Ep. 376: The Miller-Urey Experiment

Evolution explains how life adapts and evolves over eons. But how did life originate? Chemists Miller and Urey put the raw chemicals of life into a solution, applied an electric charge, and created amino acids – the building blocks of life.

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Show Notes

Miller-Urey Experiment
Miller-Urey explained
Stanley Lloyd Miller bio
Stanley Miller
Stanley Miller’s papers
Harold Urey
Harold Urey’s papers
Harold Urey bio


Transcription services provided by: GMR Transcription

Announcer: This episode of Astronomy Cast is brought to you by Swinburne Astronomy Online, the world’s longest running online astronomy degree program. Visit Astronomy.swin.edu.au for more information.
Fraser Cain: [inaudible][00:00:23] cast episode 376, the Miller-Urey Experiment. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos. We help you understand not only what we know but how we know what we know.
My name is Fraser Cain. I’m the Publisher of Universe Today and with me is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville and the director of CosmoQuest. Hi Pamela, how you doing?
Pamela Gay: I’m doing well, how are you doing?
Fraser Cain: I am doing great. So, a couple of things. One, I think this is sorta the first show that we’ve done since after the Hangoutathon. So how did it go? What was the final fundraise?
Pamela Gay: It’s over $36,000. We’re still literally waiting for some of the checks to clear but we hit our target. And while I don’t know how far over $36,000 we went, we did bring in the money to keep us going until hopefully we hear positively on the grant I submitted yesterday which is why we didn’t record on Monday as normal and are now recording on Tuesday.
Fraser Cain: Right.
Pamela Gay: If we don’t get the grant, we’ll –b
Fraser Cain: — then Hangoutathon 2016.
Pamela Gay: Yeah, yeah.
Fraser Cain: Yeah. So – but people can still contribute if they want to, right?
Pamela Gay: Yes, always. In fact, if you go to Cosmo Quest.org/donate we’d love to be able to start getting [inaudible] [00:01:30] back involved and all the little things that we’ve had to cut out post sequestration. It seems like every month one more thing goes by the wayside as grant after grant slowly winds down. And there haven’t been new calls really since sequestration hit.
Fraser Cain: Yeah.
Pamela Gay: But here’s to hoping that the future turns around. As always, every dollar you give we will stretch as far as possible towards doing science and science education.
Fraser Cain: Absolutely. Yeah, I mean, all the money just goes into science. That’s why we do it, that’s what we’re here for and with your help we can push out more science and outreach. And we really appreciate your help, everything that you did during the Hangoutathon and just all of the regular donations that come in. It’s just – it’s not for us. It’s for the science. It’s for the people who work on the projects and programs that we do. So we really appreciate your help.
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Fraser Cain: Evolution explains how life adapts and evolves over the eons, but how did life originate? Chemists Miller and Urey put the raw chemicals of life into a solution, applied an electric charge and created amino acids, the building blocks of life.
So this is this classic, right, the argument against evolution. They were like, well, where did it start? Evolution doesn’t account for how it began. Well, that’s not evolution’s job. Evolution doesn’t have to do that. Evolution perfectly explains how life changes and adapts overtime. But this nagging question, how did it all get started. I’m saying it’s aliens but it’s aliens, right?
Pamela Gay: No. Well, it could be but it doesn’t have to have been.
Fraser Cain: Haven’t you seen Prometheus? Come on.
Pamela Gay: Well yeah, but that’s the whole – we can’t scientifically say it was aliens. We can’t scientifically say it wasn’t aliens. And you and I have done entire episodes on the idea that life on earth actually originated from bits of biome from somewhere else that ended up here. But that life still had to have originated somewhere. So it is a scientifically interesting question to try and figure out on whatever world or worlds plural that life originated, how the heck did it originate?
Fraser Cain: So if you roll evolution back, I mean, there’s a lot of sorta similarities between this and the big bang, right, that they’re both these branching, evolving situations. But you can run the thin backwards and see things converge and see things come together. How far does evolution get us back?
