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Speaker 1

00:00

The following is a conversation with Clara Souza Silva, a quantum master chemist at Harvard, specializing in spectroscopy of gases that serve as possible signs of life on other planets, most especially the gas phosphine. She was a co-author of the paper that in 2020 found that there is phosphine in the atmosphere of Venus and thus possible extraterrestrial life that lives in its atmosphere. The detection of phosphine was challenged, reaffirmed, and is now still under active research. Quick mention of our sponsors, Onnit, Grammarly, Blinkist, and Indeed.

Speaker 1

00:37

Check them out in the description to support this podcast. As a side note, let me say that I think the search for life on other planets is 1 of the most important endeavors in science. If we find extraterrestrial life and study it, we may find insights into the mechanisms that originated life here on Earth. And more than life, the mechanisms that originated intelligence and consciousness.

Speaker 1

01:00

If we understand these mechanisms, we can build them. But more than this, the discovery of life on other planets means that our galaxy and our universe is teeming with life. This is humbling and terrifying, but it is also exciting. We humans are natural explorers.

Speaker 1

01:17

For most of our history, we explored the surface of the Earth and the contents of our minds. But now, with space-faring vessels, we have a chance to explore life beyond Earth, their physics, their biology, and perhaps the contents of their minds. This is the Lux Friedman Podcast, and here is my conversation with Clara Sousa Silva. Since you're the world expert in, well, in many things, but 1 of them is phosphine, would it technically be correct to call you the Queen of Phosphine?

Speaker 2

01:52

I go for Dr. Phosphine. Queen is an inherited title, I feel.

Speaker 1

01:56

But you still rule by Love and power, so, but while having the doctor title. I got

Speaker 2

02:04

it. Kindness.

Speaker 1

02:05

Kindness, kindness. In September 2020, you co-authored a paper announcing possible presence of phosphine in the atmosphere of Venus, and that it may be a signature of extraterrestrial life.

Speaker 2

02:21

Big maybe.

Speaker 1

02:21

Big maybe. There was some pushback, of course, from the scientific community that followed, friendly, loving pushback. Then in January, another paper from University of Wisconsin, I believe confirmed the finding.

Speaker 1

02:37

So where do we stand in this saga, in this mystery of what the heck is going on on Venus in terms of phosphine and in terms of aliens?

Speaker 2

02:48

Let's try to break it down.

Speaker 1

02:49

Okay.

Speaker 2

02:50

The short answer is we don't know. I think you and the rest of the public are now witnessing a pretty exciting discovery, but as it evolves, as it unfolds, We did not wait until we had years of data from 10 different instruments across several layers of the atmosphere. We waited until we had 2 telescopes with independent data months apart.

Speaker 2

03:20

But still, the data is weak, it's noisy, it's delicate, it's very much at the edge of instrument sensitivity. And so We still don't even know if it is phosphine. We don't even really know if the signal is real. People still disagree about that.

Speaker 2

03:38

I think at the more philosophical end of how this happened, I think it is a distinction and myself and other co-authors were talking about this. It's a distinction between hypothesis generation and hypothesis testing. Now, hypothesis testing is something that I think is the backbone of the scientific method, But it has a problem, which is, if you're looking through very noisy data and you want to test the hypotheses, you may, by mistake, create a spurious signal. The safest, more conservative approach is hypothesis generation.

Speaker 2

04:14

You see some data and you go, what's in there with no bias. Now this is much safer, much more conservative. And when there's a lot of data, that's great. When there isn't, you can clean the noise and take out the signal with it.

Speaker 2

04:28

The signal with a bathwater, whatever the equivalent of the analogy would be. And so I think the healthy discourse that you described is exactly this. There are ways of processing the data, completely legitimate ways, checked by multiple people and experts where the signal shows up and then phosphine is in the atmosphere of Venus, and somewhere it doesn't. And then we disagree what that signal means.

Speaker 2

04:52

If it's real and it is an ambiguously phosphine, it is very exciting because we don't know how to explain it without life. But going from there to Venusians is still a huge jump.

Speaker 1

05:06

LRW So that would be the title for the civilization, if it is a living and thriving on Venus's Venusians.

Speaker 2

05:13

CMH Until we know what they call themselves, that's the name, yes.

Speaker 1

05:18

So this is the early analysis of data or analysis of early data. It was nevertheless, you waited until the actual peer-reviewed publication

Speaker 2

05:29

to announce? Of course, and analysis of the 2 different instruments months apart. So that's ALMA and JCMT, the 2 telescopes.

