How Moon's Ridges Reveal Secrets About Its Geology

It's kind of incredible to think that humanity has walked on the moon that when we look up into the sky and we see that glowing ball that we've been there. And not only have we been there, but we're going back. Now, in addition to all of the people that have walked on the moon, there is a fleet of spacecraft that have orbited the moon, have landed on the moon, roved around the moon, and have taught us a ton about our natural satellite. And one interesting feature on the moon that planetary scientists have found are these sort of long linear structures that are some kind of fault produced by the moon shrinking over time. And recently we've learned that in fact there's a lot more of these across the moon, thousands of them, many more than we had ever expected. And this is telling us a lot about the interior structure of the moon and just how it is cooling down and that if you were an astronaut on the moon, you would experience moon quakes sometimes uh and how this sort of continuing to tremble and shake the moon. My guest today is Dr. Cole Nipover. He is a post-doal research geologist at the Smithsonian National Air and Space Museum. Cole and his collaborators have been cataloging all of these scarps, these linear features on the moon where essentially the moon has been contracting and you get this material pushed up into these regions that are uh visible from orbit and what this can tell us about the history of the moon and what people going to the moon might experience and where we can learn more about this. So, if you want to learn more about lunar geology, uh, enjoy this interview. Cole, the moon, is it dead or is it mostly dead? — I would say it's geologically very active uh in a fundamentally different way than Earth is geologically active. — Explain more. — Yeah. So, basically, Earth, you know, we have a lot of very dynamic geological processes. We have volcanism. up uh aolon processes, windblown processes like Mars. But the moon is affected by fundamentally different processes such as impact cratering uh and tectonics which is one of the fundamental aspects of my research is basically how that upper uh most that outer basically outer section of the lunar interior how does that change over time? How does it fracture and break due to internal forces as well? Now though, give me a sense of like how deep you're looking under the surface of the moon, — right? Yeah. A lot of, you know, these faults that we're identifying in the upper lunar lithosphere, this is your sort of in the very outer layer of the lunar interior. That's the crust. This is less than a kilometer uh deep in most cases. Yeah. Pretty shallow. — And would these I mean, if it's just less than a kilometer deep, are these visible from the surface? like could you find your like couldn't an astronaut walk into one of these faults and explore it? — Yeah, you know that's an interesting question. Um that's precisely how we've found them in the first place, right? So I'm a lunar geomorphologist. So in scanning the lunar surface I you know happen to notice these and many scientists and geommorphologists before me happen to notice these long suous topographic features at the lunar surface. Um and really the only geological explanation for a feature like that with positive topography is a subsurface fault structure. And um this comes from analogies on Earth, other fault formation u features on Earth as well. Um so yeah, we observe them via high resolution orbital photography and imagery. Um you know, Apollo 17 was the first time a human being went to a fault feature on another planetary body. They landed in the Taurus Litro Valley which is crosscut by one of exactly one of these features that I'm referring to these relatively shallow fault structures. Um that's the it's known as the Lee Lincoln scarp. Right. So uh once that happened uh a number of planetary scientists took that and sort of started looking for other analogous morphological features across the lunar surface. And uh at first there were they found tens of them you know all throughout the lunar highlands. Uh then digging a little bit deeper with some improved high resolution imagery from the lunar reconnaissance orbiter camera. Uh researchers started to find thousands of these features uh all across ubiquitous across the lunar surface. Um now those were primarily concentrated in the lunar highlands which are sort of the very when you look up at the moon at night they're very high albido very bright terrains um very optically very rough a lot of topography. Um, but until recently those types of features, these fault features, weren't really identified in the maria, which is sort of the dark spots that you see when you look up at the moon. Those are the these voluminous outpourings of flood basults um that

