Bizarre exoplanet clouds + Counting insects with weather radar

[WHIMSICAL MUSIC] FLORA LICHTMAN: Hey, it’s Flora. And you’re listening to Science Friday.

It seems like every week, a new exoplanet drops. NASA counts 6,000 official alien worlds, with around 8,000 more suspected. They’re stuck on the wait list till more research can be done to confirm them.

One way to spot an exoplanet is to use a telescope to carefully look at the light of a star, watching for a tiny, periodic dip in brightness as a planet crosses in front of it. But now researchers say that using this transit method, they detected not just a planet, but its clouds. And the clouds on this one gas giant some 700 light-years away are super weird. They’re made of rock.

Here to tell us more is Dr. David Sing. He’s a Bloomberg Distinguished Professor of Earth and Planetary Sciences at Johns Hopkins. Hey, David.

DAVID SING: Hello. Thank you for having me.

FLORA LICHTMAN: Thanks for being here. Tell us about this planet that you’ve been looking at and what the weather’s like.

DAVID SING: Well, this is a planet– what we call a “hot Jupiter.” It’s a gas giant, much like Jupiter. But it’s orbiting very close to its host star. And as a result, it’s heated up to very high temperatures, up to 1,500 degrees kelvin. And at those temperatures, what we normally experience as, say, rocks actually can form clouds in the atmosphere.

FLORA LICHTMAN: Like they’re being boiled off the surface?

DAVID SING: Well, this is a gas giant. So there’s no surface. But indeed, there– if you get hotter than about 1,500, there– these rocks are actually in vaporous form. And as it gets colder, they can condense into solid, small particles.

FLORA LICHTMAN: How should I be imagining these clouds? Are they puffy, like our clouds, or are they filled with little granules?

DAVID SING: Well, you can think of them as little granules, but more like micron-size tiny sand particles like, say, quartz here on Earth. So we don’t really know how puffy, and so forth, they are. But just imagining a big puffy cloud made of little quartz crystals is a good way to think about them.

FLORA LICHTMAN: Does that mean the atmosphere is doing something special to keep them aloft?

DAVID SING: Yes. Actually, it’s a big surprise. On this planet, what we find is the clouds are at very high altitudes– so well above their stratosphere, up into even the mesosphere– and actually large particles. So it was a actually big surprise to see them up there. Everyone expected something that big and heavy just to fall out. And so normally, we would see the clouds at a much lower level. And so the planet must have, actually, very vigorous mixing, turbulent mixing, to keep those sand clouds at that high in the atmosphere. It’s really surprising.

FLORA LICHTMAN: If I could bubble up below them, I guess, what would they look like in the sky? Is it like a haze or a fog, or are they like a cumulus cloud here on Earth?

DAVID SING: It would look like a very, actually, thick, dense cloud. So on this particular planet, the clouds are actually even confined to the morning side of the planet. So the morning side is completely cloudy. And the evening side is actually completely clear. It’s much hotter. And those clouds can’t form. And so I imagine it sort of like you’re in San Francisco. And in the morning, it’s all cloudy. And you can’t see anything. And then by the afternoon, they’ve all boiled off and you can see the clear sky.

FLORA LICHTMAN: They burn off, as we say?

DAVID SING: Yes.

FLORA LICHTMAN: How do you get enough resolution to be able to see the clouds? That seems amazing.

DAVID SING: Well, we’ve been studying exoplanets through the transit technique for nearly 25 years. And we’ve been mainly using the Hubble Space Telescope during that time. But now we have the powerful JWST telescope. And that’s given us, actually, two important advances to be able to make this measurement.

The one is Hubble is in low Earth orbit. It’s orbiting around the earth about every 90 minutes. And so it spends half of its time on the day side of our planet, and half of it on the night side.

Well, when we look at these transit events of these exoplanets, we’re looking at it over the course of several hours. But that means the Hubble is actually spending half of its time on the wrong side of our planet. And so, actually, you can’t even observe the full transit event continuously, which is– prevents this measurement being made. But JWST is out beyond the earth and the moon. And it can stare continuously for hours or even days.

