Reflecting our World to understand others with Dr Giulia Roccetti

Welcome to Growing Worlds, the podcast when we explore the science of exoplanets through conversations with early career researchers on the front line of discovery. I'm Lorenzo.

I'm Jenny. In each episode we meet a guest who takes us behind the science of planets, stars, environments and the tools we use to understand them.

Today we are taking a slightly unusual perspective on exoplanets. Instead of looking outwards straight away, we are looking back at our own planet. Because one of the most powerful ways to understand distant worlds is to first understand Earth as if it were an exoplanet.

To guide us through that idea, we're joined by Dr. Giulia Rocchetti from the European Space Agency. Giulia, welcome to Growing Worlds.

Hello, thank you for inviting me.

I'm so happy to have you. It's gonna be great.

Julia is an ESA Research Fellow at the European Space Astronomy Centre in Madrid. Her work sits at the intersection of atmospheric physics, climate science and exoplanet research. She develops advanced relativity transfer models to simulate how planets reflect and scatter light, often by treating Earth itself as a test case. So by observing and modelling our own planet, obviously two light-years away, Julia's work helps prepare the interpretation of future observations of Earth-like exoplanets.

So Julia, before we dive into the slightly mad idea of using Earth as a proxy for exoplanets, we always like to start from the beginning. And so we wanna know about your journey, your journey into planetary science, atmospheric science, was there a particular moment or a project that you worked on that led you to this amazing intersection of Earth, climate and exoplanets?

thanks for the question. That's a great one. So personally, I've always been fascinated about nature and about science. So since I was a child, I was always curious about maybe stars for like several weeks. And then maybe my curiosity would turn towards, I don't know, biology or... volcanoes or whatever other natural phenomena. So for me, the idea of studying planetary science, so studying planets as a whole, so going from their physical counterpart, understanding their physical properties, understanding their chemistry, putting together maybe geophysics with astrophysics, looking down from a faraway perspective together with the biology component to study astrobiology. been super fascinated. And actually the first time I started to think about these, I don't know, intersections about different scientific topics came when I was a bachelor student at Sapienza University of Rome. And over there, there was a very interesting seminar series about exoplanets by Giovanna Tinetti. So it's there that I started to really be fascinated about these brand new words that I never heard about before, which are exoplanets.

Mm-hmm. I love that you're essentially living out the childhood dream, right? Because as a child you were like interested in lots of different branches of science and now as an adult you're like, yeah, I do all of the branches of science. That's amazing.

you

And you're really able to make a good salad out of this. You took a bowl, you put inside exoplanet, which is just the latest thing that you found out, the last one, and then you just added volcanoes, biology and everything, and you basically build your own field. I mean, it's your own perspective of the field, which is a very different approach, I would say, compared to what we have heard so far on studying exoplanet, because you are using our own. Can you tell us? How did you get to use our own planet? How did you get to use this different perspective to study exoplanet and why this is so valuable?

Yeah, so when I was deciding to do a PhD, so I was in my master's studies and I was considering pursuing a PhD to do actual research because I was really enjoying the research experience I was having in my master's thesis. I was really in doubt between doing maybe a PhD in atmospheric physics, so pure atmospheric physics, to probably try to tackle something regarding climate change and how our plant is responding to, of course, the global warming and anthropogenic greenhouse gas emissions. But at same time, I've always been fascinated about space, exoplanets. So when I saw this project, which was proposed by the European Southern Observatory, the institute where I did my PhD about looking at the Earth as an exoplanet, I thought this was really the right spot for me where I could explore things from both sides. So really bringing together my expertise and the expertise I then developed in the PhD about atmospheric physics, radiate transfer, how really the Earth works in terms of radiation, together with the exoplanet perspective. So putting together our views of how the Earth will look like as we are very distant observers and we look at our planet for afar.

Mmm. I love that, like, I don't wanna choose, so I'm not going to choose. I'm gonna sort this out so that I can do exactly what I wanna do. And I love that, I love that you really have carved your own little path now in this intersection between the different sciences. Yeah, it's fab, I love that.

the very humble approach that I want it all and I'm gonna have it.

Yeah.

But I love that, why not? Why not have it all?

Yeah, I So you've been at ESO for your PhD, you said. Where were you based?

