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This is about science produced by the California Institute of Technology in cooperation with station KPCC Pasadena California. The programs are made available to the station by national educational radio. This program is about exobiology with host Dr. Robert McGregor and his guest Dr. Jerri soften. Here now is Dr. McGregor. The expression X about G has gained a fair amount of acceptance in professional circles. But I believe it's a word not well-known or familiar to the public at large. I want to Jerry if you might express to us the ideas that are in compassed within this word. I think this is really a brand new kind of biology brand new in the sense that 10 years ago there wasn't any biologist who understood what exobiology was. The word was coined by Josh lever of a Nobel Prize laureate from Stanford and what he did is contract the word extraterrestrial biology and
make it into a word called exobiology it seems to have caught on there was a period in which there were some arguments about it. But I think in general now we tend to think of exobiology as that science which searches for and understands or tries to understand the characteristics of life other than terrestrial biology. When you say the search for life and I think that perhaps have some particular meaning to each of us and something which is understandable. But when you use the expression to characterize that life what do you mean by that. Well I think that really is in a sense the essence of the whole problem. The detection of life is perhaps what one does in order to prove that there is an actual biology that is in order to prove that there is a science. It means to recognize that there is life. That's right. When you see it. That's right. If in fact we really are we there is we the terrestrial beings are the only life that exist in the whole universe. First of all it would be quite
astonishing. And secondly that will delete the science of exobiology. Not many of my colleagues and certainly not many biologists really believe that terrestrial life is the only kind of life that exists. Many of us and perhaps even most of us believe that in fact the universe probably has other life than just terrestrial life and it is that other life that exobiology addressed itself to you. Well I've certainly heard some of the statistics about the possibilities of life and extraterrestrial environments other planets around other suns and a statistics are rather impressive. And certainly suggest that if you go too far into our own galaxy that one would encounter a planetary environment where life. Well where the circumstances are like those on Earth and therefore perhaps the prospects of finding life are. Greatly enhanced. But what is there perhaps from a more fundamental basis other than a statistical one which
suggests that there is a life elsewhere. Well I think that my ologist have been tantalized by this question of really are we alone. Is this the only life that's known. Maybe it might be wise for media to make a statement first and then the background statement with some evidence. The statement is that to rest your life has a oneness about it that is that we terrestrial beings the giraffes the bacteria the dinosaurs all the beings that have existed on the earth have evolved from a single occurrence that is life generated the genesis of life the origin of life and as a single set of events. There was only one and this may not be a terribly common point of view but it is the biologist point of view that once life started in on that once all subsequent life has evolved. Since that once happened only
once the question really is was that in fact a unique event or was this the kind of event that takes place as a result of. Particular kinds of chemistry and physics that is part of a general pattern that that will happen wherever that situation occurs. The question of catalyzes biologist is was this in fact a once or was this one of numerous occasions in which were only seen in space and time. This particular one that we know is terrestrial life. Well I got an impression from some of these conversations and which out of alt something like. That. If one were given a particular set of physical and chemical circumstances on a planet. That the evolution of life is. This is essentially a foregone conclusion. This is a common point of view and I think that's a natural step in the process. Yes I think it in a sense we biologist do admit our
naivete to this and I know that you're a physicist and you do understand probably more physics than we biologist understand biology. But in the middle of the 20th century our point of view is something like this. Biology has certain aspects attributes characteristics qualities which one mate might make some statements about we don't really understand all of them. And in a sense we try very hard to define what is biology with those attributes with those aspects. We go back in time and ask whether those are in fact the essence of biology or whether in fact they are just happen to be terribly convenient categorizations or classifications of biology. For example a conventional textbook attribute of biology is reproducibility is that all it takes to define life. Well that's one that's one you know one might ask oneself if one goes
back in time. Is this in fact a necessary is it not just a sufficient but is an unnecessary attribute of biology. Was it in fact part of the beginning of biology or any one of four or five attributes that make up the textbook definition of biology or were each of those attributes the characteristics of biology. I must say that I have a particular private point of view and I like to express that private point of view. It may not be. The union formally accepted point of view but it's mine and I'd like to express that. My own view is that biology is an organized system that's capable of persistence. By that persistence I tend to include all of those or many of those attributes that biologists tend include when they talk about life. For example biologists talk about reproduction and they talk about evolution through mutation. I think those are in fact the
parts of biology that allow it to persist. Had it not encompassed those qualities it might not have persisted. And in fact biology may begin that do not have the successful attributes that this particular terrestrial biology there's nothing that says that all biology biological systems that start must in fact be successful. Ours happens to be successful through what happened years or so and. Could it cease tomorrow could see some yawns. Well one must ask oneself whether these particular attributes are the only attributes of biology which allow it to persist within the context of the change. Fireman Are you mentioned and to now that I can detect from your remarks one is the ability to reproduce that is to reconstruct itself replicate itself with appropriate instructions for replication right as well as the ability to mutate or to evolve into new forms which
