Lyle Berkey(ph).

FLATOW: Mm-hmm.

Mr. BERKEY: My question is in regards to, you know, in planets where the conditions are much different than our own, where would the energy hypothetically be derived from for these life forms? Would it primarily be through life from the sun, photosynthesis, or something entirely different?

FLATOW: Who wants - we'll start at this end and work down there. Ariel?

Dr. WARD: What we've learned also in the last 30 years in particular is that, you know, photosynthesis is probably a relatively late development in the history of the Earth, maybe a third of the way through its history, something like that, probably, that's argued.

There are other forms of life that are simpler that make use of chemical energy, that make use of chemical reactions, almost like batteries. And many bacteria, so-called archaea, in particular, do those sorts of things.

And so, probably that's what we're - that's what we tend to be biased towards, towards looking for, at least when we talk about Mars or Titan or Europa.

Dr. Blumberg: Well, in Europa, one of the potential - probably actual sources of energy is the eccentric orbit, which evolving makes it kind of oval and then circular, back and forth again, and that generates it.

And there's another interesting notion that - there's been some consideration of - and that's the possibility of small amounts of piezoelectricity. That is when you have micrometeorites which are - there's tons of them - they would generate a small amount of electricity at a local area in the ice and snow. A fascinating idea, little kind of local environment that something might happen. But I think we know very little about that right now.

FLATOW: Talking about astrobiology on SCIENCE FRIDAY from NPR News.

Thanks for that question. Dr. Blumberg, are there any real plans that go to Europa now?

Dr. BLUMBERG: I believe that it's now in the, NASA's schedule.

FLATOW: Mm-hmm.

Dr. BLUMBERG: And that it was actually kind of won out - as opposed to going to Titan because your funds are limited. These researchers are extraordinarily expensive, the launches themselves…

FLATOW: Yeah.

Dr. BLUMBERG: …cost tens of millions. So, I think Europa is back on schedule and Titan is still in reserve. Isn't it?

FLATOW: Just probe that a little bit more, so to speak. You know, Arthur C. Clarke wrote about "2001: Space Odyssey" and then "2010," and he went right to those spots. And people have been thinking about it that long to go to Jupiter and the moons of Jupiter, that this is a natural progression where science fiction is preceding science fact again?

Dr. BLUMBERG: Well, as you know, very often, we have NASA space-related conferences, we invite science fiction people, you know, we recognize them kind of leading the field. In the movie "Gattaca," by the way, one of the target for the space exploration of the time was to Titan, actually.

FLATOW: Hmm.

Dr. BLUMBERG: Yes. The great advantage of science fiction is that it's kind of unlimited by reality. I mean, that's why it's fiction.

FLATOW: But Asimov has been right. And I mean, he's been right so many times I figured that maybe he was really in on the considerations. And it was talked about amongst scientists 30, 40 years ago. So…

Dr. BLUMBERG: Yes.

FLATOW: Peter, talk - tell us about (unintelligible) ultraviolet experiments that are going on there.

Dr. WARD: Well, we are actually building laboratories and chambers, trying to produce past Earth atmospheres, but we can also produce other planet atmospheres.

And one of the things that's really scaring us to death is we look at the past mass extinctions, and for the last 20, 30 years, everybody says impact. I mean, Bruce Willis saved us from the big asteroid, and where is Bruce when the next one comes around?

And NASA and the public believes that this is the major threat. And yet we've now found that four of the past five mass extinctions were caused by microbes.

FLATOW: Mm-hmm.

Dr. WARD: Microbes attacking us and that the future of the Earth, one of warming, turns out that global warming is the scariest thing that could happen to a planet because the bad microbes come back.

So we are building situations, trying to look at Earth, let's say, 75 years from now, and what we're going to look at when we have temperatures going up five or six or even seven degrees. I think we're really on a cusp of planetary disaster that is unprecedented, at least for the last 60 million years. So, yes, just looking out in space is wonderful, but the end of the Earth is also something we should think about.

FLATOW: Mm-hmm. Yeah, that's a scary thing to think about.

Dr. WARD: Well, somebody's got to.

FLATOW: Somebody's got to do it.

