Geothermal activity on the icy dwarf planets Eris and Makemake

Sarah Al-Ahmed: Scientists find evidence of geothermal activity on icy dwarfs Eris and Makemake, this week on Planetary Radio. I'm Sarah Al-Ahmed of The Planetary Society. With more of the human adventure across our Solar System and beyond. A team co-led by the Southwest Research Institute has discovered signs of hydrothermal and metamorphic activity within the icy dwarfs Eris and Makemake in the Kuiper Belt. The lead author on this research, Chris Glein, joins us today to explain. But first, we have an exciting update from the world of US space politics with our Chief of Space Policy Casey Dreier and our Director of Government Relations Jack Kiraly. We'll also take a moment to celebrate the touchdown of the Intuitive Machines' Odysseus lunar lander with our Senior Communications Advisor Mat Kaplan. Hang out until the end for What's Up? with Bruce Betts and a new random space fact. If you love Planetary Radio and want to stay informed about the latest space discoveries, make sure you hit that subscribe button on your favorite podcasting platform. By subscribing, you'll never miss an episode filled with new and awe-inspiring ways to know the cosmos and our place within it. We've got a lot of wonderful things to share this week, starting with some United States news from our space policy team. Here's Casey Dreier and Jack Kiraly, our chief of space policy and director of government relations at The Planetary Society. Thanks for joining me again, Casey and Jack.

Casey Dreier: Anytime, Sarah, always a joy.

Jack Kiraly: Hi, Sarah. It's great to be here.

Sarah Al-Ahmed: We've been waiting for just the right moment to make this announcement. Before I give the whole thing away, I'm just going to throw this to you, Jack, what is our big news?

Jack Kiraly: So the big news, and you're right, we have been waiting patiently to make the announcement that in the 118th Congress of the United States there is now reestablished the Planetary Science Caucus.

Casey Dreier: Yeah.

Sarah Al-Ahmed: Insert applause. But really this is a big development and this isn't the first time that there has been a Planetary Science Caucus. There's a bit of a history to this, but how did this get formed?

Jack Kiraly: So you're right. There is a history to this. The Planetary Science Caucus did exist in the 115th and 116th congresses. So caucuses have to be re-upped every two years at the beginning of the next Congress. And so the 118th Congress, which started January 3rd last year, 2023, we were able to connect the co-chairs of this new iteration of the Planetary Science Caucus. Representative Judy Chu, who actually represents Planetary Society headquarters in Pasadena, California, and Representative Don Bacon, who represents the Second District of Nebraska, are our two house co-chairs who have so graciously stepped up and said, "Yes, we will be leaders on Planetary Science in the 118th Congress." So we're very grateful for their leadership on this topic and for helping really bring this together and bring this across the finish line.

Sarah Al-Ahmed: So what is a caucus? What do they do?

Casey Dreier: You can think of a caucus, it's a semiformal, so it exists in the house formally and informally in the Senate, which really at the end of the day, it's a coalition of people who share some interest in something. So this isn't structured like a committee. They don't have formal powers, but it's like people who raise their hand to say, "I care about this issue." And there's a lot of caucuses. There's some really very high profile ones. There's the Freedom Caucus, which is a very strong conservative caucus in the house. There's a lot of caucuses around various medical ailments that raise awareness and try to drive federal support for those. There's even the Seersucker Suit Caucus, people who really into wearing those in the summer. There's all sorts of interest group caucuses. This is something for planetary science for members of Congress to say, "I care about this issue. This is interesting to me." And it signals not just their constituents, but their own staff to say, this is an important issue that we care about as an office, and that makes it easier. So when we or our members of The Planetary Society go visit them or Jack and I, our members of our board go to talk about them and there's something really important happening legislatively that impacts our position on planetary science, we know that they already care and we know they already are aware to some degree about planetary science as an issue. So we can go in right away and say, "Here's what needs to be fixed. Here's the major issues," without having to start from scratch. So this creates a prewarm set of member advocates and awareness areas for planetary science within the US Congress.

Sarah Al-Ahmed: What can we actually accomplish with this caucus, Jack?

Jack Kiraly: The caucus, as Casey said, the semiformal organization that's recognized by the House leadership, right? It's an organization, actual recognized organization in the House. And as Casey said, the Senate doesn't really have a formal process, but members of the Senate can join house caucuses. It just has to start in the House of Representatives. But this can be a platform for any number of opportunities. It is to allow us to organize events, which is probably a big part of what happens on Capitol Hill is organizing briefings, what some people affectionately call lunch and learns, where a bunch of experts will come in and brief staff on emerging topics in a particular area or the advocacy priorities or principles of a specific set of organizations or organization. The caucus is also a vehicle by which statements can be made, right? The co-chair of a caucus or the chair of a caucus in that position can say, "It's not just me saying X, Y, and Z. It is me on behalf of this organization." Right? This organization of however many members. And Casey's right, there are dozens of caucuses, and in some congresses there can be hundreds of them just because it ebbs and flows with the membership. And the great part about space is that there is a broad coalition. Space is something that touches basically every congressional district. It for sure touches every state. And this is something that every member of Congress can have a stake in and can demonstrate their support. And they don't have to have a NASA center in their district to be a part of the caucus. They can be as is called rank and file, right? They can just be a member who's not on a science committee, not on appropriations. So the commerce, justice, science, which funds NASA, they can just be someone who cares about space and wants to promote the values of the caucus. And this caucus in particular aligns very closely with the goals of The Planetary Society and with the broader space science and planetary science communities, the search for life, defending the earth, exploring other worlds and supporting the robust industrial and academic base here in the United States when it comes to the research and exploration of the cosmos.

Sarah Al-Ahmed: I can imagine having a caucus like this is very helpful for advancing our advocacy goals because there's a lot about space that the common person doesn't know or understand, and the members of Congress have a lot of things on their mind. So establishing this connection with them and a basic understanding of our priorities ahead of time could probably really expedite the process.

Jack Kiraly: You're absolutely right. Again, like I said, this is a platform, right? This is a place that people can come together and say, "I care about this topic and I want to learn more." You don't have to come into being a part of the caucus as a complete expert. You can be someone who just wants to see the US continue to lead in space science, research and exploration, but not know anything else or your staff might not be as well versed as others or as experts in the field, but you want to learn more and you want to be a part of this exciting journey. So like you said, there's a lot that people don't know about space, but there's a lot to be excited about space. So that is the value of a caucus like this.

