“Houston We Have a Podcast” is the official podcast of the NASA Johnson Space Center, the home of human spaceflight, stationed in Houston, Texas. We bring space right to you! On this podcast, you’ll learn from some of the brightest minds of America’s space agency as they discuss topics in engineering, science, technology and more. You’ll hear firsthand from astronauts what it’s like to launch atop a rocket, live in space and re-enter the Earth’s atmosphere. And you’ll listen in to the more human side of space as our guests tell stories of behind-the-scenes moments never heard before.
Episode 30 features Dr. Duck Mittlefehldt, Planetary Scientist, who talks about some curious findings in meteorites and the adventures endured to procure them. This episode was recorded on January 8, 2018.
Transcript
Gary Jordan (Host): Houston, We Have A Podcast. Welcome to the official podcast of the NASA Johnson Space Center, Episode 30, Infamous Meteorites. I’m Gary Jordan, and I’ll be your host today. So on this podcast, we bring in the experts, NASA scientists, engineers, astronauts, all to let you know the coolest stuff about what’s going on right here at NASA. So today, we’re talking about some of the more unique findings that have been discovered in meteorites with David Mittlefehldt, goes by Duck. He’s a planetary scientist here at the NASA Johnson Space Center in Houston, Texas, and we had a great discussion about curious findings in meteorites, and the adventures that are endured to procure them. So, with no further delay, let’s go lightspeed and jump right ahead to our talk with Dr. Duck Mittlefehldt. Enjoy!
[ Music & Radio Transmissions ]
Host: Duck, thanks for coming to the podcast today. I know we’ve — we’ve talked about searching for life and meteorites before, and it’s — it’s such a fascinating topic, but I really wanted to dive deeper, just into like the meteorites portion. We really — we really actually had a great conversation with Dr. Aaron Burton and — and Dr. Marc Fries, not too long ago, actually, about life, but really just about the meteorites themselves. There’s a — there’s a big story there, and you’re one of the explorers that are going down and actually finding these meteorites, huh?
Dr. Duck Mittlefehldt: Yeah, yeah. I’ve done that on a number of occasions.
Host: Yeah. And it’s — is it — is it mostly in Antarctica, or are you going other places?
Dr. Duck Mittlefehldt:Well, okay, so most of the times I’ve been searching for meteorites has been in Antarctica, so I’ve been down there five times, meteorite collecting expeditions, but I — I’ve [pause] — I was on vacation in Israel once, and I met up with a couple of geologists at a coffee house, and one of them had just published a paper where they — he described, you know, old surfaces in the deserts of southern Israel that are, you know, have been stable for about 2 million years. And I’m thinking, you know, over 2 million years, you can accumulate a lot of meteorites, so, I actually went there the foll — later that year, and met up with them again, and we searched some of these areas that are — have very ancient pavements on the desert, and hunting for meteorites. We didn’t find any, unfortunately, and, you know, I’m not quite sure why, there — there should have been some there, but, you know, it was a small team searching large area over short time, so it may well be that they’re there, but we just didn’t find any, because the ones that, you know, are there are small.
The other is there were a number of issues with that particular location. Meteorites, you know, when we find meteorites, they’re typically black on the outside, because they’ve gone through the atmosphere and they’re covered with this glassy, fusion crust, which is almost always black. The area we had searched in southern Israel actually had a number of dark rocks in it, as well. So, you know, the meteorites, if they were there, would not have stood out as — like — like, you know, the beacons that you see when you’re in Antarctica, scooting across the bare ice, so.
Host: I guess that — is that the main reason why Antarctica is such a great place to find meteorites? Is because it’s these black rocks against white snow?
Dr. Duck Mittlefehldt:Well, that certainly makes it easy, because [Gary laughing] you — you can see, you know, a rock, I’m going to use metric units because that’s what I’m used to, I’ll try and remember to throw in inches and feet as I can, but, so, you know, you can find a — a black rock, a couple of centimeters across or about an inch across, from a great distance in Antarctica on the ice. And — and, as you say, it’s because you’re looking at either pale blue ice or sometimes white snow, most of the meteorites we find are on the pale blue ice. But even so, it’s very bright in comparison to rock. So they’re easy to find there. The other thing is in Antarctica, we have a convenient concentration mechanism, which is the actual flow and ablation of the ice across the continent, and where we go to find them the meteorites is — is actually in locations where the ice movement has been stalled, and ablation by the Antarctic winds and — and warming by the Antarctic sun, allow a lag deposit to develop on the surface.
So we’re actually collecting meteorites that have been, you know, shoved from a great geographic area and then left behind in a smaller geographic area. So we have, you know, base — we have both the easy-to-spot and — and the concentration mechanism working in our favor.
Host: Alright! Yeah, they’re — they’re plentiful down there. So — so you made quite a few trips. How many was it? You said five?
Dr. Duck Mittlefehldt:Yeah, I’ve been down five times. The first time was in the ’97, ’98 field season. That was my first Antarctic experience, and I loved it so much I kept volunteering to go back again.
Host: You loved Antarctica?
Dr. Duck Mittlefehldt:Oh yeah [Gary laughing], I — I love it, you know, just — just last week, well, here in Houston, we had temperatures that Houstonians think of, or Texans think of as cold, but, me, I see that as maybe a cold fall day. Because I — I was born and raised in western New York.
Host: Alright.
Dr. Duck Mittlefehldt:And at the same time, you know, my hometown was getting temperatures, okay, again, I’ve got to do some conversion here, about maybe, you know, between 0 and 5 degrees Fahrenheit. And, you know, that was the weather I grew up in winter, and I loved it. Winter was always my favorite season when I was a kid.
Alright. So maybe it’s a deep love of winter that really — because I just came from this — we’re just coming back from the holidays now, and it was — it was negative 2 in Pittsburgh when I — when I was flying home, and, I mean, I was — I was born and raised in Pennsylvania, moved around a lot, but I’m not used to it by any means. Like, I like the — I like the, everyone, you know, saying, oh my gosh, 32 is really cold! And I’m like, [laughing], I’m okay with just that.
Host: For me, I — I loved the deep winter in western New York.
Dr. Duck Mittlefehldt:Alright, a lot of snow there too.
Host: So when was the last time you were down in Antarctica then?
