Why We May Be the Only Intelligent Life in the Universe with David Kipping of Cool Worlds

is life rare we live in a solar system and a time where we know of only one example of life occurring in our own star system us earth but we are also tantalized by a number of other worlds in the solar system that might once have had or may still have life albeit in a microbial form this list includes venus europa mars titan enceladus and others but until we go to those places and see if there is indeed life or we solve the mystery in the laboratory of just how easy it is for abiogenesis to occur we won't know the answer to the question but we can glean clues my guest today has been working on a statistical analysis that could shed some light on that question how rare is life how rare is intelligent life you have fallen into event horizon with john michael gautier [Music] dr kipping is the assistant professor of astronomy at columbia university where he researches extrasolar planets and moons dr kipping also leads the cool world's lab at colombia which includes a youtube channel and a website where you can learn about their research dr kipping's other areas of research interests also include study and characterization of transiting exoplanets exoplanet atmospheres bayesian inference population statistics and understanding stellar hosts he is also the principal investigator of the hunt for the exo moons with kepler hek project david kipping welcome back to the program hey it's my pleasure to be back home thanks for having me now david you have a new paper out and this paper looks at a busy analysis of the probabilities of life and intelligence can you give us an overview yeah sure what i wanted to do was to sort of imagine if we re-ran the tape of history of earth how often would we expect life and intelligence to re-emerge now you might ask why am i so focused on re-running the tape and the reason is because i can't really if i'm being honest i can't really ask questions about other planets i wish i could i wish i could tell you about proxima centauri b and alpha centauri planets but the problem is we just don't have any data about those of the planets where those conditions are similar to the earth or not so we just in this paper focus on the earth but infertility plants are common then by extension you could apply as analysis elsewhere and the the data we use when we look at the earth is just the timings that's it the chronology of evolution on the earth so when we look at the earth we find that life started very quickly within the first quintile the first 20 percent of earth's habitable window and us intelligent life however you want to define it actually doesn't really matter too much how you define it doesn't really change the numbers too much emerged in the last quintile the last 20 percent and so in the paper we take those two numbers we ask what does that mean does the early emergence of life in the late emergence of intelligence tell us anything probabilistically and the summary takeaway point i suppose is that i can give you betting odds well really i'd say basin odds but betting odds is a bit more understandable perhaps that i would say that life is life is common life would re-emerge is nine times more likely than life would not re-emerge if you re-ran the tape that's sort of the final takeaway message and for intelligence uh it's it's more difficult to say conclusively but we find three to two odds against intelligence so it's it's very subtle i mean three to two is not the sort of odds you bet your house on or it's pretty close to 50 50 to be honest but the ad late emergence does slightly nudge us towards a more pessimistic view now if you look at the history of earth there are a couple of very telling things i think that suggest that life or intelligence is rare and one is the leap to eukaryotic life which took what 1.8 billion years before life went from very simple to something more complex does that play into the equation i mean did you account for that weird long period of simplicity yeah it's it's where do you you mention that because that's almost how i started the paper so this has obviously been a big project of mine for a while now when i first started i was very much inspired by a paper by brandon carter who i think the title of the paper was five or six steps to evolution and he was doing sort of a also a statistical analysis of the chronology of major evolutionary transitions and actually trying to figure out which of these transitions are probably critical to our our success our existence and so some of the examples would be the emergence of eukaryote cells combogenesis sex the swapping of genes there's the adaptation of multicellularity and so he comes up with a five or six of these eventually the last one is of course civilization and uh makes an argument um that if these transitions are all very very difficult then the spacing between them let's say the typical transition time from eukaryotes to multicellular life is 10 billion years that's the typical transition time then we're only here because it happened unusually quickly in fact all of the transitions are just like that we may just be a product of a series of unlikely events that just all happen to happen quicker than usual elsewhere in the universe and then if you look back at the spacing of those events even if the transitions are are different time scales as long as they're all long time scales like many billions of years time scales then they would appear evenly spread across the evolutionary record and that's kind of what you see in fact so that was a real inspirational paper for me when i was working on this but i couldn't i couldn't really figure out how to do any better than what he'd already done so i instead i kind of switched gears and i just asked what's the what's the probability of getting to that final point in the first place and i kind of by by treating it that way i can sort of fold all of those steps into just one i mean any of those transitions if you think about it is probably also a sequence of smaller steps that allows eukaryotes to happen or allows combogenesis to happen it's also a series of substeps that are probably necessary and the same way here i'm really treating all of those major transitions as just sort of part of one overall transition which is from dumb life to smart