Smells like Science

Full Transcript

Announcer: Welcome to Stuff From the Science Lab from

Robert Lamb: All right, Allison. A neutron walks into the bar and asks the bartender for a drink. The bartender says, "For you, no charge."

Allison Loudermilk: Hey, I'm Allison Loudermilk, the science editor at

Robert Lamb: And I'm Robert Lamb, a science writer at That joke came to us courtesy of listener Christian.

Allison Loudermilk: Yeah, he submitted it on our Facebook page. Thanks, Christian. I liked that one.

Robert Lamb: Some people might say that joke was a stinker, but that's the great thing about cheesy jokes. They kind of stink. We're going to be talking about a number of things that stink in today's podcast.

Allison Loudermilk: Yes, because we're talking about science and its various smells. That's the name of the podcast, Smells Like Science.

Robert Lamb: Don't run away. This is not just going to be a discussion of how the nose works or something. We're going to come it at from a number of different angles. In fact, our first angle we're going to hit is outer space.

Allison Loudermilk: How does it smell?

Robert Lamb: It's interesting. There's actually far more data on this than I possibly imagined. I don't know if you've ever watched "Futurama."

Allison Loudermilk: I have. I've seen episodes.

Robert Lamb: Okay. There are a couple of different episodes where Professor Farnsworth, the ancient, often naked, mad scientist pulls out this thing called a smell-o-scope. It looks like a telescope, except it has these two nostril plugs. He just drapes his nose over it, and the plugs go in his nostrils. That he can smell distant regions of the cosmos. Of course, this is fantastic and ridiculous, but like I say, there's a lot of information out there.

For instance, space itself, according to some people who've smelt it has an odor. This is not just people theorizing. This is coming from international space station science officer Don Pettit. Don did not smell the void directly. It's important to mention, because he might be dead. He was merely opening the airlock so a couple of his crew members could come back in from the space walk. Every time he would do this, he would notice this peculiar smell.

At first, he's like, "Is there something weird with the ventilation system?" He's probably thinking, "Is it me? Do I smell kind of funny?" No, he kept noticing it was clinging to the space suits and gear, especially the fabrics.

I should just read the quote. He kept a little blog of his time op there. He says, "It's hard to describe the smell. It is definitely not the olfactory equivalent to describing the sensations of some new food as 'tastes like chicken.' The best description I can come up with is metallic, a rather pleasant sweet, metallic sensation. It reminds me of my college summers where I labored for many hours with an arc welding torch repairing heavy equipment for a small logging outfit. It reminded me of pleasant sweet-smelling welding fumes. That is the smell of space."

Aside from him seeming to have kind of a weird thing about welding, it also reminds me of my cat, actually. I'll pick up the cat, and I can smell the cat. Not in a sick way.

Allison Loudermilk: No, you bury your nose in the fur. I totally get it.

Robert Lamb: Well, not bury, but it's like she's there, you smell her. I think, "She doesn't really smell like anything. Maybe batteries."

Allison Loudermilk: It's funny you say that because we recently went to the Atlanta Zoo. We go a lot. We have kids. I've always noticed a peculiar smell at the gorilla exhibit. To me maybe it does have a little bit of metallic odor to it, but it is a distinctly animal smell. But it does have a metallic kind of tone.

Robert Lamb: But not a monkey house odor.

Allison Loudermilk: No, not a monkey house. It's just a funky kind of metallic. Back to space. Back to space.

Robert Lamb: That's outer space itself. From there, let's head to the moon. Here you have a number of the different astronauts who went to the moon came back and had some comments, especially about how moon dust smells. Again, they were not going out onto the surface of the moon, and sniffing moon dust, but it's everywhere, and it gets all over you, so they're coming back in from their walk, and it's all over their stuff, all over the equipment, etc. They end up sniffing it. It's getting in their mouth and nose, etc.

A number of Apollo 17 astronauts -

Allison Loudermilk: Were whiffing the stuff.

Robert Lamb: Yeah, they commented on it. One in particular -

Allison Loudermilk: Gene Cernan.

Robert Lamb: Gene Cernan said that it smells like spent gunpowder. A number of the other astronauts backed him up on this.