Pamela Gay: Evolution gets us to the point of having a membrane that surrounds fluid, that is capable of consuming energy either by transforming light or through other chemical processes. You need a chemical gradient in order for this to happen. So basically it gets us to the point of having a membrane and a few organelles that also are capable of taking that membrane and organelles and splitting it in half to make more membranes and organelles.
Fraser Cain: So like DNA with a few rudimentary –
Pamela Gay: — bits and pieces.
Fraser Cain: — systems –
Pamela Gay: Yeah.
Fraser Cain: — working with the DNA.
Pamela Gay: Yeah, you need some proteins basically that cause things to happen that release energy.
Fraser Cain: And we can trace life back pretty far, what, like almost, what, 3.5 billion years, like –
Pamela Gay: Right. Basically the very first things that you might start to consider life were forming at the point where the moon was still active with volcanism, which I find it amazing to think about. Just – I mean, [inaudible] [00:05:53] life had no real sensory perception, couldn’t see the volcanism on the moon but it’s just cool to have those two pieces of science simultaneous.
Fraser Cain: And pretty much as early as life could form on the earth it did.
Pamela Gay: Yes.
Fraser Cain: The moment life had – the earth had cooled down, that the major killing volcanism, the pounding of asteroids had settled down, life appeared.
Pamela Gay: And we were still a massively volcanic world. We just weren’t a molten world anymore. So we were at the point where we were starting to have mostly solid land, mostly oceans in place but not incoming in the form of asteroid and/or comets. So the world was starting to look like something that you might see as a habitable world.
Fraser Cain: And so something, some event, some aliens – no, something took – got to this situation, right, was able to – something happened that allowed that first DNA to start self-replicating. And once you’re – got that happening then you’re off to the races and evolution can take over and it all makes perfect sense. But it’s that step – that first step. So let’s sort of go down the path that Miller and Urey tried to go to try and figure this out.
Pamela Gay: So first of all, this is another one of those cases where one of the two names is a graduate student doing most of the work and the other one is the mentor who made sure that the graduate student didn’t screw up [inaudible][00:07:41] –
Fraser Cain: Which one was which?
Pamela Gay: Urey was the mentor; Miller was the scientist who did the majority of the work, as graduate students do. And the key thing here is Miller kept doing the work throughout his career. So Miller worked with Urey. Both of their names went on the original experiment. Miller was the keeper of the experiment and the person who continued the work all the way up into the 2000s. Well, he personally really stopped in 1999 when he passed on the work to his former graduate students. But it’s really here Miller that you need to be thinking about.
Fraser Cain: And so I guess what was the – what were they trying to do?
Pamela Gay: So at this point in history, and it’s important to know, this was an experiment that took place long ago in a set of understandings that wasn’t entirely what we have today. So –
Fraser Cain: Like it was back in the ’50s, right?
Pamela Gay: Yeah, 1953 was when the experiment that everyone talks about took place. So back in the ’50s it was thought, not entirely correctly, that the early earth’s atmosphere was a place rich in lots of chemicals that are readily made into amino acids, although we didn’t quite know that at the time. So it was thought that there was high humidity. It was thought that there was lots of methane, that there was lots of ammonia, that there was lots of molecular hydrogen, maybe some sulfides in there.
So in preparing to do what has become known as the Miller Urey Experiment, they put together an experimental setup where they had one sphere that had water in the bottom, a heat source underneath the water outside of the sphere, so it was not contaminating it with anything. And they heated up the water to create, well, steam, humidity, that high humid tropical environment that you think of when you think of the early earth.
They also – so then they had a tube that ran over to another sphere. And that sphere was the place of electrical death, except it created life – or not life but the stuff needed for life. And so that sphere had electrodes coming into it and they zapped electricity back and forth between those electrodes simulating all of the lightning that was getting triggered by the still active volcanism.
There’s been article after article. I know Universe Today has run several of them, about how the environment above an active volcano actually is exactly what you need to trigger electrical strikes, lightning strikes.
Fraser Cain: Yeah, I’m sure people have seen a million of these pictures that you see these beautiful –
Pamela Gay: Amazing.