formed between 3. 8 and 1. 2 billion years ago at the lunar surface. So recently, we've been looking in those terrains and we found sort of an equivalent number of these fault structures. Um and now by doing that we've sort of now have a more globally complete perspective on recent lunar tectonics and fault formation in the upper lunar lithosphere. — Now I've walked in a fault uh in Iceland. There's this place where it's like the continental divide. You can go and walk in this like this steep cliffs on both sides and there's you know the area is like breaking apart and you know various weathering processes is happening on it. But with the moon, you know, is it getting are these getting filled in by the regalith that's constantly kind of raining back down from all of the impacts? So they're not that it took more careful uh observations to be able to actually find them. — Yeah, that's a fascinating question. So that's that gets it lunar surface evolution, which is something I'm particularly interested in my own research. So these features, the reason we've identified them as being geologically young, that is to say hundreds of millions of years old. I know that doesn't sound young, but in geological time, the moon is 4. 4 billion years old. So, so hundreds of millions of years is pretty young. Um, the reason we've identified them as being geologically young is because they're morphologically undeadrated. They're crisp, right? But when you look at the lunar surface, one of the most compelling features is not a morphological feature, but just the fact that everything is rounded, right? Like there's no if you look at something like the Grand Tetons or the Himalayas, they're very sharp, very jagged mountain ranges. When you look at the surface of the moon, everything is very rounded. That is because of the process that you asked about, which is sort of this regalith raining down um via macroscopic space weathering. Um so the moon lacks even a thin atmosphere with which to protect itself from impactors of all sizes. So from sand size micrometeoroids up until up to large uh asteroids colliding with the lunar surface. And those processes basically act to churn the lunar regalith which is the lunar soil. This amalgamation of fine grain material and fragmented brushes and rocks. Uh and over time that churning actually reduces basically crisp topography down to sort of rounded terrain that we see and that process does fill in um you know these elongated fault features that we see to some degree. So if you see a feature that is not degraded, not rounded, your mind immediately jumps to oh this is geologically young, this is undead, and it hasn't been around for a long time. — It's interesting. I wonder if that's sort of like the sniff test you can use if you're watching some movie about be people being on the moon and if there's like jagged mountains around them, you're like, "No, someone didn't do their research. " No, it should all just like smooth wavy hills. — Yeah. — And when you look in the Apollo footage, for sure, that's what you see. All the mountains around them, everything is just wavy hills. — Exactly. Yeah. I mean the exception is again features like what we're seeing these very crisp morphologic surface expressions of shallow thrust faults but also impact craters very recent recently formed geologically young impact craters are also — very crisp topography right like they have very sharp crater rims and very sharp contacts and very distinct crater floors. Um, so anytime you see that and over time that like crisp that nice clean morphology subsequently becomes degraded to uh basically a topographically muted expression that's barely visible to the human eye. So you know here on earth we have plate tectonics that is driving the faults that we experience. I live on the west coast of uh Canada and I we are made very aware of the faults that are all around us. Um so what is the process that is creating and driving faults on the moon? — Yeah. Well, so you're absolutely right. So plate tectonics on earth drives uh fault formation of all kinds, right? It at plate boundaries. You have these continental plates uh and oceanic plates which are either coming together, moving apart or sliding past one another. And those are the three primary types of faults. Uh you know, you have normal faults where you have these slabs of rock sliding away from each other. You have thrust faults where they're being pressed together and riding up over one another. And then you have places like the San Andreas faults where the faults where the rock is actually sliding past each other horizontally in the x or y axis. Um and that's all driven by plate tectonics. But on the moon we that is actually not the case. Uh so plate tectonics is actually a very interesting phenomenon in our solar system in that we are the only silicut solid body that has it. um pretty much every other solid body and moon in our solar system uh does not exhibit signs of plate tectonics. The moon, our