life and that's just treated as one parameter in the paper and that just really simplifies the mathematics the i suppose the obvious question is that okay you you have that long period between the leap to eukaryotic life but then you have another long period of the leap to intelligence and there is no guarantee of human level intelligence just very specific evolutionary pressures created our intelligence and otherwise you might just have a world of octopuses or you know dolphins or something like that that are of lower intelligence but not able to create a civilization so doesn't that factor in that you might have locked in life that's intelligent but just does not have this the physiology to create a civilization right yeah i mean this i mean a good sort of definition for thinking about this is that we really pose this in terms of the drake equation and you know when frank drake wrote that down and i think even seth shostak has directly said this that the fi term the fraction of life that goes on to form intelligence really what we mean by that are the the intelligences which could build radio transmitters really that's that's really what they're talking about in that equation and then the next term fc is is a fraction of those that go on to choose to do so so if you if you define intelligence differently and you say no i'm not going to define it as the fraction of life forms that can build radio transmitters instead i'm going to define it as anything that has an i don't know an iq higher than 1.5 or something so you know maybe relax that a lot more however you however you want to define it a certain number of neuron counts or something like this well then you would find that fc would drop dramatically so it you can define it however you want but it would affect the next term in the drake equation the definition of fc would then change because it'd be not only it wouldn't be the fraction of those who can build radio transmitters that do build radio transmitters it would be the fraction of anything with an iq greater than 1.5 that goes on to build a radio transmitter and that would be a different term that you'd be putting into the equation even though it would have the same symbol you know perhaps and that'll be confusing but it's just important that all of the terms in the drake equation are conditional upon the last term before it and so in that sense you can define terms however you want but i think when we think about the drake equation it's more useful just to focus on the things which really could communicate with us or could spread out across the galaxy now do you think that radio is the right place to look or do you favor another techno signature of you know whatever cfc's in an atmosphere or something like that or the incomprehensible you know something we don't know about do you think that we're a bit naive in looking in radio i think all of the above i think my honest answer is um we don't know we don't know how the civilizations would choose to communicate with us or even not choose to communicate with us but uh serendipitously reveal themselves you know accidentally reveal themselves through the product of their technology so this is why a multi-pronged attack is really the best we can do i mean if anybody tells you radio is the only way we're ever going to detect civilizations out there i'd be very skeptical and you should be too because maybe radio you know we're already seeing a transition away from radio technology ourselves as we move towards sending our data through fiber optics for instance that really doesn't have any leakage so it's not obvious that we can put all of our money on any single one of these bets and you could say well let's look for lasers then or let's look for gravitational waves but again we just don't know we're just we're just guessing as to the activities it's xenopsychology and we can make reasonable um we can sort of lay out all of the possibilities we can think of but we can't really say that any of them are particularly more likely than the other in regards to the drake equation over the next say two decades are we going to be able to plug in more solid numbers well we're trying to i think the next term along will be biosignatures that we can you know the the fl the frequency at which life emerges if we can detect bias signatures in the atmospheres of other planets or we could set life here in the solar system perhaps under the icy crust of europa and enceladus for instance on the subsurface of mars and we could demonstrate of course in the solar system it would need to be independent life to us but if we could i think there's a couple of experiments we can imagine doing that we have the technology to be able to do that really could allow us to constrain and perhaps even directly quantify the value of fl and of course fi it's very difficult to say i mean as as we mentioned there's possible tomorrow right now as we're talking someone is detecting a radio transmission we were just watching contact last night and and you know the scene where she detects the radio transmission is so exciting that could be happening right now but it may never happen so for that term it it's it's difficult even if we don't see anything it's very hard to translate that into any kind of upper limit just because we don't detect any radio waves doesn't mean there's no one out there it just means they're not sending radio waves so it's really challenging to quantify fi and that's why in this last paper i was really using ourselves as a as a starting point because at least that's somewhat indisputable that we exist and we exist in a certain point in earth's history but beyond that it's very very difficult to say until we have a confirmed detection but we are just a sampling of one ultimately and one data point and one has to ask a question you know science doesn't really like absolute uniqueness you know you should see other examples so we should see other examples of civilizations but it's the problem is compounded by time you may not exist at the same time as another civilization in the milky way and if it's in another galaxy it's even less likely that you would be able to detect it unless they were doing something absolutely crazy like taking dangerous stars out of the galaxy or something like that it's the so-called red spirals so it is actually a lot