Allison Loudermilk: Apollo 17 astronaut Jack Schmitt inhaled some of it, and he said it gave him a few hours of hay fever.

Robert Lamb: They were asking him, "Did any of the other astronauts have this?" He said, "They didn't own up to it." It's sort of like maybe they had it too, but they didn't want to say anything.

Allison Loudermilk: They're tough guys. All astronauts are tough guys, or tough women as the case may be.

Robert Lamb: The thing about the gunpowder is these were guys who knew their way around some guns. This was not just a theoretical - these were gun-toting Americans of the late '60s, early '70s.

Allison Loudermilk: The smell makes sense in a way when you think of what moon dust is made of because almost half is silicon dioxide glass created by meteorites hitting the moon. These impacts which have been going on for billions of years fused topsoil into glass, and they shatter into tiny pieces. Moon dust is also rich in iron, calcium, and magnesium. It's bound up in the minerals, such as olivine and pyroxene. It's actually nothing like gunpowder, but the impact thing makes sense to me.

Robert Lamb: Yeah. It sounds plausible. I don't doubt it for a second when they're like, "Huh. It smells like gunpowder up there." All right. It's gray and dusty. They also said some of it comes from gasses evaporating off the moon dust. These are gasses that get there via the solar wind. The moon is constantly exposed to hot wind, this hot solar wind of hydrogen, helium, and other ions blowing away from the sun, so a lot of that gets caught up in the dust as well.

We don't really have a firm answer of why these guys found it to smell this way, but there's some commentary on the various elements at play there.

Allison Loudermilk: Well, if I never get to the moon, at least I have a fuller sensory picture.

Robert Lamb: It makes it a little slinkier. I don't know. The space thing was really surprising, because you just think of space itself as being just kind of sterile.

Allison Loudermilk: Totally. I do. Let's talk about some of the other planets out there and what their particular odors are.

Robert Lamb: Mercury, of course, closest to the sun, doesn't have much of an atmosphere, at least not anymore. Very thin. Most of it was lost long ago. What remains is mostly sodium, which doesn't really have a smell, so don't expect to find Mercury just by using your smell-o-scope.

Allison Loudermilk: What would you expect mercury to smell like, just off the top of your head?

Robert Lamb: Being a fiery world, you kind of expect to get a sulfur hell smell, which as we're going to see, you actually do get a fairly sulfur hell smell off of some of these other planets.

Allison Loudermilk: I'm thinking Mercury may be like peppers, spicy food sort of smell.

Robert Lamb: Like curry? Like a planetary curry kind of odor?

Allison Loudermilk: Yeah. Like super chili hot. That's what I think Mercury might smell like.

Moving on to Venus, this is supposed to be a sharp, pungent smell, not unlike rotten eggs, due to the clouds of sulfuric acid, which we were just talking about.

Robert Lamb: Right. Mars, on a similar note, they say there's sulfur, acids, magnesium, iron. Put that all together in a carbon dioxide rich environment, and it's probably going to reek like rotten eggs.

Allison Loudermilk: No kidding? What a bad-smelling solar system we inhabit.

Robert Lamb: It kind of sucks for the first Mars colonist to get there, right? But they're just going to get used to it.

Allison Loudermilk: Jupiter, it kind of depends on the layer what you're sniffing on Jupiter. The lighter zones would smell like ammonia. Then ammonia and rotten eggs. Then you pass through hydrogen sulfide. Then bitter almonds, which is going to be your hydrogen cyanide.

Robert Lamb: That's really cool. It's like a lot of these planets have similar odors, but this has this rich, bitter almond poison center. It's kind of like a bonbon or something, an enormous bonbon.

Then its moon Io is kind of interesting because it's highly volcanic, and guess what. Smells like rotten eggs due to all the sulfur in the volcanic eruptions.

Allison Loudermilk: Saturn we're not so sure what it smells like, but the moon, Titan, is haze-covered over a nitrogen atmosphere, and a silled surface, pungent odor reminiscent of a petroleum processing facility.

Robert Lamb: That's not very pleasant.

Allison Loudermilk: I know.

