#355 – David Kipping: Alien Civilizations and Habitable Worlds

[0] The following is a conversation with David Kipping, an astronomer and astrophysicist at Columbia University, director of the Cool World's Lab, and he's an amazing educator about the most fascinating scientific phenomena in our universe.

[1] I highly recommend you check out his videos on the Cool World's YouTube channel.

[2] David quickly became one of my favorite human beings.

[3] I hope to talk to him many more times in the future.

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[61] And now, dear friends, here's David Kipping.

[62] Your research at Columbia is in part focused on what you call cool worlds or worlds outside our solar system where temperature is sufficiently cool to allow for moons, rings, and life to form, and for us humans to observe it.

[63] So can you tell me more about this idea, this place of cool worlds?

[64] Yeah, the history of discovering planets outside our solar system was really dominated by these hot planets.

[65] And that's just because of the fact they're easier to find.

[66] When the very first methods came online, these were primarily the Doppler spectroscopy method, looking for wobbling stars, and also the transit method.

[67] And these two both have a really strong bias towards finding these hot planets.

[68] Now, hot planets are interesting.

[69] The chemistry in the atmosphere is fascinating.

[70] It's very alien.

[71] An example of one that's particularly close to my heart is Trays 2B, whose atmosphere is so dark.

[72] reflective than coal.

[73] And so they have really bizarre photometric properties, yet at the same time, they resemble nothing like our own home.

[74] And so it said there's two types of astrophysicists.

[75] The astrophysicists who care about how the universe works, they want to understand the mechanics of the machinery of this universe.

[76] Why did the big bang happen?

[77] Why is the universe expanding, how a galaxy is formed?

[78] And there's another type of astrophysicist which perhaps speaks to me a little bit more.

[79] it whispers into your ear, and that is why are we here?

[80] Are we alone?

[81] Are there others out there?

[82] And ultimately along this journey, the hot plants aren't going to get us there.

[83] When we're looking for life in the universe, seems to make perfect sense that there should be planets like our own out there, maybe even moons like our own planet around gas giants that could be habitable.

[84] And so my research has been driven by trying to find these more tracheous globes that might resemble our own planet.

[85] So they're the ones that lurk more in the shadows in terms of how difficult it is to detect?

[86] They're much harder.

[87] They're harder for several reasons.

[88] The method we primarily use is the transit method, so this is really eclipses.

[89] As the planet passes in front of the star, it blocks out some starlight.

[90] The problem with that is that not all planets pass in front of their star.

[91] They have to be aligned correctly from your line of sight.

[92] And so the further way the planet is from the star, the cooler it is, the less likely it is that you're going to get that geometric alignment.

[93] So whereas a hot Jupiter, about 1 % of hot Jupiters will transit in front of their star, only about 0 .5%, maybe even a quarter of a percent of a percent of Earth -like planets will have the right geometry to transit.

[94] And so that makes it much, much harder for us.

[95] What's the connection between temperature of the planet and geometric alignment, probability of geometric alignment?

[96] There's not a direct connection, but they're connected by an intermediate parameter, which is their separation from the star.

[97] So the planet will be cooler if it's further away from the star, which in turn means the probability of getting that alignment correct is going to be less.

[98] On top of that, they also transit their star less frequently.

[99] So if you go to the telescope and you want to discover hot Jupiter, you could probably do it in a week or so because the orbital periods of order of one, two, three days.

[100] So you can actually get the full orbit two or three times over, whereas if you want to set an Earth -like planet, you have to observe that star for three, four years.

[101] And that's actually one of the problems with Kepler.

[102] Kepler was this very successful mission that NASA launched over a decade ago now I think and it discovered thousands of planets it's still the dominant source of exoplanes that we know about but unfortunately it didn't last as long as we would have liked it to it died after about 4 .35 years I think it was and so for an earth -like planet that's just enough to catch four transits and four transits was kind of seen as the minimum but of course the more transits you see the easier it is to detect it because you build up signal to noise.

[103] If you see the same thing, tick, tick, tick, tick, tick, the more ticks you get, the easier is to find it.

[104] And so it was really a shame that Kepler was just at the limit of where we were expecting it to start to see Earth -like planets.

[105] And in fact, it really found zero.

[106] Zero planets that are around stars like the Sun, the orbits similar to the Earth around the Sun, and could potentially be similar to our own planet in terms of its composition.

[107] And so it's a great shame, but that's why gives astronomers more to do in the future.

[108] Just to clarify, the transit method is our primary way of detecting these things.

[109] And what it is is when the object passes, accludes the source of light, just a tiny bit, a few pixels.

