 So without further ado, let me go ahead and introduce our speaker today. So Dr. Matthew Sigler is presenting the seminar and he grew up in Wayne, Illinois, which he noted for the record is very close to the Fermi National Accelerator Laboratory in Batavia, Illinois. He's trying to draw a lot of connections for this department, I think. He doubled majored in physics and in film at Cornell University, where he also became heavily involved in the 2003 Mars rover missions, as well as summer internships at Fermilab and CERN. So if you like what Dr. Sigler has to say today, keep in mind you too can apply for fellowships and summer internships and things like that at labs like Fermilab and CERN. After a year with the LHCB experiment at the University of Zurich, Dr. Sigler felt the pull of Mars once more. He headed to Los Angeles, where he did Mars related laboratory work at Caltech and then moved on to UCLA for his PhD in planetary geophysics. There he studied lunar ice, thermal modeling, and the orbital evolution of the moon. He then came to the Jet Propulsion Laboratory, JPL, as a postdoctoral researcher, and then as a staff scientist in planetary geophysics. The Planetary Science Institute gave him the freedom to move this work to SMU in 2015, where he's now a co-investigator on Mars 2020, Mars Insight, the Lunar Reconnaissance Orbiter, OSIUS Recs, and the upcoming Viper Lunar rover, which I'm sure you'll follow follow today in some way or another. So please, without further ado, welcome Dr. Matthew Sigler to speak to us about remote sensing the planets with microwave radiomics rig. Dr. Sigler. Okay, hi, and thank you very much for inviting me. It's nice to finally counted we're here for six years now, so I'm glad that I can come and talk with you guys just down the hall from you. I'm based in the geology building if anyone ever wants to bug me. Yeah, so I thought this would be an interesting topic of kind of overlapping some of physics and the planetary astronomy that I work on. So with little due thanks for the introduction, and we'll get started here. So I basically started doing thermal modeling, coming out of work that I had done for CERN. I actually designed one of the cooling systems for the LACB inner vertex detector. And so in that, I was measuring thermal conductivities of all that material and such. And that got me into thermal modeling. And then I started applying that to soils on Mars and then from that branched off into the moon and ice on the moon and all this fun stuff. And so I've worked a lot with temperature measurements, thermal infrared measurements of objects. And more recently, I've moved a lot into the microwave remote sensing. Microwave was really exciting because no one's been doing it in planetary astronomy really. Okay, it's been something that we've used for weather satellites, things like that. But it wasn't until actually on the Chang'e one and two missions that went around the moon a few years ago that we ever really looked at a solid surface from an orbiter or a lander with a microwave radiometer. And it shows some really cool stuff. And so based off of this, we've now started to develop a new instrument of JPL, which we put at the end of the moon sometime in the next five to 10 years. And so that's pretty exciting to work on. So just brief introduction to some of the things I work on. So like I said, I'm working on all these different missions. I'm a participating scientist where I've competed to be added onto the team for Mars 2020 insight and Osiris Rex. Osiris Rex, if you don't know, is the one that took a sample of the asteroid last year and it's bringing it back in September of 2023. So we have to wait a long time for projects to the Mars 2020 rover is also taking samples that will come back from Mars, but probably not until around 2030. We would expect to get those samples back. The sample return rover isn't actually even designed yet. Insight is going to stand Mars forever. And I'll talk a little bit about some of the measurements. It's done actually maybe I cut that part out of the talk. But if you're interested in that, let me know. And then I started as a PhD student, I started working a little on Lunar Reconnaissance Orbiter and I have worked on it ever since. And then Viper is the new mission that's going to land on the moon in December of 23 and have a drill that's going to drill down for ice. And so I make all these models where we expect ice to be on the moon and we figure out where to drill that. And then there's a couple of these commercial lunar landers that are precursors to this mission that are going to come up in the next few years and I'm on it. Two geothermal heat flow probes from that and then an infrared camera. So like I said, a lot of what I do is based around anything thermal on planets. So I do infrared remote sensing. I do thermal models of how, so here's the insight lander and we wanted to know how the lander itself was affecting the geothermal heat signal that we wanted to measure. And then I do global models too of here's what we expected geothermal heat flow of the moon to look like or here's geothermal heat flow of Mars, what we expect to look like. And these are from measurements from orbit around the moon and Mars with a thing called the gamma ray spectrometer, which is basically something that came out of Los Alamos lab, you know, as a as a particle physics instrument and as later kind of revolutionized our understanding of the surfaces of the moon and Mars. So we can measure things like uranium and thorium with that. And then from that we can model if that is representative of the subsurface, you know, what what heat flow would we expect. And then we go and measure it and compare our models to what we see. Most of my PhD thesis was about ice debilitating on the moon and mercury. So we had some cool papers on that. And then so I make these great thermal models of where we