So that’s one key aspect of JWST that’s important. And the other is that the telescope, JWST– it just is so much bigger. It’s– has seven times the light-collecting ability. So that means what took Hubble more than an hour to make a measurement now JWST can do in, say, 10 minutes.

And actually, that 10-minute time frame is really important because in order to separate out the spectrum of an exoplanet from the morning to the evening side, you have to wait for this little 10-minute window where only part of the planet is covering the star. But that event doesn’t last very long, about 10 minutes. And so JWST is big enough to be able to take a spectrum of a planet during that short window.

FLORA LICHTMAN: Do these clouds provide clues into other big questions, like what the planet is made of or what the atmosphere is made of?

DAVID SING: Absolutely. So there’s two key questions we can start to unravel because we’ve been looking at these planets for quite some time. And we’ve seen molecules in their atmospheres and the clouds together. But now we can separate these out quite cleanly. And we can look, for instance, at the clear atmosphere and what its chemical composition is. And these gas giants are basically like fossilized records for when the planet formed.

So we want to use these as, basically, records to figure out how these planets formed and evolved. And many of these types of planets we do not have in our own solar system, like hot Jupiters or sub-Neptunes. And some of these types of planets are actually the most common found throughout the galaxy. Yet we don’t really have a good idea how they form or evolved. And so by measuring the chemical composition cleanly with this technique, we can start to unravel that mystery.

And there’s another important aspect– was actually just studying these clouds themselves. So clouds and modeling them are the biggest uncertainty we have in studying and in modeling atmospheres. And that includes our own Earth’s atmosphere. And with these exoplanets, we’re actually using the same models that are used to measure the weather and predict the weather on Earth.

So it actually turns out that we don’t know the physics of cloud formation and how it interacts that well. So by measuring how clouds are formed and the dynamics in these different extreme environments, we can actually improve the physics of our overall models.

FLORA LICHTMAN: That’s wild. So alien clouds could help us understand our own clouds better?

DAVID SING: Yeah, absolutely.

FLORA LICHTMAN: Are clouds common on exoplanets? Is this a feature every planet has?

DAVID SING: For most planets, indeed, we seem to– it’s very common for all exoplanets that we almost see. There’s a few out there that are just so, so hot that are– they’re mostly cloud-free. But those are a tip of the iceberg, extreme planets. But more or less, when we look at an exoplanet and look at a spectra, we see clouds. And that is a similar characteristic as what we have in our solar system. Every planet in our solar system with substantial atmosphere as clouds.

FLORA LICHTMAN: I love to think of that as a feature of the universe, clouds, a consistent feature of the universe.

DAVID SING: It is. And it’s an important feature. And as an astronomer, we typically hate clouds.

FLORA LICHTMAN: [LAUGHING]

DAVID SING: But it’s actually great to study them and actually learn about what nature provides.

FLORA LICHTMAN: Dr. David Sing is a Bloomberg Distinguished Professor of Earth and Planetary Sciences at Johns Hopkins. Thanks for coming on the show today.

DAVID SING: Oh, thank you very much.

FLORA LICHTMAN: After the break, turning from alien clouds of rock to the clouds of insects flying above you right now– stick around.

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Next time you’re outside, take a moment and look up at the sky. Chances are, somewhere in that column of air above you, there are at least four insects sharing that 1 square meter of the planet with you.

That’s one of the findings from a group of researchers who used weather radar across the US to map out airborne insects over a 10-year period. Dr. Elske Tielens is an ecologist with the Swiss Federal Institute for Forest, Snow and Landscape Research and one of the researchers on that project. Hey, Elske.

ELSKE TIELENS: Hey, thanks for having me.

FLORA LICHTMAN: So to be precise, you found 4.3 aerial insects per 3 foot-ish square on average. That’s a lot. That’s got to add up very quickly.

ELSKE TIELENS: That’s right. It is quite a lot. And it adds up to 100 trillion if you extrapolate across the entire surface of the contiguous United States.

FLORA LICHTMAN: 100 trillion insects above us?