Speaker 1

05:36

I mean, it's still, I mean, it's really exciting. What did it feel like sort of sitting on this data, like kind of anticipating the publication and wondering and still wondering, is it true? Like, how does it make you feel that a planet in our solar system might have phosphine in the atmosphere?

Speaker 2

05:56

It's nuts, it's absolutely nuts. I mean.

Speaker 1

06:02

In the best possible way.

Speaker 2

06:04

I've been working on phosphine for over a decade.

Speaker 1

06:08

Before it was cool.

Speaker 2

06:10

Way before it was cool. Before anyone could spell it or heard of it. And at the time people either didn't know what phosphine was or only knew it for being just possibly the most horrendous molecule that ever graced the Earth.

Speaker 2

06:26

And so no 1 was a fan. And I'd been considering looking for it because I did think it was an unusual and disgusting but very promising sign of life. I've been looking for it everywhere. I really didn't think to look in the solar system.

Speaker 2

06:43

I thought it was all pretty rough around here for life. And so, I wasn't even considering the solar system at all, never mind next door Venus. It was only the lead author of the study, Jane Greaves, who thought to look in the clouds of Venus and then reached out to me to say, I don't know phosphine, but I know it's weird. How weird is it?

Speaker 2

07:06

And the answer is very weird.

Speaker 1

07:08

And so the telescopes were looking at, so this is visual data. That's what I

Speaker 2

07:13

mean by visual, you wouldn't see the phosphine.

Speaker 1

07:15

Well, but I mean, it's a telescope. It's remote. It's remote, you're observing, you're what, zooming in on this particular planet.

Speaker 1

07:25

I mean, what does the sensor actually look like? How many pixels are there? What does the data kind of look like? It'd be nice to kind of build up intuition of how little data we have based on which.

Speaker 1

07:39

I mean, if you look at like, I've just been reading a lot about gravitational waves and it's kind of incredible how from just very little, like probably the world's most precise instrument, we can derive some very foundational ideas about our early universe. And in that same way, it's kind of incredible how much information you can get from just a few pixels. So what are we talking about here in terms of based on which this paper saw possible signs of phosphine in the atmosphere?

Speaker 2

08:13

So phosphine, like every other molecule has a unique spectroscopic fingerprint, meaning it rotates and vibrates in special ways. I calculated how many of those ways it can rotate and vibrate, and it's 16.8 billion ways. What this means is that if you look at the spectrum of light, and that light has gone through phosphine gas on the other end, there should be 16.8 billion tiny marks left, indentations left in that spectrum.

Speaker 2

08:43

We found 1 of those on Venus, 1 of those 16.8 billion. So now the game is, can we find any of the other ones? But they're really hard to spot. They're all in terrible places in the electromagnetic spectrum.

Speaker 2

08:59

And the instruments we use to find this 1, can't really find any other 1. There's another 1 of the 16.8 billion we could find, but it would take many, many days of continuous observations and that's not really in the cards right now.

Speaker 1

09:12

I mean, how do you, there's all kinds of noise, first of all. Yes. There's all kinds of other signal.

Speaker 1

09:20

So how do you separate all of that out to pull out just this particular signature that's associated with phosphine?

Speaker 2

09:30

So the data kind of looks somewhat like a wave

Speaker 1

09:34

and

Speaker 2

09:34

a lot of that is noise and it's a baseline. And so, if you can figure out the exact shape of the wave, you can cancel that shape out and you should be left with a straight line and if there's something there, an absorption, so a signal. So that's what we did.

Speaker 2

09:49

We tried to find out what was this baseline shape, cleaned it out, and got the signal. That's part of the problem. If you do this wrong, you can create a signal. But that signal is at 8.904 wave numbers, And we actually have more digits than that, but I don't remember by heart.

Speaker 2

10:08

And ALMA in particular is a very, very good array of telescopes, and it can focus on exactly that frequency. And in that frequency, there are only 2 known molecules that absorb at all. So that's how we do it. We look at that exact spot where we know fossil absorbs.

Speaker 2

10:27

The other molecule is SO2.

Speaker 1

10:30

If there is extraterrestrial life, whether it's on Venus or on exoplanets where you looked before, how does that make you feel? How should it make us feel? Should we be scared?