expect ice to be on the moon and how deep it should be based on the temperatures on the surface and then we model how they propagate into subsurface. And with that and looking at the orbital history of the moon, we actually modeled how the moon seems to have changed the spin axis about three billion years ago and caused the ice stability to change on the moon dramatically. Then I do a lot of modeling with volatile stability. So one of the things we were looking for with your cybersurrect mission, this is asteroid Bennu, which is about a 500 meter asteroid that could, I think it has like a one in 8,000 chance of hitting earth in the next 300 years. So that was one of the reasons we went there. We're going to characterize the temperatures out at surface because that controls something called the Yurkowski effect, which is how thermal emissions off of the asteroid control how it moves with time. And so here's the dramatic sampling event last year. Then I do stuff with thermal properties, like I said, one of the things that I got into originally was doing thermal properties measurements and materials and I got into looking at thermal properties of Martian soils and lunar soils. Here's some Apollo 11 soil that I have just to show you how dark the moon really is. This is the Mare of the moon and this is just when you flashed it with a camera. So pretty dark on the moon. And then like I said, and we'll talk about today, I got more recently into microwave radiometry and what we can do with that. And can we use this both to look at temperatures below the surface to measure things like the geothermal gradient that I'm interested in and then to measure where there might be subsurface ice and such. Okay, so what is microwave radiometry? So microwave radiometry is basically looking at things we'll call microwaves, which I'm broadly saying one millimeter to 300 megahertz. Joel, we're hearing probably say something different in the range. But anyway, it's a broad part of the frequency spectrum. It's kind of fuzzy in the literature sometimes, what you call the boundaries of microwave and radio and all that. But when you're looking at a solid surface, the emission you see in the microwave both depends on the physical temperature of the surface, but also the transparency of the surface, how deep into the surface you're actually going to see. And so with this, when you have a semi-transparent medium like the regulars on the moon, you can actually see quite deep. All right, we can see just several meters with some three gigahertz radiometer that was on the Chinese instrument. And so what we're trying to do that is develop to look at the data we have and develop new instruments to see deep into the lunar surface. And then you can imagine if there's a chunk of ice down there, the temperatures might be different. The dielectric properties might be different. We could probably sense it remotely. And so it makes an ideal instrument for looking at some of the things that I've been interested in scientifically. Okay, so microwave world sensing isn't entirely new, but it is pretty new as far as what's been done. Some of the early temperature measurements we had on the moon were actually in the microwave because you can't do infrared measurements from the earth of the moon, right, because the atmosphere is in the way. And so if you looked into the microwave windows through the atmosphere, you could actually see map the temperatures on things like the moon or Mercury. And so that's where a lot of our initial understanding of the global properties of the moon came from. And we pressed forward with other earth observations in microwave. We did microwave measurements of other bodies, like microwave emissions from Mercury. There's a list of Ganymede and Galilean satellites. And then the first NASA instrument that looked at microwave is the Juno microwave radiometer that is orbiting now around Jupiter. And I'm pretty excited. Just recently I had a flyby of Ganymede. I wanted Jupiter's moon, so hopefully we're going to look at that data when it becomes publicly available, and then also Europa to measure the heat flux there. What does microwave data look like? Okay, here is a picture of these are maps of temperature, average temperatures measured at each of these things. We call brightness temperature is how we measure in microwaves, so that's the axis label that input on here is brightness temperature at each of these different frequencies. Here's where they're coming from. All right, there is four different antennas on the Changi-2 instrument here. And we can see that you're basically seeing temperature, right? You see it's cold near the north and south pole to moon and it's warm near the equator. And that's what I've been working on since my PhD thesis, right, is working on with the diviner instrument, which is one of the instruments on LRO that I'm relying on. We can measure temperatures of the equator, the moon, or hotter, and they're pulled into the poles. All right, that's all well and good, but what more information can we learn than just the moon? The poles are more with the equator. And that comes into what we're actually seeing with the microwave remote sensing and what we can model with it. So basically, any warm body is going to emit microwave radiation depending on the wavelength that you're observing at, right? The physical temperature of the medium, and that is temperature not only at the surface, but temperature as a function of depth. And then the dielectric properties that that radiation is coming up through. And so that all boils down to this term I'll use a couple of times called the loss tangent, which basically controls how transparent the material is. It's a ratio of the real to dielectric or to imaginary dielectric constant. And then I'll show a few times these things called weighting functions, which are basically a visualization of that loss. It shows