Casey Dreier: I think that's a really important point, and I think worth emphasizing that members of this caucus don't walk in with some monolithic attitude towards planetary science or what should be done. And they don't even necessarily have the same goals as The Planetary Society does, right? The caucus is a function of Congress and the two co-chairs. They run this thing. We're happy to support and provide assistance and speakers and organizational help, but at the end of the day, I think it's really about giving an avenue for ongoing engagement and education and really an opportunity. And I think as communicators at The Planetary Society, there's such a rich, almost overflowing amount of activity happening in planetary exploration right now. It's such an exciting time. And having a structured caucus like this, if nothing else, gives us an opportunity to target a really important group of people who are interested in it, to say, "If nothing else, look at this. Look how amazing this is. Look how astonishing we can... Look what things we can do with the right mix of policy and funding and optimism and effort." And if nothing else, people walk out of that feeling better about the day or look up into the sky a little more at night. That's an amazing outcome.

Sarah Al-Ahmed: Do we already have members of Congress that have signed on to this caucus?

Jack Kiraly: Yes, we do. And it grows seemingly every day. So we are continuing to build the caucus. The great part about caucuses is unlike committees which the structure of those, unless there's major changes in the membership of Congress, the committees don't change much from January 3rd or really when the leadership of the House and Senate are selected, caucuses are continuously growing. So the great part about this is that we have an action in our action center right now that you can go to, planetary.org/action, to encourage your member of Congress to join the Planetary Science Caucus that has all the information you need. You'll put in your address, it'll tell you who your members are and encourage them to join the caucus. And if they're already a member of the caucus, you can send them a nice thank you note because we want to be grateful for these members of Congress. Like you said, Sarah, there's a lot on their minds. There's a lot happening especially this year. But as time goes on, the docket that Congress has to deal with seemingly it's more and more complex. So for someone like Representative Bacon, like Representative Chu, potentially your representative, listener, they might already be a member of the caucus. And we want to make sure that they have our gratitude for standing up for this topic that we find so compelling and so important to our work, to our lives. And we want to show that gratitude. And so we're incredibly grateful for the leadership of Representative Bacon and Representative Chu, and for all the members who are standing up and saying, "Yes, space science is important. Space research, space exploration is important to the long-term health of the country, to the long-term health of humanity, and to their districts, to their constituencies, to their friends." Space is very important for any number of reasons. So please go to planetary.org/action and encourage or thank your member for being a member of the Planetary Science Caucus.

Sarah Al-Ahmed: Well, Judy Chu is one of my representatives, so it sounds like I'm going to be sending a thank you letter. Thanks so much for everything that you've done to help support this, and I feel like you're going to have some really fun lunch and learns in the future. It sounds like this is a cool space club to go to during lunch while you're in Congress. It feels like that-

Casey Dreier: We should put that quote on the website which says, "Join the cool space club for Congress."

Sarah Al-Ahmed: Cool space club.

Jack Kiraly: I mean, really that's what a caucus is, right? It's a club for members of Congress and space is that thing that brings us all together. So yeah, if you're a member of Congress and you're listening to this podcast, please join the Planetary Science Caucus. It's free. You can do it. You're a member.

Casey Dreier: And I like that. And if you're not a member of Congress, that's what The Planetary Society is for. That's your cool space club.

Sarah Al-Ahmed: Thanks, Jack and Casey.

Casey Dreier: Anytime.

Jack Kiraly: Thanks, Sarah.

Sarah Al-Ahmed: If you live in the United States and want to encourage your representatives to join the Planetary Science Caucus, you can find an easy form for that on our website at planetary.org/action. I'll also link to it on this webpage for this episode of Planetary Radio. Just a couple of weeks ago, on February 22nd, 2024, a lander named Odysseus built by a company called Intuitive Machines touched down near the Moon south pole. This spacecraft also called IM-1 is the first successful mission of NASA's Commercial Lunar Payload Services program, a NASA funded initiative that competitively funds commercial companies to build spacecraft that can autonomously land on the moon. This is the first touchdown of a lunar lander from the United States in over 50 years since the Apollo 17 mission, and it's the first commercial spacecraft to land on the moon. Here's Mat Kaplan, our senior communications advisor and the previous host of Planetary Radio to tell us more. Hey, Mat.

Mat Kaplan: Sarah, hi. Happy moon landing.

Sarah Al-Ahmed: Happy moon landing. This is such a moment in lunar exploration. We've landed on the moon before, but this is the first time in over 50 years that the United States has landed a lander on the moon.

Mat Kaplan: Isn't that amazing? And I am totally with NASA and the Intuitive Machines people who say that this was a successful landing. Yeah, sure, it's leaning over 30 degrees off nominal at least, and not everything worked exactly as it was supposed to, but boy did we learn a lot, and it's so exciting even to see that last image that was grabbed before they put the spacecraft into standby mode is really pretty spectacular.

Sarah Al-Ahmed: Part of what I was really looking forward to with this landing is that they were going to have the EagleCam actually capture that landing, but they weren't able to do that. So the fact that we actually got to see images of it before it went into its standby mode made me really happy. I think we needed those images to really convey to people how awesome it is that we're back on the moon.

Mat Kaplan: That was also my biggest disappointment when I think about the mission that they couldn't deploy EagleCam, too much going on, but Stephen Altemus, the CEO of Intuitive Machines, he said they love that payload. I think he's going to give them make good on one of the upcoming landers because they have lots more landers planned, and I hope we get that great shot of this touchdown by one of the future craft.

Sarah Al-Ahmed: Well, that brings up a great point, which is that this is just the second mission in NASA's Commercial Lunar Payload Services program. So we have a lot of other things coming up. So despite the fact that there have been some quirks so far, last time you were with us, we were talking about Astrobotic Peregrine Lander, which unfortunately didn't work, but I still count this as a huge success and it bodes really well for the future of the CLPS program.

Mat Kaplan: Absolutely. I think that this should make everybody very happy about how CLPS is going. We all say space is hard, landing is hardest, and we saw more evidence of that in this. Now we heard Stephen Altemus say that if they had not had that problem with those laser range finders, he said a couple of people with the company really beaten themselves up over that., Then they would've nailed this one, and he is absolutely sure because they did so well. They already came pretty close to the landing ellipse that they wanted, even with all the problems that next time he's sure they're going to nail it. And I think that that's probably well-founded, I think they have a good shot. And next time, if I've got this right, we're going to be even closer to the south pole and maybe dig in a little bit and get some ground truth for some of that stuff that we think is happening at the south pole or sitting there waiting for us to find out about.