earth's moon for example, uh is what's called a one plate body or a stagnant lid tectonic body. Um and that is basically you have one complete outer shell. Uh that is the lunar crust that is doesn't have these um sort of seams like the earth does along these plate boundaries. it is just one complete uh crust. Um and the deformation mechanism the reason these faults are forming on the moon is because of global contraction. So the moon is uh very slowly very subtly shrinking. Um and it there hasn't been a lot of shrinkage. This is called global contraction. There hasn't been a lot of global contraction. Um throughout lunar history we're talking tens of meters of radius change. Um, but it is enough to cause a global network of these shallow thrust faults. — Wow. And I'm sort of imagining like if the moon is getting a little bit smaller by tens of meters, then that energy has to go somewhere. And so you and so you're getting these kinds of cracks that are sort of opening up as I guess more material is trying to fill a smaller volume. — Yeah. Well Well, actually, it's going the other way. So they're not opening up. they're actually being pressed together. So these are thrust faults. So basically, you're losing volume as the lunar interior cools and as this global contraction occurs. And that loss of volume has to be accommodated some way. And it's actually accommodated in the Z-axis. So these faults form whenever basically a some of the lunar crust rides up over another section uh in very isolated occurrences that are isotropically distributed across the lunar surface. Um so yeah these are thrust faults and it's uh you know these the stresses we're talking about from global contraction are tens to maybe even hundreds of mega pascals. So it's not insignificant either. It's a um it's quite a driving stress mechanism and there's also overprinting. I mean so global contraction is the primary stress mechanism responsible for the formation of these faults. But you also have some interesting stresses acting on the lunar lithosphere from tidal interactions between Earth and the moon. Yeah. So it's not important not to forget about those, right? So they're relative to global contraction. The stresses associated are relatively minor. Um megapascals if not kilopascals in many cases, but you want to think about things like orbital recession. So, as I'm sure you're aware, I'm sure many much of your audience is aware, the moon is migrating slowly away from Earth in its orbit um very slowly, but it's enough to cause relaxation of the near side tidal bulge on the moon. So, basically the Earth's tug on the moon is causing this near side bulge. Again, we know this via uh basically laser reflectivi re reflectivity off of the near side of the lunar surface. Um and that bulge is very not a lot there's not a lot of uh a signature there but as it as earth as the moon migrates away from earth in its orbit that bulge relaxes and you get a compression compressional stress on the near side as well and then you also have a non non-ircular orbit around earth which causes uh stresses at parige and apogee in that orbit. So again those actually influence the orientation pattern of the faults that form but they don't actually cause the fault formation in and of itself. Yeah. — And I guess if the moon wasn't tightly locked to the earth, then it would be even more significant because that bulge would be moving, shifting. — Yeah. Well, exactly. Um, and this is these title stresses. Um, you can compare with something like Io or let's take Io for example, right? The uh it's the eentricity the eentricity of that orbit is enough to actually cause uh basically a fully molten interior in vcanism. I think that is an incredible amount of stress associated with the that orbital eentricity the perigee and apogee. So it's uh yeah we don't have anything the moon doesn't have anything to that degree but that's it's a similar stress mechanism. — Right. Right. That if we went further yeah that if the earth was you know hundreds of times more massive then we might start to appro have a more significant effect on the moon. Um, so you know, hopefully we're going to have humans set foot on the moon and over the kind of the long term, hopefully there will be some kind of permanent human presence on the moon. Uh, should the astronauts working at the base, will they experience moon quakes? — Yeah. Well, that yeah, that's a great question. So, um I will preface this by saying that I think the yes that moon we know moonquakes occur. Um and I'll explain how we know that. But I would say that the scientific value of the moon quakes far exceeds the danger of them. — Just Yeah. — Yeah. Well, not I'm not saying they should be worried about them, more just would they even experience them.