what depth you're getting radiation from. So here's this weighting function for these are the four channels that we had on the tiny microwave radiometer. So 37 gigahertz high frequency, you're not going to see very deep into the subsurface. And so it's weighting function piles up near the surface and you're seeing mostly in the top two centimeters. Three gigahertz, you can see down over several meters because you're penetrating more deeply into the surface. And then we can model what that would look like as far as data, right? So this is your thermal trumpet, right? So this is the maximum temperature as a function of depth and maximum temperature function of depth and the minimum temperature function of depth. And then this is at a given time. So this is near midnight, right? It's not actually always at the coldest. There are some depths that are warmer at midnight than they are at noon, right? So here's the new time temperature curve. You see that these depths here are actually colder at noon than they are at midnight. So you need to take into account that whole temperature profile of depth and that you'll see animations of this waving around like that. And then we have our weighting functions. So these are for two different frequencies. And then what I have here at the dotted line is a different loss tangent, right? So there's high loss material that has a lot of a mineral ilmenite that is very high dielectric loss. And so we don't see as deep with that material. So we're going to see something closer to the surface temperature. Surface temperature on the equator of the moon varies by about 300 Kelvin day and night or 400. Yeah, no, 300 Kelvin day and night. And so you get higher amplitudes, the higher your loss tangent is. And that's what we see in this model here, right? We have a high loss tangent. We're going to see this is the daily cycle. So this is noon and midnight. And we see that high loss results in a higher physical temperature or brightness temperature amplitude. And so we can use this to model the data. Here's the data from the equator of the moon from the Chinese instrument. We could see that for areas with low titanium, low ilmenite content, we see very low loss tangent curve here. And then in white here is the areas with high ilmenite content. And you see that they have a higher physical amplitude. And that's what's going on with ilmenite. Ilmenite is this grazing mineral that has this mineral structure here. You basically get a cation vacancy on the side of the crystal. And so your electron can kind of move up and down there and absorb. And it was very good at absorbing in microwave wavelengths that are on the scale of this crystal. And so what we can do is also look at how that weighting function changes as a function of ilmenite. And that's what we have mapped here, right, is that what we're doing here is I said, you got high ilmenite or high titanium, you would not see very deep. So you'd see a higher amplitude, something like the surface. And then if you see deeper, you see a lower amplitude. That's what we see here now is now we have maps of basically the loss tangent of the moon. And just looking at the amplitude of the microwave data. So you can see places with very high ilmenite or high absorption, high loss, right? So that could be due to an absorbing mineral like ilmenite, or it could be due to a rock, right, which will also absorb, right? You can't get, you can't see very deep into a rock. And so we can map those things as a function of depth. And so what we see here is that at different frequencies, we're seeing here's the ilmenite map of the top millimeter of the moon from spectral observations. And we can see that we were changing, you know, we're actually seeing carrying into the subsurface and how this mineralogy and density changes with depth. And you can see certain features like here is this nice crater here. This is called Gitaron Bruno crater. It is nice rays and ejecta. Those are all the rocks, small rocks thrown out of that crater. But as you get to a longer and longer wavelength, you don't see those anymore, right? Because your wavelength is too long and you're seeing right through the, those objects. And so with this, we can basically map something that's equivalent to both the ilmenite that we saw on the moon. So we're getting a mineralogy map of the moon. And then we're also getting a map of the rocks on the surface and the subsurface. We're kind of combined together, right? And because we've mapped the ilmenite separately with the spectral measurement and looking at a visible spectrum, we can actually kind of subtract that with our models. And we can get, you know, just maps of rocks. But this is kind of cool because it's not just map of rocks on the moon, it's a map of rocks on the moon at different size scales, right? These are the, you know, centimeter rocks. And these are the rocks that are 10 or 20 centimeters. And that's what I was showing in the last figure here. With thermal infrared, we can only map the rocks that stay warm through the entire lunar night. That's how we map something in a rock in the infrared. It's just something that has enough thermal inertia and high enough thermal conductivity and density that it stays warm through the entire 14-day lunar night. Yeah, there's a question online from Tom. Hi, Tom. Yeah, hi. I missed something fundamental here. Sure. Over what fraction of the moon are you observing? Okay, so the Changi one and two missions were polar orbiters. So there were observing the entire moon. I see. Okay. I will show some observations from Earth that we took later with the VLA and such. But, and those will just obviously be the near side. But yeah, this is a projection of the entire moon. Okay, great. Thanks. That helps. Okay. Yeah. So this is the near side of the moon, the Mare that we see from Earth. And then here's the far side. So you see the moon has a lot