harder to detect civilizations inherently than one might originally think as frank rick did looking for giant omnidirectional beacons which i think that's actually kokoni and morrison but this may be a lot harder than we think it is to detect another civilization do you expect it within your lifetime i don't expect it i also don't not expect to it's kind of cheating a little bit on the on my answer i i just yeah i i'm kind of uh on the fence as to i'd be delighted if it happens i i personally i'm a bit more of an optimist about the nature of contact than i think maybe you are john and others but um yeah personally i very much hope that we can i mean just to step back a little bit um i mean there is i i take your point that the it's a common observation that anything that has happened on earth therefore must be possible elsewhere and so therefore intelligent life should be possible elsewhere and that's true i think anything that can happen it certainly can happen it must be possible for it to happen elsewhere does that mean it's necessarily likely or even within the vastness of you know 10 to the 22 stars in our observable universe not necessarily if you look at a snowflake they really are unique every single snowflake is unique to each other and it may be that even though the the ingredients the things which put together a snowflake and put together what makes us intelligent are common the building blocks are common that doesn't mean that the precise way in which they're structured is necessarily anything that's likely or probable in the universe we may be snowflakes we don't know so this is why i tried to keep an open mind that it is possible i know there's a there's a common resistance to that to this an overwhelming urge to say no no surely surely there must be just look at the number of worlds out there surely it must be possible that there's uh intelligent life out there and i'd say yes it's possible but we just don't know if it's probable at all now to come back to your point really i think because i was sort of backtracking a little bit there i you're also right there that we this is going to be a long enterprise for us it could be the thing which defines us as a species perhaps it defines all intelligent species as the act of trying to reach out into the dark and just to contact someone else i mean we are inherently we evolve to be a social species some of us are quite happy to be hermits and live by ourselves but most of us reach out and really want to have contact with other humans other intelligences and i think as a species we're kind of the same we really have this urge and this need to to say hello and just to to see if if there's someone else out there in the dark um and so i think this will be the thing that we we do for many many generations um i hope we can answer it this generation but i don't think it would stop just after i pass away or any anyone else listening to this i'm sure for generations to come this will be something that we i hope continue to do and appreciate just how important it is now to dig into the paper it's a sort of a two-stage question and the first stage is how statistically common could life itself be in the milky way so in the paper we we quantify this term fi which is the fraction of life which goes on to evolve into intelligence f i and that's really as i said the term that's in drake's equation and what's kind of critical is that um we don't necessarily directly well we really don't in the paper directly estimate fi instead we consider two possibilities for fi we say either fi is a very small number or it's a very large number in other words by large i mean close to one and the reasoning behind that is based off this objective bayesianism which i talk about in my video a little bit and obviously in the paper and maybe a good analogy and i use this in the video is to think about a chemistry this was indeed actually the inspiration behind some of the objective basis and work that was done like many decades ago in the 50s and the idea was if you were going to dissolve a chemical you don't know what it is call it chemical x it's a new chemical you've just encountered and you're going to dissolve it into water and let's say you've got 100 cups of water in front of you now you would expect that either it will dissolve every time because it's the same experiment it's literally the same experiment over and over again it will dissolve every time f equals one or it won't dissolve at all in any of them f equals zero it'd be really odd if it dissolved half of the time like 50 50 or 10 90 even would be really peculiar like it's the same thing happening over and over again and so in my paper because i'm really considering replaying the tape of earth it is the same experiment it's the same conditions it's the same history of meteorite impacts everything is the same and so in that sense it would be really odd if fi was at least just focused on the earth was some in-between value and so in the paper i really consider two possibilities it's either small close to close to zero or close to one and of those two possibilities it's the rare intelligence which actually wins out that doesn't mean that f i zero just means it's a number that's close to zero but i don't specifically quantify what that number is that would be a diff a different calculation to make and a very challenging calculation to make now in the paper you also point out that the chemistry of life the initial chemistry a biogenesis had to have been fast or at least is more likely to have been fast can you go into that i mean that's that's almost an observation that uh we look at the history of the earth we see that the oceans there's evidence for oceans on the earth from 4.4 billion years ago the earth formed about 4.53 billion years ago so pretty quickly we had a delivery of water either it came from comets or some ideas that it could have even come from the interior of the earth as well but however it happened the earth had water quite clearly because we see in the minerals that are produced can only be produced with a body of water and then within 300 million years of that you find evidence for carbon 13 depleted mineral deposits zircon deposits specifically and of course life prefers to take carbon 12 over carbon 13 just because it's lighter it's sort of easier to work with energetically