Seán Jordan on the Search for the Origin of Life

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How can we detect systems becoming biology? How can we detect the pathway from chemistry to life? Hi. Welcome to the Science Fair Podcast. I'm your host, Susan Keatley. I'm a PhD chemist, writer, and I love talking to scientists. On the Science Fair Podcast, I aim to bring you conversations with scientists doing fascinating, cutting-edge work on all kinds of interesting phenomena, ranging from physics to chemistry to biology, and even the nature of science itself. Tune in every Monday for a new episode. For each scientist we interview, first we'll release a mini-episode that connects what the scientist is doing with what's happening in the high school science classroom and then the following week, the following interview. So come along. And tune in for some Science Fair. Hello listeners, welcome to the Science Fair Podcast. Our guest today is Sean Jordan. Sean Jordan is an associate professor in biogeochemistry and astrobiology in the School of Chemical Sciences at Dublin City University. He has a PhD in biogeochemistry and a bachelor's in environmental sciences, both from DCU. Sean is the principal investigator in the ProtoScience Lab where he studies how life on Earth emerged and evolved. Today, Sean is going to discuss his journey to a scientific profession, his research on the origins of life, and relate his work to key high school chemistry and biology concepts. We also happen to be recording on Earth Day, which we didn't necessarily plan, but it's kind of a cool coincidence. And we also have a guest host, Sierra Rebels. Sierra has been interning with the Science Fair Podcast and so excited to have her today on this interview with Sean. So Sean, welcome to the show. Oh, thanks so much for having me. It's great to be here. I'd love to start by asking, can you tell us about your path to becoming a scientist and what inspired your interest in the world of astrobiology and geochemistry? Sure, yeah. I think the easy thing to say is always that, you know, from a child, I always wanted to be a scientist, but I don't really feel that that's necessarily the case for me. So I've always been super interested in how the world works, I suppose, is the best way to put it. So as a kid, just interested in nature and being outdoors and curious, asking questions. And I did study science in school, but funnily enough, the only kind of, I guess you would call them a major in high school, maybe, that I did was biology. And I am not really a biologist anymore. So when I went to university, I decided to study environmental science. That was my bachelor's degree. And this was a really nice mix of biology, chemistry, and physics, but obviously focused on understanding the natural world, right? So is the perfect mix of those under the perfect framework, I guess, for me. So I really enjoyed that. And then one of my lecturers, Brian Caller, who is also an associate professor here in DCU, he encouraged me to apply for a PhD. And in his lab, they were mostly working on biology or chemistry. Biology or chemistry really is sort of what it sounds like in that it's a combination of biology, chemistry, and geology. But really, I think it's applying chemical techniques to understand links between biology and the environment, and the geosphere more broadly, shall we say. So a lot of my time there was focused on what we call lipid biomarkers. The term I like is also molecular fossils. So these are basically molecules that are left behind by organisms, some of which are preserved for hundreds, thousands, millions of years. And you can tie them back to the source organism, which I just think is fascinating. So we can tell, you know, if a certain soil horizon came from certain types of plant matter, if we know what kind of plant matter it was, we can tell what sort of climate existed at the time. So it's just a really nice way to kind of forensically look at what seems like a lump of dirt or a rock or whatever substance you happen to be looking at. So that just really excited me. My whole time with Brian was brilliant. I used biogeochemical techniques to investigate marine sediments, paleoclimate studies, archeological studies. I kind of did everything with this tool kit that I was developing. And that kind of shaped my research career then. So that's when I went on to use those tools that I built to broaden my sphere and look at all sorts of different questions from the origin of life to the existence of life on other planets. And it's been a good journey, I guess. I started my graduate studies in archaeology. So in the US, archaeology is under the anthropology department. So I was in the anthropology department. But I was just so attracted to the idea that based on these clues, we can kind of piece together what happened. But it kind of sounds like that's what you're doing in biogeochemistry in terms of trying to understand what an environment was like. Yeah, absolutely. And you know, archaeology is a good example for me because I assume you probably got the same thing. But when you go to a museum and you see like a bit of an axe or something and you think, well, someone sat in front of this and carved it out at one point almost in the same tradition I'm in right now. And it's the same, I guess, when you stand on an ancient rock and