Planetary Radio • Nov 25, 2020

More Moon Water and an Update from Venus on Our 18th Anniversary!

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On This Episode

Jane greaves

Jane Greaves

Astronomer and professor, Cardiff University

Casey honniball sofia

Casey Honniball

NASA Postdoctoral Program Fellow, NASA Goddard Space Flight Center

Bruce betts portrait hq library

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

Kaplan mat headshot 0114a print

Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

We celebrate 18 years of Planetary Radio with two great features and 10 personal questions for host Mat Kaplan from Planetary Society Chief Scientist Bruce Betts. Astronomer Jane Greaves is back with an update on the phosphine gas detected above Venus. Then we find water right out under the Sun on our own Moon. Research leader Casey Honnibal tells us how her team found it using the SOFIA telescope on a 747.

Phosphine and Venus
Phosphine and Venus Artist's impression of Venus, with an inset showing a representation of the phosphine molecules detected in the high cloud decks.Image: ESO / M. Kornmesser / L. Calçada & NASA / JPL / Caltech
Casey Honniball and SOFIA
Casey Honniball and SOFIA NASA Postdoctoral Program Fellow Casey Honniball and the Stratospheric Observatory For Infrared Astronomy (SOFIA).
Moon, SOFIA, and an artist’s impression of locked away water
Moon, SOFIA, and an artist’s impression of locked away water This illustration highlights the Moon’s Clavius Crater with an illustration depicting water trapped in the lunar soil there, along with an image of NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) that found sunlit lunar water.Image: NASA / Daniel Rutter

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Trivia Contest

This week's prizes:

A copy of Alice George’s new book The Last American Hero: The Remarkable Life of John Glenn.

This week's question:

How many of the 88 IAU-defined modern constellations have “dog” in their name? It will be “dog” in Latin, and we’re talking about domestic dogs, not foxes, wolves, or werewolves.

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, December 2nd at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

Mars Odyssey is the longest continuously active spacecraft orbiting another world. What spacecraft is the second longest continuously active spacecraft orbiting another world?


The winner will be revealed next week.

Question from the 11 November space trivia contest:

Who gave the names to most of the lunar maria that are used today--those approved by the International Astronomical Union?


17th century Italian astronomer and Jesuit priest Giovanni Battista Riccioli gave most of the names still used today for the lunar maria.


Mat Kaplan: Water all over the moon and an update from Venus this week on Planetary Radio. Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. Happy anniversary Planetary Radio. It has been 18 years, to the day, since our little show was first heard. Stick around for a sweet yet understated celebration with Bruce Betts in this week's What's Up segment.

Mat Kaplan: In the meantime, we'll do what we love to do, and that's bringing you the passionate explorers who are revealing the wonders of our solar neighborhood and the farthest reaches of the cosmos. We'll start shortly with an update from Jane Greaves about her team's discovery of phosphene gas in the atmosphere of Venus. There's news on that front. Then we'll go to the leader of work that has found water on the moon, this time, not in those permanently shaded regions at the poles, but on the brightly sunlit surface as well.

Mat Kaplan: I think you'll enjoy hearing about this from Casey Honniball. The big story in planetary science since our most recent issue of the Downlink has to be China's successful launch of Chang'e 5, the first lunar sample return mission since the 1970s. Kudos and best wishes to the international team behind this effort. Topping our stories in that November 20th edition of the Downlink is approval of the European Space Agency's Aerial Mission.

Mat Kaplan: Aerial will focus on about 1000 exoplanets measuring the chemical makeup of their atmospheres, which sounds like a big step in the search for life elsewhere. You may also want to check out the new selfie captured by the Curiosity Rover. It was snapped at a location called Mary Anning, named after the 19th century paleontologist whose discovery of Marine reptile fossils was ignored for years.

Mat Kaplan: As always, there's much more at You can also have the Downlink delivered for free every week. Here's a little treasure found by my colleague, Jason Davis. It's a young Carl Sagan's contribution to a 1963 NASA documentary about Mariner 2, the very first interplanetary spacecraft.

Carl Sagan: Many theories of the Venus environment have been suggested. However, new information eliminates at least some of these theories. Measurements with radio telescopes show that there is region on Venus where temperatures are greater than 600 degrees Fahrenheit. It is just possible that the surface temperature could then be almost earth life and life as we know it could exist there. However, it is more likely that if there is life on Venus, it is probably of a type that we cannot now imagine.

Mat Kaplan: We've learned much more about Venus in the 57 years since Carl spoke those words, but so many mysteries remain. Many of you heard Jane Greaves on our October 21st episode. Jane led the research that found evidence for phosphene gas in the Venusian atmosphere and found it at roughly the altitude where temperatures and pressures are Earth-like. I rarely bring a guest back on Planetary Radio after only a few weeks, but there have been further developments in this story.

Mat Kaplan: Jane generously agreed to return. She is a professor in the Cardiff University, school of physics and astronomy. She has led and participated in studies of planets and how planets form from protoplanetary disks around stars. She also studies the moons in our own solar system that may be able to support life. Jane was awarded the Institute of Physics, Fred Hoyle Metal in 2017. Jane, welcome back to Planetary Radio.

Jane Greaves: Thank you very much. Lovely to speak to you again.

Mat Kaplan: We first talked of course, just over a month ago, science has taken its course since then with other researchers examining your data and conclusions. And I've read that your team has done the same. What is the latest news?

Jane Greaves: Well, the main thing we focused on is the discovery that there was a bit of a calibration issue, which broke down into several small issues with our original data from the Alma telescopes. The observatory there has been super helpful in sorting that out for us as a result of which in fact, observatory performance overall will be better for other observers. So yeah, that's been our main thing.