[110] And from that, we can infer something about its mass and size and distance and geometry and all of that.

[111] that's like trying to tell what at a party you can't see anything about a person but you can just see by the way they occlude others so this is the method but is this super far away how many pixels of information do we have basically how high resolution is the signal that we that we can get about these occlusions you're right in your description i think just to build upon that a little bit more.

[112] It might be almost like your vision is completely blurry.

[113] Like you have an extreme eye prescription and so you can't resolve anything.

[114] Everything's just blurs.

[115] But you can tell that something was there because it just got fainter for a short amount of time.

[116] Someone passed in front of a light.

[117] And so that light in your eyes would just dim for a short moment.

[118] Now the reason we have that problem with blowiness or resolution is just because the stars are so far away.

[119] I mean, these are the closest stars are four light years away, but most of the stars Kepler looked at with thousands of light years away.

[120] And so there's absolutely no chance that the telescope can physically resolve the star, or even the separation between the planet and the star, is too small, especially for a telescope like Kepler.

[121] It's only a meter or cross.

[122] In principle, you can make those detections, but you need a different kind of telescope.

[123] We call that direct imaging, and direct imaging is a very exciting, distinct way.

[124] of detecting planets.

[125] But it, as you can imagine, is going to be far easier to detect plants which are really far away from their star to do that, because that's going to make that separation really big.

[126] And then you also want the star to be really close to us, so the nearest stars.

[127] Not only that, but you would prefer that planet to be really hot, because the hotter it is, the brighter it is.

[128] And so that tends to bias direct imaging towards plants which are in the process of forming.

[129] So things which have just formed, the planet's still got all of its primordial heat embedded within it and it's glowing.

[130] We can see those quite easily.

[131] But for the planets more like the Earth, of course, they've cooled down.

[132] And so we can't see that the light is pitiful compared to a newly formed planet.

[133] We would like to get there with direct imaging.

[134] That's the dream is to have the pale blue dart, an actual photograph of it, maybe even just a one pixel photograph of it.

[135] But for now, the entire solar system is one pixel, certainly with the transit method and most of the telescopes.

[136] And so all you can do is see with that one pixel, which contains potentially dozens of planets, and the star, maybe even multiple stars, dims for a short amount of time.

[137] It dims just a little bit, and from that, you can infer something.

[138] Yeah, I mean, it's like being a detective in the scene, right?

[139] It's very, it's indirect clues of the existence of the planet.

[140] It's amazing that humans can do that.

[141] We're just looking out in these immense distances and looking, you know, if there's alien civilizations out there, like, let's say one exactly like our own, we're like, would we even be able to see an earth that passes in the way of its sun and slightly dims?

[142] And that's the only sign we have of that, of that alien human -like civilization out there.

[143] Is it just a little bit of a dimming?

[144] Yeah.

[145] I mean, it depends on the type of star we're talking about.

[146] If it is a star truly like the sun, the dip that causes is 84 parts per million.

[147] I mean, that's just, it's like the same as a, it's like a firefly flying in front of like a giant floodlight at a stadium or something.

[148] That's the kind of the brightness contrast that you're trying to compare to.

[149] So it's extremely difficult detection, and in the very, very best cases, we can get down to that.

[150] But as I said, we don't really have any true Earth analogs that have been in the exoplanet candidate yet.

[151] Unless you relax that definition, you say, it's not just, doesn't have to be a star just like the sun.

[152] It could be a star that's smaller than the sun.

[153] It could be these orange dwarfs or even the red dwarf stars.

[154] And the fact those stars are smaller means that for the same size planet passing in front, of it, more light is blocked out.

[155] And so a very exciting system, for example, is Trappist 1, which has seven planets, which are smaller than the Earth.

[156] And those are quite easily detectable, not with a space -based telescope, but even from the ground.

[157] And that's just because the star is so much smaller that the relative increase in, or decrease in brightness, is enhanced significantly because that smaller size.

[158] So Trappus 1E, it's a planet which is in the right distance for liquid water.

[159] It has a slightly smaller size than the Earth.

[160] It's about 90 % the size of the Earth, about 80 % in the mass. And it's one of the top targets right now for potentially having life.

[161] And yet, it raises many questions about what would that environment be like?

[162] This is a star which is one -eighth the mass of the sun.

[163] Stars like that take a long time to come off that adolescence.

[164] When stars first form, like the sun, it takes them maybe 10, 100 million years to sort of settle in to that main sequence lifetime.

[165] But for stars, like these late M dwarfs, as we call them, they can take up to a billion years or more to calm down.