Yeah, so... Sorry. Okay. Yeah, so for my PhD I was based at ESO in Garching, so a town close to Munich in Germany. And ESO has two headquarters, one is in Germany, close to Munich, and the other one is in Chile. So it's really the center which is more connected to the observatories, which are all based in Chile and observe with these like fantastic sky conditions they have over there. being at ESO for me has been a great experience really in terms of like

Yeah.

also getting hands-on opportunities to work with the telescopes, going observing... Yeah, yeah.

I was gonna say, have you been down to Chile to see the skies? Yeah, I've been down there as well. it's just unbelievable, isn't it? It's just so much better than the Northern Hemisphere. I'm sorry for all the Northern Hemisphere listeners, but it's true.

I totally agree. I couldn't agree more. So seeing the Magellanic clouds, wow, that was fantastic. And also, again, coming like me, like I would consider myself coming mostly from a theoretical or computational perspective of the way I always approach like my research, getting these hands-on experience was great, but also

Yeah.

I'm so jealous.

really terrifying at first because I never observed with a telescope before and I got directly to Parnau with this really huge 8-metre telescope with the VLT. So that's been really challenging but it's been really an amazing opportunity.

Wow, yes.

I'm s-

incredible that you've been able to like use and control the VLT because it's just one of those like powerhouse telescopes right you just hear about it all the time you know in in big studies like the VLT is probably gonna be there you know it's such an amazing facility so yeah that's that's super sweet I bet you the buildings are just kind of like just so overpowering because it's so big it's like my god

Should I? Should you?

do you want do you want me to cut it's alright. So sometimes this happens right where we've got a list of questions and it's like, are you going to do the question or shall I do the question? So it's like, don't don't mind us. Sorry, Karen. So you're gonna have to just like, yeah, you're amazing. This is exactly what you want. Yeah, yeah.

Yeah, yeah, yeah, yeah, yeah, it's not up to you

Yeah. I was in going so far. I was in going so far.

Fantastic, fantastic. Yeah, yeah, absolutely. Let's take a bit breath and I will go for it. Okay.

you

Yeah, you'll go for it. Okay.

Chile observations. OK, so basically you've been traveling from all around for your path has been basically all around our Earth because you've been starting from Rome you say you've been into Munich, you went to Chile, now you are in Madrid. So you know our planets very well. That's why you're using it as an exoplanet maybe.

Yeah.

Back to the question that is why you think it's so important to use the herd as a reference.

Yeah, so that's a great question. in my opinion, is both a great reference, but at the same time, we should not get in the wrong direction of thinking that we're going to find really a Earth twin, because we need also to think that Earth evolved a lot in the past, billions of years from its formation until where we stand nowadays. But at the same time...

think that's a really good point actually because yeah, people are always like, yeah, let's find earth 2.0, but you're right that the earth that we live on is very different to the earth that the dinosaurs lived on, is very different to the one that was inhabited by bacteria, is very different to the one that had no life on it whatsoever. So yeah, it's like, okay, earth 2.0, but is it like 2.01? 2.0 like five like which version do you want of a

Absolutely, we need to be very careful about this because Earth evolved a lot and we need to consider that other exoplanets are undergoing the same changes, so we need to consider really the temporal variation and temporal evolution of these planets. But at the same time, it's very important to study how Earth is nowadays because this is really the only reference, observationally,

Mmm.

we can take in order to try to understand if, for example, we place ourselves far away from on the moon on the outer solar system on another planet or even farthest away on another planetary system. And we look at this tiny, pale blue dot, tiny, tiny dot, which is the Earth illuminated by the sun. And this is the only, let's say, proxy with real data we cannot have. We cannot go back in time to do an observation of how the Earth look like when

Mm.

the dinosaurs were here. So that's important really to have a benchmark, so really to see if we can replicate with our theoretical knowledge and with our models what we really observe. Because if we cannot even replicate how the Earth looks like nowadays, then it's going to be even more challenging to replicate how on like an Earth of one billion years ago or more look like back then and same for other planets.

So how do you do that? How do you like replicate earth and what earth looks like at different distances?

Yeah, that's a fascinating question for me because what I've been trying to do in my PhD, so in my research, is to do that both from a computational and theoretical approach. So with a model which should replicate the most important physical processes which we should consider when we think about the reflected light of the Earth. But at the same time, we want to validate this model with observations. For the observations, we do something that I would even call them kind of crazy, because what we want to do is actually take the light, which comes from the sun, and then gets reflected by the Earth's atmosphere, by the planetary surface of our planet, and then comes back to us on our telescope on Earth from the Moon. So what we're doing... Yeah.