of weird dichotomies, right? All of the activity pretty much is on the side that we see from Earth. And there's not as much going on in the far side, which is very interesting. Yeah. Yeah. So he's asking, so does the brightness temperature we're seeing depend on the size of the rock? So that what we don't know is does that lost tangent dependence on mineralogy depend on the total size of the crystal? So are we only seeing the large Illuminite crystals at three gigahertz, basically versus the small ones? And that I think we have to do more lab measurements to really know if there's some size dependence there. And then as far as the physical size of the rocks, that's basically what you can get out of the comparing the different frequencies that some three gigahertz we'll see right through a rock this big, but it will stop a 37 gigahertz signal. So now we're looking on expanding, how can we expand our understanding beyond what the Changi mission could measure on the surface and could we send other instruments? So we're looking at the possibility of sending a small CubeSat, which is a refly of an Earth atmospheric instrument. It's already orbiting here called Tempest D looking at the moon at 90 gigahertz and Green Bay Telescope in West Virginia happens to have a great 90 gigahertz mapper that we've been mapping the near side of the moon with. So we're trying to model this and compare that to our maps of the moon. And then that helps us constrain these models to understand what is actually going on the moon and these microwaving missions, different frequencies. And so here we have a surface temperature model. These are models of Changi here. Here's my postdoc help make these models up. Here's what the mood should look like at 90 gigahertz over the course of the month. Here's what should look like at three gigahertz over the course of the month. And what's cool about this is you see this is good revealing that we're seeing below that depth of the diurnal variations, right? So at 90 gigahertz you're still seeing well into that depth, right? And so you see a day-night cycle happen. But at three gigahertz, I challenge you to pick out the day-night cycle going on here. It does vary by about 10 Kelvin over the day-night cycle, but it's a very small variation. You might see the colors change just a little bit. And so what that's showing is that at these long wavelengths like three gigahertz, we're seeing deep enough that we're getting information about the moon below the diurnally varied layer. And that allows us to peek into potential changes in the geothermal heat production of the moon, okay? So what we're talking about here is that, and then I don't know if I have, hey, hopefully I have another slide explaining why geothermal heat is interesting later, but if not, I might go to it separately. But basically what we're seeing here is right, we have these different weighting functions for different frequencies. So this is a plot for the weighting function at three gigahertz in Lunar Mare, which have a lot of ilmenites in general, versus the Lunar Highlands, like the white parts of the moon. Basically we could see a little deeper into the subsurface. And then here's models of different geothermal heat profiles, right? So that was that maximum temperature, or maximum temperature and minimum temperature of the day-night cycle. And then below this diurnally varying layer, which goes about 70 centimeters on the moon, your temperatures as a function of depth are going to be controlled by the amount of heat coming from the interior. And that's exciting because now you can figure out what the moon is made of, right? We have lots of measurements of the surface of the moon or surface of planets, but what is the other 99.999% of the moon made of, right? One of the few ways you could tell is by looking at the radiogenic heat reductions of the body, because you have uranium and thorium are both what's called refractory elements. So when the solar nebula was there, they didn't get boiled off, basically. And other elements like aluminum and calcium are also refractory elements and make up a lot of the earth too. Silicone is almost a refractory element. So you measure this gradient, you can back out how much uranium and thorium is in the bulk moon. And then from that, you can back out how much silicon, calcium, aluminum, most of the mineralogy of the moon is explained through. And so by measuring the geothermal gradient, you're understanding what the interior composition of a planet is. And that's fun to compare the earth versus the moon. How did they form? And that tells us a lot about the formation of moon. Was the earth already differentiated into layers? Because these elements like uranium and thorium tend to concentrate in the crust and the elements that form there. And so if the moon or the earth had already differentiated into layers, and then the big impact happened that caused the moon to form, that's a different story than if the earth hadn't gotten to that stage yet when the impact happened. And then we compare this to what we're trying to measure with the insight mission on Mars, for instance, we're trying to measure the geothermal gradient there to compare, well, how does the solar system vary? You know, the disk forming the solar system varies as you get farther away from the sun. So that's the story behind what we're trying to measure this slope here. But basically, what we've found is that if we are seeing deep enough into the subsurface, we can actually measure this from space. We're remotely measuring the geothermal gradient. Traditionally, you have to drill down into the ground to measure this. But now we think on a body like the moon or Mars, we can see quite deep. We can't do this on earth because there's a lot of water in our soil. It both causes this diurnal variation. Because we have water and air in the forest space of our soil, the diurnal and