[166] And during that period, they're producing huge amounts of x -rays, ultraviolet radiation, that could potentially rip off the entire atmosphere.

[167] It may desiccate the planets in the system.

[168] And so even if water arrived by comets or something, it may have lost all that water due to this prolonged period of high activity.

[169] So we have lots of open -ended questions about these M -dwarf planets, but they are the most accessible.

[170] And so in the near term, if we detect anything in terms of biosignatures, it's going to be, for one of these red dwarf stars, it's not going to be a true Earth twin, as we would recognize it as having a yellow star.

[171] Well, let me ask you.

[172] I mean, there's a million ways to ask this question.

[173] I'm sure I'll ask it about habitable worlds.

[174] Let's just go to our own solar system.

[175] we learn about the planets and moons in our solar system that might contain life, whether it's Mars or some of the moons of Jupiter and Saturn?

[176] What kind of characteristics, because you said it might not need to be Earth -like, what kind of characteristics might be we'd be looking for?

[177] When we look for life, it's hard to define even what life is, but we can maybe do a better job in defining the sorts of things that life does.

[178] And that provides some aspects to some avenue for looking for them.

[179] In the classically, conventionally, I think we thought the way to look for life was to look for oxygen.

[180] Oxygen is a byproduct of fertic synthesis on this planet.

[181] We didn't always have it.

[182] Certainly if you get back to the Archeon period, there was, you know, you have this period of called the Great Oxidation Event where the Earth floods with oxygen for the first time and starts to saturate the oceans and then the atmosphere.

[183] And so that oxygen, if we detect it on another planet, whether it be Mars, Venus, or an exoplanet, whatever it is, that was long thought to be evidence for something doing phytosynthesis.

[184] Because if you took away all the plant life on the earth, the oxygen wouldn't just hang around here.

[185] It's a highly reactive molecule.

[186] It would oxidize things.

[187] And so within about a million years, you would probably lose all the oxygen on planet Earth.

[188] So that was conventionally how we thought we could look for life.

[189] And then we start to realize that it's not so simple because, A, there might be other things that life does, apart from photosynthesis.

[190] Certainly, the vast majority of the Earth's history had no oxygen, and yet there was living things on it, so that doesn't seem like a complete test.

[191] And secondly, could there be other things that produce oxygen besides from life?

[192] A growing concern has been these false positives in biosignature work, and so one example of that would be photolysis that happens in the atmosphere.

[193] when ultraviolet right hits the upper atmosphere, it can break up water vapor, the hydrogen splits off to the oxygen, the hydrogen is a much lighter atomic species, and so it can actually escape certainly planets like the Earth's gravity.

[194] That's why we don't have any hydrogen or very little helium.

[195] And so that leaves you with the oxygen, which then oxidizes the surface.

[196] And so there could be a residual oxygen signature just due to this photolysis process.

[197] So we've been trying to generalize, and certainly in recent years there's been other suggestions of things we could look for in the solar system beyond nitrous oxide, basically laughing gas is a product of microbes.

[198] That's something that we're starting to get more interest in looking for.

[199] Methane gas in combination with other gases can be an important biosignature.

[200] Phosphine as well, and phosphine's particularly relevant to the solar system because there was a lot of interest for Venus recently.

[201] You may have heard that there was a claim of a biosignature in Venus's atmosphere.

[202] I think it was like two years ago now.

[203] And the judge and jury is still out on that.

[204] There was a very provocative claim and signature of a phosphine -like spectral absorption.

[205] But it could have also been some of the molecule in particular, sulfur dioxide, which is not a biosignature.

[206] So this is a detection of a gas in the atmosphere of Venus.

[207] and it might be controversial on several dimensions.

[208] So one, how to interpret that.

[209] Two, is there a gas?

[210] And three, is this even the right detection?

[211] Is there an error in the detection?

[212] Yeah.

[213] I mean, how much do we believe the detection in the first place?

[214] If you do believe it, does that necessarily mean there's life there?

[215] And what gives, how can you have life in the Venus's atmosphere in the first place?

[216] Because that's been seen as like a hellhole place for imagining life.

[217] But I guess the counter to that has been that, okay, yes, the surface is a horrendous place to imagine life thriving.

[218] But as you go up in altitude, the very dense atmosphere means that there is a cloud layer where the temperature and the pressure become actually fairly similar to the surface of the earth.

[219] And so maybe there are microbes stirring around in the clouds which are producing phosphine.

[220] At the moment, this is fascinating.

[221] It's got a lot of us reinvigorated about the prospects.