you look at fossilized coral reefs and you think, my goodness, at one stage this was a coral reef. And now I'm in Ireland where it's cold and wet and rainy. It's like, yeah, just really impressive to think about how we can look at these materials and tie them back to their source. Sean, some of your past research has focused on deep sea vents as a potential site of the origin of cellular life. Can you explain more about this environment and what makes it ideal for early life? Sure, absolutely. So after my PhD, I applied for a postdoc in this field of origin of life that I'd never really heard much about or investigated much. And that was with Nick Lane in University College London. So he's kind of one of the, I guess biggest figures in the origin of life field. And he focuses his research on deep sea hydrothermal vents. So that's where I kind of got my start in the field. And he convinced me. So I'm convinced that deep sea or certainly submarine hydrothermal vents are where life probably emerged. So what we have here are basically large chimney structures that form on the bottom of the ocean. They form from geochemical reactions between the ocean water and geothermal fluids. And maybe your listeners might be familiar with what we call black smokers. So these really violent chimney structures where you see plumes of black smoke coming from the chimney. They're really hot. They're also very acidic. They're probably not where life started, right? So what we focus on, I suppose, are called white smokers or alkaline hydrothermal vents is kind of the preferred term. So these are further away from the volcanic ridges under the ocean. So they're not as hot. They tend to be a bit cooler. The fluids are between 70 and 100 degrees. And rather than these violent plumes, they're more like gently percolating fluids that pass up through the water column and through the chimney structures. And the chemistry of the early earth was very different than it is today. So we still have these kinds of vents on earth today. Modern ones that are functioning. They have vibrant ecosystems. But they're made of carbonates. And that's because the ocean is full of carbonates, right? So that's what precipitates out and forms these structures. But on the early earth, the ocean was probably written iron. And these structures then were probably also very rich in iron that precipitated the ocean. And that iron was mixed with sulfur that was coming from hydrothermal fluids, basically arising from the earth's crust. Okay? So the mixing of these fluids allows the iron sulfur minerals to precipitate. So now you have these big structures formed from iron and sulfur. And other things like nickel in the mix. Based on the name, you probably guessed that the fluids are alkaline and not acidic, right? So the opposite to those black smokers again. But the early ocean, because the atmosphere was probably rich in carbon dioxide, we think the early ocean was also slightly acidic compared to today. So maybe around pH five or something like that six. So when you have a really alkaline fluid, separated from a slightly acidic fluid with a semi-conducting barrier in the middle, that's basically a battery, right? So you have electrons flowing, protons flowing from one side to the other. You have basically a geochemical energy gradient is what we call it. So it's produced by the environment. There's no life involved. But we think that this was the perfect energy source for the first living organisms to feed off of in some way. And even prior to those first organisms, it's this energy that allowed the chemistry to develop into biology. It's not only kind of a great energy source, but it's actually analogous to what modern micro-organic energy source is. organisms do. So chemo-autotrophic microorganisms, those that live off rocks and live off the energy from the earth. They have a biological cell membrane, which separates the kind of slightly alkaline interior from the slightly acidic exterior, but they use this complicated molecular machinery to pump protons and create that gradient. And that's what allows them to generate their own biochemical proton gradient, which you know, it's kind of a mirror image of the geochemical one. And we think that that's a really nice blueprint for how chemistry may have become biology. What kind of time are we talking about here, Sean, when life may have originated? Yeah, this is such a big question, right? And it's still very contentious and no one really agrees, I guess. But there's a nice way to constrain it. The earth formed around 4.5 billion years ago. And we have some evidence of life that I would say is relatively convincing around 3.5 billion years ago, shall we say. There's evidence around 3.7. There's even some around 4 or 4.1 billion years ago, which could be seen as life, but I'm less convinced by that. And I think most people are less convinced by that. So the billion year window there, the evidence that we have a 3.5 are stromatolites. So they're the structures that are formed by microorganisms. And we see them in the rock record, they're layered structures that photosynthetic microorganisms create. We're pretty confident that they are from life. And we think that means that there must have been a pretty vibrant ecosystem at 3.5 billion years ago. So maybe a bit away from an origin of life, but actually it's