November 7, 2019

E23 – Bonus Clip: Meteorite Hunting in Antarctica

Posted by Shane Hanlon

Nina Lanza is a member of a research team hunts for meteorites in Antarctica. In this bonus clip from Episode 23, Between a Varnished Rock and a Hard PlaceNina describes the remote location where they set up camp, being holed up while the howling katabatic winds battered her tent and her brain, and explains the strategies and techniques for searching for and collecting space rocks that are lost bits of asteroids and planets. Bottom line: the hardest part is getting there.

Transcript

Shane Hanlon:  Have you ever seen a shooting star?

Nanci Bompey: Yeah, I mean, haven’t you.

Shane Hanlon:  I don’t think so.

Nanci Bompey: What?

Shane Hanlon:  Yeah.

Nanci Bompey: You go to all these remote places in the middle of nowhere.

Shane Hanlon:  I think for me though it’s I, well I guess this is a bad excuse at night, the herpetologist in me, the critter person in me always looks down. So I’m actually real bad at looking up. I don’t appreciate things above me. I only appreciate things below me.

Shane Hanlon:  So we are back for a bonus episode.

Nanci Bompey: Yep.

Shane Hanlon:  And this reason why we’re talking about shooting stars. We chatted with Nina Lanza about her work finding meteorites and this is an addition to our most recent episode with her and Chris Yeager from the Los Alamos Laboratory.

Nina Lanza:       I was lucky enough to be a team member for the Antarctic Search for Meteorites project, that’s ANSMET. This is an NSF and NASA sponsored project to go out to Antarctica and recover meteoritic material. This project is amazing. It’s been going on for 40 years now, it’s actually older than I am, and they have recovered, as a team, over 60% of the known meteoritic material on earth. So it is incredibly bountiful. And what’s incredible about this project is that you can collect materials from all over the solar system without leaving home. You mentioned Martian meteorites, the first Martian meteorite to be identified as Martian was collected by ANSMET, and that’s true for the first Lunar meteorite as well. We knew what lunar rocks looked like from the Apollo missions.

Nina Lanza:       I think it was the 1982 ANSMET team was zipping around in Antarctica and they found this rock that looked just like a lunar rock, and there was no mistaking it because we had samples of lunar rock. No one could say that this was just something from Earth that looks weird. It definitely was lunar. Then the question was, “Well, how did it go here?” Previously, dynamicists thought, “No, it’s not possible to have a rock fall from one planet onto another. Just not possible.” Well, they had to go back to the drawing board to figure out how that was possible because here is a Moon rock right here on earth. This launched a whole reexamination of meteorites in collections all over the world to see, “Well, if there’s a lunar rock here, what else could be here?” And it turns out that there are actually Martian meteorites here as well.

Nina Lanza:       I don’t know what the count is exactly. It’s on the order of 150 or so. Many of those had been collected in Antarctica. And those are the only samples of Mars that we have in our hands. Right? It’s great to do robotic remote sensing missions, but there’s nothing like having a rock in your hand that you can do analysis on in the laboratory, and do different types of analyses depending on what you find in your first assessment. You know? So this is a really big deal to be able to have access to other planets without leaving home.

Larry O’Hanlon: How do you find meteorites in Antarctica? How do you do that?

Nina Lanza:       Yeah. Well it doesn’t take any special training or talent. You look for rocks, because it turns out that Antarctica is a big white sheet of ice. There are almost no Antarctic rocks when you’re not close to a mountain range. You have maybe two miles of ice, right? Any rock that’s on the surface that came from space. But Antarctica also has this really cool conveyor belt effect because it’s all entirely glaciated. You can imagine it this way, so snow is falling in the center of the continent, and as more snow falls on top of that, it gets compressed until eventually it turns into ice and that ice starts to flow under its own weight.

Nina Lanza:       The center of Antarctica is pretty high in elevation, and all the ice is flowing in all directions outward toward the sea. So any rock that falls into that snow will eventually get buried in ice and then carried by this glacier toward the sea. Now if nothing stops it, it’s just going to fall into the ocean and we lose that meteorite, but if we’re lucky, the ice will run into something like the Transantarctic Mountains and it will slow down or even stop. And then the very strong gravity driven winds in Antarctica will be able to scour that ice, and then uncover everything that’s ever been buried.

