Date: November 23, 2009

Title: The Extraterrestrials in Your Back Yard


Podcaster: Lia Corrales from Columbia Astronomy

Organization: Columbia University Astronomy:

Description: Every day 2 tons of cosmic dust rains down upon the surface of the Earth. In this session we will explain how you can go hunting for space rocks in your own back yard. We will explore the phenomenon of micrometeorites and their journey from space to your flower bed.

Bio: Lia Corrales was inspired into a life of astrophysical research through space documentaries and Stephen Hawking. She is now a second year Astronomy grad student at Columbia University. She also enjoys dancing, rock climbing, and reminiscing about Astrocamp.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Clockwork Active Media Systems. Clockwork invents, designs, develops and maintains web applications that market, sell, streamline, automate and communicate. Visit clockwork dot net or email inquiries at clockwork dot net to get started on your web project.

LC — Lia Corrales
DT — David Tam
DE — Denton Ebel (Curator at the American Museum of Natural History)

For video, go to:

LC: Hello everyone and welcome to Columbia Mondays. I’m Lia Corrales and I’m a third year graduate student at Columbia University in the city of New York.

DT: And I’m David Tam. I’m a technician with Columbia’s physics department. The rest of this podcast has been edited down from video, so if you’re listening to the audio only version, please visit the website for the 365 Days of Astronomy, and get the link to our video.

LC: Today we’re going to talk about micrometeorites.

DT: So Lia, what are micrometeorites?

LC: Ok, so micrometeorites — my sort of definition is not necessarily a textbook definition, um, I would say is any meteorite that’s like, less than a millimeter.

LC: There’s a number of places that meteorites can come from. Kind of the first usual suspects are the asteroid belt, because there are a lot of rocky objects that exist between the orbit of Mars and Jupiter that can fall, potentially fall, into our atmosphere and become meteorites. Another thing, ah, another place that meteorites can possibly come from is comet debris, because comets can come in from the Oort cloud, which is way beyond the orbit of Pluto, come around to the Sun, and then leave. But as they get near the sun, they can break up into little pieces, and potentially fall onto the Earth as well. So asteroid belt, comet debris, uh… we can also get meteorites from other bodies in the solar system like the moon or mars. And that’s when they get impacted by a meteorite; they could spray some stuff out into space and potentially hit us.

LC: So recently, I went to the American Museum of Natural History and I talked to Denton Ebel who studies, um, meteorites and planetary sciences, and he told us a lot of cool things about micrometeorites.

DE: You know how if you slide on a rug you get a rug burn?

LC: Yes

DE: Right? So, the micrometeorites slide on the atmosphere. They slide on the air; they come in really hard. And if they’re big enough, they become meteorites, maybe if they’re the size of a basketball they might enter, hit the ground maybe the size of a golf ball, because of that oblation by the atmosphere. So they’re heating up, and when you get a rug burn on that rug, you’re leaving some skin behind. And that’s what the, that’s what the CSI guys: are going to come and pick up: the blood with they’re tweezer’s, right? So, those pieces of stuff off those meteorites get melted and then they fall right off because of friction, and those we can collect.

LC: (laughing)

DT: We’re on the roof of Pupin hall at Columbia University in New York City, and we’re here today to discuss micrometeorites.

LC: Ok so, uh David, you and I are going to collect micrometeorites, and this is how we’re going to do it. We have your magnets, and what are they made of again?

DT: These are, uh, rare earth Neodimium very very strong magnets.

LC: Great, so we are going to use these magnets to pick up little bits of magnetic rocks. So the first thing you want to do, though, is put them in a plastic bag or cover them with some sort of seran wrap. And that’s because, um, if you’ve ever run magnets through iron filings, they pick up a lot of stuff; but it’s really hard to get it off because it’s super fine, so we’re going to put plastic over that so that we can get the rocks off of the magnets. So go ahead and, nice…

DT: Ok I’m putting them in the bag.

LC: Alright so … the roof of Pupin is actually a great place to collect micrometeorites because they fall pretty much everywhere. But when they’re on the sidewalk and stuff, people pick them up on their shoes really easily. So, really the best place to find them…

DT: Are you saying that everyone is walking around with micrometeorites on their shoes?

LC: Definitely, definitely… in fact you’re probably eating some if you, like, eat outside or something like that.

DT: You know what I always wondered, if I’m walking along and suddenly I got a little spec of something in my eye and I have to rub my eye, does that, uh, is that potentially a particle that came straight from space and landed in my eye?

LC: Sure, why not? (laughing)

DT: So how do I go about actually collecting the micrometeorites?

LC: Ok so, oh, uh… So all you want to do is just wave it over the ground, maybe an inch or so away from the ground, and stuff will … zip up

DT: Up here on the railing perhaps?

LC: The railing’s ok but you don’t want to, you don’t want to touch the ground with your plastic bag, you just want to wave it around.

DT: Oh look I got some already!

LC: Oh my gosh, that’s great! Oh that’s awesome, yeah, I see some specs.

DT: So just let it float above the ground?

LC: Yeah or just leave, leave them so they don’t move and float it above the ground a little bit. Yeah, there you go. The cracks are really good spots because they’ll wash away into cracks…

DT: Ah…

LC: …and they, uh, don’t get picked up by people, animals and stuff. And um…

DT: Right over here maybe?