Speaker 1

10:43

Should we be excited? Let's say it's not intelligent life. Let's say it's microbial life. Is it a threat to us?

Speaker 1

10:53

Are we a threat to it? Or is it only, not only, but mostly, possibly to understand something fundamental, something beautiful about life in the universe?

Speaker 2

11:04

Hard to know. You would have to bring on a poet or a philosopher on the show.

Speaker 1

11:10

You don't feel?

Speaker 2

11:11

I feel those things, I just don't know if those are the right things to feel. I don't, certainly don't feel scared. I think it's rather silly to feel scared.

Speaker 2

11:18

Definitely don't touch them. Sometimes in the movies, don't go near it, don't interfere. I think 1 of the things with Venus is because of phosphine, now there is a chance that Venus is inhabited. In that case, we shouldn't go there.

Speaker 2

11:38

We should be very careful with messing with them, bringing our own stuff there that contaminates it. And Venus has suffered enough. If there's life there, it's probably the remains of a living planet, the very last survivors of what once was potentially a thriving world. And so, I don't want our first interaction with alien life to be a massacre.

Speaker 2

12:06

So I definitely wouldn't want to go near out of a, let's say, galactic responsibility, galactic ethics. And I often think of alien astronomers watching us and how disappointed they would be if we messed this up. So I really want to be very careful with anything that could be life. But certainly I wouldn't be scared.

Speaker 2

12:27

Humans are plenty capable of killing 1 another. We don't need extraterrestrial help to destroy ourselves.

Speaker 1

12:34

Scared mostly of other humans. Exactly. But this life, if there is life there, it does seem just like you said, it would be pretty rugged.

Speaker 1

12:43

It's like the cockroaches Or Chuck Norris, I don't know. It's the some kind of, it's something that survived through some very difficult conditions.

Speaker 2

12:52

That doesn't mean it would handle us, you know? It could be like war of the worlds. You come just because you're resilient in your own planet doesn't mean you can survive another.

Speaker 2

13:02

Even our extremophiles, which are very impressive, we should all be very proud of our extremophiles, they wouldn't really make it in the Venusian clouds. So I wouldn't expect, because you're tough, even Chuck Norris tough, that you would survive on an alien planet.

Speaker 1

13:20

And then from the scientific perspective, you don't want to pollute the data gathering process by showing up there. The observer can affect the observed.

Speaker 2

13:31

How heartbreaking would it be if we found life on another planet and then we're like, oh, we brought it with us, it was my sandwich.

Speaker 1

13:38

But that's always the problem, right? And it's certainly a problem with Mars because we visited the, if there is life on Mars or like remains of life on Mars, it's always going to be a question of like, well, maybe we planted it there.

Speaker 2

13:53

Let's not do the same with Venus. It's harder, because when we try to go to Venus, things melt very quickly. Yeah, it's pretty, yeah.

Speaker 2

14:00

It's a little harder to pollute Venus. It's very good at destroying foreigners.

Speaker 1

14:08

Yeah, well, in terms of Elon Musk and terraforming planets, Mars is stop number 1, then Venus maybe after that. So, can we talk about phosphine a little bit? So you mentioned it's a pretty-

Speaker 2

14:21

I love phosphine. I love phosphine.

Speaker 1

14:22

What's your Twitter handle? It's like Dr. Phosphine?

Speaker 2

14:24

It's Dr. Phosphine, yes. You'll be surprised here, it wasn't taken already.

Speaker 2

14:28

I could just, I just grabbed it. Didn't have to buy it off anyone.

Speaker 1

14:32

Yeah, so what is it? What's phosphine? You already mentioned it's pretty toxic and troublesome.

Speaker 1

14:41

What, and, outside, trouble, sorry.

Speaker 2

14:44

No, I love it. I'm gonna stop calling it troublesome.

Speaker 1

14:48

So maybe, what are some things that make it interesting chemically and why is it a good sign of life when it's present in the atmosphere like you've described in your paper, aptly titled the phosphine as a biosignature gas in exoplanet atmospheres. I suppose you wrote that paper before Venus.

Speaker 2

15:11

I did, yes, I did. And no 1 cared, you know, in that paper, I said something like, if we find phosphine on any terrestrial planet, it can only mean life and everyone's like, yeah, that sounds about right, let's go. And then Venus shows up and I was like, are you sure?

Speaker 2

15:24

I'm like, I was sure before I was sure. Now that it's right here, I'm less sure now that my claims are being tested. So phosphine is a fascinating molecule. So it's shaped like a pyramid with a phosphorus up top and then 3 hydrogens.