again are able to reproduce that and thereby modify their own configuration. Right I think it is matter fact let me give you a little bit of my own private point of view here. I think there are different kinds of challenges to the biology. There is no local challenge the daily challenge is the biology. For example able to survive a cold night given an organized chemical system change the temperature. You might not organ survive through a cold night. A biological system at least a successful one finds a way within its own single generation if the generation time is less than a cold night of surviving that cold night or cold day as it might be. One might say given several years where maybe the temperature changes maybe not over several years but several decades significantly is the next generation able to cope with that new kind of regime. The biology is faced with then that new biology must have within it the flexibility so that it can cope
with the new temperature regime. The way in which it does it is build within the various progeny sufficient numbers of variation so that some of those progeny might have the characteristics of being able to survive that little difference in temperature that would kill off perhaps the vast numbers of them. So you're talking both in terms of a short time scale as well as a long time. That's that's that's why I say my particular point of view deals with persistence rather than the specific character. Well if one were to look for a life these are two rather broad ways in which you define life. The ability to reproduce and the ability to evolve or mutate into new forms. Might these be translated into specific kinds of questions that one could ask in a quantitative way so that when one encounters life an extraterrestrial environment that one could say in fact that this is or is not life. How are these things interpreted are translatable into things that can be measured in terms of
our science of creation. Well I think as any scientist yourself included in this one starts with a series of hypotheses test these hypothesis asked the questions of these hypothesis whether in fact they are true and those of us who consider ourselves at least participating in the Acts of biology program have in fact perhaps for convenience sake perhaps for sanity sake perhaps for the fact that this seems to be the most reasonable approach. I have selected a certain sequence of hypothesis that we think are reasonable to test in terms of a program which might be actually explored. As you know NASM has a space program they really do want to find what kinds of science exists. On the other planets biology is a paramount issue. In the space program and so we have select selected for five specific hypotheses that we want to test. Well there is this basic philosophical drive to
determine the existence of life and other elements of our solar system. You say that one can't test these ideas or determine the presence of life on the basis of certain hypotheses. Are these in fact Earth based or are they constructed from our unique experience in the trustful environment. I can't imagine any other experience. I think that's probably true. After all we are still in the 20th century we haven't explored beyond our own life so we use our own experiences as scientists use terrestrial analogy recognising fact that it is terrestrial analogy and nothing more than that and build a hypothesis. What might these be right. Let me give you for example a characteristic hypothesis. Life is based on carbon. Now certainly on earth all of the life we know has carbon as its basic single molecule which is universal in terms of its ability to participate in its basic element its basic
element. And there have been notions some of them science fiction some of them really pretty reasonable to use other molecules silicon has been a common come when Boron was was once suggested. Well one has to ask oneself. Could you in fact construct an experiment based upon Boron. Could you. So could you describe the kind of life could you prescribe the kind of life in which Boron participates and describe an experiment in which it was the prime chemical element correct in which it was in the role of which carbon plays and that's restful as an analogy to carbon. Correct. And so far no one has been clever enough or wise enough or experienced enough to experience using another molecule other than carbon as the fundamental basis upon which life is based. And as a result we have constructed experiments which are limited as they may be do depend on carbon and there's nothing illogical about that. It makes perfectly good sense. It makes perfectly good sense to go and look in fact for something that we're familiar with. Well look at what
makes carbon so unique Jerry. Well carbon is a pretty remarkable molecule in the fact that it can bond to itself it can bond to oxygen nitrogen it's prevalent in the univers it in fact combines in ways that gives it one variety of activity that is considered the gaseous form of silicon silicon was a considered molecule gaseous form so it almost doesn't exist at our temperatures. The oxide of silicone oxygen is a very common molecule in the universe. The oxide of silicone is a solid it's silicon dioxide of glass. The oxide of carbon use carbon dioxide and there's one remarkable thing about about. Carbon dioxide. Since it's a gas it's capable of diffusing it's capable of interacting with many many different other molecules. So there's this great versatility of carbon to attach itself to other add up. Yes
correct. And in stable configuration right I presume. Right. So this makes it a prime candidate prime counting its prevalence in the universe also of course yes. What might be some other threshold based experience on which we might ask such questions. Well I think one of the things that that is my pet notion is that water is a necessary molecule involved in life. Water has some wonderful and remarkable qualities to it it has remarkable solvent capability it has unique he capability hydrogen oxygen are largely known in the universe. And so I personally feel that that water is going to be one of the likely molecules that's involved in life. It is able able to ionize with ease. It would surprise me to find a life that does not in some way involve a large amount of hydrogen
oxide. So we think of a carbon system and a quiz maker and you know it's not the expressions of the doers. That's that's an appropriate expression certainly carbon system and it gave me a quiz matrix are fairly well organized. It would be surprising if in fact the life that existed if there is another life in a less a VERY MUCH less simple system than exist on earth that is terribly some simple systems do not have the permutation. That's almost seems to be necessary you know or to allow for the survival or persistence that I talked about how about some other possibilities in terms of hypotheses based on terrestrial experience. Well I think that certainly one asks the question. Whether Mars which is of course a likely candidate is likely to support life if
it's in terribly small quantities. There is a hypothesis I'm asking is could life exist in extremely small quantities could in fact there be only a few elements of life in any one place. Or must there be some critical mass necessary in order simply to support itself. It is given a period of. Of hardship or difficulty would life be put out of existence. And I think there are energetic reasons why life would not be able to exist within a changing environment in less than a certain degree. Now what the degree is is subject to some opinion and we have been making some kinds of rough calculations. Could you for example find so your life in is infrequent occurrence as say one cell every kilometer. It's not terribly likely that once I was likely to get wiped out in the course of some sort of hardship or catastrophe.