Nina Lanza:       So even though meteorites are not falling on Antarctica at a greater rate, right, you start seeing more meteorites being concentrated because you have all of the meteorites that have fallen in thousands of years will suddenly be exposed at the surface in the same place. So you can actually just drive around on your Skidoo and look for meteorites. There’s actually quite a few out there. Certainly there are also some Antarctic rocks that get embedded into the ice as well, and we call those meteor wrongs because you get really excited, just find a rock and then you’re like, “This is not a meteorite,” but in fact most of the material you see out there is meteoritic.

Nina Lanza:       So we typically will only look in places where blue ice is exposed. Blue ice is the most compressed ice. There’s not a lot of air in it and it hasn’t been exposed to melt. You can see blue ice from satellite images, so the ANSMET PIs will plan the field season beforehand by looking at the most recent satellite data to say, “Okay, here is exposed blue ice. We’re going to look here.” And one of the other things they try to do too is actually search these areas more than once to see what the recharge rate is. Right? So how quickly are meteorites being exposed. The area where I went, one of the areas that I went, in the Miller range we have actually searched something like seven times before, yet we still found more meteorites there.

Larry O’Hanlon: So you just have to go out… Is this very remote from other parts of Antarctica? You have to camp out there, I mean…

Nina Lanza:       It’s pretty remote, yeah. I think I was probably halfway between McMurdo Station, which is on the coast, and Pole Station, which is at the South pole. That is probably the definition of the middle of nowhere. We were in the middle of the Miller Range, which is part of the Transantarctic Mountains. It’s actually really close to the route where both Amundsen and Scott made their first trips to the South Pole, and that territory has not changed one bit in that time. It looks exactly the same, I’m pretty certain. So we were camping in Scott tents, the same tents that Scott used, these double-walled canvas tents just on the ice, and we lived there for five weeks.

Larry O’Hanlon: Wow. That’s quite a bit of time.

Nina Lanza:       Yeah, it’s way out there.

Larry O’Hanlon: Do you have to get airdrops or something for…

Nina Lanza:       We do. We are brought there by twin otters. We have to do multiple drops because twin otters are not that big, and we have to take eight Skidoos. Every person gets their own Skidoo, so you got to put those all in a plane. We do several drops, and the team goes out in sort of waves. The first four goes out, sets up the preliminary tent camp and then the rest of the team comes with the rest of the gear. But sometimes there is quite a bit of weather and that prevents the whole team from being there. That actually happened in my season. The four of us were dropped, we got our tent set up and we demonstrated that our stove worked and the pilots were like, “We’re out.” And then they didn’t come back for five days because there was a huge katabatic wind storm, that’s the gravity driven winds. The sky above was totally blue and clear, but the winds were so fast that it was just white out conditions on the ground.

Nina Lanza:       I had a little pocket anemometer so I could measure the winds at about 62 miles an hour, which is actually really hard to walk in, it turns out, just trying to get outside, and that’s not very high wind for Antarctica, it can actually be a lot worse.

Larry O’Hanlon: There’s not too many places to hide from that either, I imagine.

Nina Lanza:       You just hide in your tent and hope it doesn’t blow away.

Larry O’Hanlon: It must be loud too.

Nina Lanza:       It’s incredibly loud. It’s so loud. It sounds like, I mean your brain is trying to make sense of what this sound is. It really sounds like a freight train or an airplane landing right next to you. It sounds crazy. It’s so, so loud. And even just when it’s less loud, it makes weird sounds blowing over all the ice. It just, it doesn’t sound like wind that you… outside of Antarctica, you would never think of this as a wind sound.

Larry O’Hanlon: Now, for the meteorites, do you find them by eyesight?

Nina Lanza:       Yeah. You just, you look for the rocks first of all, and then meteorites often have particular characteristics that could help you identify them as extra-terrestrial. The biggest one is a fusion crust. That’s when a rock falls to the atmosphere, the very surface will get very heated and turn into something very glassy and dark often. So these are these dark, shiny… They kind of look in some ways like rock varnish, but a little bit more rainbow texture because they’re actually amorphous. So it’s sort of a glassy fusion crust. So that’s the first thing that you look for. Then you can also check to see, is this a magnetic rock? Most meteorites are magnetic if they are what are called chondritics. Chondritic meteorites have these little blebs of material in it, these little circular blebs and these are, chondrites are the type of meteorites that have never been incorporated into a planetary body.