Mat Kaplan: Well, that's maybe we are witnessing once again, science at its best. Does this mean that your feelings about the level of phosphene in the Venusian atmosphere, have you had to back off somewhat?

Jane Greaves: Not entirely. I think we've just adjusted the numbers. In a way it's been the best of times and the worst of times, if I could quote, because we were very keen to use open science, so people could look at exactly what we've done, and people have indeed done that. What's been slightly less open is they didn't get back to us and say, "Here's how you think you could improve." Most of them just rushed something out which left my team, which is really small, scrambling to try and come up with scientifically valid answers.

Jane Greaves: But with the enormous help of the ALMA observatory, particularly the European and the European Southern Observatory, ESO, they've really done a superb job on the calibration. So now we can say in the ALMA observation, there is less phosphene than we originally thought, a few times less, but it does give us an exciting insight to parts of the planet where we think it peaks. And although that observation done in 2019 now doesn't look ideal, we can certainly go back and have another go.

Mat Kaplan: But what about that wonderful graph that plotted the original ALMA results against the observations by the Maxwell telescope in Hawaii? That matchup between those lines look so conclusive? Is it still there?

Jane Greaves: It's still a matchup. The lines are in the right place, but I guess as astronomer doesn't normally do planets service thinking they ought to be kind of equally absorbing, that I think is not the case. It does what lines on Venus do is sometimes the line is stronger than others. So, that's something I'm trying to do at the moment. Just see if we can get an idea of the behavior over time, because our telescope observations done with the James Scott Maxwell telescope actually took place over several mornings all the way back in 2017, but over a week. So we can look at timescales of variability as well.

Mat Kaplan: I was going to ask about that next, because I read that it seems more apparent now that the concentrations of phosphene vary over time and from place to place above Venus.

Jane Greaves: Yeah, that really seems to be the case. So the ALMA data are really exciting for looking at different places, which the JCMT data can't really do. The Alma data is still not perfect in the sense, this kind of instrument gradients across the face of Venus. I think we can point at a few places and go, "Hmm, that looks like a bit more phosphene," but the significance of the features is maybe five times the noise anyway. So we don't want to get too bold in what we say now. But we're really looking forward to more rounds of observations.

Mat Kaplan: I remember, at least I believe I remember, a month ago, bringing up with you comparing these findings of phosphene with those findings that seem to come and go of methane on Mars. Do you still see that as a pretty good analogy?

Jane Greaves: Well, Mars has the advantage that some of the rovers can explore it in situ and in some way that raises bigger puzzles. Because you're not quite sure what a waft of gas blowing past a rover turns into. And it seemed from an orbiter say much higher up looking at bigger scales. So it could be something like that. Venus probably doesn't have quite such local effects because the really high speed winds in the clouds would kind of smooth everything out. But we're just finding, we don't have quite enough information at the moment.

Mat Kaplan: Hasn't there been other recently found evidence of phosphene, or at least something that contains phosphorous in the atmosphere? And I think it was someone at a university not far from me, Rakesh Mogul at Cal Poly Pomona who looked at very old data. I think he was inspired by your work.

Jane Greaves: Yeah. That's really exciting. Because he is the mass spectroscopy data from the NASA pioneer Venus probe that went down through the clouds in 1978. And those results were mainly published in 1980. Not a technique I have any familiarity with, but they've done a very sophisticated re-analysis now to say the mass of some molecule that was detected really looks like phosphine and they need kind of bits of phosphene if the molecule was then broken up.

Jane Greaves: I think one of the most impressive things is somebody helping Rakesh with that work, was an original member of the team in 1978. So they're getting the best possible advice.

Mat Kaplan: That must have been thrilling for that original member of the team to see science coming from this old data, which happens so often, of course.

Jane Greaves: It must. And I wonder if they have to look at the garage for a notebook.

Mat Kaplan: Well, they're lucky that the data was still readable. I know that's been a problem with some other probes from when you go way back where they had to resurrect old computer drives to be able to read the data.

Jane Greaves: Yeah. I don't know how much they've actually been able to do that yet. Fortunately, it was published in 1982 with the numbers describing the matters of the molecules they saw. I don't know if they had to go back and look at, I don't know, punch cards or large magnetic tapes. I'll be exciting to find out.

Mat Kaplan: Absolutely. I think this is evidence of the continuing excitement that has been generated by your findings. There was this great quote from Sanjay Limaye I don't maybe, you know how to properly pronounce his name, is a planetary scientist at the University of Wisconsin. He says, "I've waited all my life for this." And the feeling that really, this has re-invigorated the interest in examining Venus much more closely than we have recently.

Jane Greaves: Yeah. I think interest has been bubbling away in some quarters for a few years now. And Sanjay's work's been really impressive to me. So they've put together some of the data about mysterious ultraviolet absorption in the clouds of Venus, something it comes and goes and you can see in patches. And then a few days later, it's changed. And that's been suggested because the particles responsible floating in the clouds are thought to be a few micrometers in size, which is like the size of microbes.

Jane Greaves: It's been suggested, I guess this is actual like microorganisms or perhaps the dead ones that don't make it coming and going in clouds or colonies. So I'm really excited by that parallel piece of evidence as well.

Mat Kaplan: Well, that's an exciting hypothesis. All of this means that no one should be any less interested in sending a properly equipped spacecraft to Venus.

Jane Greaves: No. I think that's correct. It may turn out to be ... we're very early in the hunt for life in the solar system. I think it may turn out to be some pieces of the puzzle or a bit wobbly, didn't quite fit, or in the case of phosphene, maybe there's some peculiar chemical source in the atmosphere that nobody's ever thought about because it doesn't happen on earth.