Robert Lamb: Then, of course, there's Uranus.

Allison Loudermilk: Yep.

Robert Lamb: Yep. They hydrogen and helium portions of the uranium atmosphere are essentially scentless. Then there's that 2 percent methane content, which I have to stress something here because we're going to discuss another planet that has some methane content.

There's this idea that methane is stinky out there, purely because of the methane component in various gasses that come out of cows, and humans, etc. Farts, essentially. It's important to note that farts also contain a number of other elements. These tiny amounts of hydrogen, carbon dioxide, methane, hydrogen sulfide, ammonia. This is all mixed in together, and this is all a recipe for bad odor. Methane on its own is not going to stink. Again, Uranus, nothing really smelly going on there. Same with Neptune. Very similar environment.

Allison Loudermilk: That doesn't surprise me because I think of Neptune and Uranus very similarly. They're like brothers in the solar system. I don't think of them as having very different traits. Do you know what I mean? I know that's not true.

Robert Lamb: Like two strange brothers that hang out on the outskirts of the solar system.

Allison Loudermilk: Then for all you guys who bemoan the lack of Pluto amongst our solar system, we do have some info on Pluto. Since it's such a thin atmosphere composed mostly of methane, you mainly got nothing going on there.

Robert Lamb: To the untrained eye, or nose, people would think, "Oh, Pluto's got a methane atmosphere. It's going to suck. It's going to really stink." But it doesn't. It's odorless.

Incidentally - if I can run through this real quick - you know all those different websites where random people ask questions and random people answer them?

Allison Loudermilk: Yes.

Robert Lamb: Somebody had asked the question, "What do the planets smell like?" and someone had replied - and these are completely not true. they said that Mercury smells like refried beans, Venus smells like gasoline, Earthy smells like unwashed socks, Mars smells like Martians, Jupiter smells like muddy dogs, Saturn smells like burnt paper, Uranus smells like dead trees, Neptune smells like a turtle, and Pluto smells like squab.

Allison Loudermilk: What's squab again?

Robert Lamb: I think it's pigeon meat.

Allison Loudermilk: Oh, right. I think you're right.

Robert Lamb: I just found that amusing.

Allison Loudermilk: Let's head back to the earth for a second and check out some of our planet's most pungent residents.

Robert Lamb: That's right. Some animals and plants certain do put out an odor.

Allison Loudermilk: Yeah. This section gave me a chance to revisit one of my favorite articles on the site. That is "Why Does the Stink Plant Stink?" It was written by freelancer Jonathan Atteberry.

In the article, Atteberry takes us back to 1878, and he imagines trekking through the Sumatran rainforest alongside botanist Odoardo Beccari. He's Italian. I think people might be able to tell.

As the Italian is exploring the forest, he gets a whiff of rotten meat. The next thing you know, the wind shifts, and a stench floods his nostrils. The smell is very, very bad. It's a symphony of spoiled eggs, road kill, and dirty laundry.

Imagine that Beccari looks toward the source of the odor, and behold, the stink plant, AKA Titun Arum.

Robert Lamb: This is a great time to do a quick Google search to see this image, or go ahead and go to that article, and look at that picture. It just looks bizarre. It's enormous. It kind of looks like a fountain, and kind of looks like something from the set of classic Star Trek.

Allison Loudermilk: It's this massive plant sporting a massive pillar. It is kind of phallic, thus the scientific name Amorphophallus titanium. The stink plant is an inflorescence. What does that mean? It's a group of flowers clustered around a central column known as a spadix. It's surrounded by this leafy structure called a spathe.

Why does the corpse flower smell so terrible? Take a guess.

Robert Lamb: To attract insects.

Allison Loudermilk: Of course. It's such a large plant that it can take a year or more for the plant to store enough energy to bloom. Even then, the plant can only sustain its bloom for a couple of days. It has this really terrible smell, but it's fleeting. Because these plants are located so far apart from one another and they bloom on such an infrequent basis, they want as much insect attention as possible.

Robert Lamb: So they get a whole bunch of bees, and beetles there, crawling all over them. Spreading the pollen around, right?

