Elizabeth Fessler
Welcome to Longitude Sound Bytes, where we bring innovative insights from around the world directly to you.

As part of our series focusing on scientific expeditions in harsh environments and the individuals who are advancing it, our conversations aim to shed light on fascinating projects that help us understand and improve our planet.

I am Elizabeth Fessler, a student at Rice University pursing a degree Art History and History with a focus on museums and cultural heritage.

For this episode, I had an opportunity to speak with Dr. Cari Corrigan from the Smithsonian.

Dr. Corrigan is a curator at the Smithsonian National Museum of Natural History. Here at Longitude, we are putting together an exhibition of photos from the US Meteorite Search expeditions in Antarctica, I wanted to speak to Cari about the role of the Smithsonian and also to understand her role as a curator.

We began our conversation with background information on her role at the Smithsonian and what led her to it. Enjoy listening!

Cari Corrigan
I am a geologist at the Smithsonian, and I study meteorites. So, my main job is really in two parts. I do research on meteorites and try to figure out how they fit into the bigger puzzle of how the solar system formed. And I also curate meteorites. So, I’m the curator of the Antarctic meteorite collection at the National Museum of Natural History, which a lot of people don’t realize the Smithsonian has something like 17 different museums, and we’re just one of them. All the meteorites that get brought back from the US National meteorite program go through Johnson Space Center, and then they come to me, and my job is to figure out what kind of meteorite it is.

Elizabeth
So, your work generally is revolving around meteorites and Antarctica? How did you become interested in this specific field of study?

Cari
I started out studying astronomy and I took a geology class as a sort of a, an elective science class that fit into the astronomy program. And I was like, Oh, actually, this is really cool, too. And so I talked to the professor and they said, Well, there’s a thing called planetary geology, which I was like, what is that? And like, Okay, this is what I’m going to do for a major. I figured there’s no way I’m ever getting a job doing this but at least I will enjoy the four years of my life. Well, I have to get a degree and learn how to study something. So as part of that, I ended up with an advisor randomly, who was doing a meteorite project and said, Oh, this fits into that perfectly. I did a project with him, which led to doing an internship at Johnson Space Center. And the advisor I had there had this picture of himself standing in the snow with a bunch of people. And I was like, What is this? Like random guys on a snowmobile? And he said, Oh, that was when I went to Antarctica to look for meteorites. This guy was a total joker. He was always making up funny jokes. And I was like, oh, okay, haha, right, that doesn’t exist. And he was like, no, no, really, we go down there because they’re, they’ve been sitting there for hundreds of 1000s of years and they’re just waiting for us to go down and pick them up. So, we go down and collect them on the ice. And then I was sort of hooked. And it turns out that the guy who ran that program ended up being my PhD advisor. That one summer changed all my perspective on what I wanted to do.

Elizabeth
I’ve seen that you’ve actually traveled to Antarctica yourself. Could you tell us a little bit about that experience and what you were there to do?

Cari
I was there as part of the same group, the Antarctic search for meteorites group, which we call ANSMET. I was there twice to collect meteorites on the ice in Antarctica. It’s like six weeks at a time that you go, and you basically spend six weeks in a tent, looking for meteorites, which sounds silly, but it’s true.

Elizabeth
So how does the group determine where to look for these meteorites? Where do you start on such a large continent?

Cari
Right, like you said, it’s a huge continent, and it’s covered in white stuff, right? So, we think like, how do you even see meteorites sitting on the snow, but actually, there are places along the trans Antarctic mountains, which is a range of mountains that basically crosses the continent, where the ice cap for Antarctica is shaped like a dome. And gravity pulls that ice like, just like any glacier, it flows downhill. So the ice gets stuck up against those mountains. And in those places, the wind is really, really strong, and it’s really, really dry there so the ice actually sublimes away. And leaves the meteorites that have fallen and gotten incorporated into that ice just sitting in places, certain places we call stranding surfaces, or stranding fields. You just end up with meteorites sitting there. Sometimes you’ll find 1000s in one place. Sometimes you won’t find any in the same kind of place. We call these blue ice fields where the pressure of that ice being stuck, it pushes out all the bubbles in the ice. The ice turns blue. And you can actually see that by a satellite or airplane images. You can see these blue ice fields and so those are what we target.

