The asteroid hunter

Sarah Al-Ahmed: OSIRIS-REx was amazing, but the story gets even better when you hear it from the mission's principal investigator, 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. Behind every space mission is a harrowing tale of hard work, love, and perseverance. Our guest this week, Dante Lauretta, is the principal investigator for NASA's OSIRIS-REx mission. He'll share stories with us from his new book, The Asteroid Hunter. Then Bruce Bets, our chief scientist answers a question from our audience and shares a new random space fact in this week's What's Up. 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. In 1999 researchers discovered a near-Earth object that posed a potentially grave threat to our planet. The asteroid, which was later named Bennu, through a Planetary Society naming contest, could someday collide with Earth. While the data shows that this won't happen anytime soon, the discovery marked Bennu as an object of deep fascination. Our guest today, Dr. Dante Lauretta and his team were tasked with unraveling Bennu's mysteries. Their spacecraft was called the Origins Spectral Interpretation Resource Identification and Security Regolith Explorer or OSIRIS-REx mission and embarked on a quest to retrieve a sample from the asteroid's surface. One that could not only teach us more about the early solar system and the origins of life, but potentially give us a deeper understanding of asteroids that could someday help us save the world. The OSIRIS-REx spacecraft launched in September 2016. Seven years later after an epic adventure through space, it deposited its precious samples on earth. They landed in the Utah Desert in the United States in September twenty-twenty-three. Dante Lauretta's new book, The Asteroid Hunter tells the story from Dante's childhood in Arizona staring up at the stars to the remarkable sample retrieval. It's a really moving portrayal of this complex and beautiful mission and all of the people along the way that touched Dante's life. Dante Lauretta is the principal investigator of the OSIRIS-REx asteroid sample return mission and a Regents professor of Planetary Science at the University of Arizona, Lunar and Planetary Laboratory. His book, The Asteroid Hunter was released on March 19th, 2024. Hi, Dante.

Dante Lauretta: Hello.

Sarah Al-Ahmed: It is wonderful to finally meet you after all this time following the OSIRIS-REx mission. You're like this mythical creature that I've never met before, so it's lovely to meet you.

Dante Lauretta: Wow. Well, thank you for believing in me.

Sarah Al-Ahmed: I mean, after everything you've been through, personally and with this mission, I feel like it really is one of these moments for me.

Dante Lauretta: Well, that actually means a lot to me. Thank you. I appreciate hearing that.

Sarah Al-Ahmed: Yeah. I think too, that I'm really grateful to have this book because from the science communicator perspective, you can get really into the weeds on the arc of this mission, but when you see the human perspective behind it, the story of your life and all of the people that worked on this mission, it gives me an even more profound feeling about that sample return and how massively successful this mission has been.

Dante Lauretta: That's amazing for you to say and for me to hear, that it's really what I was trying to accomplish with the Asteroid Hunter. It is a human endeavor. This was an expedition that we relied on each other. We were challenged constantly, and we persevered through the dedication, the unity of the team, which is really amazing, and the sense that we were all part of something much bigger than ourselves. I've often felt like I got swept up in OSIRIS-REx and fortunate to be at the helm, but it's kind of like riding a tsunami. You're like, okay, I just got to keep hanging on and make sure that I stick with it until this wave is over.

Sarah Al-Ahmed: I loved how throughout this book you had these interludes that were all about these two carbon atoms that originally were born together in the heart of a star, a star that was an ancestor of our sun, and how these two carbon atoms eventually came back together in the form of you meeting the OSIRIS-REx sample in the desert, and this book would've conveyed that profound connection to the universe just on its own. But these little interludes really I think help solidify that connection between us and the broader universe.

Dante Lauretta: Yeah, I was really inspired to add that because I always felt like there was this underlying draw to be part of this program because there were plenty of days where I thought, man, this is so hard. Can I just walk away? Is that possible? And the answer was always no. I was always compelled to just keep going, to push through to find the strength to rally the team. And it was just this cosmic meeting that I knew had to happen and I wanted to capture that in the story of the two carbon atoms is that feeling manifest in their journey?

Sarah Al-Ahmed: It's really deep and profound to think about just how long the arc of histories that led to this sample return and all of the interconnectivity between us and our stars as ancestors. And to be able to actually reach out into the solar system and touch this asteroid, bring a part of it back, everything that had to go right in the universe for this moment to happen is just absolutely startling.

Dante Lauretta: I say in the book early on when we were discussing the concept now over 20 years ago, it seemed like magic. I was talking to my boss, the director of the lab, Dr. Mike Drake, who was the original principal investigator and invited me on as the young kid to help with the science and lead the science program, and Lockheed Martin who builds amazing spacecraft and had done a lot of interplanetary work before, and they're like... I'm 33 years old, and they said, "Dante, we need you to pick an asteroid and we'll work on a mission to bring samples back to your lab." And I was like, "No way. That sounds crazy." I know it would take decades to do something like that, and it's just a phenomenal science achievement and technological achievement, and I was skeptical at the beginning about whether I wanted to take it on because it's a huge commitment for me, for my family. I talked with my wife a lot about it and she was on board and agreed it's going to be a family activity. We're all going to be involved, and the kids who showed up along the way their whole life, that's what dad's been doing, is running the OSIRIS-REx program.

Sarah Al-Ahmed: Ultimately, you ended up studying this asteroid called Bennu. And early on you try to impress upon everyone just what an interesting target this is, but also the danger that it could pose to humanity. What is it about Bennu that makes it so potentially hazardous to people on earth?