Sarah Al-Ahmed: What about the south pole made this such a great target for this lander?

Mat Kaplan: Well, I mean, it's wonderful that nobody has ever come this close. I mean, I think they're at, I believe, 90 degrees south and that in itself was a major challenge for putting a lander down. But of course, what we want to do is get inside one of those permanently shadowed areas like the Aitken Basin and find that ice that we're all pretty sure now from observations from orbit is there, but there's nothing like in situ research to actually have something land in an ice field or dig down a little bit to where it's hiding out and show us that those millions and millions of liters or gallons of water are actually there as we now are pretty close to confirming.

Sarah Al-Ahmed: Were any of the payloads on board actually able to take some of their data despite the lander being askew?

Mat Kaplan: IM has not been real forthcoming about the data that they've collected. They definitely say that they got data back from all but one the science payloads. So I expect that they're going to be releasing that sometime soon, but at least at this point as we speak, I have not seen that. They were getting this stuff back, as somebody said during one of the press conferences, it started out a soda straw and now it became sort of a boba straw, but it's still a straw. So they're still working with that data to find out what useful stuff they've gotten out of it. But let's hope that we're going to get some real science out of this. Although any science is going to be gravy, it's going to be on top of the minimal standards for success that NASA and IM set years ago and did achieve.

Sarah Al-Ahmed: Despite the fact that we don't know whether or not these instruments actually captured their data. This is still a huge success, and personally I find it pretty funny and inspiring all of these different missions from around the world landing on the moon and this progression from Astrobotic's Peregrine Lander not correctly doing its thing. Then JAXA's moon lander landing completely upside down, and now we have this Odysseus lander finally standing on its own feet, but a little skew. So it sounds like we're progressing in the right direction, and I think I'm going to count this as a huge success, whether or not it did everything that we wanted it to.

Mat Kaplan: I am totally with you on that and also on the need to keep sending these missions, not just to prepare for Artemis to get humans there safely and let them do the great science that humans can do with their own gloved hands, but also because there's so much we still need to learn about the moon. Everybody thinks, oh, we've sent all these robots. We brought back hundreds of kilos of rocks. We still have so much to learn. And by learning about the moon and its origin, we're going to learn about ourselves as always in planetary science.

Sarah Al-Ahmed: And as we've seen with places like Mars, even getting samples back from one place or researching a single location on a world is not enough to get a whole picture of that world. So being able to go to the south pole and really take a look there, especially knowing what we know about the potential for water and other things there can really give us a more full picture of our planetary neighbor. So now we have this lander on the moon and it's gone into the standby mode. Do we have any idea whether or not it's actually going to come back to life like we saw with JAXA's lander?

Mat Kaplan: Yeah, let's hope that we're going to see the same kind of unexpected pleasure that the Japanese, the JAXA did with SLIM. They didn't really expect it to wake up. It didn't have anything to keep its electronics warm during that frigid nighttime. Who knows? Maybe IM-1 will have the same sort of resurrection story. We can certainly hope so, and that means we can start pulling some data through that boba straw once again.

Sarah Al-Ahmed: Do we know when we might have an idea of when that thing might come back to life?

Mat Kaplan: Going to be a couple of weeks. But the good news is as the IM people shared that when the sun rises in that spot near the pole, it's going to be very well-oriented. It's going to shoot those photons directly into that leaning solar panel. Let's hope that if nothing's broken, we're going to have plenty of power and see some great things.

Sarah Al-Ahmed: This is a moment to celebrate, and I was very grateful that we all got to share this moment of the landing and our member community. I know you were in the chat talking with everyone as well, but being there with everyone for this moment might be my favorite part of this entire experience.

Mat Kaplan: I loved it, sharing the excitement, sharing the tension. I mean, my goodness, it was nerve wracking, especially in the 15 minutes between what they knew should have been the landing and getting the first few bits of data back. There was really nothing like it. And you could feel the tension among our members in the community, but also from the people with IM. We got this little clip from Stephen Altemus, the Intuitive Machine CEO, where he really expresses the passion and his joy over this success.

Stephen Altemus: What we've done in the process of this mission though is we've fundamentally changed the economics of landing on the moon, and we've kicked open the door for a robust thriving cis-lunar economy in the future that's compelling. And so I think this CLPS experiment, this first landing, the success on the moon first time in 52 years is really a point in history that we should celebrate as we move forward to subsequent missions around the moon.

Sarah Al-Ahmed: That was a beautiful moment, Mat. Thanks for sharing that.

Mat Kaplan: Oh, yeah, absolutely. And thanks for the opportunity to talk about this great success.

Sarah Al-Ahmed: Anytime. Thanks, Mat. Let's move from one story of exploration to another. In the vast cold expanse of our outer Solar System beyond the orbit of Neptune, there's a realm filled with ancient and icy objects called the Kuiper Belt. Everyone's heard of the dwarf planet Pluto, but there are several other dwarf planets out there, including Eris and Makemake. Both Eris and Makemake were discovered in 2005. Eris is more massive than Pluto, but slightly smaller. In fact, its discovery was pivotal to the reclassification of Pluto as a dwarf planet. Eris also has a moon named Dysnomia. Makemake is even smaller than Eris, but it also has one confirmed moon named MK2. These dwarf planets aren't really well understood because they're so far away from us. Thankfully, new data from the James Webb Space Telescope or JWST are revealing these world's secrets and the results could actually change our perception of the Kuiper Belt and the icy worlds that it harbors. A team co-led by the Southwest Research Institute in San Antonio, Texas USA has made a fantastic find. Using data from JWST, they detected signs of methane on the surfaces of Eris and Makemake that suggests something really remarkable, hydrothermal or metamorphic activity inside of these distant dwarf planets. This points to the presence of warm, if not hot geochemistry inside of the rocky course, which is actually really weird when you think about it. This situation is really different from the cold and inert bodies that we thought that these dwarf planets were. The data suggests a dynamic interior at work in both of these worlds capable of generating methane or possibly even harboring liquid water beneath their icy surfaces. This week's guest is Dr. Chris Glein, a planetary geochemist and lead scientist at the Southwest Research Institute. He was the lead author on this research. Alongside him, Dr. Will Grundy, who's an astronomer at Lowell Observatory and their team, they've published a paper that not only presents these findings, but also paves a new understanding of these trans-Neptunian objects. Their paper called Moderate D/H ratios in methane ice on Eris and Makemake as evidence of hydrothermal or metamorphic processes in their interiors: Geochemical analysis was published in the April 2024 edition of the journal Icarus. Welcome back to Planetary Radio, Chris.