Elizabeth
How are you determining whether these rocks that you’re finding are meteorites or just from Earth?

Cari
That’s a really good question, too. Because most of the places we go, we’re right up against those mountains, right? And glaciers do what glaciers do, which is to erode big valleys and carve chunks of the rock off of the mountains and so you do end up with lots of terrestrial rocks sitting there as well. So you’re in a glacial moraine, which is sometimes, you know, is almost all rocks from Earth. So a lot of times you’re walking around, sometimes crawling around, looking at the ground, trying to find any rock that looks different from the rocks that are on the slopes above you or the majority of the rocks that are around. You’d be amazed how quickly your eye can pick up the differences. You know, some of it is coal so that’s pretty obvious, looks different, like black and shiny. But then you’ve got a lot of sort of brown rusty-ish rocks, and you have a few light colored rocks. But then the meteorites have a fusion crust on the outside, which is a layer of glassy melted rock from when it passed through the Earth’s atmosphere. And so for the most part in Antarctica, it’s cold enough that that doesn’t erode away. If that fell in the US anywhere, the rain would erode that off pretty quickly. But in Antarctica, it’s so cold, you know, there’s nothing washing away the outer surfaces of these rocks that you ended up with the fusion crust just staying there and it’s pretty easy to determine which ones are and which ones aren’t. But it does take your eyes some time to get used to it. The program has taken teachers and artists and lots of non-geologists and they do just as well as people who’ve been studying geology their whole life in figuring out which ones are the meteorites pretty quickly.

Elizabeth
That’s really interesting. So then, once you’re finding these meteorites, what’s sort of the next step after you put them like in a bag?

Cari
We try really hard not to touch them so we use tongs and put them in these bags. We give them a number. And we take pictures of them and measure them. We do some little notes about them. Because for the most part, once you’ve looked at enough of them, you can tell roughly what kind of meteorite they are so we’d make little guesses in the notebook. Or if anything, like, oh, somebody touched this with their glove, or somebody accidentally ran over this one with their snowmobile or whatever, you know, just so that people who are then doing research on the meteorites later, will know that something may have happened to the rock that they’re studying. So, they go, back to McMurdo, which is the main U.S. base in Antarctica where we go in and out of the continent. They wait there until the one ship every year leaves the continent, so they stay frozen. We leave them in a cooler. Where we’re camping, it’s frozen anyway, so they’re fine. They go back to the base, they stay frozen, and then the ship is a freezer ship. So, they stay in the freezer part of the ship. They go all the way to Port Hueneme, California. And then they get in a freezer truck. They drive to Houston to the NASA Johnson Space Center, where they stay in a freezer, until they’re thawed out in a nitrogen tank, like a big glove box. So, they’re putting their hands in these gloves, and working with the rocks inside of this glove box with a nitrogen atmosphere that keeps the rocks from weathering or rusting. There’s a lot of metal in most meteorites so it oxidizes really quickly so we try to keep that from happening. And then from there, they send a piece to me at the Smithsonian of every meteorite. They do an external description of the rock and then I figure out what kind of meteorite it is doing chemistry on it. Then we announce it to the world in a newsletter twice a year and say, you know, this six months, we’ve classified 350 New meteorites, and we put them into a catalog online database and people can request them, put in a proposal to do research on them. Then we meet twice a year to review those proposals. We have a group of scientists, volunteer scientists from all over the world who participate in this so there’s eight or so people that rotate in and out. It’s kind of a fair system and it’s not just me every time, saying like, Oh, I don’t want this person that I want to give them anything. It’s a very fair, unbiased process where we look at what they want to do, and whether or not they have the capability to do it. Have they asked us for the wrong meteorite? And they asked us for way too much of a meteorite or wait a minute, we know you can’t do this research without more of this meteorite, so we might have to give them more than they asked for. But then they get sent out to the meteorite researchers all over the world. And people then write papers, do their research, write papers, presented conferences, and hopefully learn new things.