Dante Lauretta: Yeah, we call Bennu the most potentially hazardous asteroid in the solar system, and I totally lean into that on the prologue, where I imagine what would happen if Bennu impacted the earth, which if it's going to happen, it's 2182, very far in the future and it's a low probability event. I want everybody to make sure we know that. It's 0.05% chance. Still the highest of any asteroid that we know of, which is what puts it at the top of the list. It's also relatively large at 500 meters in average diameter. We put the City Killer asteroid at 140 meters. It's much bigger than that. It would take out a large city if it hit. It's not an extinction level event. It wouldn't be like a dinosaur killer that was 10 kilometers the object that hit 65 million years ago, but it would be a major natural disaster, and of any object that's going to hit us, this is the one that's most likely to do that, which is why it's at the top of that list.

Sarah Al-Ahmed: I've been making jokes about how the OSIRIS-REx mission reminds me of dinosaurs, because of the 'REx' on the end now, but I love that you actually made that connection in the book. It wasn't just me in my mind. There actually is a connection here between the objects that destroyed the dinosaurs, at least the non-avian dinosaurs and this mission.

Dante Lauretta: Absolutely. We are a security mission. It's part of our acronym. We do feed planetary defense in many different ways. One is understanding the orbits of these objects. You would think we figured out gravity with Newton and Kepler, but those equations don't explain where the asteroids going to be in the future, because there's a lot of things besides gravity that influence their orbits, especially the energy balance between sunlight and heat, the asteroid gets hot when the sun hits it. It cools off very quickly when it rotates into the night and that photon emission changes its orbit, accelerates it, and we measured that more precisely than it ever been measured before, which is why Bennu is going to be pretty far into the future. And then one thing I've been proud to see that it's kind of the unexpected outcome of the mission is now Department of Defense and other agencies around the world are simulating asteroid deflection technologies on computers, and Bennu is the target because we know so much about it. We have the mass and the rotation and the surface structures, and so they use it to kind of game out some different scenarios for asteroid deflection.

Sarah Al-Ahmed: Which is fantastic. We've only had our first actual planetary defense mission, the double asteroid redirection test, and similarly, that thing was pretty rubbly. We don't have all of the results yet. We're waiting on the European Space Agency's HERA mission to go there and check it out afterwards. But I have a feeling that this rubble pile nature of asteroids is really going to make a deep impact. Forgive me for saying that, on how we redirect these things, knowing more about Bennu and how flaky it was when you got there, could potentially be the difference between humanity being saved and humanity totally messing up a planetary defense mission?

Dante Lauretta: Yeah, it's been amazing over the course of the mission, which for me is over 20 years to see our understanding of these small objects just grow enormously. It was a hotly debated topic 20 years ago, whether asteroids were coherent shards, as we call them, big chunks, kind of like you imagine if you watch Star Wars or the famous Empire Strikes Back scene, versus rubble piles. And it turns out the small asteroids, especially, the ones in the near-earth population, appear dominantly to be piles of rubble. So it's kind of like if you just scooped up a handful of gravel, if you had giant hands and then you just kind of packed it into the sphere and just let it float, it would barely cling together with its own microgravity. And that seems to be what most of these asteroids are.

Sarah Al-Ahmed: And of course, other impacts of asteroids and comets around our solar system have impacted the political will behind this mission. Shoemaker-Levy 9 as an example when it plowed into Jupiter, definitely increased the will for people to want to fund these missions. But then in the middle of producing this asteroid sample return mission, that object over Chelyabinsk, Russia exploded and then added fuel to the flames.

Dante Lauretta: Yeah, I talk about that day in the book. That was quite memorable for me because that was my first appearance on TV as a NASA scientist. It said NASA scientist under my name, and I was just in heaven. I was like, "Wow, that's a dream come true. I'm representing NASA on TV." And I was still pretty young and just getting started in the job, and we weren't talking about Chelyabinsk. We didn't know that was going to happen. We were on TV because there was another asteroid 2012 DA-14, which was coming close to the earth within the geocentric satellites, and it was making headlines, and we thought this would be a great way to just introduce OSIRIS-REx. It's a new mission. We're just getting started. Let's use this as an opportunity to educate people about asteroids. And then I get on, and I'm not supposed to talk about asteroid impacts and playing out in real is an asteroid impacting the earth and exploding over the city in Russia, and I'm totally ignorant about it. And I'm like, "No, it's not going to hit the earth. We're all safe, don't worry." And then they're like, "No, it already hit the earth." And I'm like, that's impossible. It's not here yet. It's not going to be here for a few hours. And all the while there's this footage of this giant explosion and people are injured and buildings are knocked down. And it was this Asteroid Friday, I call it, just because it was this amazing cosmic coincidence.

Sarah Al-Ahmed: But of course, this mission is about so much more than just planetary defense. The goal ultimately was to get these samples for so many reasons. We want to know more about our solar system and its formation and potentially the role that these objects play in the creation of life, which comes back to the beginning of your career. You got into this because you were, well for many reasons, but because you were passionate about the search for extraterrestrial intelligence, how do those things connect together?