Chris Glein: Hi, Sarah, great to be back.

Sarah Al-Ahmed: Last time you were with us, we spoke about the detection of phosphorus on Saturn's moon, Enceladus, and now you're back to share even more surprising news. But this time from what's going on in the outer Solar System, in the Kuiper Belt. Specifically, these are James Webb Space Telescope's results on the dwarf planets, Eris and Makemake, which I think we don't hear enough about.

Chris Glein: Me too. We're going from 1 billion miles to almost 10 billion miles now.

Sarah Al-Ahmed: It's not an easy thing to be able to observe these worlds. They're so far away. It's so cold and dark out there. How did JWST enable you guys to actually do this research?

Chris Glein: So these worlds are almost like terra incognita, right? So we've known that they exist for over 20 years, but they've just remained these dots in the sky for the most part. And we had previously detected, or not me, but other scientists had previously found different ices like methane frozen on their surfaces. But beyond their masses and sizes and the presence of some of these ices, we didn't really know much about processes that might be happening on these worlds. So with James Webb, our team was very eager to take advantage of these new capabilities to learn something new.

Sarah Al-Ahmed: And I love that because it's not like it's easy to get time on JWST. So the fact that you decided to prioritize this because we knew so little is actually a really cool use of the telescope.

Chris Glein: Right. And I can't take credit for this. I joined the project late. So late in 2022, I joined the project. There's some people who have been on the project, like John Stansberry and Jonathan Lunine and Will Grundy for several years planning these observations and eagerly awaiting the data. And they had the foresight to recognize that these were high priority targets for JWST.

Sarah Al-Ahmed: I mean, how else would we do this kind of work? This is one more reason why I wish we had so many more JWST size and scale observatories out there because there's so much we could learn if we had more telescope time.

Chris Glein: Exactly. I totally agree.

Sarah Al-Ahmed: Well, we're going to get into the science behind this result in a moment. But the headline is that these worlds are showing evidence of geothermal, hydrothermal, and even metamorphic processes. That's pretty surprising given how far away they are from the sun. What did your team expect to find in this data?

Chris Glein: I don't know what everyone expected to find. I had this image from some of my previous work where I imagined that icy dwarf planets, like in the Kuiper Belt, might be seen as supersized comets because you might imagine that they formed through this planetary accretion process where little bits become larger bodies and the building blocks might've looked like comets. And we know something about cometary ices. So we knew that methane is in cometary ices. It wasn't inconceivable to imagine that these bodies could have inherited methane from commentary building blocks. And that was my default assumption going into this project really it was, "Okay, we got these new measurements from JWST. Let's first test out the giant comet model for Kuiper Belt objects and see if that works." And then if it doesn't, then we start thinking a little bit more about other possibilities.

Sarah Al-Ahmed: It's funny because I had a very similar idea of what was going on there in the Kuiper belt until the New Horizons mission went out to Pluto and completely changed the way I thought about Kuiper belt objects. Every time we get more data from out there, every single time, it's completely surprising to me. So that's a really fun area for people to get into research because there's just so much we don't understand.

Chris Glein: Yeah, you're totally right. And Pluto was a real game changer too, because Pluto was also thought to fit into this mold of like an icebox where all the remnants of the primordial Solar System were frozen like relics from 4.5 billion years ago. And then we learned that Pluto is actually a much more active and dynamic world than I think any of us, or at least anyone I know, could really imagine when New Horizons made those spectacular observations in 2015.

Sarah Al-Ahmed: It's cool that that's sparking more people to go back and look at these objects. And as we gain more technology to do so, who even knows what kind of surprising weird things we're going to learn? And this is a really great start, but your team looked at the ices on these worlds, primarily the methane ices, and it's a little complicated because it's not just like you were looking at plain old methane. What you were doing was analyzing specific isotopes of hydrogen and carbon, hydrogen and carbon being the atoms that make up methane. So how did you determine the relative abundances of these chemicals?

Chris Glein: Yes, I'm going to have to warn any of the listeners here that we're going to start diving into some chemistry, so you have to bear with us. Having said that, so what we use James Webb for was to look at the infrared spectrum of Eris and Makemake, specifically from one to five microns in wavelength. And what was spectacular about JWST data is previously we could only really look in detail up to about two and a half microns from Earth because a lot of our ground-based facilities are limited by your ability to see through the Earth's atmosphere. So like the water vapor and CO2 gas in Earth's atmosphere acts as a block. It blocks you from seeing these critical wavelengths of light. So me and the other scientists on the team, we are really excited about the possibility of looking at this new region of the spectrum from Eris and Makemake because a lot of the molecules that we think are there or we thought were there, they have telltale absorptions. These are when the molecules can absorb light with different wavelengths. And so when you see the spectrum, you see a little dip at certain wavelengths and that tells you, okay, you have a methane molecule or you have a nitrogen molecule, these other kinds of molecules. So what we did is we first looked at the shorter wavelengths and we found that we could confirm what we already knew. There's a lot of methane on both Eris and Makemake. The surfaces are chockfull of methane. So that was great and very exciting. And then we looked at the four to five micron regions. This is a region we couldn't really see before, and we found these two absorptions for deuterated methane. This is where a methane molecule has one carbon atom. It's surrounded by four hydrogen atoms, and then if you pluck off one of the hydrogens and you replaced it with a deuterium, so this is a form of hydrogen. It's called an isotope where the nucleus has one proton and one neutron. That makes deuterium and a hydrogen, we call it protium, that's the technical name, only has the one proton and no neutrons. So deuterium has a heavier mass and it gives you a slight shift in the absorption in the infrared spectrum. So we're able to say, "Aha, okay, we got CH3D, that's deuterated methane." And initially that was very, very exciting. Before I joined the project, the James Webb project, they had a small mini conference where they presented all the results and I was just somebody in the science community. I heard about James Webb launching and deploying successfully, but I didn't know anything about the data. I tuned in on YouTube and watched this conference in real time and someone, I think it was Ian Wong, he's a member of the team who reduced the data, the raw data for JWST from Eris. He showed the spectrum and he had one of the peaks labeled CH3D, and I went, "Oh, whoa. Okay, so this is exciting," because I had worked on D/H chemistry for other bodies. So I saw this, I thought, okay, this could be an opportunity, but I didn't quite know yet how far we could take this. And so I contacted the PI of the team, John Stansberry, and these folks are very welcoming also. So if anyone who's listening as a scientist who might be apprehensive about trying to approach other scientists to collaborate, don't be apprehensive because everybody is extremely welcoming. I was like an outsider who came in to help out. Anyways, what happened next is then another person on the team, Will Grundy, he's an astronomer at Lowell Observatory. He took the data, the spectrum from Ian Wong, and he was able to use models based on lab data to then derive what's known as the D/H ratio. This is the number ratio, how many deuterium atoms divided by the number of hydrogen atoms do you have in methane? And I like to emphasize this is a hard measurement. So if you have like 10,000 hydrogen atoms, the hydrogen atoms are in methane molecules. If you have 10,000, you only have two to three deuteriums per 10,000. So it's really like picking out that needle on a haystack. But the JWST data are so spectacular and Will's extremely talented scientists that we are actually able to recover the D/H ratio from these ices. Just to give you a sense of scale, Makemake is at about 50 astronomical units. Eris is almost at a hundred AU. So this is way out there, but yet we're able to then say something useful. We know something about the chemistry now of things on the surface.