— Yeah, it's certainly possible. Right. So, um we can go back to the Apollo program. Um, so between 1969 and 1977, the Apollo lunar seismic package, which was a series of seismometers set on the lunar surface by the Apollo astronauts, that experiment package detected about over 13,000 seismic events in the lunar interior. Now, those aren't all violent moon quakes. Um, in fact, the vast majority are very were very subtle events. Uh, most of them were labeled as what are known as deep moon quakes. So these are uh if seismic events that occurred sort of at the core mantal boundary of in the lunar interior very deep. Um the other larger percentage of them were seismic events from impacts. So they could detect asteroids and meteoroids uh colliding with the lunar surface at 17,000 plus kilometers per second. Um now that said 28 of those seismic events were shallow moon quakes with pretty significant magnitudes pretty significant shaking associated with them. And now the leading hypothesis is that those shallow moon quakes this 28 were associated with fault formation in the upper lunar lithosphere. So the basically the formation or the slip associated with these faults. So when you have the you know those bodies of rocks sliding past one another that's that releases a tremendous amount of energy. uh and that energy manifests at the surface as a moonquake shaking in the horizontal uh horizontal and vertical direction. Um yeah, so it's certainly possible that if you were on the surface near one of these features that could happen. Um but when you do some, you know, some quick statistical math, 28 shallow moon quakes over the course of 8 years um is not a high recurrence interval. uh and the likelihood of any one of those happening in a specific location is even less so. So, it's uh but yeah, the answer to your question is yes, it's possible. And these types of features, these faults are something that you need to be considerate of when thinking about a long-term lunar outpost or any sort of long-term habitation. For sure. — Yeah, we had done some reporting on Universe Today about boulders that have been seen recently. You can see the trail, the track of it rolling downhill. And so some force is knocking them off of the side of a cradle rim and having them roll downhill. — Most certainly. Yeah, it could very well be shallow moon quakes from fault slip from fault formation. This there's a recent paper came out uh last year in 2025 um that documented basically in the Taurus Litro Valley in the Apollo 17 landing site. uh if there were if there happened to be a magnitude 3 earthquake form in association with that feature, what would be the geomorphic effects of that event, right? And there happened to be a lot of as you're saying boulderfalls and landslide material in the Taurus Litro Valley and interestingly enough uh all of those materials coincide temporally with the formation age of the Lee Lincoln scar. Right? So that's there's a very interesting coincidence there and that paper showed that uh it was published in science advances actually it showed that the uh the shaking associated with that event would be more than enough to topple those rocks and to cause that big landslide off the south massie in the tar literal valley. So yeah all you know those geomorphic effects are considerable and there's you know a magnitude 3 earthquake would or a moonquake would be certainly more than enough to cause them. Mhm. Now, you know, one of the things that's really fascinating about the moon when we look at the near side compared to the far side is totally different feature, totally different landscape. The near side with its lunar highlands and the mare and then on the far side it just looks craterpounded. Um, you know, has your work tried to help explain this strange symmetry on the moon? — Yeah, that's an interesting question. Um so the that asymmetry is uh is definitely something that has been of interest to lunar scientists since we've been returning images of the far side right all the way back to the lunar missions to the lunar orbiter program as well. Um is this actually here let me so what you're describing is basically so the near side is what you see when you look up at the moon. This is basically the near side here. Um, and then on the far side, you spin this around and you really don't see those dark mar patches. Right now, the hypothesis here is that you have a much thicker lithosphere on the far side. Um, and a relatively thinner lithosphere on the near side. Um, now our the faults that we're identifying don't quite get to the depth of the base of the Highlands lithosphere. So it's hard for us to constrain the thickness of the far side versus near side lithosphere. That said, there are some features there is basically a theory out there that the basically the

