Planetary Radio • Apr 21, 2021

Is ‘Oumuamua a Piece of a Pluto-Like Planet? And Ingenuity’s First Flight on Mars

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MiMi Aung

Mars Helicopter Project Manager for Jet Propulsion Laboratory

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Steven Desch

Professor, Arizona State University School of Earth and Space Exploration

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Alan Jackson

Assistant Research Scientist, Arizona State University School of Earth and Space Exploration

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Planetary Radio Host and Producer for The Planetary Society

We begin with a thrilling recap of the successful first flight of NASA’s Ingenuity helicopter on Mars. Then we meet two researchers who have come up with a fascinating explanation for the first interstellar object discovered as it passed through our solar system. Rock out with Planetary Society chief scientist Bruce Betts as we discover the ‘80s band that made a hit out of the first Space Shuttle flight.

‘Oumuamua interstellar object
‘Oumuamua interstellar object Artist’s concept of the ‘Oumuamua interstellar object as a pancake-shaped disk.Image: William Hartmann
Perseverance Examines Ingenuity
Perseverance Examines Ingenuity NASA's Perseverance Rover examines the Ingenuity helicopter on 7 April 2021 prior to the helicopter's first controlled test flight.Image: NASA/JPL-Caltech/Kevin M. Gill

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Speaker 1: Our camera data confirmed, that Ingenuity has performed its first flight, the first flight of a powered aircraft on another planet.

Mat Kaplan: Welcome. I'm Mat Kaplan of The Planetary Society, with more of the human adventure across our solar system ad beyond. That was the scene in a room at the Jet Propulsion Lab very, very early on Monday, April 19th. As the Mars helicopter Ingenuity team learned, that its years of work had led to a successful flight on the red planet.

Mat Kaplan: More Ingenuity coverage is minutes away. We'll also sit down with two researchers who believe they have found a better explanation, a purely natural explanation for that interstellar visitor called 'Oumuamua. Later, we'll join Bruce Betts for an especially fun what's up and your chance to win the Mars pocket atlas.

Mat Kaplan: Another region of Mars tops the April 16 edition of the downlink. It's a Mars odyssey orbiter false color image of the planet's polar cap, that reveals ice among dunes that look like loosely woven fabric. You can see it and much more at, including these stories. The gigantic multilayered sun shield on the James Webb Space Telescope has been neatly folded away.

Mat Kaplan: Much like how we pack the thin sail of our tiny LightSail spacecraft though on a far larger scale, that shield won't unfold again till the JWST is in space. OSIRIS-REx has made its final close pass over Bennu, it will depart the asteroid on May 10th heading for its climactic sample return to earth in the fall of 2023.

Mat Kaplan: And Blue Origin ran another flawless test of its New Shepard spacecraft. The capsule was boarded by a test crew that exited before launch. It was a run through of the upcoming mission that may finally take passengers on a suborbital flight, godspeed folks. It's Friday, April 9th, NASA and JPL have decided that Ingenuity will attempt the first flight of a heavier than aircraft in two days.

Mat Kaplan: Project manager MiMi Aung, who was my guest back in 2019 is onstage to share her thoughts and hopes. You'll first hear MiMi in this very compressed clip, followed by NASA associate administrator for science, Thomas Zurbuchen. And then a question from our reporter who was caught up in the excitement.

MiMi Aung: Well, the moment that our team has been waiting for is almost here. Each world gets only one first flight. So as Thomas mentioned, the Wright brothers achieved their first flight on earth. Ingenuity is poise to go for being the first for Mars, it's going to be a flight experiment. Flight experiments are as old as flying, right?

MiMi Aung: So the Wright brothers first successful controlled flight, powered controlled flight, it was a flight experiment. We have to test to advance. And that is what building first of the kind systems and flight experiments are all about. Design, test, learn from the design, adjust the design test, repeat until success.

MiMi Aung: Same with Ingenuity, Mars helicopter. We started with the fundamental question, really serious question of, is it really possible whether it's possible to fly a helicopter on Mars? And it's challenging for many different reasons. Most important of all the atmosphere at Mars is extremely thin, right? It's 1% compared to the atmosphere we have on earth, and it is very cold at night.

MiMi Aung: The vehicle we send there has to survive cold nights on its own. It has to charge itself, and the winds are new to us. On top of it all, this flight experiment that we are performing at Mars has to be operated from back here on earth. We demonstrate it first full flight control, controlled flight power flight in our chamber in 2016.

MiMi Aung: We went on to then develop the full-up model that is needed for the system to need to fly a test at Mars. And as we call it the engineering development model, we demonstrated full success test flight. We flew it successfully in our chamber in 2018, and then we built Ingenuity. Which we flew in our chamber in 2019.

