IRA FLATOW: This is Science Friday. I’m Ira Flatow.

Later in the hour, we’ll talk about a plan to eliminate disease-carrying mosquitoes by releasing more mosquitoes. We’ll tell you how that works. Plus, celebrating the 30th anniversary of Jurassic Park, how the blockbuster movie inspired a generation of paleontologists and dino lovers.

But first, this week, smoke from Canadian wildfires drifted south, enveloping the Northeastern United States, casting an ominous orange glow on New York City. Poor air quality continues in some parts of the country. And while climate change is responsible for extending and worsening the Canadian wildfire season, it’s still rare for this many fires so early in the season.

Joining me now to talk more about this and other top science stories of the week is Katherine Wu, staff writer at The Atlantic, based in Boston, Massachusetts. Katie, welcome back to Science Friday.

KATHERINE WU: Always good to be here, though I wish it were under better circumstances this week.

IRA FLATOW: Well, that’s true. Because for those of us on the East Coast, who have been dealing with wildfire smoke maybe for the first time in our lives, this has been a wake-up call, right, for what it’s like during wildfire season in the West.

KATHERINE WU: Yeah, it has truly been terrible. And in fact, what has been happening all over the Northeast this week has actually outstripped some of the worst wildfires out West in recent years. It is so, so, so bad. Cities are breaking air quality records. Really, we have to keep in mind that this is the most populous corridor of the entire country. There are millions of people under an air quality alert this week.

IRA FLATOW: Recap for us why we’re seeing such intense fires in Canada and why we’re only experiencing it for the first time down here in the Lower 48.

KATHERINE WU: So for the Northeast, this is extremely atypical, right? We don’t typically have wildfires burning here. But it seems to be this really unlucky nexus of two things. One is that, as you mentioned, climate change is just making wildfires, where they appear, more extreme and also making it easier for them to spread and travel really quickly.

Canada has already had a terrible wildfire season, and it’s really just getting started. Keep in mind that we’re still technically in spring. But already there has been 14 times as much burning this year than what’s typical for the last decade. There are hundreds of fires all over Canada, from West to East. And the ones burning in the East right now, they happen to be caught up in a bunch of winds that are traveling southward and exposing us to that smoke.

So a bit of bad luck on that part, but certainly the main source, the main troubling thing, is just how badly those fires are burning.

IRA FLATOW: Well, this could portend the future perhaps, no?

KATHERINE WU: Right. I mean, with climate change only getting worse, the temperatures around the globe only getting hotter, a lot of scientists are worried that this could be a norm. If this is the first taste East Coasters are getting, it probably won’t be the last.

IRA FLATOW: They’re telling us that if you must venture outside– they’re saying stay inside– there are ways to protect yourself. And pull out your old mask, right? Do you still have your COVID mask around? Does that actually afford protection?

KATHERINE WU: It really does. And we definitely do want to emphasize here that if the air quality, it truly is bad in your region– you can check your weather app or go online to Air Now, which is run by the EPA– if levels are above 150 or so, that’s definitely a good sign to stay indoors if you possibly can, run whatever air filters you have. But if you do have to go outdoors, as many of us do to commute, to do whatever it is we need to do outdoors, wear an N95 mask or something equivalent– the same top-of-the-line, really high-quality, well-fitted, good-filtering masks that helped the most throughout all of COVID and are still helping us now.

The trick is we have to flip our rules. Whereas, indoor air that was really stale and not turning over very well was not our friend throughout the worst of the pandemic, right now it’s the outdoor air that is potentially really hazardous. And that’s where you’re going to want to keep that mask on, and it might be safer actually to take the mask off when you go indoors.

IRA FLATOW: Really interesting. Let’s talk about some other news this week. There was some about how traveling in space affects the human brain. What are we talking about here?

KATHERINE WU: Right. So in space, last I checked, there is still no gravity. And so the fluid in our bodies is going to behave very differently. We know that this affects our muscles and that they can atrophy, and our bones, and that they can lose density. But the important thing for our brains is that, because our bodies are mostly water, that is going to lead these structures, called ventricles, to fill with a bit more fluid.

So without gravity to hold it down, fluid in our bodies is going to travel upward to compensate. These structures take up more of that fluid. And so, basically, your brain is getting a little swell-y if you spend, uh, more than a few weeks in space. Keep in mind that this is for longer-term space travel. This is not going to be a big deal if you’re up in space for a couple of days at a time. But for astronauts who are going up there for months at a time– maybe even six months or longer– this will have a big impact.

What scientists are now finding is that, if your brain swells during these long spaceflights, when you come back down to Earth, it takes quite some time to recover– up to three years– for your brain swelling to go back down to normal.

IRA FLATOW: Three years. Do we do we know if there are any side effects from this, or long-term side effects?

KATHERINE WU: Right. So that is a huge thing to keep in mind here. It’s a little unclear what the long-term health implications here are, if any. They’re just observing this effect that, oh, there is a big difference here. And the body probably needs some time to recover.