seasonal variations of earth go 50 meters or something under the ground. And so you'd need to see very deep. And then also, microwaves are very attenuated by water. And so we can't see very deep into the subsurface. But on a dry place like the moon or Mars, we can see low. And then because there's no air on the moon and barely any air on Mars, these diurnal variations and seasonal variations don't go very deep. So that's not a specific question. Sure. That's good. But there's a lot of discussion about the actual water content of the soil. Do you have to know what that content is to understand the data that you're getting from this in order to be appropriate or not? Not. Well, I mean, we'd love to see a change due to water ice. But I'm talking more about liquid water. Liquid water will have a very high loss. Ice actually has a very low loss. And so what we're trying to do with this instrument is we would like to fly it in a polar orbit around the moon, look at the poles of the moon, see a difference in the loss tangent in that polar soil that we could relate to the amount of ice content. And so there you're comparing soil with vacuum in its four spaces versus soil with incredibly low loss ice in its four spaces. And so it's a question of whether we can differentiate that or not. And so just to show you that the proof is in the pudding that we can see this signal, here's the three gigahertz temperatures at midnight on the moon. We can see that most of that is, you know, it's called at the north and south pole at high latitudes here. And it's warm at the equator. If we take out that latitudinal trend, we can see that there's this one region again on the moon, there's the moray on the near side here, is a lot hotter in the microwave data. Most of that's because it's darker, right? A dark soil is going to absorb more heat. And so it's going to be on average about 10 Kelvin warmer. But if we even correct for that albedo, what we see is there are areas that are still quite a bit hotter in microwave brightness temperature here than we would expect it would be given their latitude and albedo. And there's areas that are a lot colder. These colder ones are due to, this is a temperature taken at midnight, right? And so if we have a high loss area, right, we're not going to see very deep. And so we're going to see something closer to the surface temperature, which at midnight is very cold. It's like 90 Kelvin, right? So this is Mari-Trinclopotus, we're Apollo 11, we're here. It's one of the highest omenite content areas on the moon. And so we see it is cold in this map. Now you could say, oh, well, these areas must be areas that are very transparent or we're seeing quite a bit deeper. But we could see that if we could see if they were lower density than they expect with the thermal infrared measurements. And we don't see anything like that. So these areas, we think are special because they're actually having a higher geothermal heat flux. And that's exactly what we expect, right? I should pop up this picture before that. So this is the map from that gamma-ray spectrometer instrument, mesothorium. You look at the spectrum of high energy gamma rays coming off of the surface of the moon. We can actually identify different atomic structures there. So we see thorium or uranium or potassium, we can map from orbit. We put those together to create a map of what we think the geothermal heat flux would be like if that represents a substantial part of the crust. And then we can compare that to the data. So here's forward model of what we think the microwave radiometer would see at 3 gigahertz given that model. This is all theory in here, basically. And then here was the data. And just to drive the point home that if we had zero geothermal heat on the moon, we would see this. So we didn't have those spatial variations in geothermal heat or uniformed geothermal heat on the moon. So we are, in fact, I think measuring geothermal heat of the moon from orbit. And so with this, we can start to fit models of the geothermal heat of the moon. But we want to get better. And we really are only doing it with a single frequency. And so to measure a gradient, really, we'd like to measure it in multiple frequencies. But so far, the Chengi 2 data we have can only see that deep enough at one frequency. There are a few places that give us hope that they might be so warm, such high geothermal heat flux that we can see them even at a higher frequency. And so here's a few of them. You can see these guys that are bright red here. And not only are these odd places high geothermal heat flux, apparently, from the 3 gigahertz data, they're also ancient volcanoes, by the way. So these are all the things that people have been mapping as highly evolved silica features on the moon, which means part of the crust has remelted concentrated elements of silicon in there. And so these are the closest thing we have on the moon to a real volcano. We have a lot of flood basalt and such on the moon, very thin, maybe, volcanism, but this highly solicit volcanism is actually pretty rare on the moon. So here's what some of those areas look like up close. So here you can see, this is what we call a reel on the moon. So there was an ancient volcano here, and an outlet vent, lava flow here for a few hundred kilometers. This is the Marius Hills, where there's these little dots all over, these little pockmarked there, teeny volcanoes there, all over the surface here. And we see them both as higher than expected, at brightness temperature and microwave. Here's another one that's very interesting, that's very similar to Marius Hills. Here is another thing that we think this has been mapped as potentially an ancient volcanic caldera, but it's kind of flooded over by the flood basalts of the Marius here. And those maps that you're showing there are high resolution, are they coming from the same data set or a different