(Soundbite of laughter)

FLATOW: What about the gravity? How important is gravity? I mean, and having a certain amount of gravity on a planet - or do not need gravity, do you think, in space for life to - or at least crude life? Paul Davies, you want to…

Mr. DAVIES: Yeah.

FLATOW: …out of it?

Mr. DAVIES: Microbes don't breed in the gravity, so they could be perfectly happy in a comet or something like that, so long as they've got liquid water. And…

FLATOW: Why do they have to be on anything? Why can't they just be floating around in space?

Mr. DAVIES: Well, it's the dreaded ultraviolet radiation that is the killer, that and cosmic rays.

Cocooned inside a rock, microbes can be happy in space for millions of years. And that's why I'm convinced that if you've got life on Mars, you're going to get it on Earth pretty soon afterwards and vice versa.

We know there's a trade of rocks between Mars and Earth, and we know that these rocks could convey microbes and they wouldn't be dead on arrival. But naked wafting around in outer space is a pretty harsh environment.

FLATOW: Yeah.

Mr. DAVIES: And it's really the radiation that's the killer. The old idea, panspermia, which goes back actually hundreds of years but was particularly popularized by Svante Arrhenius about 100 years ago.

FLATOW: Mm-hmm.

Mr. DAVIES: Now that was before they realized the radiation hazards of space.

FLATOW: Yeah. Pretty tough place.

Mr. DAVIES: That's not a good place to be (unintelligible).

(Soundbite of laughter)

FLATOW: Well, we have to take a short break. We'll come back and take lots more from - questions from the audience. You know, please step up to the microphone here at Arizona State University.

Also, we have a new phone number for you today, 202-513-2530. 1-202-513-2530. Stay with us. We'll be right back talking lots more about astrobiology right here from Tempe, Arizona.

(Soundbite of music)

FLATOW: You're listening to SCIENCE FRIDAY from NPR News. I'm Ira Flatow, broadcasting this hour from the campus of Arizona State University with our guests: Ariel Anbar, associate professor in the School of Earth and Space Exploration and the department of chemistry and biochemistry at ASU in Tempe. He's also principal investigator of the NASA Astrobiology Institute team here.

Dr. Barry Blumberg is winner of the 1976 Nobel Prize in Medicine. And he's founding director of the NASA Astrobiology Institute, also a distinguished scientist at the NASA Lunar Science Institute and the NASA Astrobiology Institute.

Peter Ward, professor for the department of biology and The Astrobiology Program at the University of Washington in Seattle.

And Paul Davies, a cosmologist, physicist, and astrobiologist and director of The Beyond Center at Arizona State University here in Tempe.

Our number: 1-800-989-8255. And we were going to the break, we were talking about how hostile space is to any life forms.

And Dr. Blumberg, you wanted to comment on that.

Dr. BLUMBERG: I just wanted to add to what Paul had said. There have been studies, many done by Cheryl Nickerson, who's here at Arizona State University, on gene expression in the space environment, namely on experiments that were done on the shuttle over the past few years.

And there's a surprisingly large number of genes that are either overexpressed, that is, make more of their product, or underexpresssed. There's some consistency that related to stress reactions.

And the ability to have ready access to microgravity is going to allow a kind of a whole new look at molecular biology.

FLATOW: And that was the only reason they could think of why the expression was changed because it was weightlessness from microgravity?

Dr. BLUMBERG: Well, that - the space environment…

FLATOW: Yeah.

Dr. BLUMBERG: …has many things in it but that seem to be the most likely.

FLATOW: Yeah. Yeah.

Dr. BLUMBERG: Maybe they think due to changes in the physical characteristics of the flow, the stresses that flow…

FLATOW: Interesting.

Dr. BLUMBERG: And the other thing is that in the sad loss of the spaceship Columbia several years ago, STS-107, they flew a colony of C. elegans, which is an experimental small worm nematode, they survived the crash - burn up the -deceleration when they hit the ground of that cold weather in Texas at the time. And they actually reproduced during this period after they landed.

FLATOW: Wow.

Dr. BLUMBERG: So you can have organisms at least survive that last part.

FLATOW: Pretty hearty stuff.

Our number is not the 800 number this week. It's 202-513-2530.