Speaker 2

15:43

It's actually quite a simple molecule in many ways. It's the most popular elements in the universe, carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur. When you add hydrogen to them, it makes quite simple, quite famous molecules. You do it to oxygen, you get water.

Speaker 2

16:01

You do it to carbon, you get methane. You do it to nitrogen, you get ammonia. These are all molecules people have heard of. You do it to phosphorus, you get phosphine.

Speaker 2

16:11

People haven't heard of phosphine because it's not really popular on Earth. We really shouldn't find it anywhere on Earth because it is extremely toxic to life. It interacts with oxygen metabolism and everything you know and love uses oxygen metabolism. And it interacts fatally, so it kills in several very imaginative and very macabre ways.

Speaker 2

16:37

So it was used as a chemical warfare agent in the First World War and most recently by ISIS. So, really bad. Most life avoids it. Even life that might not avoid it, so life that doesn't use oxygen metabolism, anaerobic life, still has to put crazy amounts of effort into making it.

Speaker 2

16:56

It's a really difficult molecule to make, thermodynamically speaking. It's really difficult to make that phosphorus want to be together with that hydrogen. So it's horrible. Everyone avoids it.

Speaker 2

17:07

When they're not avoiding it, it's extremely difficult to make. You would have to put energy in, sacrifice energy to make it. And if you did go through all that trouble and made it, it gets reacted with the radicals in the atmosphere and gets destroyed. So we shouldn't find it anywhere, and yet we do.

Speaker 2

17:24

It's this kind of weird molecule that seems to be made by life and we don't even know why. Life clearly finds a use for it. It's not the only molecule that life is willing to sacrifice energy to make, but we don't know how or why life is even making it. So absolutely mysterious, absolutely deadly, smells horrifically.

Speaker 2

17:46

When it's made, it produces other kind of diphosphenes, and it's been reported as smelling like garlicky, fishy death. Once someone referred to it as smelling like the, let me see if I remember, the rancid diapers of the spawn of Satan.

Speaker 1

18:00

Oh, very nice.

Speaker 2

18:01

Yeah, very vivid. And so...

Speaker 1

18:03

See, You're a poet after all.

Speaker 2

18:06

I didn't call that. Someone else did. And so it's just this horrific molecule, but it is produced by life.

Speaker 1

18:12

We

Speaker 2

18:12

don't know why. And when it is produced by life, it's done with enormous sacrifice. And the universe does not sacrifice.

Speaker 2

18:20

Life sacrifices. And so it's this strange contradictory molecule that we should all be avoiding and yet seems to be an almost an ambiguous sign of life on rocky planets.

Speaker 1

18:32

Okay, can we dig into that a little bit? So on rocky planets, what, is there biological mechanisms that can produce it? And is there, you said that why is unclear, why life might produce it, but is there an understanding of what kind of mechanisms might be able to produce it, this very difficult to produce molecule?

Speaker 2

18:55

We don't know yet. The enzymatic pathways of phosphine production by life are not yet known. This is not actually as surprising as it might sound.

Speaker 2

19:04

I think something like 80% of all the natural products that we know of, so we know biology makes them, we don't know how. It is much easier to know life produces something because you can put bacteria in a Petri dish and then watch and then that gas is produced, you go, oh, life made it. That actually happened with phosphine. But that's much easier to do, of course, than figuring out what is the exact metabolic pathway within that life form that created this molecule.

Speaker 2

19:33

So we don't know yet. Phosphine was really understudied. No 1 had really heard of it until now-ish.

Speaker 1

19:40

What you were presenting is the fact that life produces phosphine, not the process by which it produces phosphine. Is there an urgency now? Like if you were to try to understand the mechanisms, the, what did you call them, enzymatic pathways that produce phosphine, how difficult is that of a problem to crack?

Speaker 2

20:00

It's really difficult. If I'm not mistaken, even the scent of truffles, obviously a billion dollar industry, huge deal. Until quite recently, it wasn't known exactly how those scents, those molecules that create this incredible smell were produced.

Speaker 2

20:16

And this is a billion dollar industry. As you can imagine, there is no such pressure. There's no phosphine lobby or anything that would push for this research. I hope someone picks it up and does it.