Sarah Al-Ahmed: It's absolutely amazing that we can learn anything about these bodies, let alone with this level of detail. It's amazing.

Chris Glein: Yeah, I'm still amazed and super excited. I was really a beneficiary just being alive at the right moment when JWST went up there as successful and now scientists are able to take the field further.

Sarah Al-Ahmed: We'll be right back after this short break.

CaLisa: Hi, I'm CaLisa with The Planetary Society. We've joined with the US National Park Service to make sure everyone is ready for the 2024 North American Total Solar eclipse. Together we've created the new Junior Ranger Eclipse Explorer activity book and it helps kids learn the science, history and fun of eclipses. If you live in the United States, call your nearest national park and ask if they have the Eclipse Explorer book. You can learn more at planetary.org/eclipse.

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Sarah Al-Ahmed: How does this measurement allow us to determine the origins of this kind of methane?

Chris Glein: Okay, so now you get to the heart of the matter. So we knew methane was on the surface. It turns out that nature can be mischievous though because there's methane is a very simple molecule. So there's a lot of ways that a planet could acquire methane or a planet could make methane. So if you just find methane someplace, it's interesting, but from the presence alone, you can't really say it must pinpoint some certain source process or reservoir. What was beautiful about getting these isotopic data, the D/H ratio, is now we can take one step further and we can start testing out different hypotheses. So this is where that first model I told you about the icy cometary inheritance model comes into play is we had a mission called Rosetta from the European Space Agency about 10 years ago now, and it orbited Comet 67P. And on this mission on the spacecraft was a mass spectrometer called ROSINA. And as luck would have it, ROSINA was able to make measurements of the D/H ratio in methane at a comet. So we had this data point, what does methane from cold cosmic objects the primordial building blocks of the Solar System, what would the isotopic characteristics of that methane look like? What's the D/H ratio? And it turns out the D/H ratio is quite high, and by high I mean it's greater than one part per thousand compared to the one part per 10,000 that we're detecting on Eris and Makemake.

Sarah Al-Ahmed: It's fascinating. I loved the Rosetta mission. I felt really connected to their entire journey trying to find the Philae lander and everything about that was great. But this is a really fascinating idea that this cometary makeup, the way that methane is being exhibited on these comets is so different from what's going on out in the Kuiper Belt. Why do we think that is?

Chris Glein: We were initially puzzled because I was thinking, like I said, okay, these bodies could be supersized comets, but apparently they didn't match. The D2H ratio was much different. So we were left scratching our heads trying to figure out, "Well, why is that the case?" So then we started to think about other possibilities. So on Earth, there are ways in which you can make methane. One example on the earth is if you go to the bottom of the ocean, there's these hydrothermal systems down there, and when people take submarines and they sample the vent fluids, they're full of methane. So one way to make methane is if you have hot sea water circulating through rocks, you can have geochemical reactions to synthesize methane, and that's known as an abiotic origin of methane. And then another process, again, you can appeal to what we know on the Earth, is you can cook out methane from organic molecules. We know that bodies like comets or carbonaceous chondrite, so carbonaceous chondrite are called carbonaceous because they contain this gooey organic material. It's like a kerogen, it's this tarry material. And if that stuff gets heated in water, you can actually cook out some methane. So that's another way of making methane is from cooking up organic compounds at elevated temperatures. And so we made models then of what would you expect the D/H ratio to look like for methane if it were produced by some kind of hydrothermal circulation processes at the bottom of an ocean, let's say on Eris and Makemake or if they have rocky cores that might be chock-full of organic compounds. And then those rocky cores were slow. It's like an oven, right? It's like slowly baking out because the radioactive elements and the rock are heating the rock up. So those organic molecules are gradually being exposed to higher temperatures which can break apart chemical bonds and release methane molecules. And as luck would have it, we found that both of those processes can produce methane with a lower D/H ratio that overlaps with what we see at Eris and Makemake.

Sarah Al-Ahmed: There's also the potential that other comets out there in the Kuiper Belt might be impacting these objects. Are we rolling that out as a possibility for the origin of this methane because of that higher deuterium to hydrogen ratio?

Chris Glein: Yeah, that's right. So if you imagine comets delivering methane molecules, then you would get a D/H ratio that doesn't match. And another problem with the comet model is we've learned, this has been known for a number of decades now, is that comets have abundant carbon monoxide. This is CO, what will kill you if you breathe CO. But CO is very abundant in comets and from the JWST data, we looked very hard and we didn't see any hint of CO in the surface ices of Eris and Makemake, so it doesn't look like CO or cometary material has been delivered to these bodies. Or if they started off looking like big comets, then those kinds of primordial materials would've needed to be processed in their interiors to change the composition to be compatible with what we see.

Sarah Al-Ahmed: We know that primordial methane on these worlds would be one thing, but then we're trying to make this claim about its origins, either abiotic or thermogenic. Is there some way for us to differentiate between those two processes or do we not have enough data that would allow us to figure that out?

