Ep. 588: Lunar Resources: Lava Tubes

Posted on Dec 30, 2020 in Our Solar System, Planetary Science, podcast, Science, Solar System | 0 comments


Ep. 588: Lunar Resources: Lava Tubes

All eyes are on the Moon. We’re going back, this time to stay… right? One of the best resources on the Moon will be the lava tubes that crisscross the subsurface of the Moon. These can provide protection from space, and a look into the geologic history of the Moon. And they can be enormous.

Download MP3 | Show Notes | Transcript

Show Notes

VIDEO: Starship | SN8 | High-Altitude Flight Test

Lava Tubes (National Park Service)

Shield Volcanoes (Oregon State University)

Hawai’i Volcanoes (National Park Service)

Entire cities could fit inside the moon’s monstrous lava tubes (LiveScience)

How Volcanoes Work (San Diego State University)

Lava River Cave Interpretive Site (USDA Forest Service)

A’a Lava (Universe Today)

Pahoehoe (Oregon State University)

Sinuous Rilles (Oregon State University)

Possible Lava Tube Skylights Discovered Near the North Pole of the Moon (SETI Institute)

PIA13518: New Views of Lunar Pits (NASA JPL)

Will Future Lunar Bases Be Underground? (Scientific American)

Lunar Reconnaissance Orbiter (NASA)

All you need to know: 2020’s Geminid meteor shower (EarthSky)

Radioactive Moon (NASA)

Solar Minimum; Solar Maximum (NASA)

Lunar Fountain? Accessible Ice Could Lurk in Moon’s Lava Tubes (Space.com)

Water on Mars: discovery of three buried lakes intrigues scientists (Nature)

Google Lunar XPRIZE (XPRIZE)

Google Spurs Amazing Robot Race To The Moon (Fast Company)

What is CAVES? (ESA)

NASA Invests in Technology to Map the Moon and Mine Asteroids (Extreme Tech)

Shape-Changing Robots that Adapt to Their Environments (Yale University)

Bigelow’s Next-Generation Inflatable Space Habitat is Shooting for the Moon (The Verge)

What Is Terminal Velocity? (Universe Today)

Boring Machines for Deep Underground Lairs and Starting Underground Worlds (Next Big Future)

Transcript

Transcriptions provided by GMR Transcription Services

Fraser:                         Astronomy Cast Episode 588: Lava Tubes. Welcome to Astronomy Cast. Our weekly facts-based journey through the Cosmos where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey Pamela. How are you doing?

Dr. Pamela Gay:         I’m doing well. How are you doing?

Fraser:                         I’m doing good. We talked about this on the preshow. Just a reminder to everybody that we record these shows live every Friday at noon Pacific on YouTube. And the shows are an hour long. So, if you wanna see more of the witty banter between Pamela and myself, if you wanna see Pamela answer completely random questions from whoever’s watching the show, then you’re gonna want to watch that. And so, the big piece of news that happened this week was the Starship. And so, I think we spent about 20 minutes talking about Starship. But for those of you who missed it, SpaceX tested Starship and it was magnificent.

Dr. Pamela Gay:         Well, I’m still giggling. I don’t know when I’m going to stop giggling. But that was the kind of goodness and light I needed in my life.

Fraser:                         Yeah. It was a beautiful test. Every part of it went way beyond my expectations. The part where it failed, where it crashed on the landing pad was the part that surprised me –

Dr. Pamela Gay:         Yeah.

Fraser:                         – because I thought that the landing was the part that SpaceX had nailed. But all the other parts were all brand new, all worked perfectly according to plan. So, I can’t wait to see what happens next.

Dr. Pamela Gay:         I would say they worked nominally. I would not say they worked perfectly.

Fraser:                         Nominally. Yeah. If ever there was a time for that word –

Dr. Pamela Gay:         And with rockets – yeah. With rockets, all you need is nominal. You do not need exceptional. You just need nominal. But there was that moment where the side of the inside of the rocket caught fire for no obvious reason, there was a great deal more smoke sometimes than others. It went nominally, which is good enough.