Jane Greaves: So it might turn out to be, there've been some false trails or it might turn out to be with everybody of being spectroscopy and the ultraviolet and us in the millimeter waves, maybe we're really onto something. So yeah, certainly a really nice case to send a mission to, in any case, a fascinating planet with a climate so different to our own.

Mat Kaplan: So the hunt continues and hopefully expands. Before I let you go, I told listeners upfront about some of your other work, but I left out a fascinating conclusion about protoplanetary disks that you and your colleagues there at Cardiff reached in 2018. One might say it's a real gem. If you know what I mean? Could you tell us about that?

Jane Greaves: Let me make sure we're talking about the right one. Give me another hint here.

Mat Kaplan: Nano diamonds.

Jane Greaves: The nano diamonds, not the one about jiminga or jiminga, which is a whole different things.

Mat Kaplan: You can talk about that one too. I don't think I read of that.

Jane Greaves: The jiminga one is search to see if there is a planet forming disc around a dead star, a Pulsar, and that's a project that's ongoing in the background. It looks like maybe it's a null result but still a dam of interest to me. So, the nano diamonds, yeah. Is nanometers scale particles, as you might imagine. And I managed to link some radio observations with some infrared spectra of these particles and suggested it's these spinning nanometer scale diamonds that are responsible for something called anomalous microwave emission around stars. So, that was a really fun project. It's perhaps a smaller area of science, but it's really nice to feel you've contributed something.

Mat Kaplan: I think I remember you saying something about when we spoke last time that you like to have the freedom to do research, to go in directions that peak your interest. And this certainly sounds like that is evidence of that, shiny objects in the sky, even if they're at the nanometer scale.

Jane Greaves: Yes. I do get perhaps it's a mental disorder. I don't mean in any disrespectful way, but something like attention deficit disorder possibly is behind the going, "Oh look, a new shiny thing," when I read the literature. But I think this is great because you can do science in a very long-term careful way building on something done by huge teams. Like the discovery of gravitational waves would never have happened without huge teams. But there's also, I think a role for a kind of, I don't know, like a deck door bird approach, poking around in shiny stuff and going, "I like this one. What does this one do?"

Mat Kaplan: I think it was Isaac Asimov, I've heard quoted saying that science is not so much, "Aha, I have found it," as, "Hmm. That's interesting. That's strange."

Jane Greaves: Yeah. I think that's very valid. So particularly the one about the anomalous microwave emission really wasn't that strange. When you talk about big data and the difficulties of gigabytes, terabytes, petabytes of data, that particular one I counted up and although it was data taken by the really large green bank telescope in the US so that does actually handle huge data volumes. The numbers that I was scratching my head over was actually 81 bytes of data. So possibly the only bit of data I've ever dealt with you could carry it around with you to tube on your arm or something.

Mat Kaplan: Wonderful stuff. Thank you, Jane. I'm very grateful. We, as I said up front, don't often have guests return so soon, but this work remains so exciting and so interesting. I'm really delighted that you were able to give us this brief update.

Jane Greaves: Well, thank you very much. It's a pleasure.

Mat Kaplan: Astronomer Jane Greaves of Cardiff university. We'll move outward from Venus to our own moon and the new water discovered there that'll be right after this break.

Sarah Al-Ahmed: What a year it has been for space exploration. Hi, I'm Sarah, digital community manager for The Planetary Society. Will you help us celebrate 2020's greatest accomplishments? You can cast your votes for the most stunning image, the most exciting mission, the most surprising discovery and more at We've also got special year-end content on our social media channels. Voting is open now at

Mat Kaplan: Magnificent desolation. That's how Buzz Aldrin famously described the moon when he and Neil Armstrong set foot on our big natural satellite. The assumption for many years was that you couldn't find a drier place in the solar system. We've now known for several years that there is water in the permanently shaded areas at the top and bottom of the moon, lots of water.

Mat Kaplan: And as you will hear from Casey Honniball, there was evidence of something that was at least a cousin to water out there on the brilliantly sunlit surface. Casey is a NASA postdoctoral program fellow with the agencies Goddard Space Flight Center. As you'll hear, her projects have brought her to some of our planet's most remote regions. She's also lead author of the paper published a month ago by nature astronomy titled Molecular Water Detected on the Sunlit Moon by SOFIA.

Mat Kaplan: SOFIA of course is the stratospheric observatory for infrared astronomy, that big telescope mounted inside of Boeing 747. I talked with Casey a few days ago. Casey, thanks very much for joining us on Planetary Radio and congratulations on your leadership of this team, which has found even more water on the moon. We've talked frequently about the water hiding up in those permanently shaded areas of the poles, but your work, your team's work has gone considerably beyond that. Welcome once again.

Casey Honniball: Thank you. Thank you for having me.

Mat Kaplan: So Paul Hertz, the head of NASA's astrophysics division said, "Now we know it's there," elsewhere I assume on the surface, are you as confident as he is?

Casey Honniball: Yeah. So, the results that I show in my recent nature astronomy paper, which were part of the NASA press release conference were actually showing definitively that molecular water, like we drink, is present on the sunlight surface of the moon.

Mat Kaplan: I want to come back and talk more about how you know this is water and not some other compound. But first and I have a soft spot in my heart for SOFIA. Since I also got to take one flight on it, just as a passenger, I'm afraid. You use SOFIA and forecast faint object, infrared camera to examine the moon. Why was SOFIA the right ... and forecast? Why were these the right tools for this observation?

Casey Honniball: Yeah, so that's actually a really interesting question. From a ground-based telescope, we can't observe this signature of water that we were looking for. And so in order to do that, you either need to be above the Earth's atmosphere as much as possible, or you need to have a spacecraft. Currently, there's no spacecraft available to make this type of measurement that we needed to look for the water and SOFIA flies above 99.9% of the atmospheric water vapor, which allowed us to make this measurement, which we couldn't have done from a ground-based telescope.