ELSKE TIELENS: 100 trillion insects on a warm, nice summer day. Those days when you yourself see an insect out because it’s nice and it’s good conditions, 100 trillion insects above the US.

FLORA LICHTMAN: And we’re just talking about airborne insects. So we’re not talking about the centipede crawling underneath my shoe right now?

ELSKE TIELENS: That’s correct. Radar are great for seeing what’s up in the sky. And so we’re not even really talking about what is at your eye level. We’re talking about what is much higher when you look up into the blue of the sky. It looks like maybe there’s nothing there. But actually, there’s 100 trillion insects up there.

FLORA LICHTMAN: We’ve seen weather radar used for tracking bird migrations. But I was really surprised that it could see the resolution of insects.

ELSKE TIELENS: That’s right. It’s a tool that folks have been developing for tracking birds. That’s the first place that people went when they realized, actually, we see a lot of biology on these weather radars. And as a meteorologist, you say, oh, that’s not what we’re interested in. Let’s throw that out. And as biologists, we said, oh, what if we throw out all of the meteorology and we throw out all of the weather, and instead we take this part that the meteorologists are not so interested in, the biology?

And it makes sense that you would be able to see insects when there’s more of them in the air because raindrops themselves are not particularly big. But when you get a cloud of raindrops, suddenly we start to see that on radar. And so in the same way that you can use a weather forecast and look at the radar to see when rain is going to come into your local area, you can see on the weather radar when there are lots of insects in the sky.

FLORA LICHTMAN: Are there some insects that are too small to see, like a gnat or a no-see-um, for example?

ELSKE TIELENS: Not so much too small, but maybe too few. And part of that is the radars are very sensitive, but there’s a lot of noise on the signal. And so there has to be sufficient signal, sufficient density of insects, for our methods to be able to differentiate and say, this is real insects.

FLORA LICHTMAN: Can you tell which species of insects you’re looking at?

ELSKE TIELENS: No, not at all. The radar totally doesn’t know and doesn’t care. And that’s an interesting thing about this tool. It’s really good for quantifying abundances and looking at a standardized way of measuring how many insects are out there. It’s the same across all these different radars, across different regions, across the entire United States. But if you wanted to know more about what’s happening specifically with this population or that, then you need to combine it with local surveys or citizen science or other types of tools that we have.

FLORA LICHTMAN: You looked at a 10-year period from 2011 to 2021. Did you see any big trends?

ELSKE TIELENS: Yeah. Interestingly, we expected– everyone’s been really worried about insect declines. Obviously, there’s a lot of studies demonstrating that insect biodiversity is going down. And in many species, insect abundances have been declining over the past 10-something years. And so we expected to find widespread declines. And instead, we found that at the continental scale, insect abundances are pretty stable. There’s areas where they’re declining. And there’s areas where they’re increasing. And it offsets each other that over the 10-year period, we don’t see a strong trend.

FLORA LICHTMAN: Although we don’t know which Insects, right? So we could be compensating for the loss of some insects with the gain in other insects.

ELSKE TIELENS: That’s exactly right. We’ve got winners and losers, probably, some species doing really well. And the species that we know don’t handle anthropogenic change so well maybe are declining. And so there’s a balancing act happening of increases and declines in different species that results in this stable trend.

FLORA LICHTMAN: So that’s really surprising because we do hear so much about this insect apocalypse. How should I interpret this data set in that context?

ELSKE TIELENS: That’s a really good question. And I think this is an important data source for that. But it’s possible that what we’re looking at is actually a shifting baseline that compared to this baseline from 10 years ago, we’re not seeing declines because some of these took place 30-40 years ago, when we had big land use change or agricultural intensification.

And so if you only start measuring after the declines have already happened, then you’re not going to capture that. But I think it’s extra important, or it demonstrates why weather radar could be a really good tool for standardized monitoring. And so 10 and 20 years later, we can come back and compare and say, oh, here’s the larger time window. Here’s the bigger picture for this.

FLORA LICHTMAN: Are there more insect-rich places in the US? What’s insect capital, USA?