[222] of going back to Venus and doing another mission there.

[223] In fact, there's now two NASA missions, Veritas and Da Vinci, which are going to be going back and before 2030s.

[224] And then we have a European mission, I think, that's slated now, and even a Chinese mission might be coming along the way as well.

[225] So it might have multiple missions going to Venus, which has long been overlooked.

[226] I mean, apart from the Soviets, there really has been very little in the way of exploration of Venus.

[227] Certainly, yes, compared to Mars.

[228] Mars has enjoyed most of the activity from now.

[229] masses, rovers, and surveys.

[230] And Mars is certainly fascinating.

[231] There's, you know, this signature of methane that has been seen there before.

[232] Again, there, the discussion is whether that methane is a product of biology, which is possible, something that happens on the earth, or whether it's some geological process that we are yet to fully understand.

[233] It could be, you know, for example, a reservoir of methane that's trapped under the surface and it's leaking out seasonally.

[234] So the nice thing about Venus is if there's a giant living civilization there, it'll be airborne so you can just fly through and collect samples.

[235] With Mars and moons of Saturn and Jupiter, you're going to have to dig under to find the civilizations, dead or a living.

[236] Right.

[237] And so, yeah, maybe it's easier then for Venus because certainly you can imagine just a balloon floating through the atmosphere or a drone or something that would have the capability of just scooping up.

[238] and sampling.

[239] To dig under the surface of Mars is maybe feasible -ish, especially with something like Starship that could launch a huge digger, basically, to the surface, and you could just excavate away at the surface.

[240] But for something like Europa, we really are still unclear about how thick the ice layer is, how you would melt through that huge thick layer to get to the ocean, and then potentially also discussions about content.

[241] contamination.

[242] The problem with looking for life in the solar system, which is different from looking for life with exoplanes, is that you always run the risk of, especially if you visit there, of introducing the life yourself.

[243] It's very difficult to completely exterminate every single microbe and spore on the surface of your rover or the surface of your lander.

[244] And so there's always a risk of introducing something.

[245] I mean, to some extent, there is continuous exchange of material between these plants.

[246] naturally on top of that as well and now we're sort of accelerating that process to some degree and so if you dig into your rope's surface which probably is completely pristine it's very unlikely there has been much exchange with the outside world for its subsurface ocean you are for the first time potentially introducing bacterial spores into that environment that may compete or may introduce spurious signatures for the life you're looking for and so it's it's almost an ethical question as to how to proceed with looking for life on those subsurface oceans and I don't think one we've really have a good resolution for at this point ethical so you mean ethical in terms of concern for the like for preserving life elsewhere not to murder it yeah as opposed to scientific one I mean we always worry about a space virus right coming coming here or you know some kind of external source and we would be the source of that potential contamination or the other direction yeah I mean they that you know the whatever whatever survives in such harsh conditions might be pretty good at surviving all conditions it might be a little bit more resilient and robust so it might actually take a ride on us back home possibly i mean i'm sure i'm sure that some people would be concerned about that i think we would we would hopefully have some containment uh procedures as if we did sample return or what you mean you don't even really need a sample return these days you can pretty much send it like a little microlaboratory to the planet to do with the experiments in situ and then just send them back to your planet, the data.

[247] And so I don't think this is necessary that, especially for a case like that where you might have contamination concerns that you have to bring samples back.

[248] Although probably if you brought back European sushi, it would probably sell for quite a bit with the billionaires in New York City.

[249] Sushi, yeah.

[250] I would love from an engineering perspective just to see all the different candidates.

[251] and designs for like the scooper for Venus and the scooper for Europa and Mars haven't really look deeply into how they actually like the actual engineering of collecting the samples because that's the engineering of that is probably essential for not either destroying life or or polluting it with our own microbes and so on so that's a good interesting engineering challenge I usually for rovers and stuff focus on the robot on the sort of the mobility aspect of it on the robotics, the perception, and the movement and the planning and the control.

[252] But there's probably the scooper.

[253] It's probably where the action is.

[254] The microscopic sample collection.

[255] So basically you have to first clean your vehicle, make sure it doesn't have any earth -like things on it.

[256] And then you have to put it into some kind of thing that's perfectly sealed from the environment.

[257] So if we bring it back or we analyze it, it's not going to bring anything else externally.

[258] Yeah, I don't know.

[259] That would be an interesting engineering design there.

[260] Yeah, I mean, Curiosity has been leaving these little pods on the surface quite recently.

[261] There's some neat photos you can find online.

[262] And they kind of look like a lightsaber helps.