and so that signature has been identified as a signature of life early on in earth's history and that's very fast 300 million years some people don't like that evidence and they claim that's not conclusive maybe there's a process we don't understand that prefers carbon 12 of carbon 13 that's not to do with biology and so they would defer to later evidence such as direct microfossils that's really direct evidence for life when you see microfossils and that would push you back to 900 million years after conditions became habitable but either way it's pretty quick within the overall landscape of earth's 5.3 billion year habitable window and so those facts especially the 300 million year one that's very quick and it make we use that that timing to make the argument that if you replay the tape given there's five billion years to play with the chances are it would it would happen again in fact i can't quantify the chances i would give you almost ten to one odds that would happen again i wouldn't give you a hundred to one odds i wouldn't give you a thousand to one odds the reason for that is that there's sort of an anthropic bias effect happening again this is an idea that brandon carter talked about a few years ago and this may be that life was had to start quickly else there wouldn't have been enough time to get to us and so the fact that life started quickly is is suggestive but it's not a complete slam dunk that's why i can only give you nine to one odds because it may be that evolution takes so long to get to us that it kind of has to happen early otherwise we just wouldn't be here to talk about it and so maybe on most plants it takes far longer than that but it's only the ones where it starts quickly where sentience evolves has time to evolve unless we can look back and say oh it started quickly so there's that there's that kind of bias in play but that's accounted for in the paper and that's why it pushes the the dial back to an optimistic but still somewhat cautious uh analysis obviously that creates a question according to your analysis is it likely or unlikely that there is another civilization in this galaxy yeah i don't think my analysis can directly answer that there's a couple of reasons why first is that we really don't know how common truly earth-like conditions are and there's a i'm sure many of your viewers and listeners know that this idea of the rare earth hypothesis so it may very well be that the conditions on earth are not necessarily completely unique but extremely rare this you know this comes back to ideas such as looking at our sun our sun just recently has been shown it's unusually quiet compared to most stars and that's interesting that may have some impact on our evolution the earth moon system is unusual in the damn moon represents one percent the mass of the earth and there's no other moon around any other planet in the solar system like that if you caught pluto a planet that would change but if you don't call pluto planet there's no other moon in the solar system which has such a high mass ratio and that large moon is important it stabilizes the obliquity of the earth when it was much closer to the earth than it is today it would have raised very large tides on that early ocean tied so large that they would have covered continents and those continent covering tides may have been conducive to life leaving rock pools of water essentially across the landscape places where life may have had a chance to have got started and even the plate tectonics may be related to the the large moon as well for instance the moon impact probably stripped some of the heavy crust the thick lid of crust that sat on top of the earth and once you remove that crust we were left with a much thinner crust and that thinner crust is easier to move around and slide about and create plate tectonics if you make it too thick it just solidifies and then you lose plate tectonics and plated tanks are of course critical for the carbon cycle so there's you know there's a few reasons you can look at jupiter people look at jupiter a lot and say there's several things about our place that may be unique so this is why i can't give you direct answer i can't take the numbers i've calculated and say that means therefore that life is everywhere and that intelligence maybe is unusual would probably be the if i was forced to choose that's probably what i would choose because i just can't say that earths are truly common and i can't also say this is the only way to arrive at life and intelligence there may be other pathways which never occurred here in the earth silicon based life you know is a common example that people speculate about maybe even completely different ways of forming intelligence other than the way that we define ourselves as intelligent life um and so this is i'm really asking the question how often do you get to something that looks like us but you know they may say both in a negative way in a positive way there are other options but i i would take it as at least encouraging there's good reasons i think to think that earth's are common and so if that's true then i would expect life to be out there in the galaxy and i'm that's sort of the direction i'm leaning to recently and intelligence i'm just very much open i i would three to two odds is not enough for me to place a significant wager and so i would just keep both options on the table at this point betting odds on the observable universe all of those galaxies the billions and billions of galaxies at some point is there a tipping point where there has to be other intelligence sure if um if fi was one in let's say it's one in 10 to the 11 then that's about the number of stars in the galaxy and so you would expect that maybe maybe it's just not quite high enough for each galaxy given that you have to have an earth-like planet and then it has to have life and then it has to go on to form intelligence maybe most galaxies don't have intelligence in them but if you take a group of 30 40 a thousand i don't know you eventually get enough critical mass that you would expect there to be and a success and intelligence does emerge of course using the framework i've discussed so far i'm saying nothing about when really that success happens i'm just saying a success happens over the history and really integrating over the history of the entire