Fraser:                         Yep. Yep. All right. Well, all eyes are on the Moon. We’re going back this time to stay, right? One of the best resources on the Moon will be the lava tubes that crisscross the subsurface of the Moon. These could provide protection from space and the look at the geologic history of the Moon. And they can be enormous. Now I think before we get on with the show, I think I need to remind everybody that I’m Canadian. I’m not pronouncing the word lava wrong. It’s how we say it. So, if you’re gonna send an email and say, “Man, every time I heard Fraser say the word lava, it was so wrong.” Let me tell you why. Pasta, lava, llama. I’ll do this all day.

Dr. Pamela Gay:         And what –

Fraser:                         So, –

Dr. Pamela Gay:         – do you call the really old, tightly bound together star clusters?

Fraser:                         Well, that is my own personal accent. Globular clusters. But yeah. If you talk to some Canadians, that’s the way they say that long A sound. Anyway. And it’s never been made more clear to me than by my Texan wife who giggles every time I say lava. So, well there you go. So, I’m aware that I have a Canadian accent. It’s an accent. It’s like if I spoke with an English accent or an Australian accent, –

Dr. Pamela Gay:         I do like –

Fraser:                         – this is a Canadian accent.

Dr. Pamela Gay:         – the Canadian way of saying lava. It does bring me joy.

Fraser:                         Full effect about it. So, what is a lava tube?

Dr. Pamela Gay:         Okay. So, the basic idea is you have some source on a world – pick a world, any world will do – where a weakness in the crust for one of many, many reasons, allows liquid rock from deeper down in the world to erupt through the surface. And for these purposes, ice is a rock. And as that stuff flows across the surface – which is presumed to be at a colder temperature than wherever the stuff originated inside the world – the surface of that stuff will solidify, allowing what’s underneath it to continue flowing. Here on Earth –

Fraser:                         Right.

Dr. Pamela Gay:         – we have basaltic lava tubes associated with various shield volcanoes. Hawaii has a ton of these. And with basaltic lava flows and related lava tubes, you have this highly flowy, liquidy lava that is going across the world – going across Hawaii in this case – and its surface cools off so that you could even walk across it. And underneath, the lava just keeps flowing. And eventually, the volcano turns off, the lava keeps going, and it will end up forming a solid structure somewhere. But behind it, it leaves the tube that it flowed through.

Fraser:                         It’s amazing because when it’s done, because the stuff is flowing so quickly, and depending on what it’s made of, it’s like a river that has built this roof over top of itself.

Dr. Pamela Gay:         Yes.

Fraser:                         And then it just keeps flowing. And as you said, ends up in some great deposit out on some plain, and it empties the tube out. And so, it’s just sitting there as a big empty tube on the surface of the Moon or Earth.

Dr. Pamela Gay:         And the only thing that really limits the size on these things is gravity. So, you have the same problem that structural engineers have – that you can only have so large of a free-standing ceiling before the ceiling runs the risk of collapsing because it doesn’t have enough structural integrity to hold itself up.

Fraser:                         Right.

Dr. Pamela Gay:         We can increase the size using domes and arches here on the Earth, but lava flows really don’t get that complicated.

Fraser:                         Yep.

Dr. Pamela Gay:         They just kinda flow and have the ceiling. So, here on Earth you can get them so that they’re a few meters to maybe a tens of meters across –

Fraser:                         Yep.

Dr. Pamela Gay:         – but no bigger than that. However, the Moon has much less gravity. And so, you could end up with lava tubes that are hundreds of meters in all –

Fraser:                         Yeah.

Dr. Pamela Gay:         – directions big enough. These are no longer so much lava tubes, as lava empty caverns you can build a city in.

Fraser:                         Yeah. You could put a city – the biggest city on Earth, the tallest towers on Earth – you could put them inside some of these tubes and they would fit, no problem.

Dr. Pamela Gay:         Yes.

Fraser:                         That’s how big these things are. Have you ever been in a lava tube?