Speaker 2

20:28

And it isn't crazy because we know that phosphine is really hard to make. We know it's really hard for it to happen accidentally. Even lightning and volcanoes that can produce small amounts of phosphine. It's extremely difficult for even these extreme processes to make it.

Speaker 2

20:44

So it's not really surprising that only life can do it because life is willing to make things at a cost.

Speaker 1

20:52

So maybe on the topic of phosphine, what again, you've gotten yourself into trouble. I'm gonna ask you all these like high level poetic questions, I apologize.

Speaker 2

21:02

No, I would love it.

Speaker 1

21:03

Okay. When did you first fall in love with phosphine?

Speaker 2

21:09

It wasn't love at first sight. It was somewhere between a long relationship and Stockholm syndrome. Yeah.

Speaker 2

21:20

When I first started my PhD, I knew I wanted to learn about molecular spectra and how to simulate it. I thought it was really outrageous that we as a species couldn't detect molecules remotely. We didn't have this perfect catalog ready of the molecular fingerprint of every molecule we may want to find in the universe. And something as basic as phosphine, the fact that we didn't really know how it interacted with light and so we couldn't detect it properly in the galaxy, I was so indignant.

Speaker 2

21:49

And so initially I just started working on phosphine because people hadn't before, and I thought we should know what phosphine looks like. And that was it. And then I read every paper that's ever been published about phosphine. It was quite easy because there aren't that many.

Speaker 2

22:08

And that's when I started learning about where we had already found it in the universe and what it meant. I started finding out quite how little we know about it and why. And it was only when I joined MIT and I started talking to biochemists that it became clear that phosphine wasn't just weird and special and understudied and disgusting. It was all these things for oxygen-loving life.

Speaker 2

22:36

And it was the anaerobic world that would welcome phosphine, and that's when the idea of looking for it on other planets became crystallized. Because oxygen is very powerful and very important on Earth, but that's not necessarily going to be the case on other exoplanets. Most planets are oxygen poor. Overwhelmingly, most planets are oxygen poor.

Speaker 2

22:59

And so, finding the sign of life that would be welcomed by everything that would live without oxygen on earth seemed so cool.

Speaker 1

23:12

But ultimately the project at first was born out of the idea that you wanna find that molecular fingerprint of a molecule. So, and this is just 1 example. And that's connected to then looking for that fingerprint elsewhere in a remote way.

Speaker 1

23:33

And obviously that then, at that time, where exoplanets already, when you were doing your PhD, and by the way, I should say your PhD thesis was on phosphine.

Speaker 2

23:41

It was all on phosphine, 100% on phosphine. With a little bit of ammonia, I have a chapter that I did where I talked about phosphine and ammonia. So I.

Speaker 2

23:51

Got it. But no, phosphine was very much my thesis.

Speaker 1

23:56

But at that time when you're writing it, there's already a sense that exoplanets are out there and we might be able to be looking for biosignatures on those exoplanets?

Speaker 2

24:08

Pretty much, so I finished my PhD in 2015. We found the first exoplanets in the mid to late 90s. So exoplanets were known.

Speaker 2

24:17

It was known that some had atmospheres. And from there, it's not a big jump to think, well, if some have atmospheres, some of those might be habitable and some of those may be inhabited.

Speaker 1

24:30

So how do you detect, you started to talk about it, but can we linger on it? How do you detect phosphine on a far away thing, rocky thing, rocky planet? What is spectroscopy?

Speaker 1

24:45

What is this molecular fingerprint? What does it look like? You've kind of mentioned the wave, but what are we supposed to think about? What are the tools?

Speaker 1

24:54

What are the uncertainties? All those kinds of things.

Speaker 2

24:57

So the path can go this way. You've got light, kind of pure light. You can crack that light open with a prism or a spectroscope or water and make a rainbow.

Speaker 2

25:10

That rainbow is all the colors and all the invisible colors, the ultraviolet, the infrared. And if that light was truly pure, you could consider that rainbow to just cover continuously all of these colors. But if that light goes through a gas, we may not see that gas. We certainly cannot see the molecules within that gas, but those molecules will still absorb some of that light.

Speaker 2

25:36

Some, but not all. Each molecule absorbs only very specific colors of that rainbow. And so if you know, for example, that shade of green can only be absorbed by methane. Then you can watch as a planet passes in front of a star, the planet's too far away, you can't see it.