Dante Lauretta: Yeah, that was really my entree into the whole space science realm. I was a college kid, pretty clueless about what I wanted to do. I'd been here four years here being the University of Arizona. I'm a professor here now, but I was a student here when I was young. And I didn't have anything that sparked me like, "This is what you want your life to be Dante." So I was floating around trying to find something and I got a NASA undergraduate space grant, and I got assigned to work with a professor on the Search for Extraterrestrial Intelligence. And that blew my mind. I couldn't believe it was a job that I would get paid to talk to this professor. And our project was; what are we going to do if SETI succeeds and we find somebody and we want to talk to them? How do you establish a language when the only thing you have in common is you know how to build a radio telescope and you're broadcasting across the stars? And I just thought, "This is it. I want to do this. I love it. It's what I've been thinking about as just wandering around the woods or the desert and looking up at the stars. Are they out there? How do we find them? Are we alone?" What is the nature of life? What is the nature of consciousness? And I was quickly dissuaded from that career path early on like, "No, you can't do that. It's not legitimate science. You got to be more serious about your investigations. And I always said, "Well, I'm going to do that, but I'm just going to do it legitimately." And planet formation was where I focused because in 1992 when I got that opportunity, we had not discovered an extra-solar planet around a sun-like star. It was still theoretical. Are there other planets? Is the solar system rare? There were scientists who argued that it's an unlikely phenomena that planets are going to be forming around other stars. And I was like, okay, there's some fundamental knowledge we need to gain. How does a planet form? And therefore how likely is it? And I was fortunate to watch the field go from Hubble imaging Orion with the proto-planetary discs to James Webb that we have now. And we're seeing the star formation. ALMA, which is mapping density distributions in growing planetary systems, and of course Kepler, which has provided thousands of extra solar planets for the community to study. It's a whole new universe compared to where we were when I was young. And it's much more legitimate now to talk about astrobiology, biosignatures, technosignatures, and the idea that yeah, there might be other life forms out there that have reached the point of technology.

Sarah Al-Ahmed: It makes me really sad thinking that there were so many wonderful scientists who might've been dissuaded from that path. But thankfully, now that we know more about the universe, there's probably a whole new generation of people that are getting into this field. I'm sure it'll all pan out in the end, but you had to make some really difficult decisions about the arc of your career. SETI was losing funding, then you pivoted to Mars. And then unfortunately another mishap with Mars Orbiter happened and you ended up kind of pivoting again. Ultimately though this still in some strange way comes back to the search for life, because as you were looking for meteorites, studying meteorites, you started finding these phosphorus compounds inside of these meteorites. How does that also connect to the search for life?

Dante Lauretta: Yeah, I was studying planet formation for my PhD thesis and I was focusing on sulfur, which is an important element. It's an important element in biology. It's used for our proteins. It makes the bridges that give proteins their three-dimensional shapes and therefore their function. So I was like, okay, I can study sulfur and still be doing biology, astrobiology, origin of life because it's fundamental, but it's critical for planet formation too. How much sulfur a planet gets determines how quickly the core forms and what kind of volcanism you're going to have. So it's essential planetary science ingredient as well. And Sulfur enters into solid material by corroding metal grains that existed in the protoplanetary disk, and it's like rusting except it's sulfur instead of oxygen. And there was one element in the metal phosphorus that didn't react with the sulfur at all, and it got more and more concentrated in the remnant core that was not getting chemically altered. And I said, phosphorus is a really interesting element for biology. It makes cell membranes. It's used in a molecule called ATP, which is how all energy currency is distributed among cells on earth. It makes our bones and teeth if you get to animals. So I was like, okay, this is neat. And astrobiology was becoming legitimate and NASA was starting to fund astrobiology research now in the late 90s, and I wrote a proposal to focus on phosphorus, look at meteorite sources and figure out how it could have gotten into a chemical system on the early earth. And it really paid off. It was an amazing study. We found a mineral from meteorites that reacts very quickly and water and makes a lot of complicated phosphorus-bearing compounds today. It's one of the leading theories for how phosphorus possibly was introduced into the origin of life scenarios.

Sarah Al-Ahmed: Wouldn't that be something? And we only just last year got the evidence that there's phosphorus in the oceans of Enceladus orbiting Saturn. So who even knows what's out there? I feel like we're just on the cusp of some really amazing discoveries, but we're going to have to be a little patient, which is not my forte.

Dante Lauretta: Well, the Enceladus discovery is fascinating, and I've been paying a lot of attention to it because we're seeing similar chemistry in the Bennu samples in terms of where the phosphorus is being concentrated. And I'm looking at.... They did some really nice models chemistry-wise in that paper, the Postberg paper where they report the Enceladus phosphate detections, and I think it's relevant to the fluid chemistry on Bennu's parent asteroid as well. So we're seeing a lot of similarities. Maybe Bennu had liquid water, not Bennu itself, but its parent asteroid, which was a much larger object that formed early in the solar system. Looks like it had liquid water and it concentrated phosphorus in that water and it left it behind as an evaporative residue, which is white, highly reflective coatings and veins that we see shot through the rocks.

Sarah Al-Ahmed: I cannot wait to get into the results once they're published. We'll share all that with our audience when they actually do come out. Everyone is waiting with bated breath. But that does bring up another great point, which is that in order to actually get the samples that you wanted in order to validate these ideas, you had to select a target that would have these materials on it. How did you go about selecting an asteroid target?