low scarps these features that form this that's the geological term for them in the lunar highlands. The length of them basically the longer features are proportional to the thickness of the lithosphere. Now that's an interesting question. Um I don't think it's been in tested at depth but it is certainly possible that we could use some of the morphometric parameters of these faults and of these features to get a better understanding of the lithospheric thickness. Yeah. — Do we see the faults on both hemispheres? — Absolutely. Yeah. So they're globally ubiquitous. So they're all over the place even at the South Pole um North Pole throughout the near side Maria um all over the place. — Is there Okay. So, if you could plan your own mission to the moon and you could send some astronauts and maybe, you know, send some more Harrison Schmidts, like some actual geologists, um, where would you want them to go? What's like, give you like a one place you're like, "Oh, I really wish I could get boots on the ground right there. " Yeah. Well, I think the South Pole is incredibly compelling from a volatile standpoint, right? Like I think that's the correct decision and there's good reason to go there in upcoming looter missions but — yeah sure fine but I want to know — standpoint — yeah yeah you know get your hands into you know those faults and learn more — really so the problem is the problem that I see is that we don't really have good constraints on how a fault forms in a planetary regalith um we know that they're there we have some very preliminary modeling done that demonstrates that these are shallow thrust faults, right? They are what we think they are. But exactly what does that look like on the micro scale? We don't have a good idea. So my what I would like to do is get to the moon with ground penetrating radar or a seismic suite that would give me some sort of subsurface imaging to look at these faults. And if we can get an understanding, if we can constrain what these faults look like in the subsurface, then we can basically constrain recent lunar thermal history because observationally these features are used to better understand how much as we've talked about how much global contraction has taken place, what is the rate at which and amount at which the lunar interior is cooling, what is the rate at which lunar contraction is occurring. That is loosely based on the geometry of these faults. And if we can get better constraints on those geometries, lunar thermal history as a whole. So, um there's a lot of these all over I mean there's over 10,000 of these fault features that we've identified to date. So, um, on the near side in the Maria, I would say that's probably my preferred location to go look at one because you get uh you can sample you can not only look at tectonic features and constrain fault geometry, but you can sample uh volcanic history, you can sample really interesting volcanic materials as well as target tectonic features. So, there's a lot of options. Ne — next time we come around with our checkbook, you need a fast answer like right here. I think there's aliens right here as well. — Well, I like it all. Yeah, it's all every area on the lunar surface is interesting to me. — I mean, one of the most fascinating pieces of research that we saw from the Chinese Chonga missions was they had these ground penetrating radar instruments on board the rovers and they were able to sort of see this slice down through the top of the regalith and you could see the particle size. So at the top it's like this talcum powder and then as you go down they just turn into larger and larger boulders all the way down and so like those instruments exist and so I can imagine yeah like if you could do a comparison take one of those across one of these fault lines and map it out. How deep does it go? How wide does it go? You know compare that to just a random spot on the surface of the moon. — It would be fascinating. Yeah. you know those the Chongi rovers uh really placed very important constraints on the regalith structure in general. So it's another long-standing question is in the subsurface you know in highlands material versus lunar maria terrains what does the lunar regalith look like as you go down um not just in the context of tectonics and fault but in general uh as I mentioned the lunar surface has been subject to four plus billion years of constant impact bombardment. Um so you know how far down is the bedrock? Is there even bedrock? These are all really interesting questions that we have yet to answer. Now you know this is just one object in the solar system and you know something that you've been analyzing quite carefully but when you look when you think sort of larger picture across the solar system Mercury uh and even some of the sort of cryovcanism and stuff that's happening on places like Europa and what's happening on Io and stuff. Are there other worlds that you feel would be an interesting comparison? You know Venus like Venus must have these things too, right? VS is fascinating from a tectonic point of view. So it's uh you know we don't have the best uh I hate I hesitate to call it image