Chris Glein: It's very difficult. In principle, you can do it. What you need, so methane is composed of carbon and hydrogen. The D/H ratio, it hones in on the hydrogen part of methane. The other half of the coin is carbon, and we can make measurements of carbon isotope ratios. So for carbon, there's carbon-12 and carbon-13, those are the main stable isotopes of carbon and you can make measurements of the carbon-13 of carbon-12 ratio. We did that, and the carbon isotope ratio actually looks a lot like most other materials we find in the Solar System, including the Earth, which is interesting. I'll describe that in a bit. But to discriminate between these two flavors of methane that abiotic and thermogenic, you need to be able to measure the carbon isotope ratio to extremely high precision. We're talking like within a few percent and we're just not there yet. This may require either a future mission or a future telescope with even more capability.

Sarah Al-Ahmed: There's a lot that we don't fully understand about the origin of methane on some of these worlds. Were there any assumptions that you had to make in this model?

Chris Glein: Yeah, we had to assume that these bodies were composed of rocks and water and they probably had some kind of icy building blocks, and these assumptions are based on what we know about comets and carbonaceous chondrites. These are the building blocks. We think of the outer Solar System. We know something about the densities of Eris and Makemake mach from their masses and their sizes or diameters. So from the density you can infer that their mixtures of water and rock, which is helpful to know, and it turns out that they are mostly rock and having rock is pretty essential if high temperature processes or geothermal activity needs to produce methane because there needs to be some source of heat. If you look, I study the moons of Jupiter and Saturn a lot, and on those worlds we think that tidal heating is a huge factor. This is like gravitational tugs between the moons and the giant planets. But in the Kuiper Belt and on these particular worlds, you just don't have that kind of energy source. So really having abundant rock is critical. The radioactive elements like of uranium or thorium and potassium, one kind of potassium, you have nuclear chemistry and this nuclear chemistry can power geothermal heating deep in the interior.

Sarah Al-Ahmed: That's an interesting point because these bodies are so far away from the sun, which is why we're so surprised by this level of activity. But can we start assuming that potentially these radioactive processes inside of these worlds are going to make way more of them more active than we thought possible?

Chris Glein: It could. I think Pluto opened that door and now the door is being open a bit further with these new observations from Eris and Makemake. But yeah, I think we're starting to learn that the observations are showing us that there must be some kind of ways to sustain a certain level of heating to promote chemistry. Now, whether all this chemistry happens today or it's from the deep dark past, we don't know that. We just see the methane on the surface today. So we don't know if methane was cooked up in the interior 4 billion years ago or if it could still be happening today. That's something that people are going to have to start modeling and we're going to think about what are the next steps for measurements that we might want to make to try to test these ideas.

Sarah Al-Ahmed: The fact that you bring up tidal heating of Jupiter's moons and things like that sparks an idea for me. Did you in any way analyze the moons of Eris and Makemake?

Chris Glein: Not yet. So there are data from Eris has a pretty big moon known as Dysnomia. It's much darker than Eris, and we know something, it looks like it's dark, but its interior is mostly made of ice. It doesn't appear to have a high density to have much rock in it. So there's some difference between Eris and its moon that isn't well understood right now, but we do have observations of Eris's moon. So I think in the future there'll be the opportunity to analyze the data and see what can we learn about its moon and what can that help us understand about the history of the Eris Dysnomia system. Because what we learned from New Horizons, the mission to Pluto, we learned that there's this very intimate relationship between Pluto and its moon, Charon, and the thinking is that Charon and Pluto actually had a collision early on and that's how Charon became a moon of Pluto, and maybe something similar happened for Eris and its Moon.

Sarah Al-Ahmed: You also pointed out earlier that there is a lot of distance between Eris and Makemake, like 50 AU difference. Was there also a difference in the types of methane and the relative abundances of these isotopes? Or were these worlds very similar?

Chris Glein: They look very similar as far as the isotope chemistry within the error bars. So although these are demanding measurements and they're unprecedented, really, there are still error bars associated with these measurements. So within the error bars, we can't really say one way or another if the isotope chemistry is really different, but there are notable differences. So Makemake is closer to the sun than Eris is. That's one thing. And Makemake is also smaller than Eris, which is interesting. So in our paper we propose that probably Eris may have a more vigorous history because it's larger. So you have this greater internal engine, this radioactive decay, the rock to drive the chemistry. You might imagine these processes would be more vigorous on Eris or more recent because you have a greater energy budget. One possibility is that this methane production, chemical cooking, the kitchen of the Kuiper Belt was open let's say in early on in the history of Makemake, maybe it has an ocean today, maybe it doesn't. For Eris, the odds are probably better that it has an ocean and there could still be some active chemistry going on in the subsurface.

Sarah Al-Ahmed: This brings up my next question, which is that there are all these internal processes that might be altering this methane or producing it. How is that stuff getting deposited on the surface?

Chris Glein: The shorter answer is we don't know. Yeah, we don't know. To answer that question in detail, we need to bring geologists into the discussion and to help them out, we're going to need a mission to actually go to Makemake and Eris for the first time, but to go back to the Kuiper Belt for a second time. So something like New Horizons 2 would be what's in store for us if we want to try to answer that because we'd have to be able to see the surface geology. So chemistry has given us this indirect window into the subsurface. We're seeing these molecules and from their isotopic signatures, we're able to peer indirectly into the subsurface and envision and hypothesize some of these processes, but to test these ideas about how's this stuff get out of the interior and onto the surface, you'd have to be able to see the surface. Are there cryo volcanoes or some kind of gigantic rifts like we find on Europa and Enceladus, which could act as pathways to transport subsurface materials? We can't see, although people are aware that JWST is so incredible. It's not like we can just zoom in on Eris at almost a hundred AU and see the surface. We can't do that. To JWST, Eris is still about nine or 10 pixels.

Sarah Al-Ahmed: So distant and so small, and it's also very dark out there, although we're looking in the infrared in this case. But I love the idea of having another mission to go out there and look at more of these Kuiper Belt objects because we've literally only done it once. I know that the Voyagers have made it out of our Solar System, but they didn't have the ability to look at these Kuiper Belt objects. So I would love to see more missions like that. Is there anything else that we can do in the meantime before we have a mission to go all out there? Because it might be a while.