Speaker 2

25:54

And it has an atmosphere, that atmosphere is far too small, you definitely can't see it. But the sunlight will go through that atmosphere, And if that atmosphere is methane, then on the other side, that shade of blue, I can't remember if I said blue or green, that color will be missing because methane took it. And so with phosphine, it's the same thing. It has specific colors, 16.8 billion colors that it absorbs it and nothing else does.

Speaker 2

26:21

And so if you can find them and notice them missing from the light of a star that went through a planet's atmosphere, then you'll know that atmosphere contains the molecule. How cool is that?

Speaker 1

26:34

That's incredible. So you can have this fingerprint within the space of colors and there's a lot of molecules. And I mean, I wonder, that's a question of like how much overlap there is.

Speaker 1

26:45

How close can you get to the actual fingerprint? Like can phosphine unlock the iPhone with its lights on? He says 16.8 billion. So presumably this rainbow is discretized into little segments somehow.

Speaker 2

27:00

Exactly.

Speaker 1

27:00

How many total are there? How a lot is 16.8 billion?

Speaker 2

27:06

It's a lot. We don't have the instruments to break these, break any light into this many tiny segments. And so with the instruments we do have, there's huge amounts of overlap.

Speaker 2

27:18

Methane, as an example, a lot of the ways it's detectable is because the carbon and the hydrogens, they vibrate with 1 another, they move, they interact. But every other hydrocarbon, acetylene, isoprene, has carbon and hydrogens also vibrating and rotating. And so it's actually very hard to tell them apart at low resolutions. And our instruments can't really cope with distinguishing between molecules particularly well.

Speaker 2

27:50

But in an ideal world, if we had infinite resolution, then yes, every molecule's spectral features will be unique.

Speaker 1

27:58

Yeah, like almost too unique, like it would be too trivial.

Speaker 2

28:02

At the quantum level,

Speaker 1

28:03

they're unique. At the quantum level, yeah.

Speaker 2

28:04

At our level, there's huge overlap.

Speaker 1

28:07

Yeah, but then you can start to then, what, try to disambiguate like what the miss, the fact that certain colors are missing, what does that mean? And hopefully they're missing a certain kind of pattern where you can say, was some kind of probability that it's this gas, not this gas. So you're solving that gaseous puzzle.

Speaker 1

28:28

I got it, okay.

Speaker 2

28:29

We can go back to Venus actually and show that. So with this, I mentioned there was 2 molecules that could be responsible for that signal, the resolution that we have. It was phosphine and SO2, sulfur dioxide.

Speaker 2

28:43

And at that resolution, it could really be 1 or the other, but in that same bandwidth, so in the same observations, there was another region where phosphine does not absorb, we know that, but SO2 does. So we just went and checked and there was no signal. So we thought, oh, then it must be phosphine. And then we submit to the paper.

Speaker 2

29:05

The rest is history.

Speaker 1

29:07

I got it. Well, yeah, that's beautifully told. Is there, so the telescopes we're talking about are sitting on Earth.

Speaker 1

29:17

What, can it help solving this fingerprint, molecular fingerprint problem if we do a flyby? Does it help if we get closer and closer? Or are telescopes pretty damn good for this kind of puzzle solving.

Speaker 2

29:33

Top scopes are pretty good, but the Earth's atmosphere is a pain. I mean, I'm very thankful for it, but it does interrupt a lot of measurements and a lot of regions where phosphine would be active. They are not available.

Speaker 2

29:47

The Earth is not transparent in those wavelengths. So being above the atmosphere would make a huge difference. Then proximity matters a lot less, but just escaping the Earth's atmosphere would be wonderful. But then it's really hard to stay very stable.

Speaker 2

30:03

And if there is phosphine on Venus, there's very little of it in the clouds. And so the signal is very weak. And the telescopes we can use on Earth are much bigger and much more stable. So it's a bit of a trade-off.

Speaker 1

30:18

So is it, are you comfortable with this kind of remote observation? Is it at all helpful to strive for going over to Venus and like grabbing a scoop of the atmosphere or is remote observation really a powerful tool for this kind of job? Like the scoop is not necessary.

Speaker 2

30:41

Well, a lot of people want to scoop, I get it. I get it completely.

Speaker 1

30:45

That's my natural inclination, yeah.

Speaker 2

30:47

I don't want to scoop specifically because if it is life, I want to know everything I can remotely before I interfere. So that's my, I've got ethical reasons against the scoop more than engineering reasons against the scoop. But I have some engineering reasons against the scoop.