MiMi Aung: So this is the result. So this little four pound vehicle, the vehicle that you're seeing is four pounds has been surviving on its own. The cold nights, the temperatures there get down to minus 90 degrees centigrade, it's like minus 130 degrees Fahrenheit. It's being surviving in its own, it has been successfully charging, it's recharging its battery during the day.

MiMi Aung: It has been communicating to a space station that resides on the Rover, ultimately exchanging information with us, and we have fully confirmed that it has enough energy and power to perform this flight at Mars. And the flight in Mars is high power, peak powers exceed 350 Watts. And the last time Ingenuity flew, was here at JPL in the 25 foot chamber with us, with our team.

MiMi Aung: And at that time we said, "Next time Ingenuity flies, it will be at Mars." Please join us regardless, we will learn whether it's success, failure, interim, but one thing is for sure we have done everything we can and if we don't make that first attempt, for sure we will not make progress forward.

Thomas Zurbuchen: I just want to go back to Sojourner, and remind everybody that Sojourner also was that tech demonstration. A tech demonstration by the way, without which we could not imagine Perseverance. We could not imagine Mars sample return, which was really pioneered with us. And for me what Sojourner did, did exactly what MiMi just said which is, if you want aggressively punch out the space in which it can operate taking risks, successively larger risks.

Thomas Zurbuchen: And a month of Ingenuity will really be a demonstration of the capability that is there, and leading to the very success I think in the long run that Sojourner has. A success that at the time of Sojourner, of course was not imagined. [Patrick 00:06:47] could be sitting here, with Perseverance there on Mars sample return. Can you only imagine what will happen after this month of Ingenuity? Just two decades from now or one decade from now.

Casey Dreier: Up next on the phone line is Mat Kaplan from Planetary Radio.

Mat Kaplan: Hi everyone. Thank you for this, really thrilled looking forward to Sunday. Going back to Thomas's comment about Dragonfly then, maybe Mars and Titan don't have a lot in common but, MiMi I'm wondering if you are trading information with those folks and I'm sure they have high hopes for your success.

MiMi Aung: Oh yes. In fact Michael Ryschkewitsch who leads the space division in APL where Dragonfly's being developed. Michael Ryschkewitsch was our independent review team chair throughout the lifetime of Ingenuity, Mars helicopter development over the years. So yes, and while Dragonfly's flying in the thicker atmosphere, right?

MiMi Aung: So it's a different kind of vehicle, it's heavier, at Mars it's all about being light and more autonomous and it's a different kind of challenge. However, where we can learn from each other is with being the first rotorcraft and a flying vehicle on another planet or in the case... Or on the moon with atmosphere, but not at earth.

MiMi Aung: It has been a challenge that Amy described and I think, and described more, how do you test this vehicle? Right? So you have the fundamental models. Yes. You spend, you generate lift and control fast enough, you can fly. Easier said than done, right? How do we go about testing it? And we've had incremental steps in how do you spin it? How do you measure the force? Check the torque cancellation.

MiMi Aung: I think that methodology that we've had to invent, in parallel to inventing our first aerial vehicle for a planetary exploration, that will be very much applicable. And Michael Ryschkewitsch is very familiar and I'm sure we'll be interacting further as they go into the V and V phase. We've had initial conversations as well.

Mat Kaplan: That first flight was not to happen on Sunday. A software anomaly was soon remedied though, and the team was ready to try again in the early hours of Monday morning. Key members of the team, including MiMi sat in front of their laptop, computers at a ring of tables.

Speaker 1: [inaudible 00:09:12] reporting having performed spin up, take off, climb, cover, descend, landing, touchdown and spin down. And our camera data confirmed, that Ingenuity has performed its flight, the first flight of a powered aircraft on another planet. [inaudible 00:09:57].

Taryn Bailey: So it was really looking at on this screen, the image from our onboard navigation camera showing us hovering above the surface of Mars, how incredible.

Kate Howells: And that's a shadow, right Taryn?

Taryn Bailey: Yes, that's a shadow. So the onboard navigation camera points straight down. So we're seeing a shadow right now. I can just hear MiMi in the background. This is real. This is real, so amazing. Yeah, everyone's really feeling it now. So we're going to wait for the Perseverance's Rover image. [inaudible 00:10:45].

MiMi Aung: [inaudible 00:10:48], I got to tell the contingency speech which [inaudible 00:11:17]. Lucky for you I had a much shorter speech [inaudible 00:11:24]. We can now say that human beings have [inaudible 00:11:30] on another planet. [inaudible 00:11:33].

Mat Kaplan: Later that morning, an exhausted but very happy team, had acting NASA administrator Steve Jurczyk begin a post-flight briefing. After Steve, we'll let MiMi close our coverage.