Dante Lauretta: We made the final selection way back in 2005. We were refining the mission concept and one of the criticisms early on was we need a better target, a more scientifically-justified target. The first set of criteria are all engineering, right? You're trying to fly a spacecraft to an asteroid, spend time at the asteroid and then collect a sample and bring it back to the earth. So the orbital constraints are pretty tight in order to make that happen on a reasonable time-scale. So you're looking at near-Earth asteroids right away. So most asteroids are out in the main belt between Mars and Jupiter, hundreds of thousands, ultimately millions will be discovered out there and tens of thousands fall into the inner solar system. So you immediately down select to a smaller subset of the asteroid population. Then you need something that's in an Earth-like orbit. You don't want it to get too close to the sun, because it gets really hot. You don't want to get too far away from the sun because you're solar-powered and you don't want to lose all your electricity. So there's kind of a little sweet spot, very similar to the habitable zone actually from exosolar planet considerations. And then you needed something that's not inclined really high relative to the orbit of the earth because then the entry velocity is too fast and your capsule will burn up. And you needed something relatively large because we wanted to pick up loose material from the surface. And if you get down to really small asteroids like 10 meters, they're probably just a single chunk of boulder and you're not going to collect something unless you break it in some way. So all of that got us down to a couple dozen asteroids. And then ultimately we looked at the composition and it was astrobiology driven. We wanted something with high carbon abundances, and that really relied on the brightness. The darker asteroids seemed like the most likely choices for being rich in carbon. And Bennu is one of the darkest in the solar system in a very accessible orbit, relatively large. And we had a great astronomical data set. So in 2005, by the end of that year, it was our number one choice for the mission.

Sarah Al-Ahmed: So it was in 2011 that NASA granted you the money to do this mission, but it was a very kind of difficult time for you personally that you talk about in the book, because Mike Drake, your colleague who had been leading this mission, unfortunately fell ill. And that meant that you had to step into that role of negotiating with NASA and doing all of that. That must have been a lot on your shoulders.

Dante Lauretta: That was one of the most difficult times of my life and on the program, because Mike was really my mentor, my friend really took me under his wing. He was 25 years my senior. He was the lab director, very famous scientist, and it was an honor, and I was excited to be able to work with him, and to be brought onto the mission for me was astonishing. I never dreamed I would be involved in a space mission. I really had thought I was a lab guy. That's the path I had gone on. You mentioned the Mars Observer mishap in 1993. I was a graduate student on that program when the spacecraft was lost. And I was like, just go in the lab. It's safer. You control your data, you can still answer interesting questions. So getting involved in the mission was something Mike urged me to do, encouraged me and supported me and tutored and taught me how to do a program like this. And we worked together starting in 2004, ultimately seven years before we won the contract. And that's a friendship forged in the trenches. We just traveled a lot. We got so close and we're rejected multiple times. And then you're downtrodden and you just think, "I just wasted five years of my career on proposals that didn't get funded and I got nothing to show for it other than a bunch of PowerPoints," which aren't going to get you any kind of asteroid sample. And then in late 2009, he got really sick and he was in the intensive care unit. Sometimes he was intubated. We thought he might not make it through the night and it broke my heart and I was panicking because I didn't think we could fly the mission without him. He was the leader, he was the intellectual force, he was the management. He had the credentials and the gravitas and I was kind of tagging along, I felt, and learning as I went. And then finally four months after we won, he passed away. And I didn't think we could do it. I thought it's it. It's over. And one of the last things he said is that it's my mission and that he trusts me and that I'm going to be the one to take it into the future. And I had to do it. I had to do it for Mike, and I figured it out. And I had a great team to help me. So that's what it ended up all being about.

Sarah Al-Ahmed: Clearly he was a fantastic teacher because you stepped up well. And I was very moved by the fact that there was a tribute to him written on the side of the rocket that launched a OSIRIS-REx.

Dante Lauretta: Yeah, thank you. Also, we had a plaque on the spacecraft, still on the spacecraft. That's a memorial to him as well.

Sarah Al-Ahmed: Oh, that's beautiful. It really, I've been thinking about this a lot lately, just how much impact a single person can have on everybody that works underneath them, and how many space missions are enabled by just one passionate person is amazing and beautiful.

Dante Lauretta: It really is. It's a field where you have to be persistent and dream big, and if you're lucky, you get to pull it off. You get to fly a program like this. I know I'm incredibly fortunate and I'm honored and always humbled to look back to see the book and think, "Did you live that? You actually did that. It's not a science fiction novel. It's real. And that was your life." And it's astonishing to me even to this day.

Sarah Al-Ahmed: There were so many challenges you faced even in just the engineering of this thing. What were some of the biggest difficulties you had before you ever got to the launch pad?

Dante Lauretta: Definitely trying to figure out the environment of the asteroid. We had the best astronomical data set you could ever get on this target. We had Hubble Space Telescope, we had Spitzer Space Telescope, we had the Arecibo data. Telescopes all over the world had looked at this and we thought, this is great. We know so much. And then you get to the actual design and the engineers are asking you questions: how hard is the surface going to be? How big are the grains going to be? How rough are big? Are the boulders? And you're thinking; we don't know any of that, can't really measure that very well. And we tried and we fooled ourselves. We thought that based on the Spitzer data, which showed the surface heating up and cooling off really quickly, the radar data from Arecibo and Goldstone, which showed a pretty smooth surface and the shape which looked like material was migrating down to the equator and building up a fine-grained ridge. That it was going to be beach-like. I said, that over and over again to the team, to NASA to the public, probably on Planetary Radio at some point back 10 years ago that yeah, this is going to be easy. It's a beach, sand everywhere. It was a scoop down. It's like a kid with a bucket out there. And so we get there and that's not the case at all. So trying to turn astronomy data into engineering design constraints was an enormous challenge and there was huge uncertainties, and those played out over the course of the mission. Our ignorance was on full display once the data started coming down from the asteroid.

Sarah Al-Ahmed: That was probably the most stressful part of the book for me. There were many moments that I was on the edge of my seat, is this thing going to work? Is it going to get there? What's it all going to be like? But then just the site selection in and of itself was just so difficult. This object you got there thinking maybe there'd be some sandy beach-like material? No, just covered in giant boulders.