Let's go to this gentleman in the audience.

Unidentified Male #1: Barry may have just touched on my question. But a few minutes ago you talked about gravity. And as I have read about embryonic -embryonic differentiation of cells both plant and life, that their orientation picks up - that the, you know, different types of cells begin based on gravity. Have the microgravity experiments on the space station confirmed or denied this?

Dr. BLUMBERG: I don't believe they've had enough experience to answer that specific question. But in space, tissue cultures maintain a three-dimensional character. That is, they're not flattened on a plate. So, they're more similar to what actually goes on in the body.

And that's a very appropriate question because if they're not confined by gravity in the sense it's, I think, it would be possible to learn much more from them.

FLATOW: Mm-hmm. You were talking a bit about the creation and recreation of life in the laboratory, Dr. Davies. I'm reminded of that old Miller experiment, which put all the primordial juices in there and look to see what happened. Are we still doing those sorts of things anymore?

Mr. DAVIES: Some people. It's been a bit of a blind alley. I think at the time that that experiment was performed by Stanley Miller in 1952, and he succeeded in making some of the simple building blocks of proteins.

Everybody thought that this was the first step on a road to life down which a chemical mixture would be inextricably conveyed by the passage of time. You just have to do more of the same, let it bubble away, come back in a million years and, hey, presto, something has crawled out of it.

But what is now recognized is that making those simple building blocks is what physicists would call thermodynamically favored. It will happen naturally, easily and automatically. And I liken it to saying, well, just because you've explained how to make a brick doesn't mean how you've explained the Empire State Building.

You've got to put all those components together in this elaborate and complex structure against their autonomic gradients. Nobody knows about that next step. So, they got that far, the building blocks, but they are a long way from the Empire State Building.

FLATOW: Mm-hmm. What would it take to get to the Empire State - well, it's no joke about New York, right turn here - no.

(Soundbite of laughter)

FLATOW: What if - if I could give you all a blank check - you know, Ariel, if I could give you a limited amount of money - and let me ask, is there anything in the stimulus package that's going to increase, you know, research that's going on here? What would you need? What would you like to further astrobiology? What - is there a tool? Is there - we'd like to send X, Y, Z to Europa or to Mars or - what would…

Dr. ANBAR: I would…

FLATOW: …further it the most?

Dr. ANBAR: I mean, everybody is going to have a different answer to that question, because this is such a broad field. I would take it in two different directions. One is - and take this conversation maybe in this direction - is thinking about life outside our solar system. There's a lot of interest now in the likelihood that there are Earth-like planets around other stars.

And the Kepler telescope that was launched just a couple of weeks ago is supposed to at least tell us if they exist. The next step beyond that would be to try to characterize their atmospheres, to try to look for signs of life. That requires a whole another generation of very expensive space hardware. So that's one direction I'd go in.

The other direction I'd go in is on our planet back in time and into the subsurface, looking at life that lives today in environments (unintelligible) extreme. So back in time we can - by studying the geologic record, we learn about what the Earth was like at different times, and that - the geologic record sort of offers us alternative Earths, alternative versions of Earth that may be more analogous to what we'll see out there than what we see on Earth today.

That's not hideously expensive, but we don't spend very much money on it. And looking at life in the deep subsurface, it may be that that's where life rides out the kind of - some of the catastrophes that fascinate Peter; there's where microbes may have ridden out some of the early impacts that sterilized the Earth's surface. And so understanding how life lived in those environments, I think, would be profoundly valuable to us.

FLATOW: Mm-hmm. Would it be possible for us if we go to the moon - we talk about the life or rocks being exchanged between the moon and Mars and the Earth all the time. Are the rocks going in the other direction?

Dr. WARD: Oh, yeah.

FLATOW: That might have some forms of life on it that are still surviving on a rock someplace?

Dr. WARD: In fact, we were just talking about this yesterday, that of course there will be Earth rocks that have gone to the moon. And Barry was - I was saying, well, surely they are pulverized when they hit. But if they're big enough, maybe they're fragment and those rocks will still be there.