Allison Loudermilk: Yeah. It's also interesting that scientists theorize that the overall appearance and smell help the plant masquerade as a giant hunk of decaying meat.

Robert Lamb: It does look kind of gross.

Allison Loudermilk: It does look kind of fleshy. You really need to check out the article. It's hard to imagine. It's like this giant pillar as long as your arm, if you were to hold your arm in the air right now, but even longer. It can be maybe a couple of feet.

Robert Lamb: Huh.

Allison Loudermilk: The stink plant is by no means the only malodorous plant. In fact, a whole group of them are called carrion flowers, which is kind of an interesting name for a flower. The two don't necessarily go together when you think about flower, carrion, carrion flowers.

Robert Lamb: We have a great botanical garden here in town and some lovely smelling flowers that I almost kind of want them to put on a carrion flower exhibit, just so I can run though real quick at least, and sniff these to really get the full experience.

Allison Loudermilk: I have no doubt that would be a big hit with the ladies of the garden club set.

Not only do these carrion flowers

smell, like we were just saying, but they also tend to look the part. For instance, the Stapelia asterias flower is coated with fine hairs. That's handy because it makes the flower resemble moldy meat.

Then we have the Rafflesia arnoldi, and that's the world's largest flower. That's another fleshy carrion flower located in Sumatra.

Robert Lamb: So Sumatra is just ripe with this stuff, like literally ripe with this stuff. What about animals? Naturally, not every animal is going to smell as nice and metallic as our cats and gorillas, right?

Allison Loudermilk: Right. So I had fun researching this part of the podcast. I came up with a couple candidates for the most pungent animal on Earth. One of the candidates I'd never heard of before. This is called the zorrilla.

Robert Lamb: That just sounds made up.

Allison Loudermilk: It kind of does.

Robert Lamb: I'm picturing maybe a gorilla with zebra stripes. Is that what it is?

Allison Loudermilk: Well, no, Robert. It's a striped pole cat. It's a skunk-like animal, and it's a member of the weasel family.

Robert Lamb: I was wondering when we were going into this. Is the skunk going to be the slinkiest animal, because that's the one that instantly comes to mind?

Allison Loudermilk: It definitely does. But we're going with skunk-like in this case. I'm weighing in on the zorrilla. Do you want to know why? Do you want to know why this convinced me that zorrillas might take the prize?

Robert Lamb: Why?

Allison Loudermilk: Because they can ward off lions with their stink. They can ward of lions!

Robert Lamb: The king of the jungle - well, the grassy plain. Whatever. Still, warding off a lion. These guys are ferocious. You'd think they wouldn't shy away from a slightly stinky smell.

Allison Loudermilk: I read one editorial about the zorrilla that said its anal glands can be smelled from half a mile away.

Robert Lamb: Ugh.

Allison Loudermilk: I have another.

Robert Lamb: That's just gross.

Allison Loudermilk: Are you ready for my next nomination?

Robert Lamb: Don't give me more of this.

Allison Loudermilk: I'm finding something to be true in this podcast series we've been doing. I think I have a stronger stomach than you do.

Robert Lamb: Maybe so.

Allison Loudermilk: With the worm in the woman's foot, and listener mail.

Robert Lamb: Well, that was worms in a woman's foot. That was kind of gross.

Allison Loudermilk: It was pretty cool.

Robert Lamb: It was cool, but it's a pretty grim image.

Allison Loudermilk: Right. So my next nomination, getting back to pungent animals, is a beetle, the Bombardier beetle.

Robert Lamb: I've seen clips of these guys.

Allison Loudermilk: These beetles, when physically assaulted, they squirt out this hot, quinone spray from their abdomens. The African Bombardier beetle can aim its spray in pretty much any direction. I was reading about this in the journal proceedings and the National Academies of Science. The reason why this beetle has evolved such an olfactory defense is if you can remember, they can't instantly take to the air. So it has to -

Robert Lamb: Stand its ground.

Allison Loudermilk: Right. It can eventually take to the air, but not instantly. An instant can be life or death, as we all know. I really like this beetle. According to the authors of the paper and the proceedings, we'll just call it that for short, it can discharge upwards of 20 times before depleting its glands. This is kind of cool. The discharges are accompanied by audible detonations. It's like its setting off these little smell bombs.