Fraser Cain: — amazing, right, where you get a volcano erupting and there’s lightning going off throughout the [inaudible][00:10:29]. Yeah, it’s fantastic.
Pamela Gay: So they were trying to simulate that electrical storm so they had electricity going off. And then they’re basically mixing ammonia, hydrogen gas, methane, all of these things together in this other sphere with the high humidity vapor coming in.
And then beneath that they had a cold trap that would allow whatever was formed to funnel down into a U-shaped trap. So they’re catching everything. This is a completely sealed experiment. And they had the ability to put a sampling probe in and sample fluids that came out of that trap.
Fraser Cain: So I guess the point here is that they’ve got this fairly pure water flowing into this. They’ve got these chemicals; they’ve got this lightning going in. And then who knows what’s gonna come out [inaudible][00:11:30] be zapping these chemicals. You’re gonna be putting water into it. It’s warmed up, zap, zap, zap, zap, zap. So what did they find in the trap?
Pamela Gay: So what they found was 11 out of the 20 primary amino acids that we worry about when we’re thinking about life here on earth. And they knew that these weren’t contaminants because when it comes to life, for whatever reason, we prefer right-handed molecules, molecules that are aligned with all the bends in one way that chemists refer to as right-handed.
But the atoms can actually bond using both right-handed and left-handed semidries. And this should be a random process, which way they form. And what they actually found is the molecules formed in that random right half right half left kind of way that let them know this wasn’t just some bacteria got into their experiment.
Fraser Cain: Oh, I see. So if they’d found a bunch of only right-handed molecules in there they would’ve known that okay, then that’s what the – then that came from the bacteria. But because they found that balance – I’ve actually heard – I’m gonna completely segue for a second here – some people thought about this idea that there’s a complete shadow ecosystem out there that is run from those left-handed molecules and that we just – we don’t interact.
Now it’s probably not big creatures. They’re probably just little bacteria somewhere maybe, but that we can’t see them because we just have no – we don’t have any detection for them. We don’t really expect to see them at all. And that they might very well exist out there. So –
Pamela Gay: And it’s one of the great confusions, why is it that life prefers right-handed molecules. But that’s sort of like why does the universe prefer what we refer to as matter instead of antimatter? This is just the way things turned out and we don’t know the answers.
Fraser Cain: Yeah, exactly.
Pamela Gay: But what was key here is with their experiment they found both kinds of amino acids. And what was literally really cool is they took the samples, or more to the point, Miller, the graduate student, took the samples and very carefully stored it in vials, sealed it off, stored all of his lab notes referring on the vials to the pages in the lab notes that corresponded with the experiments being ran, kept all of the samples.
And back in the 1950s it was hard to detect amino acids. They were actually doing this using chromatography which is one of those things that probably everyone did in school at some point if they’ve grown up in the ’80s or later. This is where you either put ink on a piece of wet tissue on the edge and you see how the different shades of color in the ink separate out at different rates.
Or if you went to a sophisticated school you actually did this with a sample of DNA and saw how the different segments in the DNA split out to different distances along the much fancier chromatography paper.
Anyways, this is a process by which you separate out amino acids or DNA segments, chromosomes if you will, and depending on the size of the molecule they travel different distances in the set amount of time along the chromatography paper. So they’re using basic chromatography. It may have been with a gel, instead of with paper, to separate out the amino acids. This is not the most sophisticated way to do things. They found 11 amino acids doing this.
Now fast forward until modern times. In the ’70s they actually went back and using modern techniques found a few more amino acids. And then in 1999, after having a stroke, Miller passed all of his lab notes, all of his equipment, everything he had to his legacy child, you might say, that student that continued on all of his work. In this case that student was still actively engaged in doing research. And this was Jeffrey Bada who’s now in the University of California system. And Jeffrey Bada reanalyzed these files and found there were actually dozens of amino acids in there. But some of them were simply at such low levels that it wouldn’t have been possible for Miller to find them with the technology he had in the ’50s.
What was particularly amusing is some of these were sulphur amino acids that other big names like Carl Sagan went on to discover later on. But they’d already been produced through the Miller Urey experiment. It just was a matter that they didn’t have the technology to know that they’d made this discovery.