Steve Jurczyk: I make a trip to JPL about once every year, and they'd always take me over to MiMi's lab, the Mars helicopter lab, and MiMi would tell me what they've accomplished and all the challenges they had and what they've had to overcome. And her just excitement and enthusiasm for making this happen was infectious.

Steve Jurczyk: I think her leadership along with the talent of the team, made me believe that they could do it and they did, so again congratulations.

MiMi Aung: Our team has been working over six years, some even longer, towards that dream of experimenting the first ever flight at Mars and this morning, our dream came true. If we can play this video. Taking off, goosebumps, it looks just the way we had tested in our test chamber, space simulator chamber here. Absolutely beautiful flight. I don't think I can ever stop watching it over and over again. And lands.

MiMi Aung: Unforgettable day, unforgettable day. And it's all about the team to start with, really our team across JPL, Ames, Langley with our industrial partners, AeroVironment, Qualcomm, Celero, Lockheed others. We were a team. I mean, just a strong team. And during this morning downlink, I did say that we had many friends who contributed to our success. Okay. And including Perseverance Rover team and many, many others.

MiMi Aung: And some of them are far away now and again as Thomas mentioned, Jacob, Jacob [Vinsiel 00:13:25] I'm sure you were watching our first flight from the Jacob overlook. So we're thinking about you Jacob. So with that, this early morning flight, what it means for our mission success, Mars helicopter Ingenuity technology demonstration project has three goals in aligned with NASA's agency level objectives.

MiMi Aung: So the first is to show on earth that it is possible to fly power control flight in Mars, we did that before we were launched. And then the second goal was to actually fly at Mars, we have done it. This is the first time I had been able to say, we've done it. And the third goal, is to get data back that will inform engineers that are going to design, that are designing future generations of Mars helicopters. And we have done that too, and we're going to continue.

MiMi Aung: So beyond this first slide, over the next coming days, we have up to four flights planned and increasingly difficult flights, challenging flights. And we are going to continually push all the way to the limit of this rotorcraft. We really want to push the rotorcraft flights to the limit, and really learn and get information back from that.

Mat Kaplan: As you may have heard Ingenuity carried a tiny piece of fabric from the Wright Flyer, across the sands of Kitty Hawk in 1903. Congratulations to everyone who contributed to this magnificent achievement of the 21st century. When we return, we'll talk with two researchers who have come up with an entirely natural, yet utterly fascinating explanation for that interstellar, interloper called 'Oumuamua. See you in a minute.

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Mat Kaplan: What was 'Oumuamua? That was the question I discussed with Harvard professor Avi Loeb not long ago. Avi's hypothesis regarding that very strange object, caused a good deal of controversy, but he believed it was the best fit for the available data. Steven Desch and Alan Jackson are scientists in the School of Earth and Space Exploration at Arizona State University.

Mat Kaplan: They have published a pair of papers that detail a very different explanation, one that doesn't rely on an alien intelligence. When I read about their work, I knew it was a story we should bring to Planetary Radio. So I was delighted to join them in the recent virtual conversation you're about to hear. Guys congratulations on a publication last month of these two papers, in the journal of geophysical research.

Mat Kaplan: Alan, I saw that you were lead author for the first one and Steve, that you took that position for the second. Sounds like you got a good partnership going here.

Steven Desch: Oh yeah, we're quite a team.

Alan Jackson: I like working with Steve a lot. It's been great fun.

Mat Kaplan: Let me tell you how delighted my colleagues at The Planetary Society were, when I told them that I would be talking to you about your recent publications. Because it was only last January that I had Avi Loeb, your colleague at Harvard University on the show. And while I enjoyed his book Extraterrestrial very much, I had some serious doubts about some of his conclusions.

Mat Kaplan: And maybe we'll talk a little bit more about that. Did you guys get to read a little bit about that? And what were your thoughts about his hypothesis regarding 'Oumuamua, Steve?

Steven Desch: Well, I have not read the book. I have read some of the papers that have been posted on the archive, preprint server and the published papers as well. And so I'm aware that they find more natural explanations dissatisfying, at least the ones they were aware of or had thought of at the time that they were publishing these things.

Steven Desch: And so feeling that they had exhausted all the possible natural explanations, they were ready to move on to some more complicated, less simple, less outcomes raiser sort of explanations. We weren't quite ready to go that far to make that leap yet and, we were convinced that there had to be some natural explanation and we pursued that.

Mat Kaplan: You may have found that as we will explore in moments, Alan, did you want to add anything?

Alan Jackson: No, I think Steve covered it quite well similarly, I have not had a chance to read Avi Loeb's book. I have read the papers that he's written on the subject. But yes, I think Steve summed up our opinions quite well.