Speaker 2

31:02

Scoop is not a technical term, but I feel like Noah's too late. It's too late to take it back. Thank you for

Speaker 1

31:06

going along with this.

Speaker 2

31:07

It's too late to take it back.

Speaker 1

31:08

I appreciate it.

Speaker 2

31:09

We don't understand the clouds well enough to plan the scoop very well.

Speaker 1

31:14

Because it's not that saturated, like there's not that much of it present.

Speaker 2

31:19

No, and the place is nasty. You know, it's not going to be easy to build something that can do the task reliably and can be trusted, the measurements can be trusted, and then pass that message on. So actually, I'm for an orbiter.

Speaker 2

31:35

I think we should have orbiters around every solar system body whose job is just to learn about these places. I'm disappointed we haven't already got an orbiter around every single 1 of them. A small, it can be a small satellite. Just getting data, figuring out, you know, how do the clouds move?

Speaker 2

31:52

What's in them? How often is there lightning and volcanic activity? Where's the topography? Is it changing?

Speaker 2

31:58

Is there a biosphere actively doing things? We should be monitoring this from afar. And so I'm for over the atmosphere, hopefully around Venus, that would be my choice.

Speaker 1

32:12

Okay, so now recently Venus is all exciting about a phosphine and everything. Is there other stuff maybe before we were looking at Venus or now looking out into other solar systems? Is there other promising exoplanets or other planets within the solar system that might have phosphine or might have other strong biosignatures that we should be looking for, like phosphine?

Speaker 2

32:42

There's a few, but outside the solar system, all are promising candidates. We know so little about them. For most of them, we barely know their density.

Speaker 2

32:53

Most of them, we don't even know if they have an atmosphere, never mind what that atmosphere might contain. So we're still very much at the stage where we have detected promising planets, but they're promising in that they're about the right size, about the right density, they could have an atmosphere, and they're about the right distance from their host star. But that's really all we know. Near future telescopes will tell us much more, but for now, we're just guessing.

Speaker 1

33:20

So you said near future, so there's hope that there'll be telescopes that can see that far enough to determine if there's an atmosphere and perhaps even the contents of that atmosphere?

Speaker 2

33:31

Absolutely, JWST launching later this year will be able to get a very rough sense of the main atmospheric constituents of planets that could potentially be habitable. And that's this year.

Speaker 1

33:45

LARS What's the name of

Speaker 2

33:46

the- MS. BELLA THORNTON JWST, the James Webb Space Telescope.

Speaker 1

33:49

Okay, and that's going to be out in space past the atmosphere?

Speaker 2

33:53

Yes.

Speaker 1

33:53

Is there something interesting to be said about the engineering aspect of the telescope?

Speaker 2

33:57

It's an incredible beast, but it's a beast of many burdens. So it's going to do, it's going to.

Speaker 1

34:05

See you are a poet. You are, yeah, I love it. This is very eloquent.

Speaker 1

34:11

You're speaking to the audience, which I appreciate. So yes, it's a giant engineering project and is it orbiting something, do you know?

Speaker 2

34:20

So, it's going to be above the atmosphere and it will be doing lots of different astrophysics. And so, some of its time will be dedicated to exoplanets, but there's an entire astronomy field fighting for time before the cryogenic lifetime of the instrument. And so, when I was looking for the possibility of finding phosphine on distant exoplanets, I used JWST as a way of checking with this instrument that we will launch later this year, could we detect phosphine on an oxygen-poor planet?

Speaker 2

34:56

And there I put very much a hard stop where some of my simulations said, yes, you can totally do it, but it will take a little under the cryogenic lifetime of this machine. So then I had to go, well, that's not going to, no one's going to dedicate all of JWST to look for my molecule that no 1 cared about. So we're very much at that edge, but there'll be many other telescopes in the coming decades that will be able to tell us quite a lot about the atmospheres of potentially habitable planets.

Speaker 1

35:26

So you mentioned simulation. This is super interesting to me. And this perhaps could be a super dumb question, but-

Speaker 2

35:34

Not much thing.

Speaker 1

35:36

I am gonna prove you wrong on that 1. You simulate molecules to understand how they look from a distance is what I understand. Like what does that simulation look like?

Speaker 1

35:46

So it's talking about which colors of the rainbow will be missing, is that the goal of the simulation?

Speaker 2

35:54

That's the goal, but it's really just a very, very nasty Schrodinger's equation. So it's a quantum simulation.