data because it's actually synthetic aperture radar data. So we don't have the best uh perspective on what's going on at the Venucian surface right now. It's those data are somewhat coarse resolution. They're from the data from the '9s. So it's really going to be really important to get higher resolution image or radar data of the Venucian surface to help better constrain these things. But uh tectonically there's all kinds of crazy stuff going on at the surface of Venus. Um and in the shallow subsurface that you're probably familiar, but there are these large corona type features, these large circular uh tectonic rings basically that are the surface expression of magmatic upwelling. So the magma actually comes from the Venian interior, presses up on the Venian crust and then relaxes and you're left with this ring of fault features. you have large planes which are just modeled with these ridgelike features that form via large scale compression. Um yeah, it's really interesting and it would help us constraining tectonics activity, tectonic activity on Venus and any of the other planetary bodies you mentioned would be really helpful for understanding basically silicut body formation across the entire solar system. I mean Mercury is a great analogy to the moon as well. It's the same processes that I'm describing on the moon have taken place on Mercury to a much larger scale. So, more mass, more internal heat, more global contraction, bigger faults, more faults. Um, all it's like the moon's bigger brother in tectonically. — Yeah. I know. There's these like weird kind of chaotic spider terrain where you're seeing these fault lines and they're a lot more kind of exposed and really look like I don't know spiderw webs almost. — So, you're referring to Venus? — No, I was talking about Mercury. — Oh, yeah. There's a yeah there's a lot of really interesting features that I think could use some further investigation and yeah would really help us understand how you know this type of uh you know one plate body tectonics the stagnant lid tectonics process works. — Yeah. Well, I'd like to shift gears now and talk about sort of you mentioned before we were recording that you're starting to sort of think about boulders on the moon. So, give me a sense of what you're investigating. Yeah, this is it's one of the things I'm really interested in recently is surface rock size frequency distributions on the moon. Um, so the moon is just covered with rocks. There's no really outcrops uh like we see on Earth. You don't have any nice road cuts where you see nice layering of sedimentary deposits. Um, really all you're left with is just a distribution of meter scale and submeter scale, centimeter scale rocks all over the place. And those rocks originate from different sources. They're frequently excavated by impacts. Impact craters collide with the lunar surface and they throw up uh hundreds and thousands of even tens of thousands of rocks and boulders depending on the size of the impact. So one interesting question is you know what is influencing the amount of amount and distribution of boulders at the lunar surface? Where did those processes vary in the lunar subsurface that could be controlling that? And how long are those boulders present? rocks present at the lunar surface? What's their lifetime given the intense micrometeoroid bombardment that occurs at the lunar surface? — So that same process that's wearing down the hills is wearing down just individual rocks and boulders on the surface of the moon. — Very similar processes. There's some subtle differences. So these rocks are very competent bodies of mass, right? They're very they're solid material. Um so it's predominantly the stress the mechanisms responsible for breaking down the boulders are one micrometeoroid bombardment sand blasting from uh very high velocity asteroids basically very tiny ones uh and also thermal fatigue. So the moon has very intense dayight cycles 14 earth day days 14 earth day nights the temperature fluctuations are immense and that actually can expand and contract and break the boulders in and of itself. um the relative contribution of those two processes to boulder breakdown rock breakdown on the lunar surface is not well constrained at the present but we know that both are occurring now topographic evol like topography evolution that we were talking about earlier that sort of hill slope diffusion is actually predominantly caused by uh secondary ejecta mantling. So you have a big impact that forms over here. It throws material over here and in addition to the micrometeorite bombardment that we talked about that sort of secondary ejecta that secondary impact cratering influences local topography as well. So they're very similar mechanisms. Um but yeah again anything at the lunar surface is subject to pretty intense weathering patterns. Now, would you, you know, without an atmosphere, you would never find solid meteorites in the way that we find them on Earth and the way they've been seen on Mars, would you? — Um, it's if it's really difficult to find them um simply because of the energies associated with the impact