Yeah

That's wild. That's wild.

So you're using like Earthshine?

Exactly, I'm using Earthshine observations.

And these listeners is how astronomers went crazy.

my goodness. Okay, so for anyone who's listening and isn't sure what earth shine is, you know when the moon is at a very thin crescent, but sometimes you can sort of see this bit that's dark, it's like very, very faintly glowing. So that gentle illumination, that's what we're referring to when we say earth shine. So it's really common to see it sort of around springtime in the Northern hemisphere because combination of factors. There's a lot of ice in the Northern Hemisphere still left over from winter and then our, sort of being more sort of tilted over towards the sun as it were, if you kind of imagine it like that. So as we're heading towards spring and summer and there's that magical combination of lots of reflective ice, more sun light. And so this is when you get maximal sort of earth shine, but my goodness. So you're using earth shine on the moon.

Yes.

You're gonna have to explain that to me again because I think the concept is just blow my brains and do it again because I just... What?

Yes. Let me try my best. So of course we have our star, which in our case is the sun. And our star, of course, is emitting photons or like radiation in general. And of course, we have part of these photons of this radiation reaching our Earth. So these photons, some of them are going to interact with the Earth atmosphere. Some of them are going to be absorbed. Some of them are going to be scattered or reflected.

Yeah. Yeah.

Some others are going to travel until the surface of our planet and again can be reflected, absorbed and so on. And then the reflected component of all this light coming from the sun can travel on the moon. And the moon is going to do the same. It's going to take part of this photon, so absorb them, and another part is going to again be reflected. So what we want to measure with our telescopes is this in this like

Mmm.

tiny faint glow on the moon, which is actually not illuminated by the sun, but it's on the opposite direction, where it's actually illuminated by the Earth itself. This is the small signal we want to measure because this contains the reflected light of the Earth.

crazy pinball. So we have light from the sun, it earth, earth light, then it's the moon, the moon light, then it's earth again, and you're collecting that one. It's like this pinball, but every time light hits something, it's also being changed by what is hitting, right? Because the sunlight is changed by the sun, let's say we have a pure source, then is transmitted through our atmosphere, reflected, transmitted again. then its moon is reflected and this is changing again the lights and then it's being transmitted again to the Earth atmosphere and then it's going through your telescope. It's the craziest bimbo. Yeah.

So I have questions about this because first of all, why not just get the reflected light from Earth? Like, is it just because there isn't a satellite in the right orbit or like don't have access to that data? Why get the light reflects off the moon? Because what is pinging in my brain is, is there not sort of changes and contamination from it reflecting off the moon?

You Yes, two great questions. totally fine. So the first one is that, of course, we have several satellites which can observe like the light reflected by the Earth. However, if we take low Earth orbiting satellites, they cannot measure at the same time the full Earth. They are actually very close by.

Two part. Yeah, two part, sorry.

the field of view.

the field of view, they're going to measure just small patches of our planet. So what you can do later on, it's let's say a post-processing where you want to try to average out over a very long temporal evolution of these observations. However, this is going to be really challenging to do in practice because meanwhile you want to average out these many different patch observations, weather systems already evolved.

Okay.

your sun direction already changed, so your incoming solar radiation direction, it's already different and it's going to alter the physical properties you're going to measure. So it's a very difficult average to perform. Otherwise, you can use what are called geostationary satellites that are, of course, farther away, and they can measure simultaneously the full illuminated side of the Earth.

Yeah. Yeah, that's fair.

However, the very big difference you have with exoplanet observations is that you are always measuring the full, again, fully illuminated side of the planet, meaning that you don't see, for example, different phase angles. So you don't see like... Yeah, I can explain that.

Yeah. Yeah, so it's like, yeah, it's not that it's half illuminated or only a quarter illuminated. It's always like a full illuminated side.

It's always full.

Exactly, which is very unlikely for an exoplanet to be observed in reflected light in this configuration, so it's not very realistic.