Speaker 1

36:01

Oh, so it's simulating at the quantum level.

Speaker 2

36:03

Yes, so I'm a quantum astrochemist. Hi, I'm Clara, I'm a quantum astrochemist.

Speaker 1

36:08

It's how

Speaker 2

36:08

we should have started this conversation. Can

Speaker 1

36:10

you describe the 3 components of that, quantum, astro, and chemist, and how they interplay together?

Speaker 2

36:18

So I study the quantum behavior of molecules, hence the quantum and the chemist, specifically so I can detect them in space, hence the Astro. So what I do is I figure out the probability of a molecule being in a particular state. There's no deterministic nature to the work I do, so every transition is just a likelihood.

Speaker 2

36:45

But if you get a population of that molecule, it will always happen. And so this is all at the quantum level. It's a Schrodinger equation on I think 27 dimensions, I don't remember it by heart. And what this means is I'm solving these giant quantum matrices, And that's why you need a lot of computer power, giant computers to diagonalize these enormous matrices, each of whom describes a single vibrational behavior of a molecule.

Speaker 2

37:17

So I think phosphine has 17.5 million possible states it can exist in. And transitions can occur between pairs of these states. And There's a certain likelihood that they'll happen. This is the quantum world.

Speaker 2

37:32

Nothing is deterministic. There's just a likelihood that it'll jump from 1 state to another. And these jumps, they're transitions. And there's 16.8 billion of them.

Speaker 2

37:43

When energy is absorbed, that corresponds to this transition. We see it in the spectrum. This is more quantum chemistry than you had asked for, I'm sorry.

Speaker 1

37:51

No, no, I'm sorry, brain's broken. So when the transitions happen between the different states, somehow the energy maps the spectrum.

Speaker 2

38:00

Exactly. Energy corresponds to a frequency and a frequency corresponds to a wavelength, which corresponds to a color.

Speaker 1

38:08

So there's some probability assigned to each color then?

Speaker 2

38:11

Exactly, and that probability determines how intense that transition will be, how strong.

Speaker 1

38:16

And so you run this kind of simulation for particular, let's say that's 17.5 squared or something like that.

Speaker 2

38:23

Exactly, 17.5 million energies, each 1 of whom involves diagonalizing a giant matrix with a supercomputer.

Speaker 1

38:31

Actually, I wonder what the most efficient algorithm for diagonalization is. But there's some

Speaker 2

38:36

kind of- There's many.

Speaker 1

38:37

There's many, yeah.

Speaker 2

38:38

Depends on kind of the shape of the matrix. So they're not random matrices. So some are more diagonal than others.

Speaker 2

38:45

And so some need more treatment than others. Most of the work ends up going in, describing the system, this quantum system, in different ways until you have a matrix that is close to being diagonal, and then it's much easier to clean it up.

Speaker 1

39:01

So how hard is this puzzle? So you're solving this puzzle for phosphine, right? Is this, are we supposed to solve this puzzle for every single molecule?

Speaker 1

39:13

Oh boy.

Speaker 2

39:14

Yes, I calculated if I did the work I did for phosphine, again, for all the molecules for which we don't have spectra, for which we don't have a fingerprint, it would take me 62,000 years, a little over.

Speaker 1

39:28

62,000 years, well, time flies when you're having fun. Okay, but you write that there are about 16,000 molecules we care about when looking for a new Earth or when we try to detect alien biosignatures. If we want to detect any molecules from here, we need to know their spectra and we currently don't.

Speaker 1

39:49

Solving this particular problem, that's my job.

Speaker 2

39:53

I think- What was that? I mean, that's absolutely correct. I could have not said it better myself.

Speaker 2

39:57

Did you take that from my website?

Speaker 1

39:59

Yeah, I

Speaker 2

39:59

think I

Speaker 1

39:59

stole it. And your website is excellent, so it's a worthy place to steal stuff from. How do you solve this problem for the 16,000 molecules we care about, of which phosphine is 1?

Speaker 2

40:12

Yes.

Speaker 1

40:14

And So taking a step a little bit out of phosphine, is there-

Speaker 2

40:22

But we were having so much fun.

Speaker 1

40:23

We were having so much fun. No, no, we're not saying bye. It's sticking around.

Speaker 1

40:27

I'm just saying we're joining, more friends coming to the party. How do you choose other friends to come to the party that are interesting to study as we solve 1 puzzle at a time through the space of 16,000?