Mat Kaplan: Is this also why you've been a part of efforts that have sent telescopes up on balloons above most of the atmosphere, and you spent some time in the auto comet as well at very high altitudes.

Casey Honniball: Yeah. And that's partly the reason that we go to high altitudes is to get above the atmosphere and get above the water vapor that kind of plagues ground-based observatories.

Mat Kaplan: SOFIA was built to look across the galaxy and back toward the beginning of the universe primarily. Was looking at something so close, we could almost reach out and touch it comparatively, was this a breeze or were there new challenges?

Casey Honniball: There were actually quite a few challenges observing the moon with SOFIA. It had never been done before. And so it was definitely a test run that we had done in August, 2018 to see if SOFIA and forecast itself could look at the moon, find the moon, not saturate and actually acquire good data that would tell us something about the components on the moon.

Mat Kaplan: So by saturate you mean just the moon being so much brighter than most of what SOFIA looks at?

Casey Honniball: Exactly. Because the moon is so big and so bright compared to these faint galaxies that were molecular clouds that SOFIA looks at, we had no idea that forecasts could handle the amount of signal it would measure.

Mat Kaplan: I got something that you just reminded me of from the briefing and from the press release that this was a fortunate accident, serendipity, this was really just a test of a forecast.

Casey Honniball: Yeah, it was a test. We only had about 20 minutes of actual observing time on the moon to see if this would work. And 10 of those minutes were actually looking at the lunar surface, trying to see if we could see this molecular water signature. So it was quite exciting when the test turned out to provide such an exciting discovery.

Mat Kaplan: Really? I'm not sure when such a short observation resulted in so significant to find, at least in recent years. Back to the water that we're following as NASA likes to do. It really is water. It's not some similar compound because that was some of the confusion in the past, where there were hints, but it couldn't be confirmed?

Casey Honniball: Yeah. That's exactly what it was. Prior to these observations with SOFIA, we had been looking at a spectral range at three microns. So a little bit further than the visible and the infrared. And what they see at three microns is an absorption band. But this band is actually due to hydroxyl, which is just an oxygen and a hydrogen or possibly molecular water, which is H2O. So at this three micron band, they couldn't distinguish between the two and which one is present is very important for processes occurring on the moon and also for potential resource utilization, because you don't want to drink hydroxyl because that's the main active ingredient in grain cleaners.

Mat Kaplan: Yeah. It was quite a different compound. When you talk about the presence of this stuff, how much of it is there?

Casey Honniball: So there's actually not that much that we measured at this time. So we looked at the Clavius Crater at high southern latitudes. And what we estimate is that there's an abundance of 100 to 400 parts per million of water present. To make some kind of comparison, if you think about the Sahara desert, the Sahara Desert is 100 times more wet than the soil that we observed on the moon.

Mat Kaplan: Wow. All right. Another comparison I heard was something like your standard 12 ounce bottle of water per cubic meter of lunar regolith. Does that sound right?

Casey Honniball: Yeah. That's correct. But instead of being at depth, that cubic meter would be spread across the surface.

Mat Kaplan: Ah, okay. So where did this come from? Or is it actually being produced on the surface of the moon?

Casey Honniball: There's actually two ways that we think water got to the moon. So one way is solar wind is constantly bombarding the lunar surface with hydrogen. Because hydrogen interacts with oxygen on the surface to form this hydroxyl compound that confuses water. Well, if high temperatures occur on the moon, like at lunar noontime temperatures, then this hydroxyl can combine to form molecular water.

Casey Honniball: But another way is that when a micrometeorite impacts the moon, it can create a high temperature environment allowing pre-existing hydroxyl that was formed from the solar wind to combine and form molecular water or the micrometeorite could have even brought in the water itself.

Mat Kaplan: How does it manage to survive? One thing that I thought of was, well, what if a comet had hit the moon? But was that considered or is the water just too volatile? Because since we haven't seen a comet hit the moon, at least in the time we've been studying it?

Casey Honniball: A comet could have impacted the moon and brought some water to the surface of the moon. But like you said, we haven't seen one hit the moon in a very long time. This would have happened when the surface of the moon, the lunar crust was still forming. And so it would have implanted water into the lunar interior. And then while this lunar interior was still molten and magma, it could have erupted magma onto the surface of the moon, exposing some water to this, bringing some water up to the surface.

Casey Honniball: But one thing that we think is happening is that the reason we're seeing the water on the surface of the moon under these harsh lunar environment conditions is because the water is actually being sheltered inside impact glasses that are formed during the micrometeorite impact.

Mat Kaplan: Are you talking about what, little spheres of essentially glass? The image that first came to me were these, you may have seen these little sealed aquaria or terrariums. They're actually little microbiomes with water and plants and Brian Shrimp or something like that, except at the microscopic level. I am not suggesting that there are Brian Shrimp alive on the moon.

Casey Honniball: What's actually really interesting is that these glass beads that we're hypothesizing are holding the water is actually this very rugged, not so sphere like gray or glob of lunar regolith.

Mat Kaplan: Nasty stuff. And of course, this is one of the big challenges that past visitors to the moon human visitors have had. And that folks are trying to figure out how to deal with when humans returned to the moon. So it's the same kind of razor sharp regolith, and yet it may have water hiding inside it, maybe.

Casey Honniball: Yes, that's exactly it. It might have water hiding inside of these little glass shard beans that are formed all over the moon.

Mat Kaplan: I imagine they'd be gone pretty quickly if these things expose the water to the sun and hard vacuum, but how long is it expected that they could survive in these tiny particles?

Casey Honniball: So as long as the glass particles or class beads are not disturbed or destroyed themselves, then the water could last for decades to thousands of years. The only way that we think that the water could be released from these glasses is if another impact hit these glass and released the water out to the harsh lunar environment.