Dr. Pamela Gay:         No. I’ve seen entrances to them.

Fraser:                         Yeah.

Dr. Pamela Gay:         Now most of them that you’ll see in Hawaii have signs on them that say, “Do not enter.” And then the next set of words is some combination of, “Rock is really sharp, danger of collapse.”

Fraser:                         Right.

Dr. Pamela Gay:         Both of those things.

Fraser:                         Right.

Dr. Pamela Gay:         And this is actually one of the major issues for exploration of lava tubes on the Moon and Mars. Basalts – basaltic lava – is really, really sharp. This is the black stuff that you can sometimes buy at a gardening store to use as edging.

Fraser:                         Yeah.

Dr. Pamela Gay:         And if you handle it without gloves, you can end up inadvertently shredding your hands on –

Fraser:                         Yeah.

Dr. Pamela Gay:         – the sharp unweathered edges.

Fraser:                         Yeah.

Dr. Pamela Gay:         Now, the stuff that you buy for your garden has been tumbled around, has collided with one another, has been rained on at some point. And it’s still that sharp. You don’t have rain on the Moon. And presumably, nothing has gone rolling around inside one of these tubes potentially knocking down the sharp edges.

Fraser:                         We’ll get to that in the risk portion in a second. I’ve been in two. So, the one was in Hawaii –

Dr. Pamela Gay:         Uh-huh.

Fraser:                         – and I ignored those signs and went right in. No problem. But the other one that I was in, it was in Oregon, at the Lava Tubes Monument in Oregon –

Dr. Pamela Gay:         Oh. I didn’t know about that.  

Fraser:                         – and it’s just phenomenal. Just absolutely amazing. It’s like a subway. It’s like you’re walking in a subway, but you definitely see chunks of rock on the ground that fell from the ceiling.

Dr. Pamela Gay:         Yeah.

Fraser:                         And it is smooth. It all just depends on the composition of the lava. And so, in Hawaii you get that “Ahh, ahh” stuff –

Dr. Pamela Gay:         Right.

Fraser:                         – which is crumbly glass that rolls on the surface. But if it’s of a different composition, than it goes more quickly and it could be a lot smoother. So, we’ve got these gigantic chasms. How do we know that they’re there –?

Dr. Pamela Gay:         Well, –

Fraser:                         – on the Moon?

Dr. Pamela Gay:         – two different ways. One is assumptions, which are generally not the best things to make. But with science, we don’t always have the robots we need to go out and touch things. What we see on the Moon are these sinuous rills – these weird features that look like someone’s splatted an earthworm or a long, skinny snake on the surface of the Moon. And they’ll often have a series of crushed places along their length. What we think these are, is lava tubes that are partially collapsed. And this pattern of sinuous structure and collapsed regions matches some of the lava tubes we see here on Earth.

                                    Now the other more exciting thing that we’ve seen, are what are called skylights. And one of the cool things about the lava rooms – I’m gonna call them, on the Moon – is you can have essentially a floodplain that lava goes across. And it creates this large, flat structure with a cavern underneath. And they have found circular cave-ins, that we call skylights, for lack of a better word. In one case, one of these was 80 meters across. So, the hole into the chamber was bigger than the diameter of your typical lava tube here on Earth.

Fraser:                         That’s crazy. The pictures are wonderful.

Dr. Pamela Gay:         Yeah.

Fraser:                         Do a search for lunar skylights, or Moon skylights, and you’ll get a chance to see them. They are these black holes –

Dr. Pamela Gay:         Yeah.

Fraser:                         – on the surface. So, it’s all regular lunar regolith with craters and all that kind of stuff, and then there are just these black gaps. And in some cases, you can even see the illumination of the floor below.

Dr. Pamela Gay:         Yes.

Fraser:                         So, yeah. So, it’s just a chunk of Moon that’s caved in.

Dr. Pamela Gay:         So, the skylight in the Sea of Tranquility appears to be based on the shadows that we see changing from orbit to orbit of the Lunar Reconnaissance Orbiter. It appears to be 100 meters deep. That’s like taking a football field, turning it sideways, and the length of the football field is the vertical depth of this cavern.