planet and saying a success happens at some point in its history so sure maybe in a bunch of 100 galaxies there's a success and that's us or you go a little bit further and we have two successes three successes but those successes could be very disparate in time there's no there's no you know it depends on l of course the capital l and the drake equation how long do these civilizations last for that's a very very critical term of course in drake's equation and again one that we we don't touch on in this paper and it's very very difficult to estimate that term so that's certainly possible in as i said we don't really have any idea what fi is directly i mean in my paper it's certainly possible that when i say fi is small it could be ten percent maybe maybe that's a little bit optimistic maybe one percent let's say fi of one percent would be pretty much consistent with my analysis but fi could also be .00000 you know keep going one percent and that would also be consistent with my analysis and there isn't really any strong preference uh in the way i framed the problem between those two i'm really just asking is it a small number or a large number and i think we are interested i'm having conversations with colleagues right now thinking about experiments we could do to really quantify that either by looking at the evolutionary record more carefully looking for artifacts here in the solar system and trying to try to think about ways that you can quantify yeah it's very difficult but could you quantify the the constraints that we see from seti to say something about fi to extend even further outside the observable universe which may be the unknowable if the universe is infinite outside of what we can see then other life must exist and indeed near copies of ourself must exist so do you do you subscribe to an infinite universe or do you think there must be limits i'm not a cosmologist and i have to admit when you you pose almost the exact dilemma i have with it and that's that if the universe truly is infinite i would go even a little bit further than what you just said and said that if the universe is infinite there's an exact clone of you not just like someone who's a little bit a civilization that's a little bit like our civilization but with infinite opportunities truly infinite opportunities there'd be an infinite number of exact use having this exact conversation that me and you're having right now out there which is really really difficult for me to get my head around um so i i i sort of hit a mind block almost when i get to that point so in a way it almost doesn't matter though because when we talk about what's outside of the observable universe it's it's almost like here be dragons because it kind of doesn't matter it's something which is causally disconnected from us it is in essence a different universe because there's no way we can interact with it barring uh faster than lights communication or technology which of course according to einstein should be impossible so we we really do think that the the observable universe at least in astronomy is all there is worth to talk about it's interesting to estimate the curvature of the universe and how far beyond the observable universe it might extend the universe does appear very very flat and that's where this evidence or the possibility i should say of an infinite universe comes from but in a way it kind of doesn't matter that much at least at least for the question of looking for life and intelligence out there in the universe as long as we accept that faster than light communication is impossible if we accept that that's impossible then there's basically no point worrying about what's beyond the cosmic horizon and we have to take a break today i'm joined by dr david kipping host of the cool world's youtube channel and when we come back link in the description below by the way and when we come back it's excellent moon time now david one area one major area of your research is exomoons yes and this is this is this is an intriguing thing because i guess we have hints of exomoons but we haven't really found one am i right yeah we've been uh it's kind of a niche field but a few of us have been looking very hard for examines for let's say the past almost ten years now we know of four thousand five thousand exoplanets that current counting something like that but we basically have i'd say half an exo moon and that's this candidate that we found about a year and a half ago i think now kepler's 1625 b i where the i denotes the the moon um it's a it remains a unconfirmed object though um i'm i'm certainly very excited about this object still it still remains to me the best bet of an exo moon we it's a very strange object though so we found this in kepler data originally the planet it orbits is a gas giant it's of similar size to that of jupiter it orbits its star about the same distance of the earth orbits around the sun and the sun is of a very similar mass to that of the of our own sun but it's a little bit older it's a bit more evolved and so it's it's growing in size now when we look at this planet we see evidence for two things we see that it appears to be wobbling around and that was actually confirmed with some hubble space telescope data that we got it wobbles around by about 20 minutes so it takes about a year to go around its star but sometimes it comes into transit 20 minutes earlier than it should do and sometimes 20 minutes later the earth moon system does the same thing the earth wobbles by about two and a half minutes this is almost ten times larger wobble and the moon you know you might guess from that that implies a large moon in your right the moon that is implied by that is very large it's about the same mass as neptune and not only do we predict its mass based off that wobble but we would of course expect it to be roughly neptune sized and we see it we actually see evidence of the moon pass in front of the star just after when the planet passed in front we can tell the size based off how how much light was blocked out and indeed it's a neptune size object when we model this system you see something really encouraging and that's that the the thing which really orbits the sun this is again true for the earth immune system is the center of mass between it's almost like the the pivot point of a seesaw the center of mass