Science Friday - How The Origin Of Life On Earth Can Help Find Life In Space

Episode Date: October 7, 2024

The origin of life on Earth has been mulled over by scientists for centuries. We now know that life’s building blocks are RNA, amino acids, and cells. But if life originated from the primordial ooze of early Earth, could that process be unfolding elsewhere in the universe?The search for life elsewhere in the universe is at the center of the book Is Earth Exceptional?: The Quest for Cosmic Life, by Mario Livio and Jack Szostak. Dr. Livio, an astrophysicist previously with the Space Telescope Science Institute, which operates the Hubble Space Telescope, joins Ira to talk about the possibilities of life beyond Earth, and where we would most likely find it.Read an excerpt of Is Earth Exceptional?: The Quest for Cosmic Life.Transcript for this segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Is there life on Mars? A new book says, don't count out the possibility. I will be in fact amazed if absolutely no sign of past life is found on Mars. It's Monday, October 7th, and you guessed it, today is Science Friday. I'm SciFRI producer Kathleen Davis. One of the biggest questions of our time is about life elsewhere besides Earth. Does it exist? And if so, where are? is it? And how do we find it? That question is at the center of a new book written by Dr. Mario Liviao. And it posits an existential question. If there is life out there, is Earth really as

exceptional as we've grown to believe? Here's Ira Flato. That question is at the center of a new book written by my guest. Mario Livio is co-author with Jack Sostak of Is Earth Exceptional, the Quest for Cosmic Life? Dr. Lov. Olivier is an astrophysicist, previously with the Space Telescope Science Institute, which operates the Hubble Space Telescope. And he joins me from Hoboken, New Jersey. Welcome back to the program. Thank you very much for having me.

You're welcome. All right, what do you mean by asking is Earth exceptional? Well, the question is really, you know, we haven't found so far life anywhere else other than Earth. And it's not for lack of trying to find. So, you know, the question is, is life extremely rare and perhaps complex life or intelligent life, even more rare, in which case it would make the earth exceptional, which is an idea that we don't like to jump into, but it definitely is worth thinking about. Yeah, is this still as big a question as it has always been? You know, some things have really changed in the past three decades or so, in that we now know that there are planets that are, many of them are Earth-size around other stars. And not only that there are planets around other stars, but planets also in what we call the habitable zone, which is that sort of Goldilocks zone, which is neither too hot nor too cold to allow for liquid water.

water on the surface of a rocky planet. So that much we know, for example, our Milky Way galaxy, you know, there are probably, you know, there may be even as many as a billion such planets. So we know that in that sense, we are not exceptional, but we have still not found life anywhere else other than life on Earth. Is that surprising to you that we haven't so far? Yes and no, I would say. you know, now that we know more about the origin of life on Earth, we realize that many things, you know, had to happen simultaneously at the same place, in the right order and so on, to actually for life to emerge.

And we don't know how to calculate the probability of that. So in some sense, even if I told you that there are a billion Earth-like planets in the Milky Way, I cannot tell you that the probability for life to emerge, even if the conditions are right, is better than one in a billion. So this is why I'm perhaps not as surprised as I might have been before we understood many things on the origin of life. Yeah, but if you multiply that billion planets in the Milky Way by a billion other Milky Way in the universe, and I'm thinking of the old Drake equation now, right?

Yes. Then the odds have to be that there's life somewhere else. Doesn't that make sense? You know, again, if you asked me this before I knew anything about the origin of life on Earth, I would have said absolutely, you know. And not just by a billion, you know, there may be as many as two trillion galaxies in the observable universe.

So the numbers get really big. But because we have no idea, honestly, at this point, no idea, what is the probability for life to emerge and certainly for life to reach a complexity that allows intelligence to emerge, you know, maybe the probability is even lower than that. It's not something I like, but I cannot tell you that it absolutely cannot be.

So are you hedging your bets then on there being life out there? Maybe Earth is not. No, you know, hedging my bets would mean that, okay, I don't know anything, and so I'm trying to minimize my chances of losing. No, what I'm saying is that on one hand, I'm a great believer in what has become. known as the Copernican principle, you know, which says that we're nothing special. Copernicus showed us that in the solar system, the Earth is not at the center. And since then, we all the time saw that physically we're nothing special. And I believe that that is the case. So I don't want to arrogantly say, oh, we are the only ones and we are great and so on and this.

On the other hand, I do realize that, you know, it does require. lots of contingencies, especially to get intelligent life. Right. And let's talk more about life here on Earth because if we're going to look for life on Earth, we have to figure out how it might have started here, right? Right. So what do we think now about life starting here on Earth? I've followed this in my career over the years and have been all kinds of chemical evolution theories and things like that. Where are we now? With where we think life started?

start. So really, you know, biochemists and, you know, have made incredible progress in the past 20 years or so. And the idea is the following. You see, what used to be a great obstacle for many years is that modern life, life of today, everything depends on everything else in a circular way. Like, you know, for example, you need DNA in order to do the proteins, but in order to make DNA, you need the proteins, enzyme proteins, to make DNA. So this was a chicken or egg type problem that was extremely difficult. But then it was discovered that RNA actually can act also as an enzyme. This was discovered in the 1980s. And once you discover that, you say, whoa, then RNA can serve as the chicken and the egg.