Mat Kaplan: Okay. That brings up another thought. We've already had an impact or two on the moon. And some that we've watched carefully to see what gets thrown up. Is there enough water in this find that an impactor would be, you know what, I would guess that that's probably not the best avenue to follow. I'm thinking maybe you'd like to see a rover look for this stuff.

Casey Honniball: Yes, definitely a rover. That would be the most comprehensive study to see what is there, how the water is being stored on the surface, because with the rover, you could take ground-based remote sensing of the surface. You could understand how much is there prior to collecting the sample, and then you could collect a sample and then you could look at the glass beads that are there and you could melt them and find out exactly how much water was there.

Casey Honniball: And you could even do a drill core, which would go down to depths. So you could understand the distribution of water with depth.

Mat Kaplan: The missions that I know of that are planned for the next few coming years, I think are mostly focused on the poles where we know there's probably almost certainly now a great deal more water than you may have found elsewhere on the surface. Do you know of any? Is there any talk about sending a mission that might be able to make these examinations?

Casey Honniball: So there's kind of few ongoing things. One particular one that I think is going to be able to answer some of the questions that have been raised is the VIPER Rover, which is scheduled to go to the South Pole in the next coming years. They're looking to understand the water distribution around the poles and they have a drill. And so I think that they're the most comprehensive, or going to be the most comprehensive rover in the coming years.

Mat Kaplan: Is there a chance then that VIPER, when it is out there in the sun, that there might be a decision, or would you hope that there would be a decision to drill down there as well as in those permanently shadowed areas?

Casey Honniball: I definitely think that they will do multiple draw chorus in the sun and also in shadow. I think that if they decided not to, they would be losing out on quite a bit of science.

Mat Kaplan: Slight change of subject here. I noted that your examinations focused on Clavius Crater. I'll bet you know the Clavius is not just any crater, at least not in science fiction.

Casey Honniball: Yes. Definitely knew that.

Mat Kaplan: Yeah, Clavius base, it's all hiding there. I guess we just haven't been told about it, that subterranean base that most of us have seen in 2001 in Space Odyssey. Was there any particular reason you chose Clavius?

Casey Honniball: So I actually hadn't seen 2001 Space Odyssey prior to choosing. So, we actually chose the Clavius creator because it is one of the largest craters in the Southern Hemisphere that is very noticeable in guider images from the telescopes. So because it was a test, we weren't sure that we were going to be able to find the moon. So we wanted a target on the moon that was going to be easily identifiable. And Clavius was one of those craters in this southern latitudes.

Casey Honniball: And then we also chose the southern latitudes because while there's a lot of focus to go down there and also because in moon mineralogy mapper from the Chang'e 1 spacecraft, they show higher water abundances in the Southern Hemisphere than in the Northern hemisphere. So we wanted make sure that we got somewhere that might have the high potential of having molecular water presence.

Mat Kaplan: China is about to launch actually, as we speak, it will probably already have launched the first lunar sample return mission. In a lot of years back since the Apollo era, when it was accomplished by the old Soviet Union. Would you like to get your hands, or are there people that on your team who would like to get your hands on some lunar regolith?

Casey Honniball: I'm sure that there's a lot of people on my team that would love to get the lunar samples from the Chinese mission. I personally do not work on the lunar samples. I'm more of a remote sensing person than a lab person, but if I got the opportunity, I would most definitely love to work with them and try and understand how the six micron emission band for molecular water changes with the three micron band that confuses hydroxyl and water.

Mat Kaplan: Something else that has occurred to me. There may be people out there who are thinking that not much difference between three and six microns, but actually you're talking about a 100% change in frequency. So you're talking about wavelength there. Do I have that right?

Casey Honniball: Yes, that's correct. It seems a very small change, but it's actually quite a big change.

Mat Kaplan: Let's turn to more of your personal experiences with this. As you said, you're a remote sensing person. Were you on that test flight on SOFIA?

Casey Honniball: I was. I actually was invited along with my advisor, Paul Lucy, to go onto SOFIA to help aid the observations and direct them where we were on the moon, if we were able to find the moon.

Mat Kaplan: It's an impressive operation, isn't it?

Casey Honniball: It is very impressive.

Mat Kaplan: Hardly the first time that you have done something a little bit exotic. I'm thinking of the work that I read about that you did in the Antarctic with some of those balloons that we've talked about, specifically, STO-2. Could you talk a little bit about that and why you needed to go basically to the South Pole?

Casey Honniball: STO-2 is the stratospheric terahertz observatory, and it is a balloon born telescope. And so what I did is I helped build, test, and deploy the actual payload telescope that went onto the balloon. So what is interesting about STO-2 is it's similar to SOFIA in that it looks at molecular clouds and the Milky Way galaxy. And it tries to understand the lifecycle of star forming regions.

Casey Honniball: The reason that we put it on a balloon is because the terahertz region, where you might want to look for water or other hydrogen bearing compounds, you also need to get above as much of the atmosphere as possible. The balloon born telescopes actually put us above more atmosphere than the SOFIA telescope does. And SOFIA flies above 99.9%. So how much more can you get above? But you can get quite high into the atmosphere with a balloon. And these balloons are huge. They're the size of a football stadium.

Mat Kaplan: Wow. This was a big telescope too. This was no small instrument.

Casey Honniball: No, it was definitely a big telescope. I think the whole thing was probably, I want to say like 20 feet high. I'm estimating.

Mat Kaplan: Must have been fun to work on.

Casey Honniball: Yes. It was fun. It was definitely fun to go down to the McMurdo base in Antarctica. I spent about a month down in McMurdo for two summer seasons to launch STO-2.