I see. Let me go back on something that you just mentioned. You said the previous of your reason was about not being able with a single observation for satellite in low Earth orbit to see the whole planet. So you have to patch different things together and it's a difficult average to do. That's to summarize what you said. It's very important this because Earth is quite diverse. It's not a uniform like when we think about exoplanet and we think about giant gaseous planet. In our models we tend to assume that they are quite kind of uniform, even though Jupiter is teaching us a different lesson. But you are observing Earth and we all know that Earth is not a uniform surface, has, well, lands and oceans to start with. So what are the details, the information that you are losing when you are synthesized, averaging everything to a single point of light? and without actual information you can keep.

Yeah, that's really a great question and at the end is the... my opinion is the interesting question of exploiting this data and this observational approach, because what you want to know is really, okay, I cannot have any more the resolved information of how the Earth looks like. I don't have an image. I just have one single spectra. when all the information is coming from a single pixel, so I cannot separate anymore the components coming from the ocean, the components coming from land. the regions which are more cloud free or cloudy. So it's all averaged out. But what you want to see is how much this impacts on your single observation. And the answer is that actually it matters a lot. We can really see like observing this Earth shine in many different nights in different geometries. For example, going from a geometry where the illuminated side of the Earth is mostly over the Pacific Ocean. The Pacific Ocean is huge, right? So you can almost replicate you're observing an ocean planet. You can have some configurations where you almost have no land in the illuminated field of view. And then you can have opposite observations where you maybe have a mixture of Africa with the Atlantic Ocean. You can see parts of South America, parts of Europe and swan. And it's a mix. Yes.

my goodness, so clever. Yeah. So then it's like a mix of water and land and, but the moon, just having it reflect off the moon though doesn't contaminate it. Or I guess does it always contaminate it in the same way? So then it's.

So. So the moon definitely contaminates. the first thing to mention is that the moon doesn't have a thick atmosphere. So let's say all the interesting atmospheric signatures mostly come from Earth's atmosphere and the reflected light through Earth's atmosphere. At the same time, of course, what moon is going to do is of course going to reduce your flux by a lot because the moon is not a mirror, of course. It's not like having a mirror in space and you point

Mm.

your telescope towards a mirror, the moon is...

Yeah, because the moon is surprisingly like not reflective. think like Earth reflects about a third of the sunlight, but the moon's only about a tenth, something like that. Yeah. So even though it looks super bright, it is not.

Exactly. Yes, roughly like that. Exactly. Yeah, regularly it is now bright and of course it's also very variable in terms of whether you observe over on a highland or a mare over the surface of the moon. You can have some kind of variability over there as well. So what we personally did as a team to try to avoid this lunar contamination is mostly observing Earth's shine in polarization.

home.

This has another layer of complexity in a sense, but okay, let me rephrase this because I'm going in a wrong direction. Okay. Yeah. So the moon is definitely like to correct for...

That's all right, take your time, it's no problem. It's all good.

the reflected light you're losing from the moon is definitely a challenge because, of course, the moon is not a mirror. has, depending on where on the moon you place your telescope, you're observing whether you are on a highland or on a mare, you can have different effects. So the moon is going to definitely play a role. And then there is a second big challenge of these observations, because if you think about that, we want to measure the let's say what I'm gonna call, disc-integrated reflected light of the Earth, meaning that we want to average out all the information of our planet coming as from a single pixel, as from a single object.

Yes.

The second thing is that with our ground-based telescopes, we are going to have this signal, after reflecting on the Moon, passing through the Earth's again.

yeah.

And that's challenging because this is going to imprint on top of our signal, again, the features, for example, the absorption lines and other features which are specific only of the sky above your telescope. So in our case, above Paranal. And that's challenging to actually eliminate because we're basically speaking about two very similar signals. Both the sky over Paranal is going to have the same molecules, the same signatures.

Mmm.

Right.

of the full-hertz signal we want to observe. So actually to get rid of this, what we can do smartly is to observe this hershine using polarization. So why...

Yeah. Okay, so how does that eliminate the issues?

Yes, that's a bit complex, but the idea is that polarization eliminates several challenges, because first of all, for our sun, our sun emits light, which is almost unpolarized. So polarization at the end is just the direction of propagation of our electromagnetic field. meaning that each photon, of course, is also at the same time an electromagnetic wave and our Sun is actually emitting these electromagnetic waves all in random directions. So in principle, there is no privileged directions in which these photons are traveling towards us on the Earth. However, when they arrive to us, for example, interacting with Earth's atmosphere or with the surface, There are several processes which can imprint a very strong direction of propagation. For example, we have molecular scattering, which is Rayleigh scattering, which imprints a very strong linear polarization component. We also have the oceans, which are very reflective. I don't know if you've ever been, for example, over to the sea, over a lake, and sometimes you can't even look at...