Chris Glein: It might be a while. I think we should start thinking about it because these kinds of things take a while to plan. It may not happen in my lifetime, but I think people who are alive now, we can start working on this to lay the groundwork for what's to come for future generations. Now what can we do in the near term because we're impatient, so we like to try to answer some of these questions. I think in the near term, what we can do is we can move into this mode, what it's called comparative planetology, looking at other worlds to gain clues about what are the commonalities or what's different about different things. We've learned from exploring our Solar System that worlds can be unique in many ways, but there are also ways that they can evolve along similar trajectories. And we now have some information from Pluto. We have information from Eris and Makemake from James Webb. We also have observations that have been made for some of the other trans-Neptunian objects. So these are objects like Haumea, which is another pretty big KBO. We have Sedna, Quaoar, Gonggong. So a lot of these objects, to be honest with you, I didn't even know what they were until I started working on this project and I learned that okay, there's a whole community of people who are very excited about this and they've gotten me excited about this. So I think the people who designed these James Webb programs, they're very smart and they figured out, "Okay, we need to study all of these worlds to try to get a grip on what's really happening out there and what's the interplay." I like to think about this field as planetary psychology. So it's like nature versus nurture, that endless debate. And on Eris and Makemake, I was originally thinking it was nature. What were their building blocks? What did they start with? Did they just start with methane from comets? And it looks like the answer is no. It is actually nurture all these evolutionary processes that are responsible for what we see, and I think we need to continue to look around at some of these other Kuiper Belt objects to try to understand what's the interplay between nature and nurture for what we see elsewhere.

Sarah Al-Ahmed: It would be really cool to know more about more of these worlds because it could not only tell us more about their formation, but potentially about the broader habitability of Kuiper Belt objects, which is mind-blowing just to say it all. As we're looking out there for life in the universe, places like Titan and Enceladus and Europa clearly are cool places to look, but Kuiper Belt object was not on my bingo card for the search for life.

Chris Glein: It wasn't on mine either. It's been really shocking to be honest with you. I've been in the field now since about the mid two thousands when I was a student and when I first started out, people were starting to talk more about an ocean on Europa, which is one of Jupiter's moons. Then we had the Cassini mission to Saturn and we learned that, "Okay, it looks like Enceladus and Titan have oceans." And now like you mentioned, it seems like there may be some hint that liquid water has played a role on these objects in the Kuiper Belt. Theirs are blisteringly cold. It's nearly 30 Kelvin on the surface of surfaces of these worlds. Yet deep down in their interiors, there could be some similarities to what we're more familiar with liquid water and rocks and water rock reactions. And when we study water rock reactions on the Earth, that's one mode of geochemistry that can support life or make an environment habitable. So I don't want to get people too excited yet because it's really early days and we don't want to be saying the L word prematurely, but finding indications of an active planetary body is a step in a planetary body being able to support life. It's step one is to have some kind of dynamic, world dynamic processes that could sustain liquid water.

Sarah Al-Ahmed: And even if they don't have life, even if they're not okay for creatures to live there in the oceans, how beautiful and strange is that even all the way out there in the dark, they can be these dynamic and interesting worlds all on their own. It really opens up the possibilities for whole new realms of worlds that are worth study that people might not have thought to even look at before.

Chris Glein: Right. So just 50 years ago or something, people talked about the habitable zone and it was really focused on liquid water at the surface of a planet where sunlight or starlight could warm the surface enough to be able to sustain liquid water. But now we're finding maybe most of the liquid water in our Solar System is actually in the outer Solar System. We just don't see it on the surfaces, but it's hidden deep down, and in order to figure out how much there is or what its history might have been, we got to be a little bit creative as far as being able to design experiments to look for different isotopes or different molecules that can help us understand the properties of that water in planetary subsurfaces.

Sarah Al-Ahmed: Do you know if there are any current plans to redirect JWST to some of these other Kuiper Belt objects to do some comparative planetology here?

Chris Glein: I don't know yet. I wrote a proposal for Cycle 1, but I was so exhausted. I skipped Cycle 3. Today is actually selection day for JWSD Cycle 3. Although people probably hear a few weeks in the future on the program, a lot of astronomers are either very nervous or excited or disappointed that today the news is broke. So I'm sure people have made plans that will either happen in the next year or the next few years to point JWST at some of these Kuiper Belt objects and other trans-Neptunian objects to try to learn what's happening in the most distant reaches of the Solar System.

Sarah Al-Ahmed: Well, even if we don't get follow-up observations anytime soon, I feel like just this amount has made these distant worlds feel so much more closer to home than they were before. So thank you for joining us to tell us more about this, and if you have any more results in the future, please let us know because it's amazing.

Chris Glein: We'll let you know. Thanks a lot, Sarah. I was very happy to be on.

Sarah Al-Ahmed: Now let's check in with our Chief Scientist, Dr. Bruce Betts for What's Up? Hey, Bruce.

Bruce Betts: Good day to you. How are you this fine day?

Sarah Al-Ahmed: Pretty good. Very excited that we have new results on Eris and Makemake. I feel like the Kuiper Belt, dwarf planets, I mean other than Pluto, are just not as appreciated as they deserve to be.

Bruce Betts: True. Very true. Yeah. It's hard when you don't have more data, but we're getting more data and there's a lot of fascinating weird stuff the more we learn as is usually the case in our Solar System or space in general.

Sarah Al-Ahmed: Well, that's so fascinating about it for me, because when we flew by Pluto with New Horizons, we realized that it was so much more geologically active than we imagined. There were even clouds and things like that, which is just not at all the world that I imagined, and now we're learning that Eris and Makemake have this potentially geothermal thing going on. Why are these worlds so much more active than we anticipated?

Bruce Betts: If I knew that I would write a paper about it.

Sarah Al-Ahmed: Nobel Prize.

Bruce Betts: It was shocking. And Pluto has so much that's going on or gone on in what would be considered recent geologic history, and that's when you got some cold, icy body out there anytime in the last 4 billion years. But it's got glaciers and all sorts of stuff going on and exotic features. It's a big giant plane that looks like Pluto, the dog. I mean, it's got a lot going on.

Sarah Al-Ahmed: What I loved were the images where they looked at the moon, Charon, all that red stuff. The [inaudible 00:59:41] on one side is just Pluto, basically spray-painting its, I want to call it a moon, but they're almost like a tiny binary dwarf planet system.