Dr. Duck Mittlefehldt:So I was down last year, 2016, 2017, it was kind of a disappointment for me, personally.
Host: Oh.
Dr. Duck Mittlefehldt:I — I — because of my experience, I’ve been down four times before, I — I left early and was going to go out on a recon sweep with the — the mountaineer field safety officer for the ANSMET program. ANSMET, by the way, stands for Antarctic Search for Meteorites, and that’s the program that goes down to collect the rocks and has been doing so every year, but once, since 1976.
Host: Alright!
Dr. Duck Mittlefehldt:But, anyway, because of my experience, I was going to go down on this recon before the main season. We were going to go to one area, check it out for potential systematic work in a future season, and then stay for the first half of the main season, going to a location deep along the Antarctic, transAntarctic mountains. Well, it turns out logistics were badly broken last year. And partly because of weather, partly because of problems with the aircraft and so on, so I got out into the field for a week, in preseason, I got back to McMurdo Station while we were gearing up for the main season, but the logistics just broke and so they were not going to go out where they originally planned. The team ended up going to where I had been out on recon, but it was — they got such a late start that it made more sense to ship me home early rather than, you know, go out for maybe a week and then come back into McMurdo and go home.
Host: Yeah.
Dr. Duck Mittlefehldt:So I — I just spend one week out in the field last year.
Host: Ahh…
Dr. Duck Mittlefehldt:Much — much to my chagrin.
Host: [Laughing] So it was just the lack of time that you spent there, that was really the disappointment.
Yeah, yeah, it was [inaudible] time, and, you know, in the brief time that John Scott [phonetic] and I, he’s the mountaineer, were out on the ice, you know, we — we’d spend a week in the field, two and a half days we were tent-bound because the weather was so bad, but even so, we found 46 meteorites in the short time we were there.
Host: That’s amazing!
Yeah.
Host: Wow.
Dr. Duck Mittlefehldt:And — and remind — and remember, this was an area that had been heavily harvested back in the 80’s, 70’s and 80’s, we were going to back to see whether there was still great potential for harvesting more meteorites there, and, in fact, I think last year they ended up coming — picking up a total of 200 and some meteorites, even with, you know, going back to an area that had been searched before, and having a shortened season because the logistics. So, I mean, that — that kind of shows you the — the quality of Antarctica as a — as a site for bringing back space rocks. It’s just awesome!
Host: Incredible! So is — is that — is it because there’s just a fresh, I guess you could call it, supply of meteorites that are landing on the surface of Antarctica, or is it things are shifting?
Dr. Duck Mittlefehldt:It’s more things are shifting. In part, you know, deflation of the surface continues, as ablation goes on, and so new meteorites are poking through. In part, it’s shifting winds blowing snow around, so an area that might have been snow covered earlier season, maybe now has been stripped bare and there’s bare ice. And so that allows you to see things. So for a variety of reasons, you can go back to the same place you’ve searched once, and — and still find meteorites out there.
Host: Incredible. And hundreds of them, a little bit better than Israel, right?
Dr. Duck Mittlefehldt:Yeah [laughter]. Might have been better than my experience trying to find meteorites in the Negev Desert.
Host: [Laughing] So — so you’re saying a season. When you’re going down to Antarctica, I’m assuming it’s the summer there, right?
Dr. Duck Mittlefehldt:Yeah, it’s austral summer.
Host: Yeah. So that means the sun is up 24/7, right?
Dr. Duck Mittlefehldt:Right.
Host: So you kind of have to deal with that when you’re — when you’re down there, right?
Dr. Duck Mittlefehldt:Yeah, you know, I’ve — I’ve become accustomed to that. The first — I was kind of — there was a guy who used to work in our building who had been down I think a year or two before me, so I took advice from him, and he said, you know, one of the things is, you know, with the constant sunlight, sometimes sleep can be a problem. So I bought a heavy, black knit hat, and, you know, I just put that on as my sleep hat, and then pulled the brim over my eyes, and so everything was black. So I — I could sleep fine down there.
Host: Oh, nice!
Dr. Duck Mittlefehldt:But the, you know, the main advantage is that because the sun’s up 24/7, you’re not really bound by the 9 to 5 time sequence.
Host: Oh, yeah.
Dr. Duck Mittlefehldt:So, as I said, when we — when I was out last year in the — in the recon site, we were there for a week, you know, we — we landed, got our gear, and then went, spent a half a day out, then the — the winds blew in, it was too windy and cold to go out, so the winds broke around noon one day, or a little bit after noon. We decided we would have an early supper and then go out and collect — harvest meteorites. So that day, we ended up getting out of the tents maybe 5 o’clock in the evening, and we worked about till 30, 2 in the morning.
Host: Woah!
Dr. Duck Mittlefehldt:The sun was up, it was perfectly fine, it was just my age and body crapping out at 30 [Gary laughing]. I, you know, I just couldn’t pick up another meteorite if — if they beat me with a stick. You know, I was just so tired. But then, you know, that’s — that’s something you can do down there that you can’t do here.
Host: Yeah, did you know the hours were going by, or did you have no sense of time with the — with the sun being up?
Dr. Duck Mittlefehldt:Well, you know, you can trace the sun, if you pay attention, you can get a sense of the day, because the sun does a lazy loop in the sky, and…
Host: Oh.
Dr. Duck Mittlefehldt:…and so, you know, once you’ve located yourself, you know where north, south is, [pause] there is still north and south, even that close to the pole.
Host: Yeah.
Dr. Duck Mittlefehldt:But, you know, you know at midnight, the sun is going to be, you know — you know, at one — at the one position, so.
Host: Right.
Dr. Duck Mittlefehldt:And it’s kind of at the lowest point far north, and so, you know, you can track it that way, but basically I didn’t pay attention. We were just so busy, you know, driving from place to place harvesting meteorites that, you know, it was just constantly moving, doing the next one, taking the data, collecting it, you know, cleanly and safely and getting it in the bag and moving on to the next location.
Host: Oh, so are you — are you not — you’re not stationary then when you — when you kind of set up camp. Are you — are you kind of mobile, like with your camp, and you just move it from one meteorite site?
Dr. Duck Mittlefehldt:No, no.
Host: Oh, okay.