Hey. Yeah. Yeah, because it's so bright. Yeah. Yeah, yeah.

the surface of the water is so bright and if you look if you look that in with like polarized light glasses you're gonna see that extremely bright meaning that water for how it behaves and really

Yeah.

how it behaves creates a very strong direction of propagation of these photons.

so then if you're looking at polarized light, can kind of, you know that certain light that's been reflected off like water will have a certain angle, a certain polarization. So you can be like, this is telling us it's water and like, this is something else and science is so clever.

Yeah, this is gonna be my next romantic dinner. I'm gonna go out on the beach in the night. I'm put polarized glasses on and I will say, honey, look at the moon. We are on that.

Yeah! See, but also this is a lesson, if you're going to the... if you're going to the lake, right? Like, don't have your polarised sunglasses, because it's gonna be really bright still. But yeah.

I just projected a picture there.

It depends. I think some sunglasses can actually reduce the polarization depending on the direction.

Which is it? On their angle, yeah. Yeah. And if listeners are still not sure what we mean by polarization, great test for this is if you've got a couple of 3D glasses where you've been to the movies. So that's how they do modern 3D films. It's not the red and the blue. One picture is polarized vertically. So the light is sort of, you can imagine it wobbling up and down. The other slightly different picture is polarized horizontally. So you can imagine that all of the light is wobbling horizontally.

or the direction on your glasses,

And when you put those glasses on, it lets one picture into one eye and one picture into the other eye, and then your brain puts it together and makes it three dimensional. And if you don't believe me, you can get two pairs of 3D glasses. And if you put them together face to face, you won't see anything because the light will cancel each other out. If you flip one of them over, then the polarizations line up and you'll be able to see through them. So a little fun experiment about polarization for anyone who's listening. So, right. So then when you're using, back to Exoplanets now, so you're using, well, Earth as an exoplanet. You're using the polarization can then help you filter out like what's reflected from the oceans and what's this and does it help with like clouds? Because guess clouds must be really interfering and actually are they interfering or are they useful? Because I guess lots of exoplanets have clouds right so is actually is there a unique signal for clouds?

Yes.

Yeah, so actually polarization is even on Earth to to actually characterize clouds and some of their properties, for example, their optical thickness or their particle size. They actually use polarization and satellite observations. And the reason is that really the way light gets polarized and then maybe pass through a layer of clouds, which actually strongly depolarize light at that point. leaves very specific imprints on these photons and on your observations, on your spectra or signal, which can really help you go back towards the first principles of the physical characteristics, in particular the microphysical properties of these clouds, meaning that observing, for example, at some specific angles, which are, for example, the angle of the primary rainbow, meaning that

Mmm. Bye.

the angle for like, in which the refractive index of water is actually peaking. So for these specific parts, if you observe like a cloud in this geometry, you can really get specific information about the particle size, about their shape, whether they're more spherical or less spherical with like coming in weird shapes. For example, for ice clouds, I'm thinking.

yeah.

Or either if you go to having more optically thick clouds, meaning that maybe your photons did a lot of multiple scattering within a cloud because this material is really thick and the photon to escape is going to really encounter a lot. Exactly. So this is very unique of polarisation and is usually very hard to infer these properties from intensity only observations. So when you measure all the photons together, because...

Yeah.

Mm-hmm.

Yeah, it's like bouncing around. Yeah.

these properties are, I would say, really degenerate, meaning that you can either have, for example, larger particles or having thicker clouds, and they're going to show to you the same effect. So you cannot really disentangle which one of the two is happening.

So then you take all of these kind of different types of observations and the way that all of these different properties and features can influence the light and then you put those into the models. And so then when we look at an exoplanet, we can be like, right, we sort of see a signal that looked like this was clouds on earth and so then that looks like clouds on the exoplanet. Is that the idea?