between the earth and the moon is a thing which truly orbits the sun on a what we call a keplerian orbit sort of like clockwork going round and round and the earth goes around that little center of mass itself and so when we look at this system we notice that if you kind of imagine around this pivot point the planet is just to the left it's coming in a little bit later than we would expect it to it transits 20 minutes later than we would conventionally expect and so you would expect on the other side the planet the moon should be coming in early and so you see that that kind of opposite phasing between the two if one comes in early they should come in late and vice versa and we see that precise phase shift between these between the planets uh wobble and the moon's relative position as well so all of these things make it a really nice case for an exo moon the downside see maybe that's enough for some people to believe it but the downside is that this object we really only have one good data point and that's from hubble hubble looked at it in may two years ago and we asked actually to get time again that's what we wanted i wanted to see this happen a second time both the dip and the wobble all of that if we get a second observation then for me it'd be slam dunk that's it there's there's no doubt anymore that this is real it's exactly where we expect it to be it's the same size that we said it would be everything lines up unfortunately you know hubble time is very very competitive for astronomers to get telescope time on it's you know it's the best telescope in the in not in the world but around the world and it's it's very challenging to get time it's oversubscribed by about 20 to one and i think that year basically no exoplanet proposals were accepted all the science was non-exoplanet science and including us we didn't get selected so unfortunately we didn't get that time and now it's now it's looking very bleak in terms of the prospect of confirming this thing you would have to almost reacquire the lock if you like over time we lose uncertainty grows over time just like predicting the weather into the future the further and further into the future you want to predict the weather the more uncertain it becomes and the same way trying to predict the positions of these two objects becomes more and more uncertain over time so i we can no longer actually make an accurate prediction as to where we would expect the moon and the planet to be and that was of course central to our my confidence of hypothetical confidence of detecting a second time would be i expect it to be here look it lands exactly where i expect it to be slam dunk so now we'd have to almost go back to the drawing balls on it so it's a frustrating situation but it is what it is sounds like we need 20 more hubble space telescopes now back in the day when i when i first became interested in astronomy which would have been something like 1990 we didn't even know that exoplanets existed but everyone assumed that they did so it comes back to betting odds given that we have a solar system that's literally full of moons chances are exo moons are ridiculously common in the milky way so it's not really that far of a stretch to expect to find one right right i mean you could say well why didn't you use that argument for life in the same way you see it happen in the solar system so therefore you immediately suspect moons are elsewhere out there and i totally agree for life it's a little bit different because that has to happen for us to exist there's like a causal connection between that event and our existence but the moons of jupiter have nothing to do with us right i mean you take if the jupiter didn't form its moons as far as we can tell they would have absolutely no influence on the evolution in our existence so it really is an unbiased fair sample and in that sense we have much more confidence using it it's it's almost better than uh you know for life we don't even really have one data point we have half a data point because of this bias for the moons we have not just one data point but three or four because you know obviously several of these gas giants all of the gas joints have satellite systems around them and so it seems very reasonable to expect that moons are common so i always say it's not a question of if there are moons out there it's just what what do they look like i think it's it'd be really strange i don't think anybody really contests that to to assume that moons just are only present in our own solar system the question i suppose the the natural extension here is habitability of exomoons are exomoons just as good of a prospect for developing life as a proper planet is i think there's pros and cons some of the cons would be when you look at most of the moons in our solar system or all of them really they're very small certainly smaller than the earth and the the earth is obviously massive enough has sufficient gravity to hold on to an atmosphere and that atmosphere appears critical to our success our evolutionary success if you took away the atmosphere maybe you could still have life but it would be very different it would probably be limited to subsurface life pre almost certainly microbial it's very difficult to imagine complex multicellular life developing without an atmosphere if because if you didn't have an atmosphere the oceans would would boil off as well so there's lots of there's lots of major hurdles of not having an atmosphere and when you make a moon you take the moon it's a it you know it's one percent the mass of the earth one point two five percent but it's about a third of the no quarter of the size it's about 25 the size of the earth you know that's not that's not too bad right not too shabby it's a quarter of the size of the earth and yet despite that it clearly doesn't have sufficient mass to hold on to an atmosphere it has one sick the surface gravity of the earth and that's evidently not enough to hold on to an atmosphere when you're orbiting the sun at the distance that we orbit the sun now if you take titan people often point at titan say hold on titan's about the same size as the moon and that has an atmosphere but that's a different story because titan's much colder titan's really distant from the sun and so because of that the molecules in the atmosphere are moving far slower they