creator formation process, right? So, a lot of times those micrometeoroids, those even larger impactors vaporize upon impact with the lunar surface. — Um, they don't slow down. They as you mentioned Yeah. Right. So, they hit with a lot of energy. So you get predominantly vaporization of the bully of the impactor. You get vaporization of the target material. And as those shock waves of the impact dissipate into the lunar interior into the lunar subsurface, you get melting of rock forming, you know, that melts actually recoagulates and resolidifies into what's called a brush, which is pretty much the dominant rock type at the lunar surface is impact Brussia, which tells you something about how much impact cratering has gone on at the lunar surface. And then even beneath that you get a lot of fracturing and breaking of the subsurface rock. That's why I question the term bedrock with as it relates to the moon earlier is because any bedrock would have been deposited billions of years ago and has been subject to impact crater this impact cratering process ever since. — Right. Right. Just constantly being kneaded and pounded and who knows what's left. But it's interesting that if you were walking along the surface of the moon and you were looking for a you know a pebble that had recently hit the surface of the moon, it would vaporize and you would get like a tiny little crater — for the most evidence exactly that this had happened. — Yeah. You would only see a crater. You really wouldn't see a bunch of little asteroids laying on the lunar surface. And it what you might see actually that vaporization that material basically comes out of the gas phase and actually resolidifies on lunar like grains of material in the lunar regalith. This is where what are called nanopase iron particles come from. And I know you had Kevin Cannon on to talk about that a while back, but you get these little uh glutenates basically is what they're called. They're little grains of regalith material that are covered with nanophase iron that has precipitated from impacts as that material vaporized. So it's one of the main components of regalith in and of itself. It's glass nanopase iron glutinates and brea for the most part. — Right. Yeah. It's man, it it'll be great if we can actually have a permanent base on the moon where astronauts are going outside and they're examining these kinds of features and finding interesting examples of different phases of different sizes because there's only so much that the Apollo astronauts could do in the limited time that they had with the vehicles that they had available to them. And there's got to be so many more really interesting places to go even within walking distance or driving distance of wherever the base is going to be from the you know the permanently shadowed craters to some of these boulders and rocks and ejecta and recent sites. I think it would be fascinating for them to find like a you know just like a little tiny crater small to hit the moon. Well, I mean, the best resolution image data that we have from orbit is, you know, about half a meter per pixel, and you're not even going to see small impact craters on the size scale that you're referring to in those data. Um, so there's a lot of subresolution geology to be done. That's really important for constraining a lot of these regulate and impact cratering processes. And it also highlights what you're mentioning, the importance of selecting the right landing site, right? So, you want to make sure this is why so much thought goes into this. You want to make sure that the rocks and the geology, the rocks you're sampling and the geology you do and answers fundamental questions about lunar geological history and solar system geological history, solar system formation, right? And you can do that with samples from the lunar surface if you pick up the right rocks, — right? Uh Cole, a question I ask all my guests. What are you obsessed with right now? Yeah, we touched on it a little bit, but constraining these rock size frequency distributions and really constraining this macroscopic structure of the regalith, right? Like where what is the lifetime of a rock at the lunar surface? What is the origin of those lunar surface rocks? Um what is the structure as you go down with depth? Uh you know, how does Regalith change? Um, yeah. — But is there a H I mean is there like a surprising hunch that you have? Like is there something that's kind of making you wonder if there's something that we're missing or something that maybe we have yet to uncover? Um, you mean in with regards to Lunar Regalith or the moon as a whole — or just the process of being obsessed with things, you know, like for me my obsessions come from what is my what do I feel is kind of a gap in my knowledge or something that I feel is like a gap in everyone's knowledge. Like there's something that doesn't seem to be resolved and that I and it nags at my brain and I have to keep thinking about it, you know? I mean that's where the Yeah, go ahead. — I was just say before it sort of assembles into something more coherent and concrete, it sort of exists in this