Yeah, that's kind of the idea. So let me start to say that doing polarisation for exoplanet is extremely challenging because first of all, already to get the reflecting light from planets, it's really something we are hoping for to do with the next generation of telescopes, either from space or from the ground. Because if you think about that, at the end, it's a very, very, very challenging problem because you have a very bright star.

Hmm.

Hey.

and you want to isolate the signal of a very tiny planet close to the star, which is reflecting just a very tiny fraction of the light which is emitted by the star. So we're still figuring out techniques on how to really isolate the tiny reflected light of the planet, which is close to a very bright star. But in general, the idea is that when you're going to do that and...

Mm-hmm. Yeah. Okay, yeah. Mmm. Yeah.

Mm.

Yeah, that's okay, because I've got another question. I can jump in with another question if you like.

No worries.

Let me just... Okay, so... Yeah, so it's going to be extremely challenging to observe these exoplanets in polarization, because the linear polarized part is just going to be a fraction of the total number of the photons which are actually reflected. So it's already challenging with the reflected photons. It's going to be even more challenging with polarization photons, photons which are linearly polarized by the planet. But at the same time, this is going to hold you much more information, both about the clouds, about the molecules, so about the scattering processes that you can really disentangle very well from the polarization signal and also about the surface. So what we were talking about before, this difference between an ocean and how much linear polarization is going to head to your exoplanet signal.

Hmm.

compared to a planet which is made by land, like made by a dry surface.

Okay, yeah, yeah.

So let's assume we can collect those photons and do this kind of science. are the assumptions that we can test?

Yes, so I think with polarization in principle, the very first thing is that you're going to immediately see whether or not your planet has an atmosphere. Because if your planet has an atmosphere, yes, because from Riley's capture, you're going to see that immediately. If you see a peak in polarization, then the atmosphere is there. Otherwise not. And then as a second thing, I would really say you can try to go and study the clouds. So

Mm.

Easy win, okay.

you need to see, for example, studying the planet at different phases. changing like how much of the fraction of the illumination you have of your planet. If you see some peaks, these peaks are going to be given by clouds and by this primary rainbow feature, which is going to show up. And from there, you can really infer a lot of information about the microphysical properties of your clouds. And as a third thing, is really, in my opinion, is really going to go towards the characterization of the planetary surface, because this is something almost impossible to do with other techniques. It's really hard to infer information whether a planet has an ocean on its surface, whether it's dry or not, because with current techniques, either with transmission spectroscopy, but also thermal emission, we cannot really say something about the surface. We can... Like once we got to know some information about the planet, we can go back with models and try to imagine what the surface might look like. But this is a direct measurement in polarization, which can tell you how really what is on the surface of the planet.

That's amazing. But this is kind of like looking to the future right where so we're not quite there yet but this is why we're working on Earth first so that we're ready. So like when you've been looking at Earth, has there like anything weird thrown up that you weren't expecting? any... so like you've made these models and then you're like interpreting Earth using these models. Has there's anything weird ever come up?

Exactly.

That's a good question. Something I was definitely looking for is a feature called the vegetation red edge. Try to see whether I could spot a bump in the reflectivity of the planet between 700 and 750 nanometers, which is due to really the chlorophyll peaking up at these wavelengths. And what I was really looking at at the beginning was again a comparison between the observations where I mostly have the ocean in views. So I was not expecting a lot of contribution coming out of the vegetation compared to...

But plankton!

You

Plankton, yeah. yeah, so.

You could like detect the plankton in the oceans. What?

So plankton is actually also contributing, it's much fainter than the contribution of the leaves you have. It's also there, so that's been also very interesting for me to see.

But it's there.

No! my god, that might be the coolest thing is that, like, looking at Earthshine you've managed to pick out signals of plankton in the oceans. I don't think I've heard anything that cool. I can't say this year because we're only in the middle of like January as we're recording this but like for months like it's just like that's so cool. That is epic. So what do you think are gonna be some issues that we kind of need to be aware of when we're trying to interpret these reflected signals from other worlds?

You Yeah, so from my experience with Earth, what I found is that there is a lot of variability that, in a sense, we need to deal with and try to see how to take into account. So even observing in different nights the Earth, which is a planet we know very well, of course, and for us. out of which we have a lot of satellite information we can at the same time monitor and check. Still, we saw a lot of variability going on from one eye to the other from different epochs. And the second thing I would like I would mention is, yeah, definitely. What do you want to mention? So ours variability and. yeah. And the second thing I would like to mention is really clouds. So clouds has been even for interpreting the earth itself a nightmare to model and to correctly interpret in terms of these observations. I was not going to explain.