Dr. Duck Mittlefehldt:The camp is usually — there are a couple — there are a couple of ways that it is done. When we do systematic searching, the camp is stationary in one spot, perhaps for the whole field season, and you just go out, day-to-day, to different locations. And that’s what we did here. We were on recon, so we — we plunked the tent down, then we searched within easy skidoo range of the camp. Sometimes, and I’ve done this before, go down on a recon time, where — where you go and you put camp down, you might prospect an area for two, three weeks, then you move camp to another area and prospect there for two or three weeks. So, there — there are — those — there are those two types of scenarios, and even in the recon mode, you know, you’re — the tent — the camp is stationary for two or three weeks, and you’re skidooing all around that area to — to search it, and then you only pick up tents and camp and move to a far distant area to recon that general region.
Host: Alright! Alright, well I’m guessing, you know, going down there so many times, you’re quite an expert in making sure that, you know, you can survive weeks and weeks and weeks in Antarctica. So, what are the — some of the stuff that you’re taking down there that I guess are unique to the Antarctic environment?
Dr. Duck Mittlefehldt:Okay, so, most of the gear you get, you get in Christchurch, so, you know, living in Houston, I don’t have a winter coat.
Host: Oh!
Dr. Duck Mittlefehldt:So, at — at the clothing distribution center in Christchurch, you’ll get outkitted — outfitted with, you know, heavy — heavy jackets, all the gloves you can want, thermal pants, fleece liners, boots, hats, everything you need to survive, and then in McMurdo Station, you actually get the camping gear, the tents, the cook stoves, the dishes, the food, sleeping bags, that sort of stuff. So all — all the intrepid Antarctic explorer needs to take down with them are personal items, like I mentioned my knit hat, that — that was mine, and that was because I knew I wanted something to sleep in. I, you know, I bought extra pairs of thermal underwear, because the first time I went down, you know, they — they give you two sets, but you’re out in the field for six or seven weeks, so you want to change, you know, once in a while. [Gary laughing] Other than that, you know, my glasses are prescription, and so I buy glasses that transition dark and sunlight, so I can just, you know, wear my normal glasses out on the skidoo, I have actually bought glacier glasses, so I have side shields and whatnot to block the light.
You want to — one of the things that really is critical down there is to block all light from your eyeballs, you know, other than what gets filtered through a dark lens, because, otherwise, snow blindness is a problem.
Host: Oh, that’s right! It’s so bright down there, right? Yeah.
Dr. Duck Mittlefehldt:So I do that, but, otherwise, you know, most of the gear they give you, they loan it to you for the time that you’re out there, and — and so, you know, you could survive on just what you get from the Antarctic program down in Antarctica. It wouldn’t necessarily be entirely comfortable wearing the same clothes, you know, for seven weeks, but you could do it.
Host: [Laughing] So — so your — this Antarctic program, that — that’s ANSMET, right?
Dr. Duck Mittlefehldt:Right.
Host: Okay, so what’s the — what’s the relationship between ANSMET and NASA, and how that all works together?
Dr. Duck Mittlefehldt:Well, originally, ANSMET was set up as a three agency agreement. So the — the — it was funded — the actual Antarctic search for meteorites was funded through the National Science Foundation, because they have — they do the scientific research in Antarctica. NASA funded the curation and allocation of meteorite samples here at NASA Johnson Space Center, and then the Smithsonian Institution did the initial classification and was the long-term repository for the meteorites collected in Antarctica. That, since — since then, they’ve changed it, and now NASA actually funds the Antarctic, the ANSMET research component. NSF still supplies the logistics, but NASA pays NSF for those, those logistics, because they — they are the, I mean, they have all the logistics in Antarctica.
And — and the rocks still go, ultimately, to the Smithsonian, a chip for initial classification, and rocks that are no longer actively being researched by scientists in the world end up being permanently curated at the Smithsonian Institution. So that is — that is still the way things are run.
Host: Alright. So — so is the ones that people are researching, and actively studying, are all of them housed here at the Johnson Space Center?
Dr. Duck Mittlefehldt:Yes. With some exceptions. We don’t have the necessary facilities to easily deal with metal-rich meteorites. So iron meteorites, stony iron meteorites, automatically go, ah, nope, I’m going to pull that back. Iron meteorites automatically go to the Smithsonian Institution. Because they are equipped for — to cut metal and — and make samples available. We do do the stony meteorites here, I forgot about that, because I’ve gotten some from here. So those that have a significant stony component are still worked on here until they become no longer of scientific interest. But, you know, even though they go to the Smithsonian for permanent curation, they’re — they’re not dead to science, so to speak. So I can request samples that have been housed at Johnson Space Center for years, and now transfer — transformed permanently to the Smithsonian if — if I find, you know, an interesting project to do on one of these old samples.
And I actually have gotten, in the past, some samples from the Smithsonian that were originally from the Antarctic collection.
Host: Wow. So back in Antarctica, when you’re looking at these meteorites and you’re trying to, you know, figure out what they are, are they, you know, more stony, more metal-rich, what are you using to — to look at them, to find out more about them and say, yes, that’s a meteorite that I want to get my hands on? How do you know what’s the good stuff?
Dr. Duck Mittlefehldt:Uh, decades of experience.
Host: There you go [laughing].
Dr. Duck Mittlefehldt:So, I, you know, I can look at a rock in Antarctica, and I can already make a preliminary classification. Sometimes I’m wrong, and — and, you know, the guy who has more experience than anyone is — is our mountaineer field safety officer, John Scott, and, you know, he — he can look at a rock, and, in many cases, give a pretty good guess as to what it’s going to turn out to be. And, you know, I can do that with a lot of different types of rocks, especially those that I’m interested in, but all in all, there — there are always those meteorites that come back that either no one has ever seen before, because it’s totally new, or it’s enough different from the norm for that class that it just doesn’t — doesn’t appear to be what you think it is, in hand sample. So, and we don’t — and we don’t, you know, in Antarctica, we don’t do anymore than a very high-level classification.