probably a global biosphere by that stage. And there was a nice paper out, not so long ago, my former supervisor Nick Lane was involved and they were basically comparing microphones, geochemistry, origin of life theory, molecular clocks, all of these interesting data points to try and figure out when the last universal common ancestor of life would have existed. Now the last universal common ancestor, which we call Luca, to nice to have a little nice name for the last ancestor of all life on earth, it would have been a species of microorganisms that basically all life is descended from. So it's not the first living organism. It's the last one that we're all related to. It's still tricky to grasp, but basically once you have the first organism, you have lots of evolution before you get to this last organism and then everything comes from that. So it's kind of a still a good way of constraining, but they think that it could have existed around 4.2 billion years ago. And what's really interesting is that the evidence suggests that not only was it kind of a simple prokaryotic microorganism. But it had some complex stuff going on. It seems to have had even the basics of an immune system of some sort. So it was likely fighting off viruses and living alongside other species. So again, quite a complex ecosystem and that's only 300 million years after the earth formed. I think if we take that at face value, I think we can say that life had to have begun in the Hadinian, which is the first, eon of earth. And it lasted from the 4.5 beginning of earth to about 4 billion years ago. So somewhere in that window, and there's lots of interesting stuff that happens in that window. The, you know, after the earth formed, it was pretty molten, but it cooled down pretty quickly. And then it was hit by a giant object from outer space. That was like the size of a small planet. And the small planets and the proto earth, remelted completely. So if there was life starting, it couldn't have survived that. Okay. So it remelted completely. The two bodies separated and the moon formed from that. So we call it the moon forming impact. So now we have the earth and we have the moon. Right. And we know that because the isotopic signature of the moon is the same as the earth. So the material that they came from had to be the same. And that's from the Apollo mission. So super excited. And we're going back to the moon. But yeah, so after that, I would say is when life was given a chance to get started. Right. So we think that around that period, it was a water world. And we're mostly covered in a giant ocean with some small volcanic land masses. So I like to think of it as a global ocean world. That's covered in like small little Iceland and Hawaii's everywhere basically. So that's the long winded way of saying about 4.2 billion years ago. So our listeners and high school biology learn about the basic components of plant and animal cells. Can you tell us more about your lab's work on lipids and the insights this has revealed about the origin of cell membranes. Yes, absolutely. So I'm really interested in membranes. They just really grabbed my attention early on. So I think that's why I started looking at lipid biomarkers because they're the remains of membranes mostly right that are trapped in the soils and sediments. And modern cell membranes then are formed from phospholipids. So a phospholipid is a pretty complex molecule. So a couple of hydrophobic tails in bacteria, they're usually fatty acids in archaea. They're usually isoprenoid molecules. And then it's bound to a phosphate head group, which is more hydrophilic. So it likes water. So the tails don't like water. The head groups like water. And the nice thing about that. What we call amphifillicity. So it's an amphifillic molecule is that it allows the molecules to form a bilayer. And then the head groups line up alongside each other and they're very happy to sit there through hydrogen bonding. And you form this ring structure where you have both sides of the membrane itself are hydrophilic. So they sit in the aqueous phase. And then the inside of that membrane is hydrophobic. So that unique chemistry is what gives them the ability to self assemble into that complex structure. What we think happened on the early earth is there were molecules that were simpler because a phospholipid is very, very complicated. Right. You know, it doesn't sound maybe that complicated. But really there's a lot of chemistry going on to get to a molecule of that size. And you know, it takes a while to get there. But on the early earth, those fatty acid tails would have existed. Okay. So in hydrothermal vents, we have what's called water rock interactions. So the water and the rock are reacting together fueled by heat from those kind of geothermal sources next to the volcanic locations. And those reactions produce organic molecules. And they produce fatty acids, they produce alkanes, alkanols, all sorts of straight chain short molecules. But the fact that they are also the molecules that make up the tails of modern phospholipids, I think is really, really interesting. And probably another clue to how the first cell membrane started to form. Right. So if you take the fatty acids and you put them in water under the right pH conditions, they will also self assemble into these bilayer membranes. Okay. Spontaneously, it's