It can both store information and transmit information and can at the same time also act as a protein enzyme. And this led to this idea of what we call the RNA world, that may be all of life on Earth started simply with RNA. Once you reach that, you say, okay, so the idea is how was RNA formed on the early Earth? And there, great progress has been made. Well, give me an idea about that. Okay. So RNA, it has a backbone that is made of phosphates and sugars, and it has four nuclear bases, which for short are called A and G and the U. Biochemists now have found ways in which two out of the four

nucleobases can be formed. There is a very plausible way of them to have formed on the early earth under the conditions that existed on the earlier. So that's only two out of four, but that's a long way forward. plus, you know, proteins are made of amino acids. These are the building blocks of proteins. They found that the same chemistry that makes the two nucleo basis can make 12 out of the 20 amino acids that all life depends on. So there is a long way, you know, well, there is still a long way to go,

but there is enormous progress. And where would they come from? Would they be found on Earth? or would these building blocks be brought in by all these meteorites over the eons hitting Earth in its primordial state? So there is no question that meteorites, you know, asteroids and so on, can bring some amino acids with them and so on. But what researchers are trying to do in the lab to actually build them from materials or compounds that are known to have existed on Earth at the conditions that existed on Earth?

And that's how they actually succeeded to do what I just told you. Yeah. The fact that we can talk about RNA being active in this creation of early life, is that because it's simpler than having to think about DNA doing it, because it's a simpler molecule? Yes. You know, RNA is single-stranded. DNA, you know, is a double helix.

DNA is better than RNA in terms of storing information and so on. but it was probably a later invention of evolution. Life started very simple. The first cells or protocells that appeared on Earth probably just consisted of some sort of membrane inside which there were maybe some pieces of RNA. Aha, and then so it evolved into DNA later on. Right.

Do you think we are close to discovering life and other places in outer space? If you ask me 10 years ago, I would have said that maybe we are a decade away. Well, you ask me now, I say we are about a decade to two decades away. But we certainly are getting there. I mean, look, we found all these extrasolar planets, which are kind of similar to Earth. and they are in the habitable zone, which allows for liquid water on their surface.

And we have ways now to try to characterize the atmospheres of these exoplanets, namely to say what is the composition of these atmospheres, especially with the James Webb Space Telescope, we're starting to be able to start a little bit with Hubble, but now with the James Webb, we're doing this even better. And with the next generation of space telescope, in particular there is one planned, the Habitable World's telescope, we hope to be able to characterize the atmospheres of, you know, two, three dozen such planets. And then we can start telling, you know, because what life does is it takes such atmospheres out of thermochemical equilibrium.

You know, it's a bit like you cannot have a bunch of graduate students and lots of pizza in equilibrium in a room. You know, one consumes the other. And similarly, you know, if you find an exoplanet that has an atmosphere that's rich in both oxygen and methane, let's say, that cannot be in equilibrium. I mean, that is driven by life. and that's what happened on Earth itself. So if we managed to find that, that would be a very strong biosignature. I mean, it will say that that planet is very likely to harbor some form of life. Now, I'm not saying, you know, there are crocodiles there, you know, or things like that.

But simple life forms, yes, bacterial life of some sort and so on. So we're looking for basically the pizza crusts that are left over from what's going on. What about our own galaxy and our own solar system, even closer to home, where do you think is the most promising place to look for life here among our own planets? Yeah, so, you know, first of all, you know, we have to think about the rocky planets and those, well, Mercury is way too hot. Earth, we know there is life. So this, you know, lives Mars and Venus.

So the one that is most looked at is Mars, because Mars, you know, formed basically from the same type of compounds that Earth formed from. And plus, we know for a fact that some four billion years ago there was liquid water on the surface of Mars. It lost it because it lost also its atmosphere and it lost heat. But, for example, some of the landers, the NASA landers, tell us that there probably is lots of liquid water, some, you know, six to ten miles deep inside Mars. So I would say we definitely have to look for signs of past life. I mean, probably no life today, but past life on Mars.