have much less energy and so you need less gravity to hold on to that atmosphere if you want to hold on to a warm atmosphere like like the earth's atmosphere then you're gonna have to be more massive so there's some argument and debate about where this threshold really happens but it's clearly heavier than one percent the mass of the earth even mars kind of struggles to hold on to an atmosphere has a very tenuous atmosphere at 10 the mass of the earth so you might a lot of us sort of point around sort of a third of an earth mass as maybe me maybe being their threshold and we don't have any moons that large in the solar system so this is maybe the downside if moons never get that big if they never get to be a third of an earth mass then we really shouldn't expect there to be any habitable moons out there at least not habitable in the sense of the earth's habitability i sometimes like to delineate and say there's uh cryohabitable cryohabitable is a term i sometimes used to define like enceladus and europa where you could have subsurface water and oceans and life and there's sort of telluric habitable which is a planet which truly represents something more like akin to the earth and i think you know obviously the the cryohabital worlds are interesting their own right but many of us are probably most excited about the prospect of detecting truly earth-like conditions or another world so this is up in the air and uh if kepler-1625bi is real that would that would kind of solve it because it would show hey there's no problem forming a third earth mass moons in fact you can get all the way up to 20 earth mass means and still have no problem making them so that's why it's a very important object and confirming it would have implications about habitability and that's the downside but there's also many positives so on the positive side a moon maybe doesn't necessarily have to be massive enough has to be massive enough probably to hold on to an atmosphere but it might not have been massive enough to hold on to a magnetosphere to have an internal dynamo because it could probably hide inside the magnetic shield of its of its home planet that it orbits uh this is work that um astrobiologists such as renee heller have been demonstrating locally so the the moon may not even have to have a sufficient magnetic field it could have a very weak magnetic field but still get sufficient protection and shielding thanks to its home planet and then another interesting example of the benefits of being a moon would be tightly locked planets around end dwarfs so of course if you're in the habitable zone of an m dwarf because the star is so much less luminous the habitable zone is much closer and that causes the planets we think to tidy lock to the stars and that could lead to atmospheric collapse you have one hot side one cold side that could be bad for the planet but you know the moon would be fine if there was a moon around that planet it would receive equal amounts of illumination on both sides this is why i like to say there's uh there's no such thing as the dark side of a moon but there is such a thing of a dark side of a planet these tiny little planets really do represent that but even if the moon is totally locked to the planet it it will still get equal amounts of elimination you know the far side of the moon gets equal amounts of illumination to the nearside that's that's a fallacy that maybe pink floyd help propagate with their album so there's many benefits of being a moon as well pink floyd roger waters destroyed astronomy by calling it the dark side of the moon david i think uh an obvious thing here is that we we don't just have europa and enceladus we have a lot of moons in this solar system that have some layer of liquid water or hypothesized layer of liquid water which opens up a completely new avenue for life because it is liquid water or a water and ammonia mix so that may be a more common venue for life than an earth-like planet but it seems to me that it would be limiting how complex do you expect that life could get in a place like a european ocean yeah i think that's a hard question for me to answer as an astronomer i think a biologist an evolutionary biologist would probably be able to give you a much better answer to that than myself so i if my guess would be that it would be somewhat limiting just the energy supply is clearly going to be less from an energetics perspective and energy is clearly necessary to develop complexity if you're really clinging on to existence you know around these these sort of black smokers that we have at the bottom of the atlantic ocean for instance you have something like this as your energy source you look at the life around it and it's it's difficult to imagine that becoming extremely advanced life at least sort of the life that might be capable of building a radio transmitter for instance if you're limited to just sort of clinging around these black smokers so um it's certainly very important and interesting to try and look for life in those in those worlds there's also a challenge of how do you do that i mean we're interested in visiting uh many of these icy moons as you say but enceladus and europe tend to be the two favorites that people talk about as a possible mission one day just because it's presumably more accessible because it's covered in ice it has a nice crust it should be easier just to drill through that or melt through it to get into the ocean but then you have the problem of contamination accidentally bring along a hitchhiker bacteria from the earth tardigrade or something that could cling onto the side of the rocket and now you've injected another life form into that biosphere if you like and especially for those icy moons you know they probably are somewhat pristine compared to mars let's say so mars has frequent you know material swapping between the earth and mars through meteorites constantly being knocked off and exchanging between them so there's a good chance of panspermia between between mars and the earth especially in the past when mars was warmer and had liquid water on its surface and most recently been seen as venus as well there's evidence that venus was habitable for a long time as well now maybe three billion years so for both of those there's probably a good chance of interchange but european insiders are not only