Mat Kaplan: So like I said, the hypothesis that you guys have come up with, much more comfortable, much more natural. And you took into account a lot of factors, which you seem to have found a quite logical and natural explanation for, as maybe Steve if you could start. Take us through a little bit of what the true nature as you guys see it of 'Oumuamua seems to be.

Steven Desch: The true nature, that's a loaded term these days. I think we have to be very careful about making sure our language is precise and adhering to the scientific method. Certainly though, yeah, we feel that this is a simple natural model that is consistent with all of the data that we have in hand for this object.

Steven Desch: And it's a very interesting object because it passed through the solar system in 2017, came by the earth. We only got observations for few months and now we will never see it again, not that particular one. And so there's a well-defined dataset. We know everything we're going to know about it and, can we explain it?

Steven Desch: And our hypothesis is that it is basically a piece of nitrogen ice, just like the ice that we observe on the surface of Pluto. So just to put it very bluntly, if you were to take a piece of Pluto's surface that is tens of meters and less than a hundred meters in size, and throw it through the solar system in a way that this object came in, it would behave and look and act just exactly like 'Oumuamua did.

Steven Desch: So to us that shows a lot of consistency. Alan can talk about those things, and they were in the first paper that he led. And in the second paper I led, we talked about the likelihood that fragments of Pluto like exoplanet could have encountered our solar system.

Mat Kaplan: So Alan, how do we explain the odd shape? I mean, originally, and in all those very popular, probably two popular artists concepts. We saw 'Oumuamua as this long cigar shaped thing and it turns out that that probably wasn't terribly accurate, but how did it... I mean, it didn't start out looking like an interstellar pancake, right? According to your hypothesis.

Alan Jackson: Yes, no, that's right. The distinction between the cigar shape and the pancake shape, they're difficult to disentangle just because all we have is just the light curve observations, or we have from our observations of 'Oumuamua is just how the brightness changes. We don't actually have resolved observations that could directly show us the shape.

Alan Jackson: So in terms of how the light curve changes, the cigar shape and the pancake shape gives you similar things, which is why there was that kind of initial, which one is it? Yeah. So in terms of how it got to that extreme shape, because whether it's cigar shape or pancake shapes, that's not something that we see in the solar system.

Alan Jackson: So how it got to that extreme shape, is much the same way that if you have a bar of soap and you've been using it in your shower for quite a long time, it starts off as a fairly chunky object. And in the end, you're left with this annoying little sliver that you're not quite sure what to do with. And it's exactly the same process that as you're removing material off the surface of it, it gradually becomes a more extreme, the elongated object.

Mat Kaplan: I was hoping you'd use your bar of soap analogy which I have seen elsewhere. What was it that changed the aspect ratio if you will of this object, as it set out from its original solar system somewhere far out there across the Milky Way? And did that process accelerate when it got to our neighborhood?

Alan Jackson: Yeah. So the way that it works is if you have an object and you're just eroding it uniformly on the surface. So in interstellar space, it would have been eroded by cosmic rays, which would be uniform on all sides in any case. You're just removing thin onion shell layers from the surface of the object. You can imagine if you have a layer that's the same thickness all the way around, and the object is slightly thinner in one direction than the other.

Alan Jackson: If you're taking the same amount off, then that's proportionately more of the smaller dimension that is of the bigger one. So the smaller dimension, the aspect ratio between the two increases. So that would have been happening very slowly and gradually as it passed through interstellar space, just through the slow arrows of action of cosmic rays.

Alan Jackson: But yes, then when it got to the solar system, you started getting the thermal sublimation as a result of sunlight taking over from that process and that sped up a lot. Almost all of the change that we see to get it to the extreme aspect ratio that it was when we observed it, happened very close to Perry Center when it went closest to the sun, because it got closer to the sun than Mercury.

Steven Desch: One of the surprising things is how much mass has to be lost. 95% of the mass has to be lost in order to get it to that very, very flat pancake shape that it's inferred to be. And that is a surprising amount of mass loss, but not when you consider that it's made out of nitrogen ice, which is stable on the surface of Pluto, but not closer to the sun.

Steven Desch: It tends to sublimate at temperatures 25 to 50 Kelvin depending, and yet it was closer to the sun than Mercury. So once you see it in that light, then you have a chunk of Pluto that is inside the hottest, or at least the closest planet to the sun. Then it's going to lose mass, like crazy.

Mat Kaplan: What a shame that we couldn't point the radar at Goldstone or the late lamented, [inaudible 00:24:39] Dish at this object, and get more back from it than just that light curve, that you talked about Alan. And I wonder if one or both of you could say something about, why 'Oumuamua's albedo or its reflectivity is one of the most important pieces of this puzzle.