I will be in fact amazed if absolutely not. No sign of past life is found on Mars. Venus, we thought that it wasn't such a good candidate, but again, three, two, three years ago, it was discovered that maybe in the upper atmosphere of Venus, there is this thing called phosphine, which is from phosphorus and hydrogen. and on earth that compound is made by bacteria. So there are some missions to plant to Venus

to also tell whether there is anything there. And the story doesn't end there. We discovered that in some of the moons of the giant planets, Jupiter and Saturn. So for example Europa is a moon of Jupiter

underneath a thick ice, there is a liquid ocean underneath. And similarly, this thing exists in moons around Saturn, like Enceladus and Titan. And so there are missions planned. In fact, a mission to Europa is just now taking off. and to study these moons to see if there is any possibility for life there. I guess Arthur C. Clark got it right to go look at those places. Yeah, well, you know, Philip Morrison, who is a famous physicist, and he basically said that, you know, we don't know the chances of finding anything,

but we know that if we will not search, the chances are zero. So we have to search. You know, we talk about looking for life. Are we, do you think, psychologically, emotionally ready for the discovery of life someplace else? Well, the real answer is that I don't know. But I want to point out to you that there was a point where an announcement was made that life may have been found in a meteorite that came from Mars, was known as ALA. H-84-001. Had those little nodules on it, right?

Right, right. Well, that turned out not to be correct, but nevertheless, when the announcement was made, sure, I mean, you know, the scientific community was very interested and so on, but it didn't really, you know, completely shake the general population. Now, maybe it was because, if at all, if they were to be true, they were just, you know, some form of bacteria and nothing more interesting than that. Maybe if we were to find a complex or intelligent life somewhere,

it would have more of an effect. But, you know, I heard once the director of the Vatican Observatory say that, you know, if religion survived things like Copernicus and Darwin and so on, probably religions would survive even the detection of extraterrestrial. life. So they're getting ready to deal with it, it sounds like. I think so, yes. Or they think that, you know, that maybe the effect would not be so large so they even don't have to deal with it. Right. What do you think about people who are fearful that, not that we would find life out there, but like in the science fiction movies,

aliens would find life on Earth? Yeah. I'm not fearful about this because, look, my feeling is the following. If there are extraterrestrial civilizations out there, you know, intelligent civilizations, it is much more likely that they are more advanced than us by, you know, maybe a billion years than the other way around. If they are more advanced than us by a billion years, they probably found us already. And they are just not interested in the same.

same way that, you know, are we trying to communicate with the worms of our world? You know, and so on. We are like worms to them. So I think that, you know, I don't fear that really too much. Do you think they might have been here and there might be signs that we don't know about that they have visited us? Look, I'm not aware of any convincing such sign that has been found. However, I will say that I'm all for searching for such signs or for all kinds of artifacts. And the reason is that, you know, such very advanced civilizations, if they send any types of signals, those may be coded so terribly that we cannot even understand that these are signals. On the other hand, artifacts, you know, are easier to understand. So,

I'm not aware that we found anything. There has been a claim that something was found, you know, in the last few years, but most of the community doesn't actually believe that. But I'm all for searching for artifacts. Yeah. And then, you know, as Carl Sagan used to say, you know, extraordinary claims requires extraordinary evidence. Do you believe in that, too?

I absolutely think that that is a correct statement to make. And by extraordinary evidence, what he really meant is that the evidence needs to be so convincing that everybody will agree that there is no other explanation than, you know, that this is extraterrestrial life. When you have a situation where, okay, maybe one scientist thinks that, you know, by the way, I mentioned the ALH meteorite, there were a few people. who continued to believe that this contained life. Similarly about the Viking experiments, you know, you remember that there were the Viking landers on the moon. Absolutely. And they, you know, thought that they found some signs of metabolism in the Martian soil. And, you know, almost everybody is convinced that those experiments did not find life.

But a few people continued to believe that they found life. And there was the Omoa-Mua, extraterrestrial object? Look, the Omoa-Mua was undoubtedly interstellar, and there were many strange things about it. You know, it was kind of a cigar-shaped. It has the non-gravitational acceleration and so on. But unfortunately, it did not allow for very deep research into its nature. And so at the moment, you know, there are explanations that while not complete, they are plausible, you know, about outgassing and things like that and so on.

So I'm not prepared to say that this represented sort of solar sail type vehicle. Well, I'm with you on hoping that we do find something or something finds us. I hope so too. And I also hope that it will happen during my lifetime. I'll second that motion. Dr. Livio, Mario, thank you for taking time to be with us today. It's an excellent book. I hope a lot of people get to read it.

My pleasure. Thank you very much for having me. Mario Livio, who is co-author with Jack Sostak of his Earth, exceptional, the quest for cosmic life. Dr. Livio is an astrophysicist, previously with the Space Telescope Science Institute, which operates the Hubble Space Telescope, and he joined me from Hoboken, New Jersey.

And you can read an excerpt from the book. Yeah, you can head to our website. Go to sciencefriady.com slash cosmic life. ScienceFriady.com slash cosmic life. And that's all the time that we have for today. A lot of folks help make the show happen, including Sandy Roberts, George Harper, Annie Niro,

Jason Rosenberg, and many more. tomorrow we'll talk about how a treatment that uses magnets to stimulate the brain is helping folks combat depression. But for now, I'm SciFRI producer Kathleen Davis. Thanks for listening.