Robert Lamb: Wow.

Allison Loudermilk: They do deter predators.

Robert Lamb: I think this is one of the ones that some scientists were interesting in in the field of bio-mimicry, looking at how nature has evolved to carry out certain processes that we might want to carry out. They're very interested in being able to take this squirting mechanism and apply it to some sort of gizmo or another. It's one of the amazing little evolutionary traits that's come around.

Allison Loudermilk: That's cool. Those are two of my nominations for most pungent animal. Of course, if you guys have ones you'd like to send us, please do feel free to email them on over or post them on Facebook.

Let's talk about one that doesn't smell so bad - and this is of course subject because smell is subjective - like a koala.

Robert Lamb: Really? They're so adorable, and yet they stink?

Allison Loudermilk: Well, a lot of people have talked about koalas smelling like cough drops. Do they in fact smell like cough drops? I have never heard this particular -

Robert Lamb: Like they're addicted to cough drops? No, I guess it's their diet, right?

Allison Loudermilk: Right. If you remember, a koala is the furry, Australian marsupial that sleeps all day. It's cradled up in the tree branches, and it wakes up maybe for a few hours, munches a couple of eucalyptus leaves, and it conks out again. This is its life.

Robert Lamb: It probably spends all that time digesting food that's not that easy to digest.

Allison Loudermilk: It reminds me of the panda in that their digestive - they have such a specialized diet. The koala just eats these eucalyptus leaves. It maybe eats a couple other random things, but mainly eucalyptus. The panda with the bamboo.

Robert Lamb: Right. They're all specialists.

Allison Loudermilk: Right. But their digestive systems have such a hard time accommodating that specialized diet, so it just doesn't really make sense to me.

Robert Lamb: That's why you don't see any specialist species building cities and ruling the planet. We're more generalist. We can eat just about anything.

Allison Loudermilk: So you're saying pandas can't rule the planet because they eat bamboo.

Robert Lamb: Exactly. And also it's like you look around a city. What's running everywhere? Raccoons, rats, foxes. I don't know what foxes eat.

Allison Loudermilk: I don't think foxes are running everywhere.

Robert Lamb: Oh yes they are.

Allison Loudermilk: Really?

Robert Lamb: London.

Allison Loudermilk: Okay.

Robert Lamb: Foxes are everywhere in London. Seriously. You don't see them as much - this sounds like something I would make up - but there are a lot of foxes, especially in the London area.

Allison Loudermilk: So getting back to koalas and cough drops for a second, off the British foxes, do these marsupials actually smell like cough drops? It eats these leaves from the eucalyptus tree. Remember that eucalyptus are grown for their gums, their resins, their oils, and their woods. Then eucalyptus oil acts as an expectorant, so it loosens the phlegm in the respiratory passages. That's great for those of us who have colds. It can be an antiseptic, and it can also function as a deodorant.

According to freelancer Julie Layton and the Australian Koala Foundation, mostly it's the young ones that smell like eucalyptus. As they get older, the smell fades, and a mature koala will smell musky, or like urine, and not so much like drugstore cough drop.

Robert Lamb: More like an old person's home, I guess.

Allison Loudermilk: I guess so.

Robert Lamb: So when cuddling up to a koala, go for the young ones. Grab the babies.

Allison Loudermilk: I did look around a little bit to see if koala breath smelled like eucalyptus, or perhaps a koala passing gas smelled like eucalyptus.

Robert Lamb: What a day of research you've had.

Allison Loudermilk: I know. It was pretty fun. So what do you have?

Robert Lamb: This is pretty interesting. I was looking at some - we're going to leave the animal kingdom. Well, most of the animal kingdom. We'll get back into the human world of scent.

I was reading a couple of studies that had to do with the way suggestion plays into our sense of smell. For instance, there was a 2005 study from Oxford University. This one reminds me a lot of our wine episode when we talked about the neuroscientist who had everybody come over for wine testing and started having all these crazy little experiments to see if people could tell good wine from bad wine or red wine from white wine that's been dyed red.