LC: Yeah, little stuff like that. Just of course, especially if you’re doing this, uh, out on the street, watch out with what you pick up, especially in New York City.

Rustling noises

LC: Just wave it above the ground. If you uh, if you touch the ground a lot, it will just wipe stuff off.

DT: Ohh, I got it.

LC: Yeah, and then also I suggest … Oh I just saw something fly up!

DT: Oi!

LC: (laughs)

DT: I can hear it. I don’t know if you can hear it in the video, but I can hear crackling and..

LC: Yeah, I can hear little crackles too. Oh nice…

DT: Oh, I picked up a giant screw.

LC: Ugh… (laughing)… Alright, so, so let’s…

DT: Oh wow, we’ve got a lot here.

LC: Let’s go down and look at that… so, under the microscope

DT: Do you want to do it up here on the ledge?

LC: No, no I want to do it downstairs where we have the light.

DT: (jingling keys) Alright here we are back at my office. Let’s go examine these micrometeorites.

LC: Ok, so we’ve just collected our micrometeorites and now we want to look at them. So what we should do is just take the bag, and release it from the magnets and then put the magnets somewhere else where the micrometeorites won’t fly onto them. And then we can uh, leave all of our powder and dust behind on this white piece of paper.

DT: So how are we going to look at these?

LC: So we’re going to use a magnifying glass. You can also use a microscope. If you use a microscope you’ll find, uh, much smaller micrometeorites and it’s pretty fun to see them there, amid all the grains of dust and other stuff.

DT: Oh yeah I can totally see it.

LC: Yeah then, and try uh, double magnifying it with the other magnifying …

DT: No it didn’t actually work.

LC: Oh, it doesn’t

DT: Well, yeah ok, I guess it does.

LC: See it? It’s kind of dark huh?

LC: We’re picking up only very iron rich meteorites because we’re using the magnets. There’s also stony meteorites but we aren’t going to pick them up with the magnets, so we’re actually getting a very specific subset of the type of space dust that falls onto the Earth.

DT: Ah…

DT: So one question I had was, of the micrometeorites that we found, the way we identified them is they were very spherical in shape; they were very round. Why is it that micrometeorites are round?

DE: They burn up, but that’s not a good word. That’s oxidation. They more or less vaporize, they also ionize the Earth’s atmosphere’s molecules, way like, 60 miles up somewhere.

LC: So do they make like trails? Right?

DE: Yeah, yeah. They’re called shooting stars.

LC: Yes.

DE: But when they come all at once we call them a meteor shower.

LC: I see.

DE: And that’s what they are. But some of those particles are entering the Earth’s atmosphere all the time, because they’re just left over from dust, and then, of space junk. And then, when there’s collisions in the asteroid belt, that stuff goes to the Earth. To be spherical it would have to melt all the way.

LC: When you go to the museum, and you see a collection of meteorites, a large portion of them will be metallic, full of iron. But the fact of the matter is that those large portion of meteorites, or that collection of meteorites that you see at the museum don’t actually represent the real population of meteorites, or the real population of stuff that’s out there in space and actively falls onto the Earth. So, in a collection at the museum, you’ll see about 30% iron, 60% stony, rocky stuff. But in reality, about 86% of it is rocky, 5% of it is iron.

DE: There’s a whole range of materials that hit the Earth’s atmosphere. Most of it, in terms of material, mass, is actually in the form of fine dust. We collect that. There’s actually a curator of cosmic dust…

LC: Yeah…

DE: …at Johnson Space Center.

LC: So also when I was learning about micrometeorites, I learned about some of the amazing ways they’re collected. So um, we picked them up using a magnet. And actually this has been done in the past. Harvey Nininger, which was a person who studied meteorites back in the 1930’s, he got like “meteorite-fever”, he opened a museum near meteorite crater. And basically what he did is he took a magnet through a lot of the dirt.

LC: But another cool way that people do it, when they’re in Antarctica, they have to make these big wells in order to get water. Like they melt… I don’t know exactly what they do, but they melt large pieces of ice in order to extract fresh water to drink. But when they melt it at the very bottom, meteorites will kind of fall and coagulate.

DT: Ahhh…

LC: And then the best, absolute best way to collect micrometeorites, is to take a spy plane, and fly it up into the upper atmosphere, about 20 km above the Earth’s surface.

DE: We collect these on U2 spy planes, re-tasked for this wonderful peaceful purpose. And these are things that float in, the zodiacal light, you see them actually in the plane of the ecliptic. Some are from comets, some are from asteroids. You can tell how fast they came into the atmosphere, roughly, by finding the temperature at which they release helium. So if they were exposed to high temperatures, they start to release trapped helium at a high temperature, because everything below that temperature has already been released that would come out, and so forth. So things that came in fast, are probably from comets, and things that came in slower, are from asteroids, because of the radius of their initial orbits.

LC: I do want to say that I learned how to hunt micrometeorites from Astrocamp. Thank you Astrocamp for teaching me that, because it’s like one of the coolest things I ever learned.

LC: This has been a podcast of Columbia University here in the city of New York. For more information about public events at Columbia Astronomy, visit Our next Columbia Monday podcast will be on November 30th. Have a great day, and keep listening.

End of podcast:

365 Days of Astronomy
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