Fraser:                         Right. I think you need to stop using cavern because it’s not like a dome, it is –

Dr. Pamela Gay:         Just flat.

Fraser:                         – dozens –

Dr. Pamela Gay:         It just has a flat –

Fraser:                         – hundreds of kilometers long. It is just –

Dr. Pamela Gay:         Well, that’s – yes.

Fraser:                         – this giant, open half cylinder that just goes on for a very long distance. And you’re just seeing one little entrance into this. Okay. So, this is how we find them. Why are they so valuable for space exploration?

Dr. Pamela Gay:         Three basic reasons. The first is, space likes to throw rocks. And here on Earth – as anyone who goes out to see the Geminids next week will notice – space likes to throw rocks at the Earth. And as these pebbles, dust grains, tiny rocks hit the Earth’s atmosphere, they generally burn up, or at least get heated enough that they explode into small pieces that generally don’t cause harm – generally.

                                    Occasionally, really big things cause harm. But that rain of pebbles, and dust, and grains of sand, and pea-sized rocks, all of that stuff we don’t have to worry about because of our atmosphere. The Moon doesn’t have an atmosphere. Mars has much less atmosphere. This means that there is a much greater risk of all that shrapnel hitting us if we’re what’s on the Moon or Mars. By going underground, you have a naturally built protection from falling rocks in the form of lava rock. So, you use rocks to protect yourself from rocks, which –

Fraser:                         Yeah.

Dr. Pamela Gay:         – works.

Fraser:                         Yeah. Totally.

Dr. Pamela Gay:         The other issue is radiation. The universe is trying to kill us. This is a recurring theme in this show. And the Moon is outside of any production that the Earth’s magnetic field could possibly provide. And the Moon doesn’t really have its own intrinsic, strong magnetic field. It just has patchy magnetism here and there. And that doesn’t do you any good. So, by going underground, the thickness of that lava can protect you from the high-energy particles, the high-energy photons, cosmic rays – all that stuff is going to get stopped by that depth of rock.

Fraser:                         So, you’re protected from falling rock, except for the rock that could be falling inside the –

Dr. Pamela Gay:         True.

Fraser:                         – but we’ll talk about that in the risks portion of this conversation. You’re protected from the radiation. And that stuff is bad.

Dr. Pamela Gay:         Yeah.

Fraser:                         You’re experiencing 200 times more radiation standing on the surface of the Moon than you would inside one of these lava tubes. So, just getting even a few inches of rock between you and space makes all the difference, on whether or not you’re going to take a solar flare in the face –

Dr. Pamela Gay:         Right.

Fraser:                         – or having increased risk of cancer when you get back from your mission.

Dr. Pamela Gay:         I just feel the need to point out that I fear for the astronauts, for the planned lunar missions that are planned as we go towards solar max. Solar max is not when I would do a return trip to the Moon. But I know the calendar and the technological developments don’t always line up.

Fraser:                         Right.

Dr. Pamela Gay:         So, the other thing that’s useful about this, is it’s thought that various resources will be easier to access. So, for instance, if there are any pockets of water as opposed to just water mixed into the mineralogy of the Moon, inside one of these permanently shadowed caverns would be a good place to get it.

Fraser:                         So, there are these permanently shadowed regions at the poles of the Moon –

Dr. Pamela Gay:         Yes.

Fraser:                         – but is it thought that you could have little ice deposits inside these tubes?

Dr. Pamela Gay:         It’s unknown. But this falls into the category of things that are improbable and perfectly allowed by science because the temperature’s inside – you’re not being hit by sunlight. It’s going to stay cold. So, volatiles are not going to be disrupted. So, if there was a comet that struck once upon a time, its materials could survive. But the question is, how did they get in there with the lava? So, it’s unknown. But there’s the potential for easier access to resources.