data set? No, so this is from the LRO, both the cameras and the laser altimeter, the use. So it has a laser altimeter looks and times the speed of light and return back, and then visible cameras. Yeah, yeah. Do you have a question? So when you have an impact, most of the impactor is vaporized in the impact. Right, this is what we sadly learned with Meteor Crater in Arizona, Beringer bought the land in 1905 or whatever, because he was sure that there was a giant block of metal sitting underneath that crater. He drilled for 30 years and finally gave up and donated the land to the state, and that's why we have Meteor Crater as a place we can go observe. But basically, normally, we don't have much remnant. That's really turned into vapor, can go far, can be broken up into little pieces. So I don't think you have to have an extremely low grazing impact to have any hope of the impactor actually surviving and leaving. So I think it's more not a problem with the measurement as much as the impact physics, I guess, is whether there would be anything to look at to survive. That is one of the, you know, talking about the ice on the Moon or Mercury. That's what we think is you could have a cometary impactor. And it's not that the comet happened to hit the pole of the Moon or Mercury, but it's that that water vapor got caught in the gravity of the Moon or Mercury and bounced around and eventually landed, caught its way in poles, which are pole fingers. So that's a way of looking at the survivor of an impactor, but normally we're lost in the And the one we're most excited about is this area on the far side, which is kind of this weird little thing, right? Nothing too dramatic about it. It's a little feature. It's about 20 kilometer wide. So it's a big feature. But it has been mapped as potentially being also called Berylite figure and its interest was brought to it because that gamma-ray spectrometer basically found that it's one of the highest thorium concentrations on the Moon. So what this seems to be is, like I was saying, when you evolve the silicon, when you re-melt the crust, right, you'll get more silicon in the crystal structure, but you'll also get more of the heavy elements like uranium thorium, which are concentrated in that re-melt material because they don't like, they have big ionic radiases, so they don't like to go into most compounds. And so they kind of get left behind in the melt. And so they're always stuck in the last melt material. And so you end up when you re-melt the crust several times, you'll concentrate these. Oh, so this is telling us that there's some feature here where there was a lot of recycling of the crust or some supply from an area of the crust that was recycled coming up to the surface. And this is what it looks like in the three gigahertz data, all right? We've got this bull's eye of about 10 Kelvin-Hotery. So unless those features are on the near side of the big world, like five Kelvin-Hotery. And there's no weird density anomaly or rocks that we've seen. This H-parameter is a measurement from thermal infrared that we go out for measuring density on the surface. And what's cool about this is not only does it, it's so hot that it shows up in the three gigahertz at our longest wavelength, but seeing the deepest, we can also see it in some of the shallower wavelengths, and potentially even in the real shallower wavelengths. And so we're actually seeing down into the surface. We have saw it also, this is the 10E1 or 10E2 mission, which was at a 50 kilometer orbit, and then the 10E1 had the same instrument, but it was at 100 kilometer orbit. So we don't usually use the data as much, but it saw the feature as well. This is just a plot of temperature as a function of distance. So what it's showing here is when something's far away, it's colder during the daily cycle at the bottom end. Then when it's right on this hot spot, it's always hotter. So it's always hotter day and night. And the only way we could come up with to get something that stays hotter day and night is to give it a high geothermal heat flux. And so then we can model for a given geothermal heat flow, right? So we think the background of the moon is something like eight, five to eight milliwatts per meter squared of geothermal heat flux. And this feature, so now taking that as a reference point, this feature is something around 100 milliwatts per meter squared heat flux, which is pretty hot even for earth standards of geothermal heat flux. That's something that you would build your geothermal power plant on one of these things. So who knows, maybe we've discovered we're 400 years and now there's going to be a geothermal heat plant on the moon. But solar power is pretty efficient on the moon, actually. So we might not need it. But yeah, so this is an exciting window into a very evolved part of the moon. And so basically it appears that we're seeing geothermal heat flux in some of these very high heat flux places with these short wavelength radiometers. And how well can we see if we could see in longer wavelengths? So now we're taking these models of brightness temperature as a function of frequency for different geothermal heat fluxes here. And we can see that it causes a little difference at the low frequencies or at the high frequencies like three gigahertz. But now if we could see lower frequencies and see deeper, right, we're just zooming in here, we can get a lot bigger bang for our buck, right? We can measure, if we look at 420 megahertz, which is this model here, we should see a larger signal for the same geothermal heat flux. And oh, here's finally a map of the thorium here again. So that's basically what's causing this model. And then we've been doing observations with the VLA, which is the big space telescope array in Socorra, New Mexico. So we've been looking at it at a couple of different frequencies here is the map from 420 megahertz. And you