Nina Lanza:       That’s the most common kind. They might be ordinary chondrites, but they’re not boring. They’re still very interesting. It’s about 85% of the material that’s going to fall on the earth is a chondritic meteorite. Those are very interesting to learn, what are the building blocks of planets, and what are the raw materials, but we get particularly excited when we have these achondritics, without chondrites, those typically are meteorites that have been, they’ve come from a planetary body that is differentiated. So that means it’s massive enough to have a core, like a metallic or heavier core, and then this more silica rich mantle. So something like the Earth, the Earth is a big enough planet, but you know also asteroids like Ceres, those are differentiated.

Nina Lanza:       We can tell that because they look a lot more like terrestrial rocks. You’ll see there’s a fusion crust, right? Because they’ve come through the atmosphere, but they won’t have those chondrules. They’ll just look like the regular old rock that you might step over if it weren’t for that fusion crest, and so that’s where we start finding the lunar meteorites, the Martian meteorites, the ones from Vesta. There are actually differentiated meteorites, and we don’t know where they came from. We have no idea. So there is some planet out there that has lost a piece of rock and we don’t know which one it is, but that tells us something about the variety of differentiated planets, and hopefully eventually we can make an identification.

Larry O’Hanlon: How can you tell the Martian meteorites from the others?

Nina Lanza:       By sight, it’s very challenging to say this one is Martian versus lunar or from Vesta. They could look very similar. It’s really in the chemistry, and in the details, and the mineralogy that tell you where these are from. The biggest indicator is the oxygen isotope ratio. It turns out that depending on where a planetary body formed, it will have a unique signature based on its distance from the sun. Actually earth and the moon have the same oxygen isotope ratio, and that’s actually because we formed from the same material. So there’s actually no difference there, but Mars is further out and so it actually has a different oxygen isotope ratio. That’s a big one. Another is that people have managed to take atmosphere out of these little voids in the rock, and analyzed it and it matches the Martian atmosphere exactly. And that’s another good example of, just a piece of evidence that says this is definitely Martian versus from somewhere else.

Larry O’Hanlon: I know Martian meteorites have been a source of controversy too, and you’re looking for life on Mars. Remember there was the famous one that had the little squiggly…

Nina Lanza:       Yes, ALH 840001.

Larry O’Hanlon: Yeah. Yeah, that went on for a long… I haven’t heard a lot about that one recently. Whatever happened with that?

Nina Lanza:       Well, that meteorite still exists. It’s in the curation collection at Johnson Space Center with the other Antarctic meteorites. That one is ALH, Allan Hills is where it was found. That was found by Anne Schmitt. It’s not a very big meteorite, it’s actually pretty small, but what was so exciting about it is that there were these little blebs of carbonate materials that some interpreted as potential cellular forms, right? So they look like little cells and they were made out of carbonate. I mean, that was really exciting because I mean, that is the first order, that is evidence of life, but of course a big claim requires big proof, and most of the community agreed that this is not big enough. It’s too ambiguous to say this is definitely from life.

Nina Lanza:       It tells us that we should keep looking and it tells us we should keep looking for things that are very specific, but the universe is a really big place and a lot of things can happen through chemistry alone. Amino acids are just floating in space. They’re not made by life as far as we know, right? So a lot of weird things can happen with chemistry, and we think that’s exactly what happened with this meteorite, this Martian meteorite, is that there’s something very interesting in there.

Nina Lanza:       I mean, I think what’s most exciting about it is that it shows that, I mean, there’s carbonates on Mars, there’s some right there, right? You can see it. They were not from Earth. It was not secondary alteration, right? So native carbonates to Mars. That tells us already that this is a very habitable environment. Carbonates disappear very quickly under acidic conditions. This means these fluids must have been pretty neutral to basic pH. It tells us there had to have been liquid water. I mean, so it’s actually not a bummer in the sense that, “Okay, we didn’t find the aliens,” but it’s telling us a lot about how habitable Mars really is. It’s just another piece of evidence.