Elizabeth
You mentioned people can publicly request different meteorites sample. What kind of reasons are people requesting those? Are this generally the research all for the same kind of questions? Or are people doing very different things with them? Can you think of like one example, someone might want a sample of a meteorite for?

Cari
So, say they asked for a piece of a Martian meteorite, for example so that’s actually looking at a piece of Mars. And in the minerals that you might find in that rock, you might be able to tell, did these formed in the presence of liquid water or was the environment that they formed in really, really dry? Or if it’s an igneous rock and you’re trying to understand the magma or the lavas would have been like on Mars at the time that it formed? You know, did it all come from one volcanic chamber or did it come from multiple different systems? From the same volcanic region? Basically, trying to figure out how Mars formed as a planet, and how, you know, it’s a whole geologic history. But we’re putting it together from something like 200. I don’t even know the number of Martian meteorites at the moment. It’s in the low hundreds, you know, two or three hundred. So, we’re trying to understand the whole history of a planet from 300 rocks, and many of them are very similar. So, there are some really large groups where you have, you know, a couple 100 or so different rocks of the same type that we think came from the same place. And then are there a few that you have, you know, just one, or just three, or four. So, we have one meteorite from Mars, that’s a breccia, like regolith breccia, from the moon would be. A breccia is a rock made up of lots of different other rock types. So that one in itself gives us just as many rock types as we have in the other groups all together. Just from this one rock so it’s actually really valuable, because we have different rock samples in there that we don’t have in all the other Martian meteorite collections, which is kind of cool. So if we find more of those, that’d be good.

Elizabeth
And so then turning a little more to your role as like a curator of meteorites, which you mentioned. Could you tell us a little bit about what that role sort of means to you? And I guess, with such a large collection that you’re constantly adding to, what does it mean to you to kind of curate that? What are you looking for?

Cari
It’s really exciting to be able to be in charge of this collection, partly because it is growing every single year. All of the meteorites that we have that come back as part of this US government funded program, come to the museum, and are available for research. So that’s one really exciting thing. I just have to make sure that these stay protected from weather, from being too humid, being too hot in the lab, or pest management, you know, the things that people worry about in museums for their samples. Just making sure that they stay in as pristine condition as possible, so that people can do their research. Keeping it so that the instruments that we have now, and the instruments that we might have in 50 or 100 years. I mean, think of the advances in instrumentation. The things that people have been able to learn from the meteorites then that they can’t do now because our instruments can’t do those things. Being able to preserve enough material from each meteorite so that future generations can do their research successfully on the same stuff that we’re working on now and answer more and more and more in-depth questions. That’s one of the most important things about curating, is to sort of make sure that we preserve enough for future generations to be able to see and study themselves. So it’s kind of like being the keeper of the rocks for future generations, which is cool.

Elizabeth
Right. So as like a keeper of the rocks, you can sort of look back on your old collection, but then you’re also getting new ones, how much do you think of your research is like looking back at that older specimens, or the things that are just coming in?

Cari
Almost everything that I do is on older things. Partly because, just like everybody else, if I want to do research on one of the meteorites, I have to request it from the panel. I can look at the thin section. So we make a microscope slide of many of them, like a very like a hair width thin slice of a meteorite that we put on a microscope glass slide. And we can look at that in the microscope. I can look at any of those anytime I want to. So, I could do just research that way. But if I want to put it in an instrument, or do any damage to it, that you know, any analyses that would damage it, or I needed to like chop up a piece or grind it up, or melt it or do any other type of research on it, that would destruct it, then I have to get permission just like everybody else.

A lot of the meteorites are the Antarctic meteorites, but then the Smithsonian also has the rest of the US collection. We try to get pieces of as many of the US meteorites as we can partly because of the US National Collection, so we like to be as representative as we can. We have a lot of really cool meteorites in there that no one’s ever studied at all. You know, and we kind of dig through the drawers and see what’s there and what looks cool. So, a lot of it is us looking through some of this older stuff. But the classification of every new meteorite means that we do see a lot of the new stuff that comes in, and we follow the research that other people are doing that can answer some of those questions that we might not have the instruments to study.