can see that basically we're observing higher brightness temperatures in this exact spot. So we're pretty excited about this result. But here we are from Earth, basically measuring the geothermal heat flux of the moon. Around 120 kilometers or so. That's the surface of the moon, yeah. And that's what we're tempted to. So we may even do this for Mars as well because on Mars, because it's a smaller object in the sky, we can actually use a bigger spacing of the antennas at the VLA and could get like 300 or 400 kilometer resolution on Mars, which it's not bad for trying to do a measurement like this. And then that's also led into, so I want to grant from to develop this instrument that we're now building at JPL to build a microwave radiometer to go all the way down to 300 megahertz to six gigahertz frequency. And so we're, we're building that right now and competing it for some of these upcoming lunar missions to hopefully measure this gradient even more precisely, either from the lander or it could be on the north. Okay. So basically it's kind of cool. What we can see is that we think we are in fact seeing subsurface temperatures on the moon and we can see deep enough that we think we're seeing geothermal heat flux so we can map this fundamental measurement of the composition of the moon from orbit or even for the near side of the moon from Earth. And we're looking into potentially, you know, can this detect ice in the polar regions and such as well. So that's what I have for here. I do have background on Mars if I have more time but if you, if you want to stop, we could stop there. Okay. Okay. Yeah, so this is what I'm doing now on the Mars rover. Now that you have the introduction on this whole process course, it would be great if we had a microwave radiometer on Mars. We don't, but the new Mars rover Mars 2020 does have a ground penetrating radar. Ground penetrating radar, it basically sends out a signal and then looks for reflections back at all these different frequencies. But this ground penetrating radar has what's called passive radiometry mode where it has an internal calibration source that it can switch back and forth to. And so it does work as a crude microwave radiometer. And so that was basically my proposal for joining the Mars rover mission. Here's where Mars 2020 landed. And insight had a geothermal heat flow probe drill. I don't know if you've been paying, you know, which was, I was a co-owner on that instrument as well, built by the German Space Agency, which if you've been paying attention to the news, it unfortunately only got to about 30 centimeters deep, right? It was showing we need to get to something like three meters deep to actually measure the geothermal gradient on Mars. So it's kind of sad. People worked for 15 years for the thing to go to Mars. It got there. We tried really hard to get it down, but it did not burrow to death. And so that's why, you know, kind of making lemonade out of that situation, they can use all the same models we've developed for insight to try to understand this measurement from the Mars 2020 instrument. And a lot of the same models I showed you that picture early on about the shadows caused by the, caused by the lander here. I can do those same models in the rover and we could predict what the temperatures function of depth will be. And now with the much lower frequencies we have in this ground penetrating radar, which go down to 150 megahertz, we can see quite deep into the surface of Mars. The loss is a little higher on Mars than on the moon, but we're still seeing probably 10 plus meters deep. And so with that, we're expecting that we could see different heat as a function of depth, different brightness temperatures as a function of frequency with the instrument. And the first date is coming in. We've got like a few data points and they seem kind of along those lines. We actually get a really good opportunity because this is a measurement that we want to do really when we're sitting in one place for a long time, we can integrate over a long time, which every other instrument wants to drive around and shoot lasers, things and trying to grind rocks and such. But there's a period called conjunction coming up where Mars actually goes on the other side of the sun from the earth, comes up in about three weeks, I think. And that is a time where the rover is out of communication with the earth for about two and a half weeks. So during that time, we're going to be sitting and doing this measurement at about 10 frequencies over this band here. So hopefully a month from now, we have some really neat new data. Yeah. And so one of the things we're going to also measure is the soil properties and how the ground is warming up over time from the presence of the rover. And this is all extra stuff. But anyway, here's what we would expect to measure, for instance, over time. So this was now geoderma gradient. Here's the day night cycle. You can see it at the higher frequencies, but not at the lower frequencies. And then as we heat the surface by the rover sitting there, because the rover has a hot, radiogenic isotope heat source, we should see it warming over time. So this is the observation we're hoping to take on Mars coming up next week here. I don't think I really had anything too much else to show there. I guess this is just an example of what that would look like at two different geoderma leaf boxes. So let's see. Hopefully we can measure that kind of difference. Yeah, you heard. That's okay. It's great. Yeah, there is some. But Mars' atmosphere is about as dense as our atmosphere is about 150,000 feet. So it's very thin. It's about a thousand times thinner than the atmosphere here in this room. And so there's not much conductive or conductive heat transfer through the atmosphere. So it's mostly you can use the same kind of radiative models. There is some heat transfer through the gas. And that's