a very easy thing to do. It's almost like making a little soap bubbles at home. Anyone can do it. It's because they also have these polar and non-polar groups. Okay. So non-polar tails and polar head groups. So this analogous structure is basically what makes us think that these would have been the first cell membranes at the origin of life. And there's been a lot of work done on those. They can allow protons to pass across the membrane. So if we go back to our geochemical gradient, now we can allow that to pass across our membrane, maybe use it for a bit of work to some, to some interesting chemistry. They can hold onto things inside the cell. So people have some studies where they can encapsulate molecules inside the cells. And really it's not that difficult to imagine those simple cells kind of gradually increasing in complexity towards something like a biological cell. In relation to your description of how the modern phospholipids are more complex, can you go into more detail about the idea behind how the early cells, how membranes formed, and how they might differ from the modern cells that students are learning about in the classroom. The major difference is how they're actually formed, right? So phospholipids are made by biology. Okay. So cells make those phospholipids to form their own membranes and to grow their membranes and then to eventually divide and form the next generation of cells. The simple cells that we have at the origin of life, these are spontaneously self assembled from molecules that just exist in the hydrothermal vents. Now people will argue about that scenario, whether it's an event or on the surface of a rock somewhere or in an ice layer, whatever, but the cells are still important because all life is cellular, right? So every single living organism has a cell membrane. So surely it makes sense that the first cells did as well. But yeah, they're much simpler. So they're very fragile. They fall apart quite easily. They don't like huge changes in pH or temperature. They don't like too much salt. If you have a certain composition. So we've done a lot of work on looking at how you need to have a diverse composition if you wanted to survive in a salty condition. So actually for a long time, it was the consensus that you couldn't have had an origin of life in the ocean because the membranes wouldn't survive the salty conditions. But our research and that of others has shown that if you increase the complexity a little bit and that's not true, makes super strange molecules or anything. It's just by having rather than having say two fatty acids, you might have five fatty acids and five alcohols, but still simple. molecules, but then they can survive the salty condition. So that gets us away from the, I would say, fragility, maybe, of the membranes. And the work is ongoing now to see what sort of membranes can survive, what sort of conditions and what sort of composition would you have needed to live in a certain environment or live as a wrong word, but to proliferate, so we say, in a certain environment. And like modern membranes are super complex, right? So they're not just lipids. They're also enzymes and ATP synthase pumps, like I said, that are pumping protons across the membrane. So there's really complex macromolecular machinery there. So the simple membranes we think could have gotten slightly more complex in terms of their composition. And then you could introduce other things like mineral clusters, for example. So you have iron sulfur minerals present in the environment. And we've shown that these conform basically nano crystals that are similar to the active sites of enzymes. So they might be capable of doing catalysis, like an enzyme does, right? So if you can embed those in a membrane in some way, then maybe you could do some catalysis on your membrane and start to do really interesting chemical reactions that would be the kind of foundations of eventual biochemical reactions. But certainly we operate in the very, very early days, so far from biology that really it's your chemistry, and it's kind of simplest. So moving on to early life on Earth, but also detecting life elsewhere in the solar system. You know, you're looking at the development of early life on Earth. You're also interested in the possibility of life elsewhere in the solar system. So our question is, what is the connection between understanding early simple cells on Earth and detecting life on other planets? I think this is really important and understandably difficult to kind of wrap your head around maybe. We can think of them as kind of separate. So there's two separate parts of this. The first part is why do these weird bubble shapes interfere with how we detect life on the early Earth and potentially on other planets? And the reason for that is that what we're producing in the lab that we know form very easily are basically little bubbles of organic matter. And like I said, they form from the molecules that are produced in geochemically active environments. So when you have these bubbles of organic matter forming in an interesting geochemical environment, there's always the potential for those to get preserved in the same way that a microorganism can be preserved in rocks from billions of years ago. So in the earliest rock record that we have on Earth, which actually doesn't come from