Elizabeth
How often are you getting meteorites that you can sort of attribute to a known asteroid or area and how often are you getting ones that could be from anywhere?

Cari
That’s a really good question and how often isn’t so much as how like the percentages and how many. It’s like maybe 99% are from just asteroids. We can tell you that it’s a carbonaceous asteroid or not. But things like the moon, or the ones from Vesta, or the ones from Mars, those make up like 1% of all meteorites. So, one out of every 100, maybe. But sometimes you’ll get a season’s full of meteorites, where they happen to have found a disproportionately large number of those, just because that randomly happens to be what’s there. So, if you go to a field site, and you find 500 meteorites at that field site, chances are you’re going to find more things that don’t fall into that 99% and 1%. Sort of pie chart, you know, pie. But the more meteorites you find from every place, like we find that the meteorites we found are the field sites where we found something in 1000s of pieces. that pie chart almost always ends up looking the same. When you get more and more and more that pie chart eventually sort of meshes into the same proportions.

Elizabeth
So then, are there any particularly unique meteorites in the collection? I know you mentioned some from the moon, that kind of thing. What are some of the most I guess, useful ones for your studies?

Cari
There are Antarctic meteorites from Mars. We have one that’s called Allen Hills 84001 that I did all of my dissertation work on. It has carbonate minerals in it. And carbonate minerals require water, liquid water to form. It’s also an igneous rock, so that rock formed in some igneous way. You know, it was probably solidified below the surface. It’s not just a basalt, it’s, you know, some subsurface igneous rock. But then, an impact happened, like from an asteroid hitting Mars surface, and mess that rock up, heated it up, broke it up, melted parts of it, and fractured it, and shot melted rock into those veins into those fractures. And then we think probably that some water got in there. And then these carbonate minerals grew. So, for just from that one rock, you can learn about the igneous history, you can learn about the impact history, you can learn about the aqueous history of this area, you know, just this one spot on Mars. So that’s a really cool one. It’s called Allen Hills 84001. And Antarctic meteorites have this naming convention where the first three letters are, where it was found. The numbers are 84001. 84 is when it was found, 1984. And then 0-0-1 was the first meteorite opened in the lab when they brought it back, because they knew it was a different one. It was big and different from all the other meteorites that they’d found. So, they knew that was an exciting one. We have plenty of moon rocks, lots of lunar rocks, that are different than Apollo rocks, because the Apollo rocks, we know exactly where they came from. So, we only have so many sampling sites from the surface of the moon. But we don’t know where the meteorites came from. So those give us a broader representation of the surface of the moon, then samples that we were brought back by the Apollo astronauts.

Elizabeth
Very cool.

Cari
I feel like the special meteorites always get all the attention. But the group of 99% is broken up into carbonaceous chondrites, and ordinary chondrites. Those can tell us tons. Carbonaceous chondrites have tons and tons of really, really primitive materials in them, that formed very early in the solar system. And probably from out farther, you know, away from the Sun than the ordinary chondrites did. And so, you know, we can learn a lot about what the really primitive solar system material and sort of how the early solar system disk, how that was constructed in terms of what kind of materials were there. There’s an interesting theory that is says that maybe at some point, when the planets were all forming, there was something happened. I think, it’s Neptune and Uranus switched places and that gravitational, unbalanced, like, completely brought tons of material toward the Sun. And so, a lot of that intercepted Earth so we have more meteorites than from out there than we may have otherwise. Which is kind of cool. It is hard to think about. It’s hard to think about planets switching places. It’s kind of a wild and crazy theory, but I think there’s a lot of evidence that it might be right.

[music]

Elizabeth
We hope you enjoyed hearing about the curation of meteorites from Cari. Please visit Longitude [dot] site for the episode transcript.

If you are around Houston this spring, be sure to stop by the Rice University library to view our exhibition of photographs from the Antarctica expeditions. Our exhibit will be available for display at other university libraries upon request as well.

If you are a college student interested in leading conversations like this for our next podcast, please write to us at podcast@longitude.site.

Join us next time for more unique insights on Longitude Sound Bytes.