Mat Kaplan: Along with all the other links we'll provide on this week show page at slash radio, there's some good stuff, including video of this work with STO-2. And the other interesting thing that I read about that makes it nice to do this at the South Pole is that a balloon can kind of fly in circles for days and days.

Casey Honniball: Yeah. So the balloons that we use fly around the South pole for onwards of 20 to 100 days. That's part of the reason that we go down to Antarctica is because the polar vortex takes the balloon in circles around the pole. Which if you were to do it above like the United States, that could be very hazardous if something went wrong and when the balloon came down. So, Antarctica is a really good place, it's a safe place. And it also allows us to recover the balloon because it goes in the circular motion around the pole.

Mat Kaplan: So what are the results from STO-2, and what's ahead in that line of research?

Casey Honniball: I actually never worked on data for STO-2. I was mainly instrumentation person where I tested and built the detector the telescope was made of. But I do know what came out of STO-2 was that they got additional funding to do another telescope, which is called Gusto.

Mat Kaplan: Well, they must have gotten some decent or at least promising results out of STO-2. I did see one mention of Gusto and I was wondering how to properly pronounce that. We already mentioned that you spent some time down in the Atacama as well. What were you doing there?

Casey Honniball: In the Atacama, I was also working on a terahertz instrument. This one was the largest 64 pixel terahertz array that has ever been built. It also looks at the Milky Way and molecular clouds. And this one, instead of being put onto a balloon, this one's put on two ground-based telescopes, ground-based radio telescopes. So the Atacama has the apex telescope on Mount Chajnantor.

Casey Honniball: And that is where I built and tested that instrument and deployed it to the Atacama Desert and installed it onto the apex telescope, which is actually right next door to Alma.

Mat Kaplan: And you told me that because it was the next door neighbor that you got to make a side trip over to Alma. Where'd you go? Did they let you go up to the high side?

Casey Honniball: So I didn't have a lot of time because I was still trying to install the instrument on the telescope and make everything run properly, or we were observing. And so I just kind of got to wander over there, look at the visitor center, and wander up to one of the lower ends and look inside of it.

Mat Kaplan: All right. Well, you've still got something to go back there for then I guess. It is a starkly beautiful area, isn't it?

Casey Honniball: Yes, it is Mars like to me.

Mat Kaplan: Yes. Yeah. And it stood in for Mars on occasion. I'm wondering about this whole professional direction that you've taken. What do you think made you so interested in helping to build these instruments that are helping to reveal the cosmos?

Casey Honniball: I've always been a hands-on person. I don't learn through reading books. I learn through doing. And so when I was an undergrad, I was accepted into a job position where I was working on building and testing PCB board components. So I would solder the computer boards together and then I would test them and make sure that they worked. And this was at a physics lab at the University of Hawaii.

Casey Honniball: And that kind of got me into instrumentation and finding that I like to work with my hands and build things and test things. And so when I transferred to the University of Arizona and the radio astronomy lab that built super cam, the 64 pixel array and STO-2, I was like, "Yes, this is what I want to do. I want to work on these instruments. I want to build them and test them," because that's the way I learn.

Casey Honniball: And so, I learned about radio astronomy through building and testing them. Through that experience, I was actually accepted into graduate school at the University of Hawaii to build an instrument to look at volcanic gases from the Kilauea Mountain lava lake, that kind of all steered me in instrumentation. And then my graduate advisor, Paul Lucy at the University of Hawaii realized that I had this radio astronomy observing background.

Casey Honniball: And he's like, "Hey, I want to get back into astronomy. I want to get back into observing. Let's observe the moon." So, yeah, that was kind of my career path.

Mat Kaplan: It's so cool. If science and engineering are independent circles that overlap on a Venn diagram, are you in that intersecting area between the two of those?

Casey Honniball: I am now. I used to be very much so on the engineering side, but now I'm getting more and more so into the research side. And that sets me up to be very unique because I can understand when engineers talk, but I can also understand when client talks.

Mat Kaplan: That is such a valuable talent. Yes. Tell me about your current position there at Goddard.

Casey Honniball: So at Goddard, I am a NASA postdoctoral program fellow and I am working on a project that uses the SOFIA telescope, but also the infrared telescope facility on Monarchia to look at the moon at three and six microns, to understand how these two bands vary with each other and to understand the cycle of water on the lunar surface and how it might migrate across the surface and be a source of water eyes to the poles, or if there's locations on the moon, like volcanic deposits that may be concentrating the water.

Mat Kaplan: So cool. I'll just leave you with this. Do you have any advice for anybody else out there, might be an undergraduate knowing that they like to work with their hands? Maybe not even in college yet. What would you tell someone like that who maybe feels like you, that they learn better by doing?

Casey Honniball: I think what's important is that you need to find what you like to work on. If you like to work with your hands, then it is important to find a school that has labs that you can apply to for a job to work in. You got to put yourself out there. If you don't put yourself out there, the answer is always going to be no. So for me, I walked up to the professor that was the head of the radio astronomy lab.

Casey Honniball: And I was like, "Hey, I want a job. This is my experience." And he was like, "Great. Let's put you to work. You got to put yourself out there. You got to work hard. You have to know what you want to do, because if you don't know what you want to do, then that's going to be hard." Right. So find your position.

Mat Kaplan: I'm just fascinated. It's a wonderful story and great advice. Casey, thank you. I look forward to hearing more great results from instruments that you have contributed to. I don't know that they'll all attract the attention that discovering, really confirming the presence of water all over the moon, not just at the poles, that may not be quite as a media present as that discovery, but I wouldn't be surprised if something else comes up like that again. Thanks so much for doing this again. And it has been great talking with you.

Casey Honniball: Thank you so much for having me.