the Hadin when we think life formed, the earliest rock record we have is from the Archaean. Okay, so all of the Hadin stuff has been completely metamorphosed. So if you do find anything really old, it's just a, it doesn't represent what it looked like originally. So we have some, the oldest materials on Earth, there are zircon crystals that preserve some nice chemical signatures, but really they're completely metamorphosed. You would never see a micro fossil in these. In the Archaean materials, we do have micro fossils, but they've been undergoing, you know, heat and pressure for three and a half billion years as well. So we don't see nicely preserved little microorganisms with all of their parts of their cell intact that we can say that's definitely a microorganism. What we see are basically round carbonaceous, well spherical carbonaceous blobs trapped in the rock. And we try and figure out whether these are actual remnants of microorganisms or not. And my hunch is that some of them are, but some of them probably aren't, even if they've been reported as micro fossils. And the reason for that is because all of the super interesting research that's been done on trying to show that these things are from life came well before anyone started thinking about, can we do the same thing with non-life? And now we're catching up. So, we're kind of coming later the game trying to develop control data for all of these micro fossil interpretation experiments. And what we're seeing when we take our little organic bubbles or lipid vesicles, we call them sometimes. And we trap them in things like silica or clays or carbonates and we preserve them. And then we also artificially alter them. So we put them under great heat, great pressure in these reactors that we have. And we look at what comes out the other side. And what we see is that the shapes are identical to what are preserved in the rock record. Okay? So you have these lovely spherical bubbles that look like nice cacoidal micro fossils. But we also get these really interesting features like what would you call them? So it's almost like you got a bubble and you pinched each side of it and it looks like it's been squeezed at the two sides, okay? And these have been reported from early Archaean deposits in Western Australia as probably biological because they look slightly complex. But we can do the exact same thing in the lab with totally non-biological materials. So in terms of the individual shapes of the cells, anything biology can do, we can do with non-biology, okay? Not only that, but they don't exist on their own as single cells, right? They group together, they attach themselves to surfaces. So they kind of look like populations of micro fossils or microorganisms that become micro fossils. And we've done some statistical work on those. And if you compare populations of lip and vesicles with populations of bacteria, you actually can't tell the difference between the two, right? Morphologically, just purely based on the morphology and what we call morphometry, so the distribution of the cells. So then the obvious question is, well, surely the chemistry is different, right? At least we can tell that they're different chemically. And so far, what we've been seeing is actually, no, the chemistry is the same as well. And the reason for that is because these are formed from very simple organic molecules. And all that's left of the micro fossils or the micro structures in the rock record are also very simple organic molecules because they've integrated for so long. And I mentioned isotopes earlier, but often you can tell the difference between one carbon molecule from life and another carbon based molecule from non-life based on its isotopic distribution. So basically you have different isotopes of carbon. And biology has a very clear signature and non-life usually has a very clear signature. But actually in these hydrothermal systems, they also produce the same kind of isotopic signatures. So you know, just layer on layer of confusing information. So it's really confusing when you look at the early Earth rock record. So when we go to somewhere like Mars, we're going to bring back samples from Mars, okay, that are from rocks that are of similar age and even older. And whether or not life existed on Mars, I think we're going to see these really interesting structures, right? So they may be from non-life or they may be from life. But right now, if you brought those samples back, I would say you're almost guaranteed that we wouldn't be able to agree on whether those microstructures are biological or not, even if they look like life and have all the chemical signatures. So what we're trying to do, it builds up lots and lots of data based on shape, size, chemistry and applying new chemical analysis techniques. And you know, really state of the Earth techniques to try and ease out differences that maybe we can use as new biosignatures. Because I think that the old biosignatures just don't fit the bill anymore unfortunately. We're still arguing that the earlier, so we need to solve that before we look at the Martian samples, I think. That is really complicated. And it's like this weird situation where the more advanced instrumentation and modeling you have, it feels like the murky or it's getting. Pretty much. I think you were addressing the next question we had in