Yes, this is a stony meteorite, it’s probably a chondrite, this is probably a carbonaceous chondrite, this is probably an achondrite, which is a type of meteorite that’s been melted. This is probably a stony iron, an iron, and so forth. And, to some extent, we need to do that because certain types of meteorites have more scientific value than others. So — so, for example, a very primitive carbonaceous chondrite is — is probably going to get a lot of research attention when it’s announced. And so we collect those in a special way to try and minimize contamination by organic compounds. And that’s why we need to be able to say, oh, yeah, you know, stand back from this guy, we need to treat him differently than — than this one over here.
Host: Alright. And then, obviously, you know, knowing where to ship it too, right? Because some of the metals one have to go the Smithsonian…?
Dr. Duck Mittlefehldt:So that — no, that’s all done here. Everything is shipped here to Johnson Space Center.
Host: Oh, everything comes here, okay.
Dr. Duck Mittlefehldt:And — but the difference is when they — when they open some that are listed in the — in the notes as probably being iron meteorites, they — they will warm them up in the dry nitrogen cabinets, look at them, and if they agree, you know, they’ll do an external description, you know, this is a brown rock, you know, 10 centimeters in size and weigh so much, and we don’t see anything in it, you know, out of the ordinary, from the outside, then the whole thing will — then that whole rock will get shipped to the Smithsonian at that point, and there, they’ll cut it open with a wire saw, if it’s, you know, indeed, probably metal, and then make a polished mount and etch it to bring out the texture and so forth.
Host: Alright! And then that’s what you mean by the facilities, right? They have the — the proper facilities to do that. So what about here? What kinds of equipment and facilities do we have to make sure that we’re handling all of this properly?
Dr. Duck Mittlefehldt:So, in the meteorite processing lab, we have [pause] — we use tools of a very limited set of composition. So, typically, stainless steel hammers and chisels, and — and the reason is, you know, no matter what we do with a rock from space, we’re going to contaminate with something from earth. So the object is to, one, minimize that contamination. So we use materials that we know are not going to, you know, just shed particles everywhere, for example, but also if we — we use always the tools of the same — of a given composition so that we know that if we see something like this in the rock, oh yeah, that must have come from the tool. And, you know, I’ve seen this, rocks are hard to break, and so, you know, your — your choices are to saw them open or to use a hammer and chisel, and I have seen on a rock that I’ve gotten, a flake from the chisel that rubbed off.
Metal, you know, it’s soft, even hardened steel will rub off on occasion. So, you know, I can see this, I can pull that contaminant off or isolate it, in the lab, but, you know, I know then I can do a simple test, yes, that’s from the chisel, I don’t have to worry about that. I’ve taken care of it, the rest of the sample is fine. So the object is to minimize contamination or to know what the potential contaminants are. And, you know, there’s no way you know of getting — there’s — with modern technology, we can’t, you know, we don’t have magnetic levitation devices that we then use a laser to slice them open cleanly. You know, we — we do with what we got. This isn’t Star Trek here yet.
Host: [Laughing] We’ll just stick with the hammer and chisel for now. So, I mean, when you’re cutting these open, and you open them up, what — what are you looking at? Are you looking at just the rock or are you taking even smaller chunks of that? How is that working?
Dr. Duck Mittlefehldt:Well, that all depends on the question that you’re trying to answer, and I’ve done both where I’ve asked for samples of a, what’s called a bulk sample of the rock, so something as representative of the entire rock as possible, and I’ve looked for individual class in the rock, little fragments that are of a specific type within the rock. All of this is basic 19th century geology, in many respects. You know, in the 19th century, geologists would go out in the field with their hammers, they’d — they’d beat on a rock and use a hands lens to look at the microscopic, yeah, microscopic texture, mineralogy in it, and, you know, a trained geologist can do the same with a meteorite, and say, yeah, okay, I can see — I can see what this is, it’s a certain type of rock type in there, and that’s what I want, I don’t want this part over here. So, you know, the traditional geologic methods,but with modern equipment, can be used, and — and, you know, there’s — there’s nothing like the human eye in the brain for sorting out who’s who in the zoo.
Host: [Laughing] So then how can you — what — what are some of the key differences for the — for the non-geologically-trained eye for whenever you’re looking at a rock and you can, you know, you cut it open and you look and you say, that’s a meteorite, that’s not from earth? Or, this is definitely from earth?
Dr. Duck Mittlefehldt:Okay, the — the first key is — – is fusion crust. I mentioned this earlier.
Host: Oh yeah.
Dr. Duck Mittlefehldt:And that — that’s where, going through the atmosphere, friction with the air causes the outer surface to melt, and actually, you know, little bits are flying off all the time, the meteorite we get on the surface is just a small piece of what entered the atmosphere. Most — sometimes the vast majority of it just ablated away in the atmosphere into little droplets or dust.
Host: Wow.
Dr. Duck Mittlefehldt:So, you know, if you see a fusion crust on the rock, right away, you know it’s — it’s a meteorite, you don’t have to go any farther than that. In terms of determining what type it is, more primitive meteorites, these are a type that still have textures and mineralogy that were inherited from condensation and accretion in the solar nebula, that’s where individual mineral grains formed out of a gas that — that was the nebula before the planets were around. And — and then they glomerate together, these mineral grains, and in the — in the solar nebula, the dust grains banged, you know, got melted into little, tiny objects which we call chondrules. So, these typical textures are plainly evident to the human eye, even without a microscope. But, you know, with a very low-power microscope you can see them quite easily.
Most meteorites, especially primitive ones, contain iron metal, it’s actually iron nickel metal. You know, you don’t find that on earth except when humans have been involved in — in smelting iron ore. But so iron metal in a — in a rock is kind of an indicator that it’s quite likely from outer space. Very few occurrences on earth of native metal in a rock. And then, as I said, in the dust in the solar nebula, went through periods of melting and formation of these little, round globules of basically melt globules, which we call chondrules, and — and from that, we get the name chondrite for these primitive rocks. Well, those stand out in, you know, if you break open a rock, depending on — on the type, you know, you can see those quite easily, and — and that’s a key.
Host: And these have never — they’ve been in space for all of time, right? They were formed in space and traveling through space, they’ve never — they’re not like from another planet or another, like, chipped off another…?
Dr. Duck Mittlefehldt:Well, most…no, actually, all meteorites, the only way we get meteorites is for bad things to happen in the asteroid belt. Most meteorites are from asteroids, and when they collide, little fragments get knocked off, and it’s — it’s from these fragments that we get meteorites. So they were originally on much larger bodies, I mean, much larger meaning asteroid size, not planet size.