Alan Jackson: Because we don't have the absolute shape. Again, we don't have the absolute size. And so the way you convert to brightness into a size is by knowing how reflective the object is. If you don't have any intrinsic expectation for what that albedo or that reflectivity is going to be, then you have to either make an assumption, which the previous assumption was that the albedo was similar to solar system asteroids.

Alan Jackson: Which when people thought, well, it looked like an asteroid then that was a logical assumption to make. But then so when we were thinking, well, okay, maybe it's some slightly more unusual thing, like a piece of nitrogen ice. Then well, what albedo should we expect that to be? Oh, we're not sure so what we did was we let that just be a free parameter.

Alan Jackson: And once we've gone through the calculations we saw what albedo fit with the rest of the observations. And it turned out rather deeply, that the albedo that works, was the same albedo that you observe for the surface of Pluto.

Mat Kaplan: Steve, it strikes me that this was one of those great aha moments in science.

Steven Desch: It was. I remember when we had this conversation online because of course pandemic. So we were in different cities, even though we usually be down the hall from each other. But we were having one of these late night chats back and forth about what the albedo should be and we realized, that there were actually two solutions and one of them was a high albedo solution.

Steven Desch: That just exactly fit an albedo of 63% or something. An albedo that just exactly natural of the nitrogen ice on Pluto is, and we realized everything fit together. It was a great moment.

Mat Kaplan: Alan Stern of the New Horizons mission, frequent guest on this show and it only now occurs to me how useful it was to have that close fly by of that planet, or dwarf planet take your pick. So that you could realize you had a very close analogy of in terms of this structure or this material.

Steven Desch: Absolutely. I think that the exploration of our own solar system and the understanding of what happened to our solar system is absolutely critical for all of this. It's certainly true that we had ground-based observations of Pluto and had inferred already that it was mostly nitrogen ice. But the remote sensing and the fly-by photos, all paint this really vivid picture of how nitrogen glaciers are actually flowing across the surface.

Steven Desch: They give us an idea of how the nitrogen came out from inside the planet onto the surface, and how much nitrogen ice there probably was in the past, all of that was super critical to shaping that thinking.

Mat Kaplan: Do we have an idea of the mechanism that might have launched 'Oumuamua on its journey across this corner of the galaxy?

Steven Desch: Yeah. It's two steps. There's the ejection from the planet, and then there's the ejection from the solar system. I think that a lot of people misinterpret our work to think we are doing it all in one step, but that's not how it would have worked in our own solar system. Did you want to cover those Alan?

Alan Jackson: Yeah, sure. In the early history of our solar system, we believe Neptune and Uranus were originally quite a lot closer to the sun. So the giant planets, were in a more kind of compact configuration. And then at some point in the history of the solar system that changed, there was some instability that stirred them up and Neptune migrated outwards.

Alan Jackson: In that process, so it migrates outwards into the primordial Kuiper belt, and swept away most of what was originally there. The Kuiper belt we see today is only something like one thousandths of what was originally there. At some point in the early history of the solar system, they were probably a few thousand objects like Pluto whereas now there's only a couple.

Alan Jackson: As you can imagine, if you're throwing thousands of Pluto sized objects around, some of them are going to crash into one another.

Mat Kaplan: Maybe, in spectacular fashion no doubt.

Alan Jackson: Indeed, yes.

Steven Desch: Yeah. So we calculated all of the impacts that would have happened onto the surfaces of these actually thousands of Pluto size objects. And determine the total amount of mass that would have been injected as collisional fragments. It adds up to something close to a 10th of an earth mass, which is quite a lot of mass.

Steven Desch: I mean, it's like a Mars mass of fragments but, it's actually a very small fraction of the total mass that was in the primordial Kuiper belt. So these fragments were flying all over the place, it was a very messy environment, like the comets that were ejected by Jupiter mostly. Some of them being placed in the [inaudible 00:29:59] cloud and a larger fraction being ejected from the solar system altogether.

Steven Desch: These collisional fragments also would have been ejected from our solar system. And if other solar systems were doing the same thing, then they also would have ejected collisional fragments of ice from the surfaces of these Plutos which would have been largely and to ice.

Mat Kaplan: What can we infer if anything, from the speed at which 'Oumuamua passed through our solar system, and possibly also the vector it was on, the direction it was coming from? Do we know how long it may have taken to travel here and where it may have come from, Alan?

Alan Jackson: Yeah, so we have some rough estimates on the basis of what speed it approached the solar system [inaudible 00:30:47]. The stars and the sun are all orbiting the center of the galaxy, but on top of that there's these random motions. So if you average out all of those random motions to just get the orbital motion, you get what's called the local standard of rest.