Dante Lauretta: Covered in giant boulders. And then as soon as we get into orbit, the surface starts erupting. There's particles flying around and the thing looks like popcorn. Everything's flying in our camera fields of view, and we're panicking and thinking the whole mission is going to be redesigned and we're going to be months or years delayed because of this. Yeah, Bennu is a trickster. It loved to play with our minds. To me, it showed how different things are in microgravity. You try to use your intuition and your common sense, but we live at the surface of a massive planet and the acceleration is 1G, and that drives material behavior enormously. And it's like all of our equations kind of blow up. When you turn the gravity variable down to zero, you're like, "Well, what's left?" And so what controls how particles flow down a slope if there's very little gravity to do that? And that's why we were so surprised by Bennu. We just didn't understand that realm. It's a whole new area of astrophysics dealing with material properties in microgravity like that.

Sarah Al-Ahmed: You mean all that time you spent on the Vomit Comet didn't totally teach you everything about micro G?

Dante Lauretta: We tried. Yeah, we flew on the, so-called Vomit Comet, which was NASA's reduced gravity aircraft for testing these kinds of apparatus. And we couldn't get to the gravity at the surface of Bennu even on that airplane. It was still about a thousand times stronger. It was what we call milli Gs or 1000 of a G. And Bennu, you're talking a few micro G's. So it did not behave like the surface did in the Vomit Comet tests. It was completely different. So we weren't able to simulate it in that facility close to the way the real system behaved.

Sarah Al-Ahmed: Here I was in California putting together power points on the last four selection sites. Maybe they'll go here, maybe they'll go there. Oh, that's a cool rock. But from your perspective in the book, it was like pandemonium. Everybody in rooms just trying to argue it out. No one being able to figure out which site to actually select. The algorithms not totally telling you everything. And here comes Brian May, of all people, this rock star to come and help your team have a more 3D perspective on these sites. How did that work?

Dante Lauretta: That obviously was one of the coolest experiences. I'm a super fan. I love the fact that Queen was founded in 1970, the year I was born. I've literally been listening to Queen my whole life, and I was a super fan as a teenager, and I got this email right after we launched, and Brian May and I are both part of Asteroid Day, which is an organization to raise awareness of asteroid science, asteroid impact hazards, and it's a United Nations-sanctioned commemorative day every June 30th. And he said, "Hey, congratulations. I'm interested in the science you're doing and just kudos for a beautiful launch." And I was showing my wife, all my friends, "Hey, I got an email from Brian May, how cool is this?" And we talked a little bit over email. He'd been to Tucson, he really liked it and we talked about that. And then I never heard from him again for a year or more. And I thought, "Well, he is a busy guy and he is a rock star." And I corresponded with a childhood hero, so I'm happy. And then we started putting images during the approach phase up on our website and Brian grabbed a couple of those along with his collaborator, Claudia Manzoni. They're really a team. And he started sending me stereo pairs and he sent me some of his viewers, which I keep here all the time. I still enjoy 3D stereo views of Bennu. And Brian's working on some 3D of the sample too. So he's still working and producing stereos. He just loves it. And I started looking at the 3D images he was producing, and it was astonishing. All of a sudden the surface pops up and how rugged it is really comes through. You're thinking, oh, that rock doesn't look so bad. Then you see it as this towering behemoth that's like 10 stories tall and you're like, "Oh goodness, I hope the spacecraft doesn't have to get anywhere near that because that would definitely take us down." And the real conclusion was we were seeing these small, about 10 to 20 meter diameter, bowl shaped craters that had a lot of fine material in them. And that's where we started to say, "Hey, this is where the Sampleable stuff is." And the spacecraft team was like, "Well, you can't go there. We can't go into a bowl. We're going to definitely tip over because there's all kinds of crazy slopes and angles." That was when we knew the challenge that we were up against.

Sarah Al-Ahmed: We'll be right back with the rest of my interview with Dante Loretta after this short break.

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Sarah Al-Ahmed: Ultimately, you ended up selecting a site. What I really did love is that there was a large boulder in that area that you named Mount Doom, and I truly hope that when all these samples are analyzed, we don't find out that we have to return them to the fires from which they came because that would be terrifying.

Dante Lauretta: I kind of like that, actually. Wouldn't that be the worst thing? We'd have to go back to Bennu, which I hope I get to do someday.

Sarah Al-Ahmed: Wouldn't that be cool when it swings back around again?

Dante Lauretta: Yes.

Sarah Al-Ahmed: This is a slight tangent, but speaking of nerd culture, we're big fans of your board games over at The Planetary Society, and I know in this book you talked a little bit about the time that you spent playing Dungeons & Dragons with your family and speaking about it with your colleagues. Was that part of why you ended up with this side hustle making board games not like you needed any more to do in your life?

