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0:00 Signs of life on an exoplanet. What's up with that? I got with me David Kipping. David, welcome back to Star Talk. Nice. Pleasure to be back. Yeah. Yeah. So, this is not the first time we've seen an announcement of biomarkers indicating the possible existence of life. So, it's not the detection of life, it's the detection of gases involved in life as we know it. Yes. Yeah. I mean, how do you detect life directly? We don't we can't even decide what life even is. So, coming up with a way to detect it directly is very difficult. These are just the uh the contaminants that they would release essentially into the atmosphere that we can then detect and say, "Hey, maybe this Wait a minute. Is the oxygen from a tree a contaminant?" I mean, in a way,
0:45 it's a waste product in a way, right? Photosynthesis produces that. So, if you're a tree, yeah, I wouldn't think of it that way, but the tree might. So, uh, just remind me this is 120 light years away. It's a planet discovered from the Kepler mission. Yeah. Kepler 2. It had a failure after four years. It couldn't stare at the same stars anymore, but it could do a second phase of the mission where it looks at the ecliptic plane only. So during that phase, it detected K28. Just to get the the physics of the detection straight. So you've got a star, you got the exoplanet orbiting the star. Light from the star goes through the atmosphere and comes to you after it's been touched by the gaseous signatures in the atmosphere of the planet. Contaminated even contaminated. You need the web telescope
1:32 to make this measurement. Yeah. And you can do it with other telescopes. I mean Hubble has looked at this before with widefall camera chemistry. That's an instrument on there. In that case they weren't able to detect anything conclusively. And so once WST came around, everyone was very excited because this is one of the best targets. It's a nice puffy atmosphere around a bright star. It's nearby. So, everyone knew this would always be a good planet. Oh, they knew that. Okay. Okay. So, what does it mean for a planet to have a puffy atmosphere? Puffy atmosphere. The three ingredients are low surface gravity ideally. This doesn't really have that, but it's not too bad. You want a hot, warm planet. That's useful because it puffs up the gas. It heats up the gas. Right. Exactly. So, you get a puffy atmosphere. And you want a light molecular gas because that can go higher in the gravitational well and made a larger atmosphere. And we have a puffy atmosphere as it passes in front of the host star. Yeah. There's more there's
2:20 more for us to see. More for you to see. Yeah. And the list of biomarkers, last I checked, is pretty large, even methane. Yet, we have lakes of methane on Saturn's moon, Titan. Mhm. But no one's saying it's a place thriving with life. So, it's not just the existence of the chemical, it's the conditions under which you expect to find the chemical. Yes, the context is extremely important. So for instance with this planet there is some debate about what the planet really is. One idea is this is an ocean world called a hian world. So this is a thin hydrogen atmosphere. Yes. And beneath it you have ocean. So there is a surface hyen. Your guess is yeah, I think it's h and an important detail here is that if
3:06 it really was a hasten world, even having methane alone would basically kind of prove there was life actually just the methane because there's no way it should be able to sustain meth in its atmosphere if it really was a hasten world with this thin atmosphere. Um it would require a biosphere to make that. I don't know the numbers, but I know from reading my colleagues papers on this that you would expect there to be parts per million level of methane if there was no life. But this thing has percent level of methane. So it has way more than it should do when you do the photochemical. What's the best way to get methane from life? I guess bacteria probably I would guess. So I've always seen methane connected to life that's anorobic. So like deep in our gut the microbes there are all anorobic and so methane is one of the byproducts. Right. That's why cows fart methane and fart
3:53 methane. Yes. So if we already know the methane's there but we're not sure of the environment then what else did they find? So here they were reporting stronger evidence for not only dimethyl sulfide but also dimethyl dulfide. So these two molecules which are on earth only really produced by phytolanton in the oceans. Why do you even care about the dimethyl sulfide if you had the methane as evidence because it isn't necessarily a high world. Not everybody believes that. So if it's just simply a a shrunken down Neptune, take Neptune, shrink it down by about a factor of one and a half to two and that is maybe what this planet is. In that case, there would be this deep there's no real surface, right? You can just fall all the way down. There's no real land. Yeah, exactly. Gas all the way down. And so there would be methane, ammonia, and
4:39 these other gases being produced in the inside of the planet, the interior, and then they would swell up through convection currents and come up to the upper atmosphere where we could see them. So the fact we see methane is consistent with that picture. We would expect also to see these other things like ammonia. Presently the current data isn't actually good enough to distinguish that. It is possible it could be one of these worlds and the amount of ammonia is just below our detection sensitivity. So it's not a super Earth. Well, that's a good question. We don't really know what it is. I mean an open question is it's about two and a half times the radius of the Earth. Neptune's four times the radius of the Earth and obviously Earth's one. So it's somewhere in between. Okay. And we don't really know what that is. We don't have anything in the solar system that looks like. We don't have a counterpart. No. So we are guessing here what it really is. All right. So this chemical which is new to me. I didn't know the dimethyl sulfide.