Host: Okay.
Dr. Duck Mittlefehldt:And they were broken up and then distributed to the earth. You know, one of the, sorry, I’m going to — I’m going to sort of go back into — and get into my way back machine and go back to when I was a grad student.
Host: Please do!
Dr. Duck Mittlefehldt:When I — you know, when I first started learning about meteorites, one of the mysteries at the time was there was a group of chondrite meteorites called the L chondrites, L was just the name, you know, the — the name applied to them. That had ages on the order of 500 million years, and this was really odd, because all meteorites are about four and a half billion years old. Well these, they — they — these meteorites were originally about four and a half million — billion years old, but were somehow affected by an event that reset the ages about 500 million years ago.
Host: Woah.
Dr. Duck Mittlefehldt:And so, you know, this was, you know, just kind of an anomaly. We knew something bad had happened to an asteroid then, about that time, well, fast forward to, I think the 90’s, a Swedish geologist started finding in terrestrial sediments fossil meteorites. And, you know, all that’s left is a few mineral grains. You — you can tell, they were found in fine grain limestone, you know, formed on an ocean floor, and all that you could see was this halo of odd stuff, please a few mineral grains that remained from the original meteorite. Well, you know, this guy, and his compadres, studied these mineral grains and they — they found out they were from the same type of meteorite as these chondrites that were about 500 million years old, and they were in layers in the rock of the earth that were about that age. So, sometime, 500 million years ago, you know, a couple of asteroids collided, and a whole rain of meteorites of this type hit the earth at about, you know, within a few million years when that occurred, and we can find them now.
This layer in Sweden that’s just chock full of these fossil meteorites. And, you know, to me, that’s one of these really neat kind of science stories. Where everything starts tying together. And then to get even further, astronomers looking at what they call asteroid families, so they — they find an asteroid, they find a whole bunch in orbits similar to it, spectroscopically, they all look to be about the same, and so they — they figure out, well, these are all, you know, fragments of something that broke apart. Well, they found an asteroid that they figure, you know, based on the spectroscopy, it could be this type of, you know, that formed these L chondrites, and the — they calculate the age of the family based on dispersion of the fragments, and it’s about 500 million years. So, you know, between, you know, meteorite scientists, terrestrial geologists, and astronomers, we — we’ve kind of got a neat picture of somehow, you know, about the time of dawn of — of multicellular life on earth, two asteroids smashed together, and rained down on the earth, and we’re still finding fragments coming down to earth now that we can confidently date when this happened in terrestrial laboratories.
It’s just kind of one of these things that, you know, I find fascinating!
Host: [Laughing] I find it — I mean, a lot of this is over my head, because I don’t have the same background as you, but I just find it fascinating that you can look at these rocks and — and get a story, get a story out of it, you know? Like the story of two asteroids around the time that cellular life was developing coming down to earth and raining down in these locations and telling their story, that’s fantastic!
Dr. Duck Mittlefehldt:Yeah, and multicellular. So this is when…
Host: Multicellular.
Dr. Duck Mittlefehldt:This is when, you know, fossils, shortly after the time when fossils started becoming really abundant in the terrestrial record.
Host: Wow.
Dr. Duck Mittlefehldt:So, yeah, it’s just a neat story, and, you know, basically I think that’s what got me into geology, originally, was, you know, all you’ve got is — is a rock on the surface and somehow you can, you know, if you’re smart enough and — and do the right work, you can start to piece together an entire story of what the earth was like at that time, and so, you know, that’s kind of what drew me into geology.
Host: That’s fantastic. I love it! Especially from — from my background, marketing and journalistic sort of background, the story telling aspect is just fascinating to me. And that’s kind of like, that, you know, the title of this episode is going to be, Infamous Meteorites, and that’s kind of like what I really wanted to dive into is, you know, we’ve talked about where you’re finding these meteorites, and then what you’re doing with then, you’re actually cracking them open and studying them, but then what are you finding? What are you finding inside of these meteorites? What stories?
Dr. Duck Mittlefehldt:Yeah. Well, exactly!
Host: Yeah, so, you know, one of the ones that I know that was brought to my attention was one of them called Allan Hills, and — I’m going to — is it 84001, or do you call it by something else?
Dr. Duck Mittlefehldt:No, I call it that.
Host: 84001? Okay.
Dr. Duck Mittlefehldt:Sometimes it’s simply referred to as that rock.
Host: [Laughing] Because it’s that infamous, huh? Wow! Alright, so what’s the story behind — behind this rock?
Dr. Duck Mittlefehldt:Okay, so, this came — this was found in Antarctica in 1984. And it — it’s [pause] — it was originally classified as a — as a type of asteroidal igneous rock that I, at the time, I was studying those — those types of rocks. You know, my — my background is heavily-weighted towards an interest in magnetic processes on the earth, the moon, Mars, and asteroids, and — and so that’s why this one was particularly of interest to me. So, I was studying that, along with a bunch of others, that were thought to be basically the same classification of rock, and, unfortunately, Allan Hill’s had some puzzling features in it that were — were a little bit off normal for — for that rock type. But not so much so that I — I really stayed up at night worrying about it.
Host: [Gary laughing]
Dr. Duck Mittlefehldt:And so I wrote a paper on — on this group of rocks, finally, and sent it in, and one of the reviewers said, well, you know, you point out that there’s this anomaly in this rock, and you really ought to try and chase down why it’s — what’s going on there, why it’s different. And, you know, being a — a moderately good scientist, I said, okay. I, you know, he has pointed out, it’s a problem, I knew it was a problem, but now I’ve really got to do something about it. So I started working at it, and, honestly, I — I could not find out what was wrong with this particular rock. It — it — there was one mineral phase in it just did not match what anyone would expect for the class. Quite by chance, I got another sample of that rock for another reason.
And but it really wasn’t the sample I had asked for. So there was as mixup in the thin section. So a thin section is a very thin slice of a rock, it’s about 30 microns thick, doubly polished on both sides, and it’s used by people who look through microscopes to look at the minerals and textures in a rock, and then you can put that section into an electron microprobe and actually do analyses of the mineral phases in it.