ELSKE TIELENS: I think the Gulf is insect capital, USA. And I think that this is true, anyway, when you drive down there. You really notice people talk a lot about, ugh, when I was growing up, how many insects went splat on the windscreen. You take a road trip down to Texas or down to Mississippi or coastal Georgia, and you really do see that there are so many insects out there.

And I think the other thing is the radar is really good at picking up insects that are high up in the sky. And so areas where the conditions are really good for insects to move long distances in the sky, such as above the Plains– those are also areas where we see lots and lots of insects.

FLORA LICHTMAN: Where are the insect deserts?

ELSKE TIELENS: So one finding from this study was that areas where in the winter we see a lot of warming, insect populations have been declining. And there’s some covariation there with development, areas where we’ve had a lot of human development and changes in land use over the past 10 years, is also areas where we see greater declines in insects. And so in your urban areas, of course, some insects do really well. But we see fewer insects.

FLORA LICHTMAN: I was just thinking about the cockroaches of New York City and how there’s probably 100 trillion of those just on this island alone.

ELSKE TIELENS: But thank goodness they don’t fly so high. And so they don’t show up on the radar.

FLORA LICHTMAN: Has this data always been in weather radar and it’s a matter of using machine learning to pick it out, or is this an advance in the radar itself?

ELSKE TIELENS: We had to develop the methods to say, how do we pick out the insects from the radar? But you can go back 50-60 years to early years of using radar and find studies of people identifying this.

Even when people first started using radar and thinking about it as a tool to see planes flying over, folks would report, man, we’re seeing these things we call angels on the screen because there are these echoes. And they don’t correspond to a plane flying in. And so it must– if it’s something that you can’t see. So maybe it’s an angel. And it turned out actually, those were mostly birds that showed up. But that was before we thought about biology as being visible on a weather radar.

FLORA LICHTMAN: Are the insects migrating or moving?

ELSKE TIELENS: It depends on when you’re looking. You definitely see huge abundances of insects migrating. Especially when you’re looking in the fall, a lot of the abundances come from insects that are coming up from Wisconsin or coming up from Minnesota and moving down to escape the cold weather, the cold winters that they get up there.

But in the middle of the summer, it’s just activity of all the local populations that take to the sky and fly really high up. And so it differs at– you have different insects, maybe, that are really abundant at different times of the year. So you get these mayfly explosions over the Great Lakes just for a couple of days, or if you’re looking out West, you see big numbers of grasshoppers that show up on the radar really well.

FLORA LICHTMAN: You did this research while you were a postdoc in Oklahoma. You’re now in Switzerland. Are there differences in the insects that you see on the radar where you are now?

ELSKE TIELENS: Yeah, totally. There are definitely different species in these different areas. And I think one of the things that’s striking is the US is such a diverse place. There’s so many different regions and so many different biomes included in the vast network of weather radars that we have such an amazing resource to have a huge land area that is covered by radar that we can do this kind of continental-scale study on, whereas in Europe, it’s a little bit more challenging.

All these different countries have their own little radar networks. And they need to talk to each other and get the data to align. And so in Switzerland, maybe the species that you’re looking at is a much smaller subset because it’s a much more specific type of habitat.

FLORA LICHTMAN: So it’s hard to compare the European insect population to the US?

ELSKE TIELENS: Exactly. And one of the things that I’m working on right now is to try and compare across countries or understand how we can get these different types– these different radar networks to provide data that we can align with one another so that we can do a large-scale study in Europe as well.

FLORA LICHTMAN: I am here for it. Come back and tell us about it.

ELSKE TIELENS: Absolutely. I’d love to.

FLORA LICHTMAN: Dr. Elske Tielens is an ecologist with the Swiss Federal Institute for Forest, Snow and Landscape Research. Thanks for talking to me today.

ELSKE TIELENS: Thank you.

FLORA LICHTMAN: If this podcast has you on high, up in the clouds– you pick the strained metaphor– why not leave us a review wherever you get your podcasts? This episode was produced by Charles Bergquist. I’m Flora Lichtman. And thank you for listening.

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