Now, the late heavy bombardment, which probably sterilized our planet many times, right up to about 3.8 billion years ago - the Earth is 4.5 billion years old. It's not inconceivable that there was some form of life before that final sterilization event and that this form of life, fossilized, is there on the moon in an Earth rock that went there maybe four billion, 4.2 billion years ago.

So if we could identify those rocks, it could be a bonanza, a window into the past that's been totally obliterated right here on our own planet.

FLATOW: Could you identify that?

Dr. WARD: Oh, right. Well, you…

FLATOW: Details, details.

Dr. WARD: It's not an easy thing, and of course the moon is being hit all the time by other meteorites. It's churning out the surface and so things tend to get buried and so on. On Earth, though, there are people who are very good at spotting meteorites. They can cruise around and they know intuitively where they are.

Doing it on the moon is a much tougher proposition, but they're there all right. There'll be Earth rocks there, for sure.

FLATOW: Let's go to hear this question from the audience. Yes, sir.

Unidentified Man #3: Hello. Thank you for taking my question. One of the reasons why Earth looks so hospitable to life is that life has changed what Earth looks like. So would that be a way of looking for life on other planets? And do we know what sort of changes weird or alien life would make to other planets?

FLATOW: Good question. Ariel?

Dr. ANBAR: So in terms of putting telescopes in space to someday look at the atmospheres of the planets, the first thing we think of to look at actually is evidence of how life has affected the atmosphere of those planets. And what we've turned to, actually, is looking for evidence of oxygen in those atmospheres.

The accumulation of oxygen in the Earth's atmosphere, we're quite convinced, is a result of photosynthetically produced oxygen. That's - you know, without that you wouldn't have so much oxygen. And a by-product of having a lot of oxygen in the atmosphere is having some ozone, and ozone is something that actually, believe it or not, even in trace amounts you can detect from great distance because it has unique - absorbs light in unique ways.

So that's one of the major emphases in thinking about what you might want to look for, it's exactly that, life's imprint on a planetary scale.

FLATOW: Peter, how would you react to that?

Dr. WARD: Well, Jim Lovelock was the person who first showed the Earth's atmosphere is all out of equilibrium of what it should be, unless life did it. And he was such a pioneer at this, and he took that to another step and he took it to produce what we now call the Gaia hypothesis, that life makes the planet better for more life.

I personally rather detest that whole idea. My own sense is that life is rather like Medea, a very nasty mother, not a good mother. And life does have effects on atmospheres, but they may not be the effects that we Earth-loving, oxygen-loving creatures like best. As we know, microbes can produce massive quantities of hydrogen sulfite, which is really tough to breathe.

FLATOW: Let's go to the phones. Let's go to Jared in Portland, Oregon. Hi, Jared.

JARED (Caller): Hi. How's it going?

FLATOW: Hi, there. Go ahead.

JARED: Hi. Well, you mentioned (unintelligible) falling through space and whatnot, and I was specifically concerned about mold spores or fungal life being of extraterrestrial origin and being able to hibernate and somehow being (unintelligible) on Earth or other Earth-like planets.

FLATOW: That's a good question. Spores are pretty hardy, aren't they, here on Earth? Could they be floating around, waiting to land on something? Ejected by those rocks we talked about, hitting the Earth, going towards the moon, who knows? I know, Paul, you'd like to comment on that one. Go ahead.

Dr. DAVIES: Fred Hoyle gave me my first job, and I always feel like I should say something nice about him.

(Soundbite of laughter)

Dr. DAVIES: And he was the one who pioneered the idea that microbial spores could travel through space. Now, I mentioned earlier about it's a pretty harsh environment and that radiation is a real killer.

But a slight variance of this I think does work, and that we've already discussed, that asteroids and comets slam into planets with enough force to splatter rocks all around the solar system. And some of these rocks inevitably will convey microorganisms into space. It's very easy show that they can be lifted off a planet that's small enough that the shock of ejection doesn't kill them.

And they, in spore-like form, they can survive, it's estimated, for millions and millions of years in outer space. And so some fraction of those will find their way to other planets. So I think that basic idea works.

People say, well, couldn't I spread all around the galaxy that way? The answer is, I think, no. Within our solar system there's a very good chance - I think the figure is 7.5 percent of miles (unintelligible) hits Earth eventually.