Alan Jackson: Relative to that, the sun is moving at about 20 to 30 kilometers per second. 'Oumuamua when it approached the solar system, approached the solar system at about I think it was 28 kilometers per second. But most of that was because of the motion of the sun. In some sense, the solar system crashed into it rather than it coming into us.

Mat Kaplan: It was almost standing still.

Alan Jackson: Yeah. So relative to that local standard of rest, 'Oumuamua was only moving at about nine kilometers per second. So quite a bit slower than the sun. If you look at stars, that random motion relative to the standard of rest isn't constant over time. It slowly increases as stars get older and they have more encounters with other stars that gradually puffs them up a bit in terms of their velocities.

Alan Jackson: On the basis of the fact that it had a relatively low speed you can say it was no more than about two billion years old. So no more than about half the age of the solar system, in terms of directions I think it was coming from roughly the direct... Well, it looked like it was coming from the direction of Vega, but that's because that's the direction the sun is moving in.

Alan Jackson: Because it's relatively young, then this was a more speculative thing. We suggested that perhaps it originated in the Perseus Arm because there are lots of young stars there. And like I said, young stars would be moving slower relative to this random motion. And that would have meant that it was traveling for about half a billion years, which made sense.

Steven Desch: Right. Yeah, it was coming from the direction of Vega, but coming from much further away than Vega presumably. And it has been traveling for an unknown amount of time, how long it's been traveling depends on how much you think we understand the erosion by cosmic rays, while it's [inaudible 00:32:45] also what we think its original shape must've been as it left the solar system.

Steven Desch: And because those things are not well known I think we have to call this part speculative but, it would be a typical age we think to be traveling through the galaxy for about a half a billion years. And given the speed, it was coming up solar system with, with respect to local standard of rest this would mean it had come from the next spiral arm over, which is the Perseus Spiral Arm.

Steven Desch: And that definitely makes sense because it has to come from the young solar system, based on the fact that its overall velocity with respect to this local standard rest. But also the instabilities that are required to eject these objects, probably only happened very early on, in solar system's history [inaudible 00:33:32].

Mat Kaplan: I'm just blown away. In spite of how immature our understanding of these objects and the mechanics behind them are, at how much we are still able to infer in the way that you guys have. Regarding that speed of 'Oumuamua, one of the questions that I asked to Avi Loeb in January. Of course his hypothesis was that it's a LightSail, that it was probably propelled by giant lasers or something else that would have moved it up to a substantial portion of the speed of light one would think.

Mat Kaplan: My question for Avi was, well then why is it going to so slowly? And frankly, he didn't have a great answer for that. And your hypothesis, your theory seems to coincide much better with what we've observed.

Steven Desch: Thank you.

Alan Jackson: Yes. That is something that, that issue with the point of LightSail is you want to accelerate it to a significant fraction of the speed of light. Yeah. That is an issue that I have thought about with obvious idea myself.

Steven Desch: It gets into these questions about the scientific method and outcomes raiser, and of course it could be a LightSail in principle. Or we should probably look at some of the implications of that for example, was it directed towards us and functioning and keeping the same face towards the sun? No, apparently not.

Steven Desch: If it was tumbling, so if it was not functioning and how many of these objects are just randomly flying through space? Either way, you either have to explain the tumbling or by invoking incredibly large number of such objects. And these are testable I suppose. I'm not sure exactly how, but you quickly get into these questions of what are the motives of aliens.

Steven Desch: Can we get into their heads? And there was an amusing article by [inaudible 00:35:30] I believe, UCLA arguing that it couldn't be artificial because no self-respecting alien would built a thing. Which is also I guess a defensible position. But you can see, we quickly get into territory where you can't test things.

Steven Desch: Because we simply can't get into the psychology of aliens. So let's try to exhaust all the natural explanations and see if we can find one that that makes sense. And it doesn't mean, that there are no alien artifacts. It certainly means we should probably try to imagine the simpler explanation first.

Alan Jackson: Extraordinary claims, extraordinary evidence, right?

Steven Desch: I just think it's freaking cool. There's a piece of an exoplanet where it just pass through our solar system. And it's to me a little bit of a shame that, that's overshadowed by, "Oh, it's not aliens." I think it's a pretty profound discovery and a really cool object.

Mat Kaplan: Getting into the alien's heads, that's assuming they have heads. Do you expect now that we know that they're out there, that we will find more interstellar visitors like 'Oumuamua and should we make a point of watching for them, Alan?

Alan Jackson: Yes. I mean, I think it's always the case that once you found the first one, then you look for them more and then you find them more frequently. And I mean, from that perspective we are well-placed to do that. So the Vera Rubin Observatory in Chile, it was originally supposed to be coming online later this year. I imagine they've been slightly delayed because of pandemic.