Dante Lauretta: I'm a huge gamer. I've always loved board games since I was a kid, especially teenage and college years. I was into large scale like tactical board games. I would go for days and days and that's what we would do. Total nerding out. I'm not ashamed of my nerdiness. I embrace it. In 2013, there was a very unfortunate decision that NASA made, which is to remove the Education and Public Outreach Program from the OSIRIS-REx budget. And I was so excited. In fact, when Mike Drake recruited me, one of the things I told him is I want to lead the education program. I wanted to be a professor. I love being in the classroom. I love teaching, working with young people, inspiring them to think big and dream. And I was devastated and furious that they were going to cut the education part of the mission out because in my opinion, it was a low end cost investment. The biggest return on the mission you can get is the inspirational value for people in your country, but really all over the world. And so I talked to some friends and I said, "Look, what can we do to try to recover some educational components from this mission?" And I just started going to the Boys and Girls clubs after school and starting a science club, just to do something locally. Because I grew up in the Boys and Girls Club in Phoenix. It was a really important place for me, a safe place where I could go when I needed one. And so I just said, "Let me just go hang out and do something. I feel like I'm making a difference." And it was pretty popular because at the Boys and Girls Club, you're volunteers. The kids can come into your activity or they can go play basketball, they can play bumper, pool, whatever they want to do. So you have to lure them in. And we started doing talking about rockets and we'd have little rockets like gas rockets, we'd launch out on the lawn and they didn't know how a rocket worked. First stage, second stage fairing spacecraft. They thought it was the thing that goes into space and goes to the asteroid is the thing you launch. And so I started doing flashcards. Here's the first stage, here's the second stage. And I did Atlas and Delta, which were two of the big rocket lines. And the kids, they kind of said, "This is like a trading card game. And that's when the spark hit me." I was like, "Hey, cool." I said, I bet we could make a game about building a rocket and going places in the solar system. And that turned into Extranaut, which it was for me, instead of playing games, that part of my life, which was a big hobby, became designing games, which I did with my kids. And it was a family affair and activity, and so still was a hobby, but it also had a purpose.

Sarah Al-Ahmed: Well, I hope more people now that they know about that will get to play the OSIRIS-REx Extranaut version. I've got a version sitting on my desk right now.

Dante Lauretta: Thank you.

Sarah Al-Ahmed: A lot of fun. But of course, after all this stuff, you got the site selection down. You tried to get the sample out of this thing and ended up burying the sampling arm almost two feet into this asteroid. Which is funny because even after everything that you did to model this asteroid, knowing about the fluctuations in gravity around it, all the density changes, you only thought you were going to get that arm maybe half an inch into the asteroid and then it full-buried itself. Do we think that these samples that were going to be able to actually look at are going to tell us more about why that happened?

Dante Lauretta: The key parameter is what we call the granular cohesion. That is how do two particles stick together on the asteroid surface? And it goes back to our earlier conversation about turning gravity down. You turn gravity down and it's like intergranular cohesion should be the main force keeping these things together. And it should be pretty strong, just based on our understanding of materials and how they operate on earth and on Mars and even on the moon. There was no cohesion. That was why it was so dynamic of an event. It was like a fluid, the material just flowed away. And we were just plummeting into... I always use the analogy, the ball pit at the kid's playground. You just keep sinking really until you hit the bottom. We had spent a lot of time and effort trying to model exactly that interaction. And I had funded three different groups around the country that we're using different code and different approaches. Some were early career people, some were senior scientists. I wanted a wide diversity. And they came back and they said, "You're probably going to go in about three millimeters," was the average depth. There were a few cases where it did plunge in to the kinds of depths that we were talking about, but that's when they turned cohesion off. They said, "Well, let's just take that variable out of the sim." And everybody said, "There's no way that we're going to have a cohesion-less surface. It has to at least be what we call a kilopascal." That's the unit of measurement for cohesion. That would be 1000 Pascals. We measured it or constrained it from the spacecraft interaction at less than a millipascal, which means at best we were off by a factor of a million. And that's pretty bad. That means you really don't understand the system at all if you can't estimate a parameter within six orders of magnitude. And that was our low estimate. It went all the way up to a megapascal, another three orders of magnitude. So we really learned a lot about the nature of asteroid surfaces from our interaction, and that will be important for any future missions that are going to try to do something similar.

Sarah Al-Ahmed: Thankfully, even with all those difficulties, you still managed to get out with the samples. And then again, even more issues with the sample container not being able to close correctly because it got too much stuff in its mouth, essentially. There are these larger rocks that blocked the whole thing. And you said something very beautiful about each one of those particles could have been someone's PhD thesis, but thankfully you guys managed to get it closed and then you brought those samples all the way back to earth. What was that day like for you? I've heard stories of you riding it on the helicopter triumphantly when the samples returned to earth. What did that feel like after all these decades working on this?