So I think it's very likely that if we find some not that we'll find lots of it but that we'll find not it in terribly quantities. So there's kind of a minimal population is not the idea that your god is saying I think it's so that if one attempts to detect life in a. Extraterrestrial environment there are certain bases on which you can ask a question of one in terms of what you look for. The carbon chemistry possibilities. Certainly the water matrix that we've talked about and the fact that if there is life there must be some reasonable abundance of life like us. So these are premises on which you can construct then experiments or scientific measurements. Could I mention one of my own pet. You have another not well I have one in which I'm pretty equally involved with personally. Since. I've been at JPL I've been terribly involved with this question of form morphology. It is my opinion that due to certain physical chemical reasons life is going
to take on a certain form that is. It isn't that we can predict specifically the form but that there are certain characteristics of form that are precluded or that are included as a result of life formations certain geometry certain genome figuration geometry symmetries. And I think that this may well be involved with the kinds of chemistry that's involved in the kinds of problems that life is faced with life for example is faced with a surface to volume problem. It must get rid of certain substances it must incur certain substances given for example the problem of. Taking on certain substances if it gets larger and larger and larger. There is a limiting point by which the volume becomes so limiting that it can in fact get rid of these things because the surface area limits the amount of intake and output. Absolutely. As a result support the chemical processes going on within the organ and it's right now of course there are ways out of that problem for example will solve the problem it has in fact taken
in things into its body but we don't expect oceans on Mars at least there's nothing been detected like that so I suspect that the kinds of life that are on Mars will have certain kinds of geometries that are particularly adapted to their particular biological and radiological problems so that you think that one can ask these questions in terms of the shape and form. You know there's must be some logic in our terms right which provides a construction for it. Absolutely. What is that what about the matter of energy. Since we rely upon it in the solar system and any star system the sun as a source of energy doesn't this come to a particular unique detection Carol but you're very perceptive. That is it's quite obvious that life exists within a closed system you know in particular. Global configuration one can't imagine an isolated case in which this life is independent and
operates independent. It must have some form of energy intake some prime source of energy right must rely upon and there must be some mechanism. Now it's wildly possible that could develop using nuclear and nuclear energy but that's pretty wild and as a result most biologists feel that there is likely to be some form of photosynthesis or some form of Sun's energy intake. Now whether the force synthesis is specifically the four sensors that we enjoy on earth. That's not quite the problem the problem is does it in fact pick up any of the sun's rays. Does it in fact convert these in some way to energy and utilize them. Does it have to do this in a direct sense does a life itself have to. Car like this solar energy and convert it to its own used or can it rely on some intermediate process which has nothing to do in life. Well that's an efficient way of doing it that is that's a guarantee that if the clouds come up of course it isn't it isn't a handicap when a life process itself can capture the sun's energy and I can fact convert it but there's nothing to preclude In fact the possibility of some sort of chemical
reaction taking place for example in the upper atmosphere in summary non-biological right now. That would of course limit the amount of biology that would be limited by the amount of proto chemistry takes place in history. Your remarks don't suggest that if one is looking for a life then one might look in terms of circumstances in which solar energy is collected and utilized. Yes does that mean then that you would look at the atmosphere at the surface where solar energy is incident. Well it certainly would make both sensible that it would not be sensible not to look at the atmosphere since that's in the sensor. A pretty easy way to do it. If one could in fact find those kinds of chemistries that were not explainable in terms of the normal physical chemical properties of the atmosphere then one would in fact have indirect evidence that our life was quite possible and in fact there has been some recent evidence by a colleague of mine that strong suggests that the Mars atmosphere is a bit out of
equilibrium and this is a form of disequilibrium. As has the words go and I are you saying here Jerry that. The environment itself will reflect the presence of life because certain ingredients. And yes For example suppose you were in a Rose Garden. And you smelled a rose. You wouldn't have to see the rose in order to predict that the rose was there he would only have to know that the smell of roses don't come about by the normal physical chemical reactions that take place in the atmosphere normal equilibrium of the environment is is quite extraordinary. Yeah you know if we find something in the Mars atmosphere and we suspect we may have that is not a normal product that's caused by the physical chemistry there. Then we have to find reasons why this thing might be there which gives us then some encouragement that to think that there is some biological processes that that builds our enthusiasm for this whole problem. Can you give us a terrestrial experience which