5:26 Yes. I mean it's it's actually a a molecule you may have experienced cuz it's in truffles. It's actually this the truffle smell is associated with I like this molecule now. Okay. So that is produced on earth. How uh typically on earth it's phytolanton. So these are tiny microorganisms living in the ocean. photosynthesizing plankton correct in the ocean. Okay. How much of that do they make on the earth? It's hardly anything. It's like parts per billion levels concentration. We don't know any other way that could be made naturally yet. I mean, this is it's always No, no. On the Earth, we don't know of any other way. Okay. So, they've discovered these molecules on the on this planet. Yeah. So, we're thinking phytolanton in an ocean. It could be. It could be. And they found much more of it at a
6:11 higher concentration on that planet than we have those chemicals on our planet. Much more. I mean 10,000 to 100,000 times higher concentration. So we're talking about a thriving biota with these microorganisms. If you believe the detection and if you believe the only way to make it is via something like phytolanton. So if you if you're a skeptic, you'd have to say, "Let me think hard about how else you'd make it that didn't involve life." Exactly. Which no one has come forward yet. Well, we know of we certainly don't have a good idea for mechanisms, but we do see DMS on comets. So the comet 67P that we landed, the Rosetta um mission on that comet that which is a dead comet, you see this molecule. We certainly know it can occur in the absence of life. Whether you could ever
6:58 get as much as is seen here is another question. Got it. Okay. Are the data contested and is the interpretation of the data contested? Yes and yes. Okay. I mean so this is all kind of X and Twitter reactions at this point. So there's no published article that has called out these is incorrect. But the discussion I'm seeing amongst my colleagues is a the significance level claimed of three sigma. There is skepticism about the reality that is as high as it could be that the signal within the spectrum of this molecule is not as strong as claimed. Yeah. I mean to give you the the zoom out picture here that there's a spectrum and there's these two little bumps that look like this molecule but you know when you do these searches you have a catalog of possible molecules you could check for and there's boatloads of them. There's
7:43 trillions of molecules you could check for really. So they they guessed initially here's 20 molecules we think are plausible in this atmosphere and they they fit it to the data. They get a good fit and that's actually only two sigma significance for DMS when you do it that way. Then they say, "Hold on. Um, we don't think all these other molecules are there." So they strip it down to just four that they think are most likely. So that would boost the significance and that boost if you do that. Yes. Then they get their three three plus sigma number. Okay. So that's where there's some skepticism. You know, is this kind of engineering of the number or is this a reasonable thing to do given the data? So let's start out with just wrapping our head around what a two sigma result would be. So what's your best explanation of a two sigma result? It it quantifies a probability. So in that case, it's 5%. So it really means if you did the same so one in 20 one in 20 correct if you did the same experiment 20 times one of those 20
8:31 times you'd expect to get a detection even though there's nothing there to detect it's just a spurious result. So that's your confidence level 95% 5% chance of being wrong and so you get three sigma that's one in uh a thousand times and in you know five sigma would be like the gold standard and that's like one in 10 million so that's kind of the Higs Bzon level of confidence that we had when that was announced you know with the Nobel Prize my own discovery. This is not yet five sigma. It is claimed to be three sigma one one in a thousand. It may in fact be less than that depending on who you believe. Um and so that's why you know it's still exciting. I still think you know two sigma is still exciting but historically there are a lot of two sigma detections that disappear under subsequent scrutiny. There's then the question of let's assume it's true. Let's assume this molecule e is there. Does that
9:17 prove life? Which is another very challenging question to unpack. That would be the interpretation of the result being correct. Correct. I mean there are many skeptics who say even no one single molecule will ever be convincing proof of life. You can't just look at a silver bullet like this. It doesn't exist. In fact Sarah Seager who was the PhD advisor to Nikki Medusen who published this paper published a paper the next day saying exactly that. There's no such thing as a silver bullet biomarker. So it's kind of funny these the timing of these two. He's coming after student slapping on other reasons. I think it was coincidence these things came out. But it was amusing to see that timing. Yeah. So I think the community is skeptical because one molecule, who knows? Maybe there's some weird geology on these planets we've never seen before
10:02 that is making it. One molecule by itself just isn't enough to convince us. So what I've tried to convey every time I'm able is that anytime scientists disagree, there only really one of three outcomes. One is wrong and the other is right. Well, that person's wrong. They they're right or they're both wrong. It's usually the case. Usually the case. Uh and but they don't fight. They say we need more or better data. Yeah. And it's the start of a of a continuing conversation. So is is this high on the list of JWST to uh make another round? I should think it will be. I mean, this is I'm sure going to be proposed in the next cycle. And even if you're a skeptic, I think you would want James Webb to go back and get more data and
10:47 remove the ambiguity because look, scientists like everyone else, we don't like uncertainty. We don't like it's something being 50/50. There's life there and not there. We want to know the answers for sure. And so does everybody else. We have to go back. We have to get the data and figure it out. Yeah. Yeah. What's the period of this planet? It's once every 33 days. That's how long it takes it to go around its year around the star. Oh, okay. So, and you can only get data when it's in front of the star. Correct. So, that's sort of convenient that it doesn't take a whole year, right? And it's actually convenient that the star is I mean, if you're in the solar system, the sun, if you're a 33-day orbit, which is closer in the Mercury's orbit, you'd be scorching hot. So, the fact this star is cooler means this is actually still in the temperate zone, the habitable zone of its star despite having a 33-day orbit. So, this place counts as a cool world to you, I'd
11:33 say. So, I mean, it is it's at the right distance, right, where you'd call it a cool world, far enough from it. Cool. I meant like a dope world. Dope world. Yeah. Down with a kids world. Yeah. So, this is just an overview. You're going to on your own platform, you're going to do a deep dive into this and bring in some of the expert. We're going to get a lead author to come in and tell me why he believes this is real. I'm going to get a critic to come on and tell me his opinion. And then I'm going to try and break it down for the audience. So, if you want a bit more depth, that's the place to look for that. And that's coming out soon. We'll look for it. Yeah. next week. Yeah. Yeah. Yeah. And you can find more of David Kipping in our archives. He's visited us twice to talk about his cool worlds. Always a pleasure. This has been yet another What's Up With That Life on Exoplanets.
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