                                    Now on the Moon, this is probably not something that’s actually going to be relevant. There’s the potential, but it’s a low probability. On Mars, where there’s subsurface water that we already think is there, getting underground could put us into a significantly more habitable ecosystem where you have access to water, you have protection from radiation. And this is definitely a good place to go looking for life, which also means that’s the last place we should send people.

Fraser:                         Right. And thus, we wanna find cyanobacteria everywhere we go.

Dr. Pamela Gay:         True.

Fraser:                         So, you definitely have a geologic history –

Dr. Pamela Gay:         Yes.

Fraser:                         – in sort of the same way that a crater digs out material, you’re gonna have material building up around the lava tube that you can then look at and explore.

Dr. Pamela Gay:         And this is actually one of the things that’s going to make exploration that much harder because lava tubes aren’t nice, smooth rock on the inside. They are sharp, lumpy – not healthy for most robots. And there’s efforts being made here on Earth to develop robots that are capable of navigating the terrain without shredding themselves. But because you have to be underground, you can’t rely on solar. And any cables that you might drag behind you for communications purposes are gonna get shredded, unless they’re super, super protected. In which case you now are dragging behind you really, really heavy cable, or you’re basically pooping out radio relays as you go, which is another option for robots.

Fraser:                         Yep.

Dr. Pamela Gay:         But either way, it’s going to require a lot of technological development that we just don’t have yet.

Fraser:                         So, let’s talk about this then. What plans have been put in place, or have been thought through to explore them? You talked about some of the challenges, but what would a mission to a lava tube kind of look like?

Dr. Pamela Gay:         So, the earliest ideas that are likely to fly – some of the Google Lunar XPRIZE teams had plans to have little, itty bitty, tiny, tiny robots, which means they don’t weigh very much. And the gravity’s already pretty low. And the idea was for them to essentially dangle themselves down, lower themselves into the tube and just give it a good look around. So, here a good old handy-dandy, big wheeled, works upside down and sideways robot – it’s all you really need. For something larger, there’s consideration of how do you build something that has 300 feet of cable it can drag behind it?

Fraser:                         Yeah.

Dr. Pamela Gay:         And there’s folks trying to figure out how to do that here on Earth.

Fraser:                         Yeah. There’s the team for the European Space Agency, to have the CAVES Program where they are testing out exploration methods in lava tubes in Europe. I’m not sure where they’re operating out of, but they’ve got wonderful pictures. They’re some of my favorite pictures –

Dr. Pamela Gay:         Spain’s Canary Islands is –

Fraser:                         Yeah.

Dr. Pamela Gay:         – where a lot of this work is being done. And so, this is the European Space Agency. They’ve developed various rover prototypes. One of my favorite things about their prototypes, is their wheels look like starfish rolling along. They have that slightly curved starfish in the wind look to them. Because that gives them better traction as they go. And by working in Earth’s younger, more protected environments, they get things that aren’t weathered as much as they might be in other places.

Fraser:                         Right. Right. There’s been a couple of mission concepts that have gone through the NIAC Program.

Dr. Pamela Gay:         Yeah.

Fraser:                         And a couple that are fairly recent – this is the NASA’s Advanced Innovative Concept Program. I’m a huge fan of these. Many of the stories we cover on Universe Today are this. And so, one was a mission that would send a drone to one of these lava tube skylights and scan above it for a while. It would essentially fire a lunar lander. It would just sort of propel itself around taking pictures in high-leveled lidar of the whole area. And then a spelunking craft that would lower itself down and take pictures, as you said. And the other thing that’s kind of interesting is the idea of rovers that can kind of change their shape –

Dr. Pamela Gay:         Yeah.

Fraser:                         – depending on the structure of what it is that is they’re rolling over. Because the surfaces of the tubes at the bottom – they’re very rough and they can have huge boulders and it’s a very complicated environment to roll around in. So, you’ve gotta have a rover that could actually change its body shape depending on what kind of terrain it’s rolling over top of. But it seems like it’s everything we need. If you wanna live on the Moon, it’s the perfect place.   