Host: Wow.
Dr. Duck Mittlefehldt:And so I was — that’s what I was interested in. And this particular rock, which I thought I had, I was interested in the composition of sulfide phases in the rock. So I put the sample in the electron microprobe without actually looking at it in the microscope first, because I had seen this rock before, I knew what it was like, I knew what to expect, I just went straight to the electron microprobe, which actually probably was good because I may have turned the rock in and asked for a different one otherwise. But I’m getting — I’m looking at it in the microprobe, looking for the mineral phases I’m looking for, and they just really aren’t there in the abundance that I expected. Finally I found a grain and I’m — I’m banging at it with the electron beam, collecting compositions, and the compositions weren’t making sense. I was expecting it to be, so I was looking for sulfide phases, so I was expecting to have iron monosulfide, so one iron, one sulfur atom, and the composition that was coming out just was not right.
And I checked the calibration, the calibration was perfect, so what’s going on? I was looking at the data, not in atoms, but in mass, so weight percent. So when I converted it to atoms, I realized I had two sulfur atoms for every iron atom instead of one, and that’s when it hit me what was wrong with this rock. I then backed off, looked at the — looked at the texture in more detail in the electron microprobe, and realized I had a sample of Allan Hill’s, not the meteorite that I thought I had, and I knew which type of rocks had pyrate, the iron disulfide, instead of the iron monosulfide, and I knew those were martian rocks. And so, you know, it was — it was probably the most satisfying moment I’ve ever had in my life, excluding when my children were born, and — and when I got married [Gary laughing], and if my wife listens to this, I hope she hears that, was, you know, suddenly it dawned on me that this was a martian rock that was totally unlike any other martian rock, except the key minerals were in it, and so, you know, it was just one of these aha moments that — that you live for.
And, you know, it was just so much fun.
Host: Amazing.
Dr. Duck Mittlefehldt:I tell you.
Host: So what were those — the key minerals? What — what story did they tell?
Dr. Duck Mittlefehldt:So the key was because it had the iron disulfide pyrate instead of the iron monosulfide troite, I knew it was martian, and it was a rock type not known amongst the martian meteorites. So what it meant was we had a new type of martian rock that was going to tell us even more about the geologic evolution of Mars then we already knew. And, you know, all of this hit me within like a fraction of a second when I realized what it was.
Host: Wow!
Dr. Duck Mittlefehldt:So, I mean, I immediately recognized it, it was an, you know, important meteorite. And that it would tell us big things, and, in fact, you know, it has opened up a whole host of, you know, basically this rock ultimately became a founding member of what you might consider astrobiology, and that came when my colleagues here at Johnson Space Center, Dave McKay, Edward Gibson, and Kathie Thomas and now Simon Clemett is at it, and then there were Simon’s dissertation advisors, Stanford was on the paper and several other people, you know, they — they proposed that a certain both mineralogical and compositional and textural objects in this rock were possibly signs of microscopic life that existed on Mars at one point.
Host: Wow.
Dr. Duck Mittlefehldt:And, you know, to some extent, then this really allowed the whole discipline of astrobiology to blossom because suddenly we had to figure out, you know, what — how do we understand, how can we possibly search for life and other objects, other planets, you know, what do we need to look for? Because we’re used to looking for life on earth, you know, it’s — it’s simple. Just walking over here, I, you know, I had to wait while an opossum walked past me in front of, on the walkway. You know, life is everywhere on earth, whereas on Mars, you know, maybe it’s not everywhere, and if it was there, how are we going to tell that it was there? What — what do we need to do? So I would say the import of Allan Hill’s not so much that it was hypothesized that life — fossils of life are in that rock, but that it caused scientists to really take a much more rigorous look at how they will search for life other places of the universe.
Host: Wow. And that’s — that’s kind of, you know, like you said, the birth, maybe not the birth, but really the blossoming, and that was the word you used of, of astrobiology, life forming outside of earth. That’s just a wild concept. How is that even possible?
Dr. Duck Mittlefehldt:Yeah, and, you know, the other thing is it did, it was a strong impetus to driving NASA’s Mars exploration program, you know, it is — – a lot of it is geared towards finding evidence for habitability locations on Mars, and, ultimately, you know, from locations where we think there may have been a chance for life, you know, bringing back or — or studying in situ samples for possible evidence of microbial or — or larger life on Mars.
Host: Yeah, and you said you were, before we started recording, you said you actually were working with Opportunity too, one of the rovers on Mars.
Dr. Duck Mittlefehldt:Yeah. I, in 2005, I got attached to the Mars Exploration Rover mission. At the time, we had two rovers going, one Spirit in Gusev Crater, and the other, Opportunity, in Meridiani Planum. Subsequently, Spirit froze to death one winter. Basically, so Spirit lost mobility of one of its wheels, so we were driving backwards, dragging one of the front wheels like a boat anchor through the soil…
Host: Oh, man.
Dr. Duck Mittlefehldt:And we, you know, the Rover drivers and scientists are very careful. We drove over an area that looked like it was going to be solid, trafficable ground, but it turned out there was a basically a hardpan; layer on top of soil hardpan is kind of an indurated layer that’s a little bit stiffer, so it didn’t look like it was, you know, loose sand, but it turns out we broke through and got mired in a deep sandpit, basically, and we were unable to extract the rover from the sand, in spite of heroic efforts by the engineers, the Rover drivers at JPL, and the solar panel was tilted at a bad angle for, you know, the oncoming winter sun. So when the sun started getting lower and lower, relative to the tile of the — of the solar panel, we — we simply were not getting enough power to keep the rover going and although we tried to contact it again after that winter, we never heard from it again, so it basically just froze to death on Mars.
Host: Oh, man, but is Opportunity its twin? Is it the…
Dr. Duck Mittlefehldt:Yep, Opportunity is it’s twin.
Host: And that one’s still going, right?
Dr. Duck Mittlefehldt:And that one’s still going. We’re now so — we’re not — what day is today?
Host: The 8th.
Yeah, we’re now about two weeks away from the anniversary, the 16the anniversary of landing on Mars for Opportunity.
Host: 14 years? Wow!