terms of deciphering non-life versus life and like the rock record and micro fossils. Can you also talk about the leopard spot patterns that were found by the perseverance rover, what those patterns in the minerals, what they indicate and how to decipher those? NASA announced in Las Olangos that they found these leopard spot patterns on the surface of a rock on Mars, right? So super exciting. They're really old rocks, they're dating back to around three billion years ago and they have these tiny little bleached spots. So it's a red rock and then you have these little kind of not white but almost white spots that are on the surface and they're almost surrounded by a darker band so they look really interesting. They're tiny, they're only millimeters in diameter, so they're really, really small spots. But they look like things that we see in the rock record on Earth that we attribute to biology, right? So microorganisms like to do redox reactions, which are reduction and oxidation reactions and when they interact with inorganic materials like iron, they change the color basically through these redox reactions and these spots are reduction spots it seems and they're really exciting. I think the question is still open as to whether they are absolutely biological or not. What I really liked about NASA's announcement on this was that they kind of called for people to do more research and to, you know, is there a way you can make these a biologically? And that's a far cry from further or from previous announcements. where maybe they just said this was life and deal with this where they were wrong in the end. So the scientists have been really, really balanced on this. And I think the jury is still out. And I know that people are doing work. Everyone's kind of working crazily at the moment to try and reproduce these structures. Colleges of mine at the University of Edinburgh have reproduced these structures. So Sean McMan's group there, they've reproduced these structures using microorganisms. So they've kind of shown that microbiology can definitely do these kinds of spots, right? Which is great because we don't have many examples that show similar, similar results. And this is an experimental example that's clearly similar to what the rover is seeing. We're now trying to do it a biologically and I know Sean McMan's group are doing the same. We're working together on that. And so far I can say we haven't been able to do it a biologically. But yeah, I think it's just about, you know, trying as much as possible. And I'm sure there are many groups across the world trying to do the same thing. But it kind of ties back to this original question, which is that we're always chasing our tail. You know, so we find something and we go, oh, this looks like it could be biological. And then we have to try and catch up with the a biological ways. So I think that will probably always be the case because you can't conceive of every possible signature that you may remain affined. And then you just have to test it. That's the way it works. Right. But it wouldn't hurt to have a bit more work. There are lots of group that work on a biotic reactions that conform these things. But I think more research into the a biological weirdness that can happen and the structures that conform and the chemical signatures that conform would really help us to understand all of these potential biosignatures a lot better. And that's going to get even weirder when we go to places like icy moons. And you know, everything changes again. It's not a rocky planet. It's not like what we see on earth Mars is more similar to earth. It's a little easier maybe. But yeah, so I think the more we can do in that before we find these things the better. I have a listener question. This is from a high school student in New York. How do nebulae connect to the creation of the earth? This is a very sensible question. And definitely one best put to an astrophysicist. But I do I do do a kind of hand wavy job of explaining it to my own undergraduate students. So I can do the same hand wavy job here. And then I'll accept criticism from all astrophysicists that listen essentially nebulae our clouds in the universe that form the solar system. So there are big clouds of dust that collapsed under gravity, formed a star, which in our case was the sun. And then all of the bits of material that was left. Started to move around the sun due to gravity and we have that same orbit today, right. And all of those pieces then basically started a glomerating together and those eventually formed planets and asteroids and planetesables and all the interesting stuff we have in our own solar system. So the nebulae is the birthplace of our star, which is the birthplace of our planet and all of the planets in our solar system and every solar system would have started with these nebulae. And it's what people say we are also the stuff that stars are made of because every single atom in our solar system basically comes from these nebulae. So all stars, all planets, but also us thinking of Joni Mitchell singing we are star dust. Yeah, yeah, for sure. For sure. There is also a theory that suggests life on Earth originated on Mars traveling to Earth via media rates. And can you give your scientific opinion on this and then kind of like walk us through your thought process. Why you why you have that