Dr. Pamela Gay:         And the only issue that it’s gonna be annoying to try and solve – is the cheapest, easiest way to build habitats – is inflatables. But building an inflatable in what is essentially a spiky glass, shardy cave –

Fraser:                         Right.

Dr. Pamela Gay:         – really a good way to destroy your inflatable. And a lot of these shape-changing robots are also doing it by inflating themselves into different kinds of shape. So, this is really gonna be a cool challenge for material scientists to develop that highly flexible Kevlar, essentially, that will allow it to take a beating with sharp, shreddy glass and not spring a leak.

Fraser:                         And so, when you look at that picture – for those of you who hopefully you’ve Googled “lunar skylight” – and you’ll see sort of the classic example. You get the part, the sunlit portion that is in sunlight. And so, you could have solar panels that are in that sunlit portion, but you can be outside in the darker portion, away from the radiation. So, that would work. So, let’s talk about the risks then. What are the challenges to – if you do have a crew of astronauts down there in a lava tube – what kind of risks are they gonna face?

Dr. Pamela Gay:         Well, it’s the same risks that we have with caving here on Earth, just much harder to deal with. So, here on Earth when you’re caving, you always have to worry about getting stuck in a tight space, about cutting yourself, about how do you drop down into a cave that you enter through a pit above? And so, the initial issue is going to be, how do we safely belay robots or humans through a skylight? And this is really Mission Impossible stuff here –

Fraser:                         Yeah.

Dr. Pamela Gay:         – get to the bottom of the cave. And we don’t know how smooth or lumpy it’s going to be because we’re going in where there was a cave-in, people. Figure out how to create a path out of the rubble pile at the bottom of this thing you’ve just belayed into. And then go off and in the complete darkness of the tube, work on creating illumination, and building a safe habitat somehow.

                                    Now you also have to worry about, well, if a big enough space rock hits above you, that could trigger a cave-in. And so, it’s one thing to build a habitat that can be quickly mended, can be self-healing when it gets punctured. But what do you deal with when that rock – instead of exploding one room on your habitat – has just caved in the wall, the ceiling of your habitat?

Fraser:                         Right. Well, and there’s no terminal velocity on the Moon –

Dr. Pamela Gay:         Right.

Fraser:                         – because it’s a vacuum.

Dr. Pamela Gay:         Yeah.

Fraser:                         And so here on Earth, if a small rock falls, it’ll hit terminal velocity for whatever its shape is, and then it’ll stop falling. Literally, you could have a small rock dropped on you from pretty much any height and it’s not going to hurt you that badly. But you can imagine – boulders – they’re gonna fall a kilometer, and just accelerate the entire way and then smash into your habitat.

Dr. Pamela Gay:         Yeah.

Fraser:                         So, you need to be building that.

Dr. Pamela Gay:         Yeah. Yeah. It’s something where we need to build better robots to figure a lot of this out. And one of the things that is a bit disturbing is – because human life on Earth costs so little – we haven’t already developed these robots for mining purposes. And so, once we have the kinds of robots that can very readily go into these kinds of environments, it’s going to basically make it so that we don’t need miners going after diamonds, miners going after coal, because we’ll have robots that can fill those roles.

                                    So, it’s the, “We can’t do it already because human life is cheap, but once we can do it, we’re gonna be unemploying people.” And so, that is ethical conundrum of the, “I don’t know what to do with this information and this is why I’m an astronomer.”

Fraser:                         Right. Well, I mean the challenge of machines replacing humans is one as old as time. And the way that –

Dr. Pamela Gay:         Yeah.

Fraser:                         – works out is, the machines replace humans.

Dr. Pamela Gay:         Yes.

Fraser:                         That’s how that ends every time.

Dr. Pamela Gay:         That’s true.

Fraser:                         But I think people are kind of imagining that you would fill the tube with air and then try to live in there – but no. You’re gonna have a little pup tent –

Dr. Pamela Gay:         Yeah.

Fraser:                         – at the bottom of the lava tube that you’re gonna live inside. You’re not going to be trying to seal it. I wonder if you could –

Dr. Pamela Gay:         Yes. Yes.