Dr. Duck Mittlefehldt:It’s still going strong, and we are still actively exploring the geology of Meridiani Planum. We don’t have all the instruments we had when we landed, but we’re still making great scientific discoveries, even with the limited rover ability.
Host: How about that? So how is — how was, you know, working with a rover on Mars different from looking at meteorites? Maybe even martian meteorites, like the Allan Hills, here on earth? How is that different?
Well, so, you know, here on earth, I have the luxury of taking a sample into the lab and — and using state-of-the-art scientific equipment to — to tease out, tease out its story. On Mars, we have cameras that we can use to image the terrain. So right away, textures, and we have a microscopic camera, so textures allow us to, you know, make inferences about what the rock — how the rock might have been formed. We have a camera with 13 color filters on it, so we can do some limited spectroscopy of the rock that helps us compare a limited set of mineralogical variations in the rocks, and then we have the alpha particle x-ray spectrometer, which allows us to do bulk compositions of surfaces. So, between them, we — we can — we can get a fairly good handle of the mineral — well, mostly the textures and bulk composition, and, to some extent, neurology of a rock, and that helps us understand what processes might have formed the rock altogether.
And, you know, to some extent, where Opportunity is a high-tech version of a 19th century terrestrial geologist. [Gary laughing] But, you know, the, obviously the spectrometer is better than what they had in the 19th century, and the chemical composition is as — as good as we could do then and actually better for many elements, but we’re still not at the cutting edge, as you — as you could do if you had a, you know, a mobile laboratory up on Mars.
Host: Yeah, definitely. And that’s kind of your — your trade-off, right? Is like, here, you know, you can bring into a lab with all the latest equipment and — and study these meteorites, but, like you said before, like there’s a certain amount of contamination that’s going on with just the fact that a meteorite has come through the atmosphere and hit the — hit the — surface of the earth, you know, you have to deal with that, but then you have limited instruments right there on — on Mars. So, I guess you just kind of have these tradeoffs [laughing].
Dr. Duck Mittlefehldt:Yep.
Host: So another one that you mentioned, another infamous meteorite, was one called Orgueil, and that’s one — that one’s much earlier than the Allan Hills one, right?
Dr. Duck Mittlefehldt:So Orgueil fell in France in 1864, if I — if I remember right, and what’s key here is it’s a — it’s a very primitive type of meteorite. It’s a carbonaceous chondrite. The — the two letter name for it is a CI carbonate — chondrite. These are amongst the most primitive materials, primitive meteorites that we have for study. They’re bulk compositions, basically are identical to what we see for the photosphere of the sun, excluding the most volatile elements like — like helium, hydrogen, and oxygen and so forth, but if you could take the sun, you know, a cubic kilometer of the sun and condense out all the condensable matter, it would — the composition would be very much like a carbonaceous, CI carbonaceous chondrite. So, these have always been the touchstone for understanding the chemical evolution of the solar system. They are our — our basis for seeing who has varied from the original composition.
But they’re highly-altered, so they are almost completely made up of clays and other low-temperature alteration phases. So the original high-temperature phases have been replaced. So, at some point, these things were altered by water in their parent asteroid to the point where all that’s left is — is basically clay. This makes them [sigh] — this made Orgueil susceptible to nefarious individual, tempting to prove something, what don’t know, because we don’t know who that individual was, but, you know, I would call Orgueil the Piltdown Man of meteorites. So Piltdown Man was — was this fake fossil made in about 1912 I think to look like it had some of the attributes of an ape, but some of the attributes of a modern human, because someone that that’s the way human evolution went, and they wanted to show that we had fossils that fit in within that theory.
Well, Orgueil, at some point, was broken open, and it turns out, because this is clay, you can — if you get it good and wet, you can kind of break it open like clay, and then they had stuffed in terrestrial seeds and plant fragments and coal, and then put it back together, and coated the outside with glue to make it look like it still had the fusion crust on it.
Host: Oh my gosh!
Dr. Duck Mittlefehldt:And then this sample was sealed in a bell jar in a museum from 1864, so apparently it happened very early, we don’t know who did it, or why, you know, what were they trying to accomplish by this? Because it was going to be sealed in a bell jar, you know, did they think someone was going to then take it out and look at it, I don’t know, but this — this came to light in 1960’s then.
Host: Oh!
Dr. Duck Mittlefehldt:And so, a well-known meteoriticist, by the name of Ed Anders, very famous, very smart man, he led a study that was published 100 years later, in 1964 in science, where he uncovered, you know, all of this forensic meteoritic work where he showed that, you know, the seeds were, you know, terrestrial seeds, the coal fragments were in there, that glue had been used to put it back together and make it look like it was whole, and — and all of this, and — and so that’s why, you know, this is an infamous — infamous meteorite for those who are in the know. Most people won’t have heard of it, but, you know, like I said, it’s kind of the Piltdown Man of meteoritics.
Host: Wow!
Dr. Duck Mittlefehldt:So someone had an agenda, they wanted — they, for some reason, they wanted to show that life could form on an asteroid or — or in space, or something, I don’t know, but, obviously, they had — they had some agenda when they did this.
Host: Yeah, I know, but seeds and glue are not really a good way to convince people [laughter].
Dr. Duck Mittlefehldt:
No. You know, back in the, you know, mid-19th century, you know, had it been opened up and studied then, maybe it would have caused quite a furor, but, as far as I know, this was only discovered in, you know, a century later.
Host: Wow! A hundred years of people thinking this is some kind of like capsule of extraterrestrial life, how about that? So, you know, all of these kind of tell a story and, unfortunately, some of them, this [laughing] — this particular one is a little bit of a lie, but, you know, we are cracking these open to search for evidence of — of whatever we can find, right? Maybe — maybe the formation of a planet, maybe the formation of solar system, maybe the formation of life. So, you know, what, in a perfect world, I guess, what would you like to do — what would you like to study? What would you like to see and do to really maximize what you can find about learning more about our solar system and about life in the universe
Dr. Duck Mittlefehldt:Well, I mean, that — that’s kind of a difficult question for a scientist to answer, because, you know, truth be told, we’re all paid to pursue our hobbies, and so we all have our own hobby horses. So, as I — as I mentioned, you know, my particular interests are in igneous processes, I, you know, on the earth, moon, Mars, asteroids, I — I like magmatic rocks, and, you know, I couldn’t tell you why, it’s just the way I am [Gary laughing]. So, one of the things — one of the things that’s very curious about asteroidal igneous rocks is that asteroids were melted very early in the solar system, probably within a couple million years of the formation of the earliest-known solids in the solar system. So something had to heat up relatively small objects, maybe a few hundred kilometers, you know, 200 miles in — or in radius, something like that, to the point where they were melted and then cooled down and then they completely shut off after that.