conclusion. We call this it is a version of pan spermia right so this is where life was delivered to the planet from extraterrestrial places. Another version of pan spermia is that not life necessarily but the building blocks of life were delivered to Earth and to form life. I'll give you my opinion on on both sides of that. I'm not a fan of either to be honest. So let's talk about life first. So it is really interesting to think about how maybe life could be transported here and I think it's very fair to say that this is a hypothesis that is worth investigating right because we don't know for sure. But I just don't think it's them to me to my mind. It's not the most plausible thing or plausible hypothesis. Essentially what you would need is you would need microorganisms to survive the ejection from their own planet where they evolved. The transport through deep space to this new planet. The passing through the atmosphere and the intense temperatures and pressures that come with that not to mention all the cosmic rays that they'd be bombarded by as they flew through space. And then the subsequent impact as they hit Earth. Then they have to set up a life here. Right. So there's been some actual experimental work done on this and I would say the experimental site is very limited. There's a bit more modeling computational modeling, but it looks like some microorganisms that form spores and really embed themselves in the kind of deep interior of a meteorite of some sort, especially if it was a really, really big one that they could be protected from things like cosmic rays and the vacuum of space and the temperature. And they could reach the Earth. Okay. But that would make them a pretty special organism. Right. That's pretty specialized that at and hardy at surviving those extreme conditions. So what happens when they just land on a clement part of the earth. And it's not so extreme. Maybe they're just floating around in the ocean. Does that suit them? Can they survive a nest? To my mind, it's unlikely they're evolved to survive in this. It would want to be some sort of super microorganism. I think that could survive the whole journey and then also set up camp on Earth and evolve and pass on its genes and basically colonize the entire planet. It's interesting and exciting and I'm happy to be proved wrong on this, but at the moment, I don't think the evidence supports that theory. The other side of things where you have the chemistry being delivered from outer space, the building blocks, things like amino acids and lipids, even like I mentioned, this 100% happened and still happens because meteorites we know are covered in organic molecules. That's been shown we've taken meteorites that are found on Earth and we've been able to detect organic molecules in them. They've traveled to asteroids in the solar system and seen different types of organics, including amino acids. Right. So all of these things exist and certainly would have been delivered to the early earth. If we go back to what I was saying about the timing of the origin of life around this time, we had two possible events. One, well, it's kind of the same event, but two possible ways it could have happened. So this is the late heavy bombardment, which is after that moon forming impact, it seems to have been a really active time in the early solar system and we were probably being hit by a lot of these impactors. That may have been in kind of a sustained period of impact over say a few hundred million years or it could have been a really intense early level of impactors and then a declining level. So a bit longer, but declining over time. We don't know which was which, but either way we were hit with a lot of stuff at the early and the early earth. So lots of organics were probably delivered here. You've no life on earth to gobble up all those organics. So it makes sense that those could be concentrated over time. I don't love it as an origin of life theory. And my reason for that is because there's no sustained delivery of those exact types of molecules. And also let's say you're given all of your amino acids and your lipids and everything and even things like nucleotides or whatever and you start to bring those together to form a cell or some sort of biological system. Then you kind of have to go back and rework how to make all that stuff yourself. Right. So if you're given all of this stuff, then it's harder, I think to try and figure out how to make it again, not impossible. But to my mind, it makes more sense if we can do most of the chemistry in situ. So in one location, it's more sensible to me that you would have a supply of organic molecules that would gradually, gradually increase in complexity, forms, cell membranes, produce things like amino acids through different chemical reactions, probably in a gradient doesn't have to be the geochemical when I talked about earlier. It could be a temperature gradient, pH gradients, all these other pH gradients, salinity gradients, all these things can do interesting chemistry, right. But yeah, to my mind, I think it makes more sense that you start with a very, very simple organic molecule. And one thing I didn't mention earlier actually about our battery system and the hydrothermal vent is that this geochemical gradient was probably sufficient to reduce carbon dioxide into very simple organic