would be a suitable analogy. Well for example oxygen certainly of the earth when it was first formed didn't have this enormous amount of oxygen and we have 20 percent oxygen in our atmosphere now. What do you mean by it why is it enormous enormous and let's send Well 20 percent is a very high. Percentage of oxygen to our own atmosphere in terms of the chemical time in Amec equilibrium of the environment that the normal environment could not support that much oxygen that's quite right. So when I ask the question where does all this oxygen come from. In the answer most likely is that it's formed by plants during photosynthesis in which case plants pick up carbon dioxide in relatively small amounts and convert this carbon dioxide to oxygen and piling up in a rather sizable amount. This is in fact quite out of equilibrium with what one would expect with an atmosphere such as our own. You're saying then that if an observer on some distant planet were to examine the
earth spectroscopic link. And detected this large amount of oxygen in our atmosphere and knowing our having determined the physical and chemical law constitution it would be quite surprised he'd be quite surprised he'd say Why on earth is all the socks establishment as a matter of fact if I were a Martian and discovered all this action I'd say they're burning up. It is a matter of fact you know you might ask the question why aren't terrestrial beings burning up an oxygen. And the answer really is only in terms of the kind of physics that that this particular planet enjoys. That is when sugar is oxidized we actually use the oxygen in the atmosphere to do this but we have a very unique way of trance leading this energy from the high energy of of sugar down to its lower energy levels. We have suggested in our remarks that one can then take these hypotheses and construct from them specific scientific questions which would test the presence or non-presence of life.
It's pretty very hard to test the non-presence that's the that's the dilemma perhaps in this whole problem how do you detect the non-presence in life but I agree with you that positive a positive statement is easily determined right. What I thought to ask is the following. Would you suggest some experiments that one might construct based on these hypotheses which would test their validity. Right. I think there's there's certainly this is the kind of thinking that we my colleagues myself and others around the country have been thinking about. How does one for example test the hypothesis that. Life is ubiquitous on the planet. Well one of the things we do is examine the possibility of a particular site and look for life that resembles that was another hypothesis doesn't in fact involve carbon chemistry set up an experiment that involves the testing of Life As We Know It. Now cite a particular example of this kind. One of the things that
is quite casually known by every high school student is that life is capable of reproduction. It grows. You put it in a proper medium and medium and it it makes more of itself. So one of the things one might do is set up an appropriate medium put the life into that medium and ask the question does that life. You mean that sample of the Martian or some planet extraterrestrial. Let's put it in that mean new medium this soup or something right in the soup. Well let's let's go through in fact the whole experiment that that's perhaps a good exercise. One sends an experiment it lands on Mars. The experiment then is capable of collecting some of the Martian soil hopefully including some of that Martian life. The sample is then inoculated in very much the same way that we do in a biological laboratory into the soup. As you say we call it a medium that soup then allows this life to reproduce itself. It makes more of itself and by various methods to a minimum and it
allows itself to make more. And this biological amplification is in fact the way that we detected this population increase population increase. The most obvious ways of doing this is by shining a light through the solution and asking the question did in fact the population cause the light to be attenuated. That's one conventional way of doing in effect then counting. That's right counting the population and second we might be to ask the population to digest some radio trace radioactive tracer which could then be subsequently detected. So there's a metal metabolic process there and you're looking for the flu and you know what material yes. Thank you very much Ari thanks very much for the opportunity. This was about science with host Dr. Robert McGregor and his guest Dr. Jerri soften. Join us again for our next program when host Dr. Peter listen will lead a discussion about planetary
atmosphere about science is produced by the California Institute of Technology in cooperation with station KPP C. Pasadena California. The programs are made available to the station by a national educational radio. This is the national educational radio network.
About science
About exobiology
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California Institute of Technology
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University of Maryland (College Park, Maryland)
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This program discusses exobiology, the search for life beyond Earth, and the effects of extraterrestrial environments on living things. The guest for this program is Jerry Soffen.
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Interview series on variety of science-related subjects, produced by the California Institute of Technology. Features three Cal Tech faculty members: Dr. Peter Lissaman, Dr. Albert R. Hibbs, and Dr. Robert Meghreblian.
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Guest: Soffen, Gerald A.
Host: Hibbs, Albert R.
Producing Organization: California Institute of Technology
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