Fraser:                         – could you seal – if you could fix the skylight or pick a different part of it and seal that up – could you then pressurize the interior and –

Dr. Pamela Gay:         Yes.

Fraser:                         – turn it into – wow. Okay.

Dr. Pamela Gay:         And you’d have to coat the sides. But this is where you start imagining the under city – the under river boring machines that we already have – that as they bore, will line the cave that they’re boring with cement or some other polymer of some sort. Where here, what we’re looking at is, we just need a robot to polymer the inside of it so that it’s completely sealed. There’s again, more robots please.

Fraser:                         Yeah. Yeah. Yeah. Absolutely. It’s a fascinating idea. And again, I highly recommend that you search for the ESA CAVES Project –

Dr. Pamela Gay:         Yes.

Fraser:                         – because they’re really pioneering just every aspect of this – both human and robotic exploration of lava tubes on Earth but imagining what it would be like as astronauts attempting to do it. And it’s a fascinating idea to think about. And it’s like the best, worst place. If the Moon is the worst place, then lava tube is the best part of the worst place.

Dr. Pamela Gay:         And there are some adorable Google Lunar XPRIZE plans for exploring some of these with tiny add-on robots that drop on tethers and things like –

Fraser:                         Yeah.

Dr. Pamela Gay:         – that.

Fraser:                         Yeah. Not gonna lie, I have devoted a ton of my journalist career reporting on lava tubes, in both human and robotic. I’m tickled by the idea and I just think it’s so great. And it really feels like you will see people living in lava tubes once –

Dr. Pamela Gay:         So, I have one question that you may know the answer to. The word spelunking gets used to describe going into these caves. And I had always thought that spelunking was reserved for caving in water. And that is not the case. So, why do we call it spelunking to go caving on the Moon or Mars?

Fraser:                         Oh, I have no idea.

Dr. Pamela Gay:         Okay.

Fraser:                         Yeah. I don’t know.  

Dr. Pamela Gay:         These are the open questions we discover –

Fraser:                         There you go.

Dr. Pamela Gay:         – doing Astronomy Cast.

Fraser:                         So, instead of writing an email about my Canadian accent, write us an email explaining why spelunking is a term. And maybe what you would call it if it was on the Moon or Mars. Would it be spelunking? Because if Moon dirt is called regolith, because it’s not actually dirt it’s ground up rock –

Dr. Pamela Gay:         Yeah.

Fraser:                         – is there a different term for –

Dr. Pamela Gay:         It’s caving.

Fraser:                         – going into a cave?

Dr. Pamela Gay:         You’re going caving.

Fraser:                         You’re caving, yeah.

Dr. Pamela Gay:         I’m just gonna stick with that.

Fraser:                         All right. All right Pamela. That was awesome. Do you have some names for us this week?

Dr. Pamela Gay:         I do. As always, we are supported thanks to the generous contributions of people like you. It’s a rough year for a lot of people and I cannot tell you how grateful we are to those who are still doing okay and have shared the fact that they’re doing okay, with us, through their contributions. We are part of a tax-deductible non-profit, which means that if you donate now, it will help you with your 2020 taxes. So, if you’re doing okay and you need a tax write-off, think of us.

                                    And one of the best ways that you can donate is through patreon.com/astronomycast. And this week I would like to thank our patrons: Catherine McCabe, Jeanette Wink, Emily Patterson, div, grad, curl and all that, Ed loves science, Helge Bjørkhaug, Gordon Dewis, Joshua Pierson, Bill Hamilton, Frank Tippin, Richard Rivera, Alexis, Jack Mudge, Thomas Sepstrup, William Andrews, Jeff Collins, Harald Bardenhagen, BenFloss, Marek Vydareny, and Arcticfox. Thank you to all of you for everything that you’ve given that allows us to do all the things we do. Thank you.

Fraser:                         Thank you everybody. And Pamela, we’ll see you next week.

Dr. Pamela Gay:         See you later. Bye-bye.

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