Fraser Cain: So did they pretty much then produce all of the amino acids required for life?
Pamela Gay: I don’t know if they have taken the time to analyze them enough to find all of them, but they’ve certainly found the bulk of them. But this isn’t without controversy unfortunately.
Fraser Cain: Right. So let’s explain the controversy and then talk a bit about some variance of the experiment because there were a lot of other variations which actually bore a bunch more fruitful results. So, yeah, let’s talk about the controversy.
Pamela Gay: So the controversy isn’t anything too big but unfortunately it’s kind of fundamental. Like I said at the beginning of the episode, all of this work was based on the idea that things like hydrogen gas, methane, the ammonia, all of these things were readily available in the atmosphere. And truth be told there is this little thing called nitrogen that was in large quantities, still is.
Fraser Cain: You’re breathing it right now.
Pamela Gay: Yeah, exactly. And had you just grabbed a random part of the earth’s atmosphere back then, the chemical mixture would’ve been really different. And if you ran this experiment with the, now we believe thanks to better research, thanks to sampling of rocks formed at the time and things like that, you wouldn’t have gotten these results. You still probably would’ve gotten a few amino acids but not in the numbers, not in the variety that were described [inaudible][00:18:01] experiment.
Fraser Cain: So they got the primitive atmosphere wrong?
Pamela Gay: Yeah.
Fraser Cain: Right, okay.
Pamela Gay: It was the ’50s. It’s okay. They tried. But while they got the primitive atmosphere wrong, which was one of the foundational ideas behind their experiment, that atmosphere that they described did exist in other places on the earth. And they ran other experiments that were more correct that nobody talks about for some reason.
So for instance, if you decided to instead of being somewhere random on the planet earth with lots of lightning going on maybe, this experiment wouldn’t have been correct because the atmosphere was wrong. But if instead you moved over to hover near one of these volcanoes, the atmosphere right outside of the volcano did fairly closely resemble the atmosphere these designed.
And more to the point, in later experiments that Miller did he simulated the pressurized jets coming out of volcanoes as part of the experiment sending those jets of material through the simulated lightning, his electrical shocks. For some reason though, whether it be frustration, exhaustion, illness, he never published those results but he kept all of the samples. He kept all of his lap notes.
And Jeffrey Bada, after getting all of this equipment, notes, everything else in ’99, he went through a period of not dealing with it but then later did get the curiosity to start going through the samples. And in the 2000s realized that in these later experiments designed to simulate the environment around volcanoes, even more amino acids were produced in greater varieties. More things that we don’t know how they would’ve been involved because we don’t exactly have the bacteria from back then, but these later experiments were huge unpublished successes.
Fraser Cain: Right. So you can kind of imagine the situation around these volcanoes that it’s like if you go near the place where the lightning is getting produced, you also get an atmosphere that is similar to what you would need. But, I mean, this is just one possible environment. I know that a lot of researchers had very fruitful experiments looking at the environment around black smokers, sort of the vents that come out of volcanoes at the bottom of the ocean. So it’s a different environment happening but different kinds of things are possible there. So wherever you have excessive energy, you’ve got various chemicals coming together in interesting ways.
Pamela Gay: And just to step back a moment, when we say amino acids, what we’re talking about aren’t molecules that are particular to life. These are rather simply a molecule that includes an amine chemical group. This is an NH2 component as part of the molecular structure. We have nitrogen with at least two hydrogens attached to it. They can have more hydrogen attached to them.
And then they also tend to have the COOH group that includes a carbon that’s double bonded to one oxygen and then also bonded to an OH molecule. So when you have these two different components to this giant organic molecule or occasionally smaller organic molecule, anything that has these two structures is a kind of amino acid. So there’s actually dozens and dozens and dozens of amino acids that you can construct and that exist in nature. Not all of them are used in life. Some of them are probably quite deadly to human beings.
Fraser Cain: Right.
Pamela Gay: So what they’re doing when we talk about these experiments is taking simplistic molecules, ammonia which is NH4 for instance, taking these simple molecules and providing the energy necessary, and sometimes the time scales and pressure necessary to allow these smaller building block molecules to form into larger and larger molecular structures.