Bruce Betts: Yeah, that's pretty much what they are since they rotate about a point that's not inside Pluto, which makes it a little more exotic, more of a spinning dumbbell system rather than one thing we're orbiting another. Charon's cool. I mean, that's just weird. There's just so much weird in that system and all over the place in our Solar System. And what's really amazing is when you see these places, we never stop being surprised and we never know when people say, "What are you going to find?" "Well, we don't know. That's why we're looking." Anyway, yeah, it turns out I'm a fan of this planetary exploration thing.

Sarah Al-Ahmed: I really wish though that we had more missions that we could send to these worlds. Imagine a dedicated Makemake mission or an Eris mission, and hopefully some way to slow them down so that they can stay near those. Although that is technically challenging, but there's just... I don't know. There are so many things that I feel like I'm not going to get to see up close in my lifetime, and it makes me even more grateful for instruments or telescopes like JWST that can actually show us a little bit closer or tell us a little bit more about these because I don't know, I might not even live to see us go back to Uranus and Neptune. Fingers crossed I can, but Eris and Makemake, I don't know. My children's children's children maybe.

Bruce Betts: Wow. You're bringing me down.

Sarah Al-Ahmed: I'm bringing you down.

Bruce Betts: I mean, I'm happy for your children's children's children's children to the 5th power, but I was just on a happy roll. Those places are cool and we got to see some of them.

Sarah Al-Ahmed: I know, but I do have a happy thought, which is that this telescope really does show why advocating for space really helps because JWST was in such a long development. It took so much love to keep this program going, and now we're seeing the results and what it's telling us about the universe, about exoplanets, about stuff in our own Solar System is so far beyond what I even hoped in my wildest dreams.

Bruce Betts: I know it's a spectacular success that could have been a disastrous failure in any number of ways, including being canceled because there were serious budget and schedule issues as there often are, but there were really serious and they had to have a bunch go right, and they had amazing engineering, and now they have amazing science, and it's a treasure, it's a true scientific treasure for all sorts of observations, including Solar System. I mean, we're getting to see things. Uranus and Neptune pictures, we're seeing rings that we've never seen them from Earth. So I'm writing books about children's books about each of the planets and out there, on the one hand, it's like if we didn't have JWST, I'd have nothing since the 1980s to show them that was that clear. Now it's still on Voyager. It's still better to be there, but it's a great improvement. It's good stuff. I'm a fan.

Sarah Al-Ahmed: It's such an interesting time in space science and exploration, but-

Bruce Betts: It's a great time.

Sarah Al-Ahmed: It's a great time. But we've seen how these budget negotiations and stalemate and Congress have impacted institutions like JPL and programs like Mars Sample Return. So I'm really excited that we can finally share with people that they're reestablishing the Planetary Science Caucus in Congress. That's a really great tool for us to help connect with the people that make these decision making points so that we can advocate more effectively for programs like JWST and these kinds of missions that really kind of change the way that we understand our Solar System.

Bruce Betts: It's a great thing and we'll keep pushing for it. That's part of what Plenary Society does. But yeah, it's always a mess. The budgets and canceling and advocating for things, I mean, that's been going on. That was part of the motivation for starting The Planetary Society.

Sarah Al-Ahmed: Yeah, that's why we're here.

Bruce Betts: It's one of the reasons we're here.

Sarah Al-Ahmed: It's one of the important reasons we're here. Not defending the Earth isn't also important or finding life.

Bruce Betts: Yeah, totally.

Sarah Al-Ahmed: We've got a cool job, Bruce.

Bruce Betts: Yeah, totally.

Sarah Al-Ahmed: All right. What's our random space factor this week?

Bruce Betts: Ah, it's a goodie. So just announced fairly recently was the final determination of how big the sample was that OSIRIS-REx got from Bennu 121.6 grams of rocks and dirt that is less than the mass of a baseball, although not that far off. And more significantly to put it in terms everyone will understand, it's about the mass of three Twinkies. It's actually slightly less than the mass of an old style Twinkie and slightly more than the mass of three new style Twinkies. So they're a little smaller and lighter now.

Sarah Al-Ahmed: That shrinkflation.

Bruce Betts: It is indeed. So what will be interesting is of course, whether they find any evidence of Twinkies in the samples, but nothing obvious yet. Maybe cream filling.

Sarah Al-Ahmed: I'll ask Dante Lauretta in an upcoming episode. We're going to be discussing his new book, The Asteroid Hunter. So we'll ask.

Bruce Betts: Dante is a pretty fun guy, so you can ask him that. He may look a little weird at you, but yeah, no, this is a man who develops games based upon space explorations in his spare time when he is not flying missions to asteroids. So yes.

Sarah Al-Ahmed: I know we're bringing a copy of the OSIRIS-REx board game that he created to our Eclipse-O-Rama Festival, so I'm hoping people get a chance to try that in our board game room, myself included.

Bruce Betts: Yeah, it's cool. Xtronaut 2.0, and they have other games too.

Sarah Al-Ahmed: Super cool.

Bruce Betts: And what's interesting about the games that game is it actually presents things with some of the realities that you don't think about when you are watching science fiction or something like budget. Your budget has been cut back, you can get canceled. You've been shifted to another rocket. You've got two years delay. So it's interesting that him having lived through that as the PI is still wanting to play with those fun things.

Sarah Al-Ahmed: Do not pass go. Do not collect $200.

Bruce Betts: Do not collect $200 million. All right.

Sarah Al-Ahmed: All right.

Bruce Betts: All right. Everybody go out there. Look on the night sky and think about fluffy squirrel tails. Flipping, flipping, flipping in the wind. Thank you and goodnight.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week with tips on observing and imaging the upcoming total solar eclipse in Mexico, the United States and Canada. We'll also have some stories from an Eclipse chaser. We've got less than one month until the big day to prepare. Love the show? You can get Planetary Radio t-shirts at planetary.org/shop, along with lots of other cool spacey merchandise. You can help others discover the passion, beauty, and joy of space science and exploration by leaving a review and a rating on platforms like Apple Podcasts and Spotify. Your feedback not only brightens our day, but helps other curious minds find their place in space through Planetary Radio. You can also send us your space thoughts, questions, and poetry at our email, at [email protected]. Or if you're a Planetary Society member, leave a comment in the Planetary Radio space in our member community app. Planetary Radio is produced by The Planetary Society in Pasadena, California and is made possible by our members who love every dwarf planet. You can join us and support even more amazing planetary science at planetary.org/join. Mark Hilverda and Rae Paoletta are our associate producers. Andrew Lucas is our audio editor, Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. And until next week, ad astra.