[263] So, yeah, to me, I think I tweeted something like, you know, this weapon is your life.

[264] Like, don't lose it, curiosity, because it's just dumping these little vials everywhere.

[265] And it's, yeah, it is scooping up these things.

[266] And the intention is that in the future, there will be a sample return mission that will come and pick these up but it's I mean the engineering behind those things is so impressive the thing that blows me away the most has been the landings especially I'm trained to be a pilot at the moment so that's the sort of watching landings has become like my pet hobby on YouTube at the moment and how not to do it how to do it with different levels of conditions and things but with the you know when you think about landing on Mars just the light travel time effect means that there's no possibility of a human controlling that dissent.

[267] And so you have to put all of your faith and your trust in the computer code or the AI or whatever it is that you've put on board that thing to make the correct descent.

[268] And so there's this famous period across seven minutes of hell, where you're basically waiting for that light travel time to come back to know whether your vehicle successfully landed on the surface of not.

[269] And during that period, you know in your mind simultaneously that it is doing these multi -stages of deploying its parachute, deploying the crane, activating its jets to come down and controlling its descent to the surface, and then the crane has to fly away, so it doesn't accidentally hit the rover.

[270] And so there's a series of multi -stage points where any of them go wrong, the whole mission could go awry.

[271] And so the fact that we are fairly consistently able to build these machines that can do this autonomously, is to me one of the most impressive acts of engineering that NASA have achieved.

[272] Yes, the unfortunate fact about physics is the takeoff is easier than the landing.

[273] Yes, yes.

[274] And you mentioned Starship.

[275] One of the incredible engineering fees that you get to see is the reusable rockets that take off, but they land, and they land using control, and they do so perfectly.

[276] And sometimes when it's synchronous, it's just, it's beautiful to see.

[277] And then with Starship, you see the chopsticks that catch the ship.

[278] I mean, there's just so much incredible engineer.

[279] But you mentioned Starships is somehow helpful here.

[280] So what's your hope with Starship?

[281] What kind of science might it enable possibly?

[282] There's two things.

[283] I mean, it's the launch cost itself, which is hopefully going to mean per kilogram, it's going to dramatically reduce the cost of its sort of the level, even if it's a factor of 10 higher than what Elon originally promised, this is going to be a revolution for the cost to launch.

[284] that means you could do all sorts of things.

[285] You could launch large telescopes, which could be basically like JWST, but you don't even have to fold them up.

[286] JDBST had this whole issue with its design that it's six and a half meters across, and so you have to, there's no fuselage, which is that large at the time.

[287] There is four, it wasn't large enough for that.

[288] And so they had to fold it up into this kind of complicated origami.

[289] And so a large part of the cost was figuring out how to fold it up, testing that it unfolded correctly, repeated testing and there was something like 130 fail points or something during this unfolding mechanism and so all of us were holding our breath during that process but if you have the ability to just launch arbitrarily large masses at least comparatively compared to JVST and very large mirrors into space you can more or less repurpose ground -based mirrors the Hubble Space telescope mirror and the JVST mirrors are designed to be extremely lightweight and that increased their cost significantly.

[290] They have these kind of honeycomb design on the back to try and minimize the weight.

[291] If you don't really care about weight because it's so cheap, then you could just literally grab many of the existing ground -based mirrors across telescopes across the world, four meter, five -meter mirrors, and just pretty much attach them to a chassis and have your own space -based telescope.

[292] I think the breakthrough foundation, for instance, is an entity that has been interested in doing this sort of thing.

[293] And so that raises the prospects of having not just one WST, that just, you know, WST is a fantastic resource, but it's split between all of us, cosmologists, star formation, astronomers, those of us studying exoplanets, those of us wanting to study, you know, the ultra -deep fields and the origin of the first galaxies, the expansion area of the universe.

[294] Everyone has to share this resource, but we could potentially each have, you know, one JWST each that is maybe, just studying a handful of the brightest exoplanet stars and measuring their atmospheres.

[295] This is important because if you, we talked about this planet Trappist 1E earlier, that planet, if GDPC stared at it and tried to look for biosignatures, by which I mean oxygen, nitrous oxide, methane, it would take it of order of 200 transits to get even a very marginal, what we'd call two and a half sigma detection of those, which basically nobody would believe with that.

[296] And 100 transits, I mean, this thing transits once every six days.

[297] So you're talking about four years of staring at the same star with one telescope.

[298] There'd be some breaks, but it'd be hard to schedule much else because you'll have to continuously catch each one of these transits to build up your signal to noise.

[299] And so J .RU