Fraser Cain: And so, I mean, I guess the big question is, what’s the gap? What’s the gap from a jumble of amino acids, the building blocks of life to something that’s capable of – in some rudimentary form replicating itself or at least drawing those amino acids out of the environment and turning them into something that can then go another generation? Because evolution needs something to get its hooks into it, right?
Pamela Gay: Right, right. And this is where we start looking at exactly what point do you start claiming something is alive. In the ’60s John Orna did experiments that started creating the nuclear tides. I mean, there’s four separate nuclear tides that bond together in specific ways to form DNA and RNA.
So by using hydrogen and cyanide and ammonia and water he was able to create in environments that you might find deep in the ocean and in groups in large amounts starting to show how you get the [inaudible][00:23:40] nucleic acids. And, well, all of the [inaudible] that we see in humans and all other life forms.
So the question starts to be, at what point is a molecule that will undergo continuous creation versus a cell that is specific in how those molecules are aligned. Where do you define the difference between a molecule and a life form? The basic definitions that we work from is life form has from generation to generation a evolving through slight mutations structure that is as a whole consistent that process energy and turns it into cell walls and other cellular things.
Whereas a molecule is something that just undergoes a chemical reaction. But the cell is undergoing the chemical reactions within the cell. It gets kind of muddy.
Fraser Cain: Right. And it’s a huge leap. It’s a huge leap to go from a soup of amino acids, even if you have those building blocks, it’s how do you go from a pile of space Lego pieces to an [inaudible], right?
Pamela Gay: Right.
Fraser Cain: So that’s the problem.
Pamela Gay: And we haven’t been able to artificially put together DNA, stick it in a cell membrane and get the [inaudible] reproduced. We have to start with cell lines, take them apart and put them back together. But we still have to start with that cell line. We just can’t create it.
Fraser Cain: Right. And so – and even if we could do that, that still wouldn’t necessarily figure out how they got that first assembly. But the point is, that’s science so just keep looking. Just keep experimenting both – and so scientists are pushing on both sides of this question, right. You’ve got the scientists on the one hand looking for that last common ancestor and trying to either create it or try to – now how simple can you make life to the point that it’s able to do this job of replication? And that – there’s tremendous work going on on that realm.
Was it – some of the scientists are trying to create an artificial life form from the simplest possible connection. And then on the other side you’ve got these people who are following in the footsteps of Miller Urey, let’s keep trying to see how we can make more interesting, more complicated molecules, amino acids, collections of amino acids, as you say, nuclear tides come together in ways that maybe we can get at something that’s gonna be a lot more like life as we understand it.
And eventually, hopefully those two paths will connect like two sides of a tunnel being taken through [inaudible][00:26:16] –
Pamela Gay: And it’s just going to require the right combination of creativity and tenacity. One of the big questions we’re still just trying to understand is, did life originate on the surface of the earth, deep in the ocean at a volcanic vent, or did it just form out of the clays and rich organic compounds of thermal gradients that existed in the soils? We don’t even know where life originated.
Fraser Cain: Or did it fall out of the sky?
Pamela Gay: Exactly, but we’re gonna keep looking. And hopefully along the way we’ll be able to figure out how did it start and what are the chances that it started not just here but maybe multiple places here and multiple places around our universe.
Fraser Cain: Yeah, and as we’ve said many times, right, that the mystery is what’s exciting. The fact that we don’t know, the fact that there’s discovery to be made, that there are experiments to do to try and get to this question, that’s what makes it wonderful. And it’s totally fine to say, I don’t know. Who knows? We don’t know yet. Let’s figure it out. It’s okay.
Pamela Gay: And this is our journey of exploration.
Fraser Cain: Absolutely. Well, thank you, Pamela. And thanks to Miller and Urey because that’s a terrific experiment.
Pamela Gay: And thanks to Jeffrey Bada for continuing it and his continued work publishing the legacy of his graduate advisor.
Fraser Cain: That’s awesome. All right. We’ll talk to you next week, Pamela.
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