much further out they're they're in the outer solar system and it's hard for material to go that direction to because you're going against the currents of the sun's gravity if you like to to leave in that direction it's harder and then even if you are a meteorite that makes it to europa you have like several kilometers of ice to get through before you can get into the ocean and contaminate the life there so this is why people are very interested in like the vostok ice lakes uh you know in these antarctic ice lakes as pristine tombs of ancient life that may have been present on the earth and in the same way i think uh there's a big challenge with how do you go around exploring confirming life on these sub in the subsurface life for europa enceladus without accidentally bringing in the thing that you're looking for and you know earth life might out-compete the the life that's there which of course would be disastrous you're basically killing the thing that you're interested in so this is very challenging not sure how we're going to solve that problem well prudence i suppose would dictate that we solve the problem before we even go there to make sure that we actually independently confirm another genesis of life on europa without you know muddying the waters but at the same time if we did that and we found that europa has life and it's genetically related to us then that brings panspermia to a completely different level because then it isn't really alien life it's it's either we are from originally europa you know or mars you know a rock got blasted off of mars and landed here and seeded life yeah or vice versa and i think to me that's going to be the most interesting question that in the next coming centuries to answer is that if we did find life on these worlds is it related or isn't it and if it is related where did we originate did life start on mars and come here through pennsylvania or vice versa and because earth was really not that great of a planet for life when life seems to have arisen so you're you're left with this question of was there a better place and at the time mars sort of looks attractive so we may end up being martians do you think or even or even venus or venus well as i said that's also on the card yeah yeah and and questions about you know venus's upper atmosphere if it still might be habitable and that anything that you know microbes or whatever that that that might have came into being on the surface of it when it had water might still be in that upper atmosphere and have evolved to deal with you know the conditions of it and i think people forget that a lot that that venus is actually a very attractive candidate for microbial life and it's actually an attractive candidate for human colonization if you're in the upper atmosphere because that's basically the most earth-like conditions in the solar system is in venus's upper atmosphere so i think it gets ignored venus gets ignored too much but ultimately though that sort of points towards there are a lot of possibilities for habitability at least microbial in this solar system alone and the rest of the galaxy it has to present the same conditions right yeah we would think so that's only the conclusion of my recent paper and i think astrobiologists tend to be optimists in that same sense and that's you know there's the the consensus wanes for the factions of the time but i think certainly there's a lot of optimism that uh the processes which formed life even from a from a chemical perspective you know looking at the early you know the miliyuri type experiments seems that you know making complex organic molecules isn't that hard and these things are abundant even in comets you can find them for instance and interstellar dust you can find uh urea so there's like complex organic molecules everywhere so i think there is an optimism that um that life may be common when we look at uh when we're looking for these signatures of life elsewhere outside of the solar system that's it's a very different game though in a way these icy moons as fascinating as they may be it's going to be very difficult very difficult to imagine how we would possibly confirm evidence for life in an icy exomoon because the the signatures of life are all hidden from view underneath this lid that's hiding the the interesting stuff away from us when we think about more like earth-like worlds earth-like moons or planets at least then the atmosphere is accessible and if life is on the surface it should be presenting itself indirectly into the atmosphere and we can detect those signs as well so in terms of the prospects of detecting life in our lifetimes i think earth-like planets are almost certainly going to be the big focus for us just because we we have a sense that we could do it but we're certainly not discounting those icy moons but my best bet would be if those have life on them we're almost certainly going to find that in the solar system before we start having any chance of seeing it for exomes all right david we are out of time thanks for joining us again and i look forward to our next chat yeah my pleasure thanks for having me john beatrice villarreal sent us an email about a project she's working on and i volunteered you to help hmm beatrice you say she was a great guest i'm intrigued you're always talking about citizen science so beatrice has asked us to help her out well that sounds interesting i love citizen science the vanishing and appearing sources during a century of observations fasco is a project that uses images of the sky from the 1950s and compares it to images of the sky today i like the sound of that i thought you mind so maybe our viewers could help too the link's already on screen [Music] [Applause] [Music] you

Channel: Event Horizon

Views: 210,687

Rating: 4.8117542 out of 5

Keywords: rare earth hypothesis, David Kipping, rare earth, science, space, alien civilizations, Fermi paradox, why we may be the only intelligent life in the universe, John Michael Godlier, Event Horizon, Cool Worlds, Astrophysics, space physics, astrobiology, the universe, math, statistics, anthropic principle, alien life, intelligent life, Are there alien civilizations?, physics (field of study), extraterrestrial, exomoons, titan, europa, Enceladus, mars (planet)

Id: AC-6okOWXLs

Length: 54min 4sec (3244 seconds)

Published: Thu May 21 2020