molecules. So you can go from inorganic carbon dioxide to simple organic molecules, and then they can react really to order to build up more and more complex organic molecules. So that kind of stepwise increase in complexity, I think it's a better pathway from chemistry to more. biology in my mind. But again, I'm happy to be proved wrong on that because there are a lot of good people doing interesting work on on delivery of organics. And I can see the sense in, you know, a shallow hydrothermal pool on the surface of the early earth getting filled up with these organics. And maybe the reactions can happen in that way. One of my PhD students pointed out to me that, you know, microbes are always kind of reinventing themselves. So why couldn't the early systems have done it too? And she's not wrong. So I prefer the other hypothesis, but who knows? Sean, are there any hypotheses you're excited to investigate in the future projects in the future that you're quite excited about? I just wrote a piece which hopefully is coming out soon on my new kind of hypothesis that I've been working on that I'm super excited about, which is the idea that we should probably be searching not just for signs of life in the solar system, but signs of the emergence of life. So if, for example, somewhere like Mars, that was quite similar to earth in its earliest days, began forming life. Okay. So the chemical reactions that led to life on earth were also happening on Mars, but it never became biology. So you have all these weird chemical systems floating around, right? A varying degrees of complexity, but they never actually became biology. So you never had a complete colonization of microorganisms and all this stuff. My gut feeling is that if we landed on that world and looked at the data, we would have no idea what we were looking at. And it would just confuse us for decades at the very least. So in the in the spirit of trying to get ahead of the curve, I think we should be trying to develop those tools and techniques now because it may not be Mars, although maybe it was, but places like Europa or in Saladus, those icy moons that have deep oceans, who knows, maybe life is actually beginning to form there now. And we have weird chemical systems, but we don't have microorganisms. Again, I don't think we would know what we're looking at if we saw those kinds of systems, right? So my kind of future direction, and I hope others will also get involved is to try and figure out, okay, how can we detect systems becoming biology? And so we call these proto biosignatures. So the original biosignatures, but obviously not actually biology. And yeah, I'm hoping that that's where we're going to spend a good bit of time for the next few years. It's exciting to think about seeing like life on the precipice now. Is there any advice you have for any high school listeners that might be interested in pursuing a similar path to yours in scientific research? Yes, absolutely. Go first. That's the first thing I would say. I love my job. I wake up every day. I'm happy to go to work. It's great. You spend a lot of your life working, so you should really try and enjoy it. I think my one main piece of advice is follow your curiosity. So good scientists are really, really curious. They're probably the toddlers that asked why all the time. Maybe more so than the average toddler curiosity is key. It drives everything. You have to be asking questions. You have to ask questions of the world around you yourself, the people that you work with, and just be really interested and open to the answers as well. Questions are not worth much if you're not listening to what the answer is that comes back. Another thing that I would say on that is that beware of the naysayers, because especially in my field, if you start to think about weird and wacky questions, there'll always be people that push back, which is good, and ask you more questions, but are overall encouraging. But sometimes there'll be people that maybe just don't have the imagination to think about these great ideas that you were thinking about. That doesn't mean that you're wrong. It just means that maybe you should push even harder. If I stalk every time someone told me that what I was pursuing was madness, then I definitely wouldn't be where I am today. Well, thank you so much, Sean. This was so interesting. I think it's making me think so much about that transition from the early chemistry to the early biology. Thank you so much. Especially with your idea of looking at those proto-biosignatures. That's so neat. Yeah, yeah, I'm really excited. But yeah, and look, it's a real pleasure to be here. So thanks a lot for having me here. Are there places online where people who listeners who want to learn more can go maybe like your lab website or articles you can think of? Sure, yeah, we just launched our website actually. So it's proto-signlab.com. We also have @protosign on Instagram. We have myself, my own kind of professional account on Instagram is @originsSean, S-E-A-N. Yeah, we kind of share a lot of stuff up there, which is fun. We're preparing for field work at the moment so we can out hiking and getting fit for field works. There's some fun stuff to follow along with if anyone's interested. Thank you for listening to today's episode of Science Fair. 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