what's kind of interesting. It's the heat transfer through the soil is also mostly dependent on that heat transfer through the gas. And the pressure of Mars' atmosphere is right at some boundary where you go from what's called Fickian to Newton diffusion. And so it's right at that controls the thermal conductivity of the material. And so there are sometimes on Mars' history where the atmosphere pressure was different and would change the way the heat flow through the soil pretty dramatically. And that's actually a complication in this. And now I have to exit from the slide to see if I included slides like that in here. No, I don't have that in here. But yeah, but basically Mars' climate history is actually going to be recorded in this heat flux measurement if you really did it super precisely. Yeah, that's actually been a proposed you know about the moderate minimum on earth where the during the Middle Ages there was a period where there weren't sunspots. And it looks like Europe was a couple degrees colder. One of the tests to see that whole thing all holds together and it was really colder because of the sun changing versus some people say, oh, it was cloud cover changed because he didn't have as much solar activity as to if you could really precisely measure the temperature as a function of depth on the moon, then you could see that bump in the history of the heat conducting down. You could actually measure things like that. But those are very small changes. Okay, well, yeah, that's I already showed you my extra slides. Here's where you played it safe that I was not on my own computer, so I didn't go to other presentations. All right, so let's start with folks online. Any questions from anyone online? Just go ahead and raise your hand if you have a question. Okay, I don't see a hand. Anyone in the room have a question? Oh, yeah. From other talks that you can use kind of the history of cometarium tasks and you weren't used to the comet based on the water isotope ratio. Is that something this can grow or is it not real? So, not at these low frequencies like I'm looking at to see feet, but high frequency microwave geometry was actually used on the Rosetta mission to the comet. They had a high frequency microwave kilometer that looked at I think it's 562 gigahertz. And what's cool about that is there's a when you have water in a vapor form, which you could get if you like crash the rocket into the falls and moon, which we did before about 10 years ago and maybe we'll do it again. But if you observed it with one of these microwave instruments or you observed the comet with the microwave instrument, the water vapor has a rotational band there. And what's cool is that if you have different isotopes, your oxygen for instance in there, you'll actually rotate at a slightly different frequency. And so you'll see that wave length shift. And so you could see a peak for if you have a really precise microwave spectrum over that band, you could see the water with 016 and water with 018 and water with 017, which is what they say. I think they didn't quite get the old 17 measurement as well as they hoped there was that instrument. But yeah, that's so that is certainly a thing you could do but with higher frequency microwaves and what we're talking about here. So yeah, so it would probably be a separate instrument than this. You could imagine a really super broadband instrument, but for those higher. So we have our instrument we're developing has 4,000 channels between 6 gigahertz and 300 megahertz. But that'd be very low resolution as far as the spectrum or we want thousands over a short wavelength band. Any other questions? All right, I'm going to ask one of them. So you mentioned that cube set. Tempest was up in there. And it's already in orbit around Earth. So is it just a matter of orienting it and pointing it at the moon? Where is that a technical challenge to do that? I mean, basically, it's a matter of space and resolution, right? So the 90 gigahertz maps I showed from Green Bank on the giant Green Bank telescope was about the same distance from the moon as Tempest, right? We're about 20 kilometers resolution. So now you can imagine taking the resolution loss when your telescope is this big. Yeah, in order to get high resolution with that, you need to be orbiting the moon. Okay, but Tempest can't be put in orbit around the moon. Yeah, I mean, it doesn't have to do something. Yeah, I mean, the same way the space station can be put around the moon. But I mean, that cube set really is stuck in orbit around the moon. So it's really a matter of it's a small aperture for observing the moon. And that becomes your limiting problem. Yeah, okay. But I suppose it could turn and look at the moon as a, probably it's just as a point source. Okay, interesting. Okay. Yeah, we actually, one interesting thing of that, we tried to lobby for, was it WMAP and an official to look at the moon in some of these frequencies for this same reason, because that, that could get really high. I'm assuming that wasn't successful. No, no. And then when that didn't work, we tried to, after the Elkrash impact, Elkrash impact in the polar moon, they were actually, we did really push for WMAP to collide it into the polar moon to create another plane. But they ended up, they kept it in a parking orbit. Yeah, I can see how that wouldn't have worked with the collaboration. It's not probably how they imagined it. This is how we're thinking of these big astrophysical observatories. It's things we could crash into the moon. How did we smash it into the moon? It's really the fundamental thing. Okay, so now I know we could watch out for you guys. Don't run out of project. Smash you in the moon. Any other questions about things we could smash into the moon or Mars if we're thinking big? Okay, I don't see anything else. So let's thank Matthew one more time and we'll close out for a second. Thank you.