Alan Jackson: So at some time in the next year or so, the Vera Rubin Observatory should be coming online. And what the purpose of the Vera Rubin Observatory is, is to find astronomical transients. So objects that change on short timescales, things like... And still objects passing through the solar system. You can think of it as being a super version of the Pan-STARRS Observatory that discovered 'Oumuamua in the first place.

Alan Jackson: So we expect that Vera Rubin should find a lot more of these objects, which will then let us look at them in a more statistical way, and test the ideas that we and others have had for it.

Steven Desch: And it should be noted of course there was a second interstellar object, the Comet Borisov that was discovered the following year. To my knowledge, those are the only two but it does suggest that maybe not every year but with current technology at least. But every 10 years or something in that window, we should expect another visitor.

Steven Desch: We're very keen to get at the statistics of this. One of the things that our papers tend to predict is that, these collisional fragments like 'Oumuamua are probably not the many a year, number. It's probably going to be a somewhat rare event that may be hence on the survey capabilities. But I wouldn't be too upset if we found one every 10 years, I think that would be a expected outcome.

Steven Desch: But we should definitely look for them because these are samples of exoplanets that are brought to our doorstep and made available for close study if we can just get a little closer to them, and in this regard, the Comet Interceptor mission concept from ISA and the other mission concept developed in US, to actually be on the ready.

Steven Desch: And when you see an interstellar object through a high velocity trajectory be intercepted and take lots of pictures and spectra all this, that would be just an invaluable dataset. So I'm looking forward to this eventuality then.

Mat Kaplan: Very, very exciting option for the future. Something to look forward to and sure, yeah, Borisov and 'Oumuamua, two data points not a whole lot to base things on. Do you think that you're going to continue to follow these objects as we hopefully discover more of them?

Alan Jackson: Yes, I certainly hope so. As and when we find the next one, obviously one of the things we would like to do if it looks similar to 'Oumuamua is to try and detect the nitrogen gas that it must have been producing them. So if 'Oumuamua is indeed a piece of merchandise, then it should have been releasing nitrogen gas. It's just that we weren't expecting to look for that. So we didn't see it, but if you're expecting to look for it, then you can go and look for it.

Steven Desch: Yeah. To be specific, you need to observe in a very specific wavelength band that is not difficult. Very [inaudible 00:40:10] ultraviolet. And only in that way, is it possible to find [inaudible 00:40:16]. Otherwise, it's an invisible gas, as we know from earth.

Mat Kaplan: I'm looking through some right now.

Steven Desch: Yeah.

Mat Kaplan: As we get close to wrapping up, I don't want to ignore the other portions of your careers, the work that you guys are doing. Steve, I'll start with you I read that you are also working on ways, like a lot of people to find signs of life across the galaxy, or at least our corner of it. Can you say something about this NASA study that you lead?

Steven Desch: Yeah. And I've been leading this project at ASU for six years. It's wrapping up now unfortunately, but it's funded by the Nexus for Exoplanetary System Science by NASA. And this institution funds various universities and [inaudible 00:41:12] to devise strategies for looking for life in the universe. Astrobiology is a major focus of NASA, and it's insulting to hear somebody claim that scientists aren't open-minded to the possibility of life in the universe, or aren't trying very hard.

Steven Desch: We're trying very hard to figure this out. One of the main problems is that you will probably find signs of life around another planet by atmospheric transmission spectroscopy, by seeing what light is absorbed by terrestrial planet's atmosphere as it passes in front of its star. And this will tell us the composition of the atmosphere, but that alone is not sufficient information.

Steven Desch: We think it is, because we see on earth we have oxygen in the atmosphere, and oxygen is made by photosynthesis. So if we see oxygen, that should mean life but it's really not that simple. There are a lot of false positives, and that's a lesson that a lot of people working in the field of astrobiology have taken to heart.

Steven Desch: That it's not enough to come up with an idea that if we look for this maybe we'll find it and maybe that would mean life the same as it does here. You have to imagine all of the other alternative possibilities. And in our case, we were funded to study the geochemical cycles on terrestrial planets with very different chemical compositions.

Steven Desch: And imagine what the false positives that could give you oxygen and methane in its atmosphere without life. And that's the lesson we take forward and I think other scientists should too, it's not just enough to imagine the one plausible thing you have to also eliminate all the other things.

Mat Kaplan: You remind me of the ongoing discussions regarding the presence or non presence of phosphene in the atmosphere of Venus. And we go back to Occam's razor again, don't we?

Steven Desch: It's a lesson we must learn repeatedly.