cloud in my brain that keeps diverting my attention to this subject and that's sort of, you know, that's how it manifests for me. — I know exactly what you're talking about. I mean, that happens. So, yes, that has happened recently in the context of, you know, this lunar rock and lunar regalith investigation and project that I'm working on. It also this is how I came upon the you know my research with lunar tectonics and fault formation was I was really obsessed with these papers from the Apollo era on the Lee Lincoln scarp in the tar literal valley and I was really obsessed with all these papers on these faults in the lunar highlands and I was reading them and trying to understand them and I came to the realization that these are all describing fault features in the highlands which is 83% of the lunar surface and they there were no fault features no geologically unfault features described in the other 17% of the lunar surface which is made up of the lunar maria. So at that really drove me crazy. So I started looking for them and my goodness did we find them. We found thousands of them across the lunar maria that hadn't been described previously. So it's it's been a it's an interesting story and I don't think it's over yet. I think there's a lot to learn about lunar tectonics and lunar tectonism uh in general. Um I will say that similar story is also playing out in my mind right now in the context of regalith uh specifically on the lunar mari deposits. Um you know there's a hypothesis out there that proteolith basically the mechanical properties of the substrate of the basaltt itself uh the minologic properties of it can control how many rocks are produced whenever that protoolith is impacted by an asteroid or meteoroid of some kind. Right? That's an interesting hypothesis and it's one that I'm really interested to test because the other competing hypothesis there is that you know you have an older surface on which regalith accumulates over time that kind of intuitive right you have a rock that is continually turned into regalith the more impact bombardment that rock is exposed to the more regalith accumulates on top of it that root regalith then inhibits the amount of you know rock production that can occur when it is when the substrate is impacted. Um, but if protoolith properties actually control surface rock populations and rock production on the moon, then that throws a whole new series of variables into the equation. Um, so in other words, it's not just a direct correlation between surface rock populations and age. It's then becomes um, you know, a correlation between surface rock populations age and the geochemistry of the underlying basults, which is really an interesting question to to answer. Well, you gave me a new word. Prolith. — Oh, that's a great word. Yeah. — Yeah. I haven't heard that one before, but essentially it's like it was the whatever was the original volcanic flow that created the material that then got pounded up. — Exactly. Yeah. That's interesting. — And I mean that logic follows, right? Like an older Mari basalt flow has been subject to more bombardment. Therefore, it should develop more regalith on top of that particular protoolith. and a younger Mario basalt flow should have accumulated less regalith overlying. Um but it may not always be the case. — Yeah. It's a fascinating time and it's you know we're standing here now just a handful of years away from this resurgent of missions to the moon. Whether it be from the Chinese, private space flight like SpaceX, or whether, you know, it's NASA's Aremis missions, we're going back to the moon and hopefully we'll find out a lot more information. Cole, thank you so much for your time and good luck with your research. — Thank you so much. I appreciate you having me on. — I hope you enjoyed this interview about the geology on the moon. Uh, I'm going to give you some final thoughts, but first I'd like to thank our patrons. Thanks to Abe Kingston, Andrea Pretty, Bear League Roofing, Brian Bod, Kedwin, Chuck Hawkins, Commander Bail, Cooper and Ellie, Darkfinger, David Gilton, and David Mats, Evan. Propro, Greg, Phy, James Clark, Jeremy Madden, Jim Burke, Jordan Young, Josh Schultz, Marcel Smiths, Michael Parcel, Nordspace, One Stepstep for Animals. org, Porlbuck, Rank Haidu, Richard Williams, Sean Sergeant, Steven Fley, Munley, Team49, Telescopes, Canada, Wolfgang Clots, and Zeldaorg Galactic Defender who support us at the master of the universe level, and all our patrons. All your support means universe to us. Man, I am so excited about humanity returning to the moon and like I don't care how um if it if the Chinese do it, if NASA does it, if private space flight does it, then that's going to be incredible that we will be able to look up into the sky and know that there is a permanent human presence on the moon. In the same way that we look into the sky and we see the International Space Station fly overhead, we there astronauts up there looking back at us. And the moon is so accessible compared to every other place in the solar system. And yet it is has gone through the same kind of history that the other worlds have. That

Mercury, that Venus, that Mars, all of these worlds have gone through this history and are continuing to go through this history. And a lot of the secrets that we have are available to us just there on the moon and we just need to go back. But even if we don't set foot, we can still learn a ton from sending landers, rovers, and orbiters to the moon. All right, we'll see you next