But the chances of a rock that's knocked off here, for example, ever hitting another Earth-like planet in another star system or that way away is infinitesimal. So I think it won't go farther than one planetary system.

FLATOW: We're talking about astrobiology this hour on SCIENCE FRIDAY from NPR News. I'm Ira Flatow here in Tempe, Arizona, at Arizona State University.

And a tweet came in from Red Roy(ph), who wants to know how does an Earth rock get to the moon to begin with? I mean, it's a hard concept for we to understand. How - I mean, we see rockets taking all this kind of fuel to blast off from Earth; how can a rock do it?

Dr. DAVIES: You know, when comets and asteroids slam into the Earth, there are big…

FLATOW: Even today?

Dr. DAVIES: Absolutely.

FLATOW: Yeah.

Dr. DAVIES: Even today, there is a finite probability that a large enough rock will hit Earth to knock Earth's rocks to the Moon, to Mars and elsewhere into solar orbit, absolutely.

Dr. WARD: When the asteroid hit the Earth 65 million years ago, it threw a whole lot of Earth rocks up there. So, it's not inconceivable that we have dinosaur bones on the moon. We certainly have shown that…

FLATOW: That would be a reason to get us to go back, won't it?

Dr. WARD: Well, there's probably more early Earth - pristine early Earth rock on the moon than on the Earth because of the heavy bombardment and the enormous quantities of chemically not heated, not metamorphosed Earth rock made it up there and sits there. One percent of the Earth's soil is - one percent of the litter soil isn't from the moon.

There's a enormous quantity. And the other great thing we could get there is Venusian rocks. We don't really know what the surface of Venus is like, and the moon is going to have a lot of them there.

FLATOW: So when we think of the moon as a barren place - and biologists don't want to go there because they think there's nothing worthwhile looking - it's an astrobiology storehouse then. It's a treasure trove; Earth's attic is on the moon. Barry?

Dr. BLUMBERG: The question is what's the flux of meteorites coming down. There are quite a few small meteorites. There was one just discovered, its trajectory was seen, and it was actually found on the ground following, you know, a human search for it, and pieces were retrieved.

But one of the things - the images from the lunar orbiters that were - there were five of them - that were sent up before the Apollo mission - they have very high resolution images taken with a telescope. And those - the tapes of those have now been rediscovered.

And the possibility or probability is that you could study those tapes from 1966, '7, and compare them - compare those images with contemporary ones - and we have a mission leaving quite soon, this month, for another orbiter - and determine how many new impacts you found to get some idea of the current flux.

FLATOW: What, so you could see how much - how active the bombardment of the moon has been. I think it's fascinating to think that if you really want to find the oldest part of the Earth, you go to the moon to find it. And if you want to find the oldest part of Venus, you go there too. Would that rule out the other planets? Would Mars be the same way or - were they collected, you know - or we don't need to. We could just go to Mars to find that stuff.

Dr. DAVIES: Right. Earth rocks certainly have gone to Mars, as I have indicated. Now, the problem with Mars, it's got an atmosphere so it's - a lot of them will burn up, but also because the surface of Mars is not inert. It's -there's not a great deal of tectonic activity about - sand drifting around and so on and stuff will get buried. It would be easier to identify it on the moon.

FLATOW: Okay.

Dr. DAVIES: But still, a tough proposition.

FLATOW: Great. That's a new reason to go back. I'm always looking for another reason to go back to the moon. So we've run out of time, gentlemen. I want to thank you all for taking time to be with us.

Ariel Anbar is associate professor in the School of Earth and Space Exploration and the department of chemistry and biochemistry at Arizona State University here in Tempe. He's also a principal investigator of the NASA Astrobiology Institute team here.

Dr. Barry Blumberg is winner of the 1976 Nobel Prize in Medicine and founding director of the NASA Astrobiology Institute. He's also a distinguished scientist at the NASA Lunar Science Institute and NASA Astrobiology Institute.

Peter Ward is professor for the department of biology and astrobiology program at the University of Washington in Seattle.

And Paul Davies is a cosmologist, physicist and astrobiologist, and director of the Beyond Center at Arizona State University. Thank you all for taking time to be with us today.

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