What is probably going to be the safest course of action going forward is to make sure that astronauts that are going on these long spaceflights are really trying to space them out. You can think about it roughly like if you stretch out a rubber band repeatedly, it’s going to lose its elasticity. You kind of burn out the rubber band a little bit.

But if you use it less often, if you don’t stretch it out so often, it’ll have more of a lifespan. That’s the similar idea here. If there is an effect, we want to make sure the brain has some time to recover, go back down to its normal size, so it can retain that flexibility the next time you go into space.

IRA FLATOW: Our next story takes us in the totally other direction, literally. Scientists, for the first time, have dug up pieces of the Earth’s mantle. What is the mantle, and why are they interested in these rocks?

KATHERINE WU: So the part of Earth that we are most used to seeing is the crust. That is the outermost layer. But the crust is really hardly any of Earth’s composition. You can think of Earth as a giant cake-pop. And the vast majority of what’s in the middle is actually the mantle. There’s the liquid core, but the mantle is really most of the stuff that is in Earth. And right now, we’re sitting on top of a very thin layer of icing.

To really understand what is going on in our planet, we need to get the recipe for the cake and not just focus on the icing or the frosting. So really, having these samples is a pretty big deal. It can help scientists figure out how our planet formed and also even how volcanism happens at the surface. Because deep in the mantle is where magma is melting and separating out and then getting extruded up to the surface to create volcanic activity.

IRA FLATOW: Cool. Let’s move on to a story about ancient parasites. Scientists uncovered the oldest case of dysentery. How did they figure this out?

KATHERINE WU: Well, as you can imagine, this story gets very slightly gross. They were basically digging through an old archaeological site. This is from Jerusalem– or Jerusalem’s Iron Age, about 2,600 years ago. They found a bunch of latrines and were able to analyze a bunch of fecal samples.

And they found evidence that people, even in the richest echelons of society, had Giardia. Which is a parasite that causes some pretty gnarly bloody dysentery.

IRA FLATOW: Well, OK. Let’s move on a little bit. I know you’re a cat person. And this week you wrote about research into a new type of contraceptive shot for cats.

KATHERINE WU: Yes. This is incredibly exciting. So this is basically a one-and-done injection that scientists in a small trial saw was able to block ovulation in a small number of cats. So this hasn’t been taken to clinical trials yet. This is not going to be on pharmacy shelves tomorrow. But the potential here is really big.

If cats are able to get just a single injection and not be fertile any more, potentially for years– maybe even a lifetime– this could someday be an alternative to spaying.

IRA FLATOW: And you wrote about how the most useful application of this cat contraception could be in feral cat colonies. Tell me why that is.

KATHERINE WU: So spaying is something that happens to pretty much all female pets in this country. It is a very important thing to do. But it’s also something that is really important for population control. There is an estimated 500 million free-roaming cats on Earth. That is a lot of cats.

IRA FLATOW: Wow.

KATHERINE WU: And their numbers are potentially only growing. Because you get a couple of cats in a room together, and they are probably going to try to make more cats. This is a big deal. It’s a nuisance for people. It’s devastating for the world’s birds. And a lot of these cats are just not very healthy.

So there’s an option to cull them, which is brutal and a lot of people consider it inhumane. There’s an option to catch them one by one by one by one, surgically sterilize them, and release them. But that’s a lot of time and money. If a single shot can replace that, we could maybe reach more of these cats and keep them and other wildlife healthier.

IRA FLATOW: Right. Finally, let’s end on a word your eighth grade science teacher taught you– parthenogenesis. Scientists discovered a female crocodile who gave birth without the help of a male crocodile.

KATHERINE WU: Yeah. Incredibly impressive. She was just hanging out in a zoo. But then she laid a clutch of eggs in January of 2018, even though she’d had no contact with any males for 16 years. It’s a very cool sperm-free mystery.

IRA FLATOW: That is cool.

KATHERINE WU: And what they think happened is she was able to just produce some eggs sort of sort out her own genetic material, and produce a crop of offspring that were genetically identical to her. The sad thing here is none of the offspring actually made it to term, but some of the embryos developed enough that scientists were able to verify, oh, these are exact, pretty much, carbon copies of mom. No dad involved.

IRA FLATOW: This is not unknown in the animal kingdom, right?

KATHERINE WU: Right. So this parthenogenesis phenomenon has been observed in snakes, fish, lizards, birds. It’s not that uncommon. It’s something that a lot of animals will turn to often in times of desperation. Like, if there’s truly no male around, you might as well make a copy of yourself and see if your daughter has better luck finding a mate. But it’s the first time we’ve seen it in crocodiles.

What’s kind of cool about that is if this behavior is common among these groups, especially reptiles and birds, maybe that points to this ability being present in a common ancestor– maybe even dinosaurs or pterosaurs. And that just tells us a lot about how this might have evolved and to whom it was useful.

IRA FLATOW: Well, Kathrine Wu, you’re always useful to us. So thank you for bringing us great stuff again each week. Katherine Wu, staff writer at The Atlantic, based in Boston. Have a good weekend.

KATHERINE WU: Thanks so much. Always glad to be here.

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