Hmm.

So yeah. So do you think that the thing that we need to get right now is clouds? Like the water's pretty good, the land is good, the plankton's good, but it's clouds that are the big thing to sort out now.

Yes.

Yes, absolutely. I... maybe very naively at the beginning of my PhD, thought, okay, actually this project is not sound, doesn't sound like a very difficult task. mean, we know a lot about the Earth. So in my model, I'm just going to put like very realistic cloud, cloud properties that I can get from satellite observations, I can get from weather forecast models. And this is going to work out. We know clouds on Earth and it's going to be very easy in principle. And then

famous last words.

Wanna? And when I tried this out, it was really a nightmare. So I had really a hard time understanding why clouds came out with so many biases and with so many weird things that I need to correct for. And this is also where I connected a lot with the atmospheric physics community to get, of course, expertise from that side and what I fully understood, like how complex are clouds and also how important they are both for studying the Earth as an exoplanet, but even just for our climate interpretations of the Earth itself and predicting how the climate is going to evolve in the future, there are so many uncertainties related to the clouds which make them worth really studying, in my opinion, from both perspectives.

Yeah, so actually the work has got really important implications for our daily lives here on earth.

Yeah, so I think like what I found completely unexpected that at least from in my point of view, pursuing this PhD project on studying, let's say the Earth as an exoplanet is that even looking at the Earth from this very different perspective can even have implications and our way we model the Earth for like remote sensing studies or climate studies for Earth applications, which is something I completely didn't expect to actually find and to really start wondering about while doing this research.

That's so fascinating.

And I think that is amazing. I think that's a beautiful note to end on that actually being curious about our planet as an exoplanet has ended up with us understanding our own world more as we start to seek an understanding for all those worlds out there.

Yeah, if I can add on this. What is really interesting is that, of course, for like when we do Earth remote sensing studies, most of the time we focus maybe again on like small regions of the planet. want to validate like again these like confined regions out of which we have satellite observations, which is great. And this is extremely important work. But many times we overlook about the validation of the global planet. So the planet has a wall and all its effect that we need to take into account. that's also where this work, in my opinion, started to contribute a bit and hopefully is going to contribute in the future really on improving the way we really model clouds, we interpret them in both for again, ultramod sensing, but also for climate applications and for the future of climate change.

Julia, before we wrap up, unfortunately we are very interested in this casio, we are at end of our time together. I can't go off, yeah, I'm just listening amaze, I'm just like, I can't go off for all night, unfortunately our time together is over tonight. So our signature question now, if you had to choose one celestial body or

I love that. I know, I could talk to you for like another hour. Mmm.

maybe one hard feature that represents your work. What will it be and why?

Okay, so for the planet I'm going to be very... I mean, my favorite planet is the Earth. I think I got in love even more with the Earth by studying and modeling all its different physical properties that...

Yeah Mm.

I find it so fascinating and I'm really looking forward to, let's say, the faraway future where we're going to be able to really start wondering about these different cloud and surface properties for other exoplanets because I think it's going to be such an exciting time. And then if I need to pick a feature about the Earth, I think is either really the 3D representation of clouds, so really the 3D patchiness and how they really come up in a 3D structure, or the ocean glint. So really this strong reflected light out of an ocean and how much this impacts the brightness and the reflectivity of the planet.

Hmm.

And the black... Jenny is just doing the black tone, into black tone, yes.

I'm just obsessed with this idea that you can detect signs of plankton from earth shine. Like, it's just inspiring. I just can't believe it. It's incredible.

So we know what to do for Jenny's birthday. We're gonna prepare a picture of a plankton reflected on the moon. that's gonna be... I think that's... I'm just gonna win the bet of the best present. That's gonna be me.

Yeah. Yeah. Yeah. That's it.

Perfect.

Yeah, that's it. That's it.

Giulia, thank you. Thank you for being with us. Thank you for reminding us that sometimes the best way to understand distant worlds is to look at our own reflection in a moon mirror with fresh eyes.

you

And thank you to everyone listening. Join us next time on Growing Worlds as we explore another corner of the universe and the people helping us make sense of it.