So, it was a very, very intense heat source that acted early, died out, and then never came back. You know, we think we know what — what caused this, but there, you know, and so the — the leading contender is radioactive heating by a very short-lived isotope of aluminum. It has a half-life of about 730 million years, and so, and aluminum is a — is a major element in rocks, so, if you — if you accumulate an asteroid early enough, when there’s this aluminum-27 still alive, you’ve, you know, — you’ve then encapsulated a very potent heat source inside that rock. And so that’s what we think happened, but, still, you know, we can admit, as scientists, we can imagine this process going on, but geology is always much more complicated than our imaginations. So there are things that I don’t understand, things that, as far as I know, no one really understands about how asteroids went from being primitive objects that accumulated from minerals formed in the solar nebula to basically a molten ball that then crystallized out igneous magmatic rocks, similar to what we see on earth.
I would desperately like to get, you know, be able to find out more about how — what was going on, you know, what have we missed, because we, you know, we tend to think of things in — in the simplest terms, you know, it was heated up, melted, crystallized, that’s it, well, we know that — that’s not all the story.
Host: Yeah.
Dr. Duck Mittlefehldt:And I think all meteoriticists have, in the back of their minds, for their particular hobby horses, just things they don’t quite understand. They know the — the broader picture, but what are the finer details that went into — to this. We — we know we’ve got the basic story, but what are, you know, all the chapter and verse that go into this basic story?
Host: Wow.
Dr. Duck Mittlefehldt:So, you know, that’s what drives me, and it’s all — it’s all a matter of, you know, learning something new that — that, you know, pushes forth human knowledge. You know, what I do is — is nowhere near applied science. It’s pure basic science. So I can’t — I can’t talk to someone and say, you know, tomorrow, you’re going to be able to have a better life because of what I do, only if, you know, unless you think a better life means knowing more [Gary laughing]. But you never know, because, in — in general, a large fraction of basic research ultimately does find an application. Right now, I don’t know what that application might be, but I won’t say there’s never going to be some application for what I do, but, for me, it’s — it’s this sense of learning something that — that drives me.
Host: Yeah. Why learn if you don’t think it’s going to end up, you know, giving you a better life. I mean, honestly, like, you know, learning things kind of helps you understand things, helps things come together, to me, that makes me pretty happy. So I could see that, you know, better understanding, giving me a better life.
Dr. Duck Mittlefehldt:Yeah, well, I mean, you know, humans have always been curious, and, you know, I suspect the reason we’re curious is because it’s beneficial for survival, because, you know, when — when you’re out on the savannah hunting lions, or hunting gazelles, if you see something moving the weeds over there, you know, okay, is that a gazelle or is that a lion about to eat me instead? So, you know, humans are geared to being curious about their environment, because it’s a survival mechanism.
Host: Yeah.
Dr. Duck Mittlefehldt:And, for scientists, we have now transposed that, you know, away from worrying about whether we’re going to be eaten to just, you know, a broad knowledge in general.
Host: [Laughing] Well, I think last time we sat down with Dr. Burton, he said, he kept talking about this time machine, how easy it would be — how nice it would be to just kind of hop in a time machine, watch these processes take place, and be like, ah [snapping fingers], that’s how — that’s how it takes place. I mean, and then there’s whole philosophical idea of, well, is that going to alter the universe if you go back in time and watch these things? So, you know, that was another tangient we could have gone on and we didn’t, but [laughter], but it would be nice to, you know, for the, you know, to improve our knowledge a little bit of how all this stuff works and comes together. Alright, so, Duck, I think — I think that about wraps it up for today. So, thank you so much for coming on the podcast and kind of…
Dr. Duck Mittlefehldt:It’s been a pleasure. I hope I’ve imparted something that makes sense to the listeners and — and that they will find interesting.
Host: It’s actually you know, you know, we’re talking about rocks, if you think about it, but it’s absolutely fascinating, what you can found and the stories behind these rocks and what they tell you about the universe, and even just your trips to Antarctica are pretty fascinating as well, so, again, thanks so much for coming on and telling the stories of these beautiful rocks and your trips to Antarctica, and, yeah, hopefully we’ll — we’ll find some cool evidence of life or, you know, you’ll find that key ingredient as to why, you know, the asteroids did what they did.
Dr. Duck Mittlefehldt:Yeah, well, I hope so, and thank you very much for the invite!
Host: Absolutely.
[ Music & Radio Transmissions ]
Hey, thanks for sticking around. So, today, we talked with Dr. Duck Mittlefehldt about some of the cooler, infamous meteorites that have been discovered throughout the years, and then some interesting stories about Antarctica and how he’s finding them, it’s really a cool process, and he works with the ANSMET, it’s the Antarctic Search for Meteorites. So if you want to learn more about ANSMET and some of the adventures that are going on in Antarctica, and some of the curious findings in these meteorites, especially some that may or may not be life, it turns out there was some, you know, fake meteorites at the end of there, which is kind of disappointing, but that’s okay.
You can go to ares.jsc.nasa.gov to get the full scoop on all of these cool meteorites, and — and you can learn how to get your hands on one of these meteorite samples to study them. If you go to social media on the NASA Johnson Space Center accounts, or if you go to ARES, or astromaterials, NASA astromaterials, we got pages on Facebook, Twitter, and Instagram where we like to share these stories, just use the hashtag, ask NASA, on — on your favorite platform to submit an idea, or if you have a question about meteorites, or if you want to submit a new topic for the show, to make sure to mention it’s for, Houston, We Have A Podcast. So this podcast was recorded on January 8th, 2018. Thanks to Alex Perryman, Greg Wiseman, Tracy Calhoun, and Jenny Knots, and thanks again to Dr. Duck Mittlefehldt for coming on the show! We’ll be back next week!