This guy, Professor Edmond Rolls, invited volunteers over and had them smell cheese, except sometimes he labeled the cheese cheddar, and other times he labeled it body odor, just to see what the reaction would be. Then, of course, his team scanned the volunteer's brains. It wasn't a great dinner party, I guess.

They scanned their brains to see what's going on in their heads when they're smelling these things. So when the cheddar cheese was labeled correctly - when it's cheese that's labeled cheese - higher areas of the brain that interpret smell were activated. Then they would give them a whiff of just clean air labeled cheddar cheese, and it activated the same areas, but to a lesser extent. It's kind of like the suggestion is still doing a lot of work, but not as much as the real thing would do.

The researchers also made sure to check how big a sniff they were taking to see if that was making any effect. That didn't have any effect on the results.

Anyway, the result of this experiment was that they found out that the pleasantness of the odor is being modulated in a part of the brain called the - and I may get this wrong - the orbitofrontal cortex, which is involved with emotions.

This is like a high level influence on how you're smelling things. This is the same area of the brain that's sometimes damaged in dementia cases, or if someone's in a severe accident. That can alter your appetite in some cases. It can apparently even make you more prone to obesity. The appetite thing is key because scent plays a key role in what we like to eat. That's a really interesting case of just somebody telling you how something smells.

I don't know if you've found this with kids, but I've often heard people talk about when you're feeding kids new foods, you never let them say it smells bad. You certainly never refer to something as stinky. Have you come across that?

Allison Loudermilk: That makes sense.

Robert Lamb: Do you let your kids say food is stinky?

Allison Loudermilk: I don't know if they know the word stinky yet.

Robert Lamb: Wow. You are doing great.

Allison Loudermilk: They know some other words they shouldn't know, but stinky's not among them yet.

Robert Lamb: Another interesting case that I came across goes back to April Fool's day in 1965. This is obviously an April Fool's joke on BBC TV.

Allison Loudermilk: Did it involve foxes?

Robert Lamb: No. No foxes. A professor from a university comes on, and they go through this whole thing where they're going to unveil smellovision. They unveil some sort of hokey, kind of like a "look around you" esque explanation about how they're going to transfer the scent molecules into smaller digital molecules. Something like transfer it through the screen. So basically, you'd be able to get close to your TV and smell.

Allison Loudermilk: That's the most hilarious image of everybody getting close and sniffing their TVs.

Robert Lamb: Apparently people fell for it and were like - they put some coffee or something up there, and people were like, "Yeah, I can totally smell it."

Then in 1977, a Bristol University psychology lecturer named Michael O'Mahoney tried the same thing. He told viewers that they were going to smell hay and grass, and no cow crap or anything. Just a nice field. A pleasant outdoor environment. Again, people claimed to have smelled it. They wrote in. Some of these people may have been lying. They factored that into it. But a lot of people said, "I can totally smell it." One person even complained of hay fever.

Allison Loudermilk: No kidding? Just like that astronaut.

Robert Lamb: Yeah. Maybe he was smelling the moon dust. Anyway, so we've touched on stinky animals, how space might smell, how things smell differently depending on what kind of other sense data we're combining with it.

Allison Loudermilk: I enjoyed this podcast. I had a lot of fun researching it.

Robert Lamb: It's kind of a smorgasbord, but it's kind of like you put all the elements together, and it really shows you varied the world of - at least our own - scents perception really is.

Allison Loudermilk: Definitely. If you guys want to tell us about your favorite smells or your favorite bad smells, or what you think Uranus might smell like.

Robert Lamb: Yeah. I'm especially interested if anybody out there really knows what they're talking about with the atmosphere of other planets and has additional ideas, even contrary ideas about what some of these places might smell like, I'd love to hear it.

Allison Loudermilk: Yeah. Send us an email at You can always hang out on Facebook. We're on Facebook with StuffFromTheScienceLab or Twitter as well with a LabStuff handle.

Robert Lamb: Give us a cool science joke. Give us your name and where you're from, and we'll throw it up at the front of the podcast.

Allison Loudermilk: Cool. Thanks for listening.

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