Mat Kaplan: Casey Honniball, lead author of the work that has confirmed the existence of water in the moon's Clavius Crater. We'll celebrate our 18th anniversary with Bruce right after this.

Bill Nye: Season's greetings. Bill Nye here. The holidays are racing toward us. We've got the perfect present for the space enthusiast in your life. A gift membership to The Planetary Society will make her or him part of everything we do, like flying our own LightSail spacecraft. Two of them. Advocating for space exploration, keeping our planet from getting hit by an asteroid, and this show.

Bill Nye: Sure. You'd like to give them a ticket to the moon or Mars, but I promise you, this is the next best thing. Membership start at $50 a year or just four dollars a month. We've got discounts for students, educators, and seniors. Visit us at to learn about the benefits of membership and how easy it is to give someone special the passion, beauty, and joy of space. That's Thank you and happy holidays.

Mat Kaplan: Time for the 18th anniversary edition of What's Up on Planetary Radio. Here is my partner in this segment for all of those years, whatever, 900 something episodes, I think. It's Bruce bets, the chief scientist of The Planetary Society. Happy anniversary.

Bruce Betts: Happy anniversary Mat. I am very excited about this and you should be very, very proud. You've created an amazing thing for an amazing number of years. It of course doesn't feel like it should be 18 years, but-

Mat Kaplan: No.

Bruce Betts: ... it's been fun all the way along.

Mat Kaplan: It has been. Thank you. Thank you for being part of it all the way along. I certainly didn't do it alone.

Bruce Betts: Now to celebrate the 18th anniversary, I've got 10 questions for you to help the listeners get to know you. Mat has not heard these yet, so we'll go through-

Mat Kaplan: That's true.

Bruce Betts: ... these and you can give me quick answers for most of them anyway. Where did you grow up?

Mat Kaplan: Los Angeles, California. Earthquake.

Bruce Betts: I'm telling you, most of them are. Now you were a swimmer like in high school and such. What was your favorite stroke?

Mat Kaplan: Well, once I mastered it, butterfly. I had a lot of trouble getting it down, but once I mastered it, that was my claim to fame to Narbonne High School and elsewhere. I wasn't great. You were probably a better swimmer.

Bruce Betts: Not necessarily. A bonus question, I'm throwing in. What was the mascot of Narbonne High School?

Mat Kaplan: The gaucho.

Bruce Betts: Nice. All right. Now a character you enjoyed playing as an actor.

Mat Kaplan: Gosh. It's not like I was any good at this or did it very often. How about Mayor Shinn in the Music Man.

Bruce Betts: Nice. All right. Where did you go to college?

Mat Kaplan: I went to USC, the University of Southern California and I wasn't really happy there, I have to say. So I transferred to UC Irvine where I was much, much happier. And did college radio. You got it.

Bruce Betts: First job.

Mat Kaplan: First job. Very first job when I was 16, I was a courtesy clerk at a Safeway supermarket.

Bruce Betts: Nice. First radio show you-

Mat Kaplan: No, it wasn't.

Bruce Betts: No. All right. First radio show that you did.

Mat Kaplan: These could have all been short answers, but the first radio show I ever worked on wasn't my show. I ran the mixer board for a guy who did a public affairs show at KUSC. First radio show I ever did. Okay. I take it back. It was on the Intercom system at our high school, at Narbonne High School at lunchtime. We would play records and do silly stuff over the intercom.

Bruce Betts: Nice. All right. This one requires a little more thought. Someone you met and were star struck by.

Mat Kaplan: Well, Bruce Betts. The other staff.

Bruce Betts: That was the right answer.

Mat Kaplan: I'll leave it at that.

Bruce Betts: All right. Most common noise or noises that interrupt your recording of this show.

Mat Kaplan: Gosh. There are so many to choose from. Navy helicopters, because I live under that flight path in San Diego. Our dog, Dennis. Dennis, the first. We didn't give him the name. Those are the two biggies right there.

Bruce Betts: All right. Favorite radio hosts besides yourself?

Mat Kaplan: Oh gosh. Of all time, there are two, Lohman and Barkley who anybody who grew up in L.A. at the time that I was growing up in L.A. probably knows who I'm talking about. They owned the Morning Drive in Los Angeles for many years. They were wonderful men. I met them several times and even did a little bit of TV. They were just great. And Roger Barkley had a restaurant for many years near Pasadena.

Bruce Betts: Named Barkleys?

Mat Kaplan: Yes.

Bruce Betts: I've been there.

Mat Kaplan: I've never been. Is it still there? Is it still open? Because I knew he passed away.

Bruce Betts: I don't know. I never leave my house.

Mat Kaplan: All right. Well, we're going to have lunch there.

Bruce Betts: Someday. Okay. Bonus question. Favorite daughter. Just trying to trick you.

Mat Kaplan: Nice try. Nice try. Love them both. Absolutely equal.

Bruce Betts: And most importantly, favorite person to end Planetary Radio episodes with.

Mat Kaplan: Is this a trick question?

Bruce Betts: This isn't supposed to be hard.

Mat Kaplan: Bruce Betts.

Bruce Betts: Thank goodness. There you go. Needed that. Okay. Now we can go on to normal stuff. Happy anniversary.

Mat Kaplan: Thank you. Thank you for those. Happy anniversary to you once again.

Bruce Betts: Let's talk about the night sky. We'll do a quick rundown. We got Jupiter looking really bright near Saturn, looking yellowish in the evening in the southwest. And also in the evening sky, you got Mars high overhead looking still really bright and reddish. Although it is dimming over time. And in the pre-dawn east Venus still there, still dominating. Preview Geminids meteor shower peaks, December 13th and 14th. We'll talk more about it next week.

Bruce Betts: We move on to this week in space history, 2011, curiosity launched for Mars. Still going, still driving. Onto random space facts for Mat Kaplan. Happy anniversary.