Dante Lauretta: Oh my goodness, that was such a tense morning. I got up early about 1:30 in the morning. I was staying at the Dugway Proving ground, which is part of the Utah test and training range, the Department of Defense region where we were coming in and we had some spacecraft activities to do in particular the go-no-go poll for releasing the capsule. It wasn't guaranteed that we were going to release the capsule. We had to meet all the safety criteria, make sure there was no harm to people or property, and the Air Force could have waved it off if there was something on the range that would've prevented us from accessing the sample. So it was low probability, but every time you have a decision like that, you always worry and quite honestly, spend most of your time talking through the low probability catastrophe that might happen. So I woke up, I wear a fitness tracker. I checked my heart rate was 120 beats per minute on waking. So my first thought was, "Today's the day like you've been thinking about this for 20 years and today it's happening and it's do or die. Either this thing's going to work or it's going to be a disaster, and your whole career will be for nothing." Not quite, because we got the asteroid data, but still the sample return was what it's all about. Fortunately, it was go, everything looked good. The batteries came online that are inside the capsule, which are necessary to fire the parachute switches. And then within a couple hours I was in a helicopter and we were tracking the capsule as it was streaking across the sky, came in over California. It spent two seconds crossing the state of California, give you a sense of how fast it was moving. And by the time it entered Utah airspace, it was still moving at 8,000 knots. And I started to panic because it was over... 100,000 Feet, a parachute was supposed to deploy, called the Drogue, a small chute to stabilize it as it transitions to Subsonic flight. Didn't come out. The Air Force wasn't calling it. The Air Force is saying, "We're seeing it. There's no drogue." And I just started thinking about Genesis, which was a NASA mission that crashed in the Utah Desert almost 20 years earlier because the parachute switch was installed backwards. And I know we didn't do that because we tested that switch 100 times and it was installed correctly and it should have deployed the parachute. And that was the longest three minutes of my life. For three minutes we were flying with no shoot when the shoot was supposed to be out. And I just thought, "We lost it. I'm going to have to get out of this helicopter. There's NASA cameras everywhere. It's live TV, and I'm going to be an emotional disaster. I am not going to be able to function in front of this audience and I'm going to have to." That's what I just kept telling myself, "You're just going to have to just be the PI, talk through the facts and you're going to deal with it. Whatever it is, you're going to deal with it." And then main shoot, and I cried. I just literally broke out into tears. I was like, "Thank you, whoever made that happen." And we got beautiful shots of the parachute coming in and on the ground and there it was, the capsule, my friend that I hadn't seen for seven years just came screaming through the atmosphere, charred and blackened. You could tell it just been scorched, but beautiful and perfect, a perfect little landing. It didn't move. It stuck it on the nose cone. It was perched upright, a few tens of feet from a road, which was really unexpected because we thought we could have been in mud, we could have been in standing water, we could have been way out of the middle of the range under harsh conditions, but it was very benign environment. We very quickly got it secured, and that's when I felt the profound accomplishment of what we had just done because there was four helicopters. I was in number four doing the environmental survey, so we were going to be the last ones in the field. The other three took off with the capsule and the cameras and the technicians. And there was this moment of silence where I just got to appreciate the beauty of the Utah Desert. I love the desert. I love wide open spaces. You could just hear the wind and the nature of where we were. And I was like, "Dude, you did it. It's here, it's home." And what seemed theoretical and quite honestly impossible 20 years earlier was manifest. And I was in awe of the team of the accomplishment and the science that was ahead of us because I get to go back in the lab now.

Sarah Al-Ahmed: Now you get the fun part after decades of stress and work, the culmination of so many people's lifetimes of expertise, so many hopes and dreams, and now we have those precious samples and we can compare them to the samples that the Japanese Space Agency got from the Hayabusa missions. So we're at a perfect moment now. We're about to learn so much about the universe or our solar system because of your work, and now people can go along for the journey with you with this book. So I'm really glad you this.

Dante Lauretta: Thank you. It was quite fun. It was cathartic in many ways to go through that long history and to tell the story, I wanted it to be an action/adventure. So hopefully it reads like that. There's challenges around every corner, and I have a great set of heroes, the characters I chose to develop in the book where some of my closest colleagues, and they also personified elements of the team because I couldn't write a story with 500 characters. So a few characters get elevated and represent Arizona, Goddard, Lockheed Martin, the team members that made this a success. And again, amazing honor to be able to lead this. Paying it forward as much as we can. We've got new graduate students that are coming to get their PhDs on venue sample analysis projects, which is where I'm really having fun. And it is an amazing sample. I can tell you I am beyond thrilled. That's an Astrobiologist's dream come true.

Sarah Al-Ahmed: Well, I would love to have you back on when we have all the results from those samples. I know our listeners are just chomping at the bit for those, so that'll be a beautiful moment for us.

Dante Lauretta: If they're in the right place, you can go see samples. We have one on display at the Smithsonian National Museum of Natural History in Washington, D.C, one at Space Center Houston, outside of Johnson Space Center, and one here in Tucson at the Norville Gem and Mineral Museum. So if you're in any one of those locales, go visit Bennu. You can see it with your own ice.

Sarah Al-Ahmed: Sounds like I know where my next vacation is after the eclipse. Thank you so much Dante, and congratulations to you and everyone on the team.

Dante Lauretta: Thank you.

Sarah Al-Ahmed: I really enjoyed this book and it was beautiful to finally speak with Dante Lauretta. Many of our listeners are super excited to learn more about the results from the Osiris-REx samples. Several of you have written to me. And rest assured, when the first science papers are actually released, we're going to have Dante back onto the show to talk about all of the exciting things that they're learning. It might be a little while because the release of the papers got delayed a little bit, but it's always worth waiting for good science. Meanwhile, the OSIRIS-REx spacecraft is onto its next big adventure as Osiris-APEX. You can learn more about that in our recent episode called OSIRIS-REx becomes APEX with Scott Guzewich. He's the new mission's deputy project scientist. I'll link to that on the Web page for this episode of Planetary Radio at planetary.org/radio. Now let's check in with Bruce Betts, the chief scientist of The Planetary Society for What's Up. Hey, Bruce.

Bruce Betts: Hey there. Hi, there. Hello there, Sarah.

Sarah Al-Ahmed: I finally got to speak to Dante Loretta. That was

Bruce Betts: Awesome. That is cool. We've worked with Dante a lot and over the years, and that's great. I look forward to hearing the interview.

Sarah Al-Ahmed: I mean, what an arc of life. It's always really interesting to get into the personal details of these kind of mythic figures within the Planetary Science community.

Bruce Betts: Mythic figure.

Sarah Al-Ahmed: But at some point in the book early on, he's talking about what happened with the Shoemaker-Levy 9 incident where it crashed into Jupiter. And I was rather young at the time. It's not something that I remember being big in my understanding of the universe. But what was it like for you and the rest of the Planetary Science community when that happened?