Mat Kaplan: That was wonderful. That was the best anniversary present yet.

Bruce Betts: What a terrible anniversary you've had.

Mat Kaplan: I haven't gotten any others.

Bruce Betts: I've really should have themed it on you or the show. I'm sorry. It's just a random-

Mat Kaplan: You're doing great.

Bruce Betts: It's truly just a random space fact. Some binary stars, so star systems with two stars orbit each other with periods of less than an hour. For example, [am kanom benaticorum 00:47:34] consists of a white dwarf and a semi degenerate or white dwarf companion. They're so close. They're orbiting about every 20 minutes. And one of the white dwarfs is gaining matter from an accretion disk from the other.

Mat Kaplan: First of all, that's just wonderful. What a terrific random space fact. Second, I of course immediately thought of the great line from a movie, The Graduate. And I wonder if anybody's ever said to that star, "You are a degenerate."

Bruce Betts: Physics degeneracy is just really very different. Maybe that's what they meant in The Graduate. I doubt it.

Mat Kaplan: I doubt it. He did become a star, of course, Dustin Hoffman.

Bruce Betts: Yes, he did. Speaking of stars, actually not. We move on to the trivia contest and we'll get to stars, but we're going to start with the moon. I asked you who named most of the Luna Mario with the names that are used today by the IAU. And how'd we do Mat?

Mat Kaplan: Well, here it comes. It's provided by the poet Laureate of Planetary Radio, Dave Fairchild. If you check the Mario, the dot the lunar face, most of them have labels that the IAU embrace. Riccoli, well, nope. See, I got it wrong. I checked this with my Italian wife. Riccoli, no. Riccoli is the man who earned his everlasting fame since 1651. We've used his nomenclature name.

Bruce Betts: That was a really good poem, except it was kind of weird in the middle with all the pronunciation stuff.

Mat Kaplan: Yeah. You can't blame Dave for that.

Bruce Betts: Okay.

Mat Kaplan: Well, was he right? I have it. Here it is for Norman Cassoon in the UK. Giovanni Battista Riccoli.

Bruce Betts: Yes, that is correct.

Mat Kaplan: You want to tell us anymore about him? I've got stuff here from some of our listeners.

Bruce Betts: Why don't you tell us stuff from the listeners and I'll fill things in.

Mat Kaplan: Sure. 17th century, Italian astronomer and Catholic priest, a Jesuit, known among other things for his experiments with pendulums and falling bodies made arguments regarding the motion of the earth, widely known for discovering. Well, here it is again, the first binary star. Marcel Jean Krigsman in the Netherlands added, he also did the first precise measurement of G, the force of gravity on earth.

Mat Kaplan: I haven't told you the winner is yet, Jason Hemsley in California. This is going to drive some people out their crazy. It's the first time Jason has entered and Giovanni Battista Riccoli. Riccoli. Emphasis on the first syllable, I am told. Jason, congratulations. You have won a copy of Bill Nye's Great Big World Of Science by Bill Nye and Gregory Mone from Abrams publishing. And we will make sure that gets out in the mail soon. We'll even have the science guy sign it for you, if you like.

Mat Kaplan: Mark Little in the UK says, "When Ricolli's enthusiasm for astronomy rose, he actually said this a rose within him. He could never extinguish it. So he became more committed to astronomy than theology." Here's what I love from Laura Dodd in California, who says, "Yes, he was a priest and this was half the time, of course, that Galileo had gotten himself in hot water for talking about Copernicus.

Mat Kaplan: Riccoli couldn't officially endorse Copernican theory, but instead, he put Copernicus's name on a crater along with Galileo and Kepler. Subtle fellow," says, Laura. Finally this from Devendra Rourke in Colorado. Apparently if you name hundreds of things at once, you can get away with naming something after yourself. It's true. I bet you knew. Riccoli named a crater on the western or left edge of the moon after himself.

Bruce Betts: Cool. Although we know to his credit, he didn't pick one of the brightest ones.

Mat Kaplan: Yeah, I guess not. He did give those to other people. Even gave one that's bigger to his partner in all of this. I guess the guy who drew the pictures that they made of the moon. That's it from this end. You got something new for us?

Bruce Betts: I do. Here's a question? How many of the IAU defined 88 modern constellations have dog in their name? And of course, it will be dog in Latin. And just to be clear, we're talking domestic dog. Things like wolves and foxes don't count. Go to

Mat Kaplan: Well, that's cool. You have until the first Wednesday in December, December 2nd at 8:00 AM Pacific time to get us the answer. Here's the prize, a brand new book published just two weeks ago. The Last American Hero about John Glenn. It's by Alice George. Is from Chicago Review Press. I have read a good piece of it. I haven't finished it yet. Very well-researched. He really was a hero. Absolutely fascinating man.

Mat Kaplan: Deserve all of the attention that he got throughout his life finishing as still today, the oldest man or woman to go into space. That may change sometime soon, but there you go. It's The Last American Hero.

Bruce Betts: You're still planning your space trip, aren't you?

Mat Kaplan: Yeah, but at the rate I'm going, I might take John Glenn's record.

Bruce Betts: All right everybody. Go out there, look up the night sky, and think about how Mat Kaplan hasn't changed in 18 years. Thank you. Goodnight.

Mat Kaplan: If only it were so. Of course, it's Bruce who still looks exactly the same, full head of hair. I will assure people of that. He joins me every week, he and his hair, on What's Up. Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by its members. Some of whom have been supporting Planetary Radio right from the start.

Mat Kaplan: Help us celebrate by visiting Mark Hilverda is our associate producer, Josh Doyle composed our theme, which is arranged and performed by Peterson Shlosser at Astra.