Bruce Betts: I was just transitioning into a pseudo-real job after grad school, but it was exciting. Everyone was trying to figure out what was going to happen because you had these 20 some odd pieces of broken comet, thanks to Jupiter, and they were going to hit over several days. So there was a lot of predictions that we wouldn't see any effect of it, at least leftover effect and a lot of prediction. Well, most of the predictions were that way. I'm sure some people got it right. And then the fact that these cometary parts started hitting, and not only did we see at least the Galileo spacecraft was able in an angle to see the impact flashes. And things that looked like giant bruises appeared on Jupiter, and it just blew people's minds, the fact that you had darker material being dredged up from way down. Well, I mean, not compared to the size of Jupiter, but compared to human reality was just rather awesome. And so it was an exciting time. And there was that period where it's like, what's the next one going to do? Oh, the big one's coming, and it was cool. We should do it again.

Sarah Al-Ahmed: We should do it again. What a cool moment to really study what these objects do when they plow into a gas giant, because we have all this evidence of cratering and all these rocky bodies. But what happens when a giant object crashes into a gas giant is something that we don't have a lot of evidence of. So that was a cool moment.

Bruce Betts: It was. And in more recent years, we've got people including at least one person funded by our Shoemaker Neo grant program who just keep staring at Jupiter with their telescopes. And we've seen a few smaller impacts of bodies as they happen. So it's getting hit. It's big, and it has a powerful gravity, so it likes to rip things apart and then destroy them as they come crashing into the belly of the beast.

Sarah Al-Ahmed: Belly of the beast. I hope someday humans look back at this point in history and are like, "I'm so proud of those planetary defenders for saving the Earth." It's going to happen Sooner or later.

Bruce Betts: They'll say they're mythic.

Sarah Al-Ahmed: I also wanted to ask you a question that someone in our member community submitted to us, because a few weeks ago we did an episode talking about potential geothermal hydrothermal activity on the dwarf planets, Eris and Makemake. In the show, I described how far away these objects are. And they take a really long time to orbit the sun. So one of our members, Albert Hegge from Oregon, USA, wanted to ask you what object in our solar system is known to have the slowest or the longest orbit around the sun?

Bruce Betts: I think of ones we know about, that's still Sedna, which is arguably classified as a dwarf planet, might not, but it's a pretty big object out there, and it's ridiculous. It orbits in more than 10,000 years, it takes it to go around the sun. And it doesn't even make it to, I think, twice the Neptune orbit. That's where it's Perihelion closest point in the sun is. But then it goes out way out, over thousands of years. And of course, we all recall from thinking about orbits that the objects move slower as they are farther away from the sun. And so it spends a lot of time on the outward part of its orbit, thousands of years. And I think it's Sedna in terms of the objects that we track in stable orbits. Now, I'm not sure about comets because you have comets coming in from the Oort cloud, and some of them are on their parabolic orbits where they may or may not just leave and say, "I'm done with you, Solar System," but they're going way, way out. So possibly comets. But in terms of things that are going round and round that we've detected out in the deep part of the solar system, I'd vote Sedna. If I'm wrong, someone can write in and correct us, but it's pretty amazing. But you remain very young because you only have a birthday every 10, 11,000 years if you live on Sedna, which I'm sure many creatures do.

Sarah Al-Ahmed: I remember celebrating my first birthday on Saturn when I turned 29 and a half years old.

Bruce Betts: That's awesome.

Sarah Al-Ahmed: Yeah, I really encourage people to look up how long it takes these objects to go around the sun and then celebrate those moments for yourself. At least I did. But I wonder how many objects are in the deep, deep solar system that we just haven't found yet. There's got to be things out in the Oort cloud that take tens of thousands of years to go around the sun.

Bruce Betts: Tens of thousands, I think. Yeah, we've already discovered a few thousand objects out beyond Neptune, little known fact, but there are thought to be millions of objects out there now, in terms of the larger ones. There are going to be fewer, but still a lot of stuff out there now. It becomes a very, very large volume of space when you're out that far. So it's still pretty darn empty, but there are a lot of objects.

Sarah Al-Ahmed: It's really cool. There's a lot to explore out there, and I bet as soon as we get to learn more about those, they're going to weird us out too. All right, Bruce, what is our random space fact this week?

Bruce Betts: Well, stay out in the distant parts of the solar system. Pluto and Charon, its largest moon are tidally locked with each other. A lot of people remember that, so they both just like the moon faces us with the same face all the time. Pluto, they actually are doubly locked, so that same side of Pluto faces the same side of Charon all the time, but we take it one step further and farther out, Eris and its moon, Dysnomia, are also tidally locked, so they both rotate and have orbital periods of something like 16, 17 days, earth days, and they face the same side towards each other, which is a weird concept. You're like on the other side that you don't even know it's there.

Sarah Al-Ahmed: I always find these systems that are completely tidally locked to each other, kind of romantic, right? It's like their interactions with each other over the scale of time allowed them to always face each other and kind of dance together. It's just-

Bruce Betts: Gazing into each other's craters. And so those are the two systems as far as I know, the only two we know so far that are doubly tidally locked.

Sarah Al-Ahmed: It's beautiful, Bruce. Thank you. All right, let's take this out.

Bruce Betts: Okay. All right. Everybody go out there, look out the night sky and think about circles and their importance in your life. Thank you and good night.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week with advice from an optometrist and an astrophotographer on how to enjoy solar eclipses without burning your retina. Boy, do I have stories about that one. Don't stare at the sun, folks. You will regret it. Love the show. You can get Planetary Radio T-shirts at planetary.org/shop, along with all other kinds of cool spacey merchandise. Help others discover the passion, beauty and joy of space science and exploration by leaving 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 lots 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 work tirelessly to support missions like OSIRIS-REx, and the amazing people that make them possible. You can join us as we help defend Earth and unravel the mysteries of our place in space. 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.