Alan Jackson: I know from having spoken to Steve and the other people involved with... They probably asked you a lot over the last few years. One of the really difficult things that perhaps you don't think about initially, is that finding something on earth that hasn't been affected by life is really difficult. And so it's difficult to claim something that doesn't have life to compare with.

Mat Kaplan: Life finds a way. Steve, I also read that much closer to home, you are doing some thinking and perhaps some work related to climate change. Can you say something about that?

Steven Desch: Right. And this is one of those unfortunate situations where I'm not funded to do it. So it's a hobby in a sense, but there isn't really a funding mechanism for geoengineering, and I'm not advocating geoengineering per se. But I am advocating that we need to think about ways that we can actually intervene in the climate because we are anyway and we're not going to stop.

Steven Desch: And so we need to have a plan for the case that's coming very soon where climate change will spiral out of control too quickly, and there'll be a climber to do something about it. And so in a paper in 2016, we demonstrated through this thought experiment that it would be feasible, to help reconstitute the sea ice in the Arctic and by pumping water basically, and helping freeze.

Steven Desch: Just a thought experiment, showing that the numbers are big, dollar announcer in the hundreds of billions of dollars but it is a feasible thing. And so why don't we study this and think about it more because this is a place where climate change is happening more quickly than anywhere else, and where these are mitigation efforts might have to fix the other arm.

Mat Kaplan: What you've just described Steve, this approach. I know that you're familiar with the author, Kim Stanley Robinson and in his most recent novel, Ministry for The Future where he addresses climate change and how we're going to deal with it. I think what you are describing regarding generating more Arctic ice is something that he includes in the book.

Steven Desch: I wasn't aware of that book, and I'm really pleased to hear you tell me about it. I've read his other books, including the Climate Change Trilogy and [inaudible 00:45:33] says about him.

Mat Kaplan: I recommend the book very highly. Alan, I think upfront I described this as the golden age or the beginning of a golden age of exoplanet research, and that seems to be where your focus is. Would you agree?

Alan Jackson: Yes, I think that's a reasonable description. Yes, I started off more in exoplanets and have shifted a little bit more into the solar system since then, but yes, I still think about both of them a lot.

Mat Kaplan: So what else are you up to in your research when you're not coming up with explanations for interstellar visitors?

Alan Jackson: One of the other things that I work on quite a lot is debris disks. Obviously we can see planets around other stars, but we can also see analogs to our asteroid belt and Kuiper belt. And this was one of the reasons why 'Oumuamua was exciting to me. Because we see things that look like our Kuiper belt, around other stars quite a lot.

Alan Jackson: They're actually a lot easier to see than planets, because you can imagine if you take a small amount of flour and throw it into the air, you can see it very easily even though was a tiny amount of mass there. And it's works the same thing with the disk of debris. It's a lot less mass than a planet, but it's in much finer pieces so you can see it's not easier.

Alan Jackson: But when we are looking at one of these Kuiper belt analogs, all we're seeing is the very small dust particles. You have like a hundred micron kind of size, and all we can do in terms of thinking about what larger things like Pluto kind of size things that might be there, is to make inferences sometimes based on the structure of the disk.

Alan Jackson: But then with 'Oumuamua we can actually kind of directly say, "Yeah, okay, this came from one of them." So that was really exciting for me and they connected those two pieces of work. It's connected to what you Steve, you were saying about the Comet Interceptor kind of mission as when we have another one. Say okay, we've found all of these extrasolar planets, most of them are very long way away.

Alan Jackson: I mean, even Alpha Centauri, it's 4.2 light years away. We're not going to get there for thousands of years if we wanted to send something there. So observing an exoplanet up close is not going to happen in the lifetime of Western civilization, nevermind our lifetimes. But when we have a piece of an extrasolar of the planet, come through the solar system, then we actually can do close up observations of a piece of an extrasolar planet in our own lifetimes and that's amazing.

Mat Kaplan: Steve, I think again, I'm getting evidence of why you guys have forged such a great partnership.

Steven Desch: It's really great. Yeah. Having exoplanets and planetary signs all in the same package and we each bring something to the table.

Mat Kaplan: I want to thank both of you for joining me on Planetary Radio, but also for this work, which has given us, as you pointed out a much more natural explanation for 'Oumuamua. That first ever discovered interstellar visitor to our solar neighborhood, good hunting and I wish you the greatest of success in all this other work that you have underway as we keep working to understand our universe better and better.

Steven Desch: Thank you. It's a real pleasure to be here.

Mat Kaplan: Astrophysicists, Steven Desch and astronomer planetary scientist, Alan Jackson of Arizona State University. We've got links to their work and much more on this week's episode page at I'll be right back for a good time with Bruce Betts. Time for what's up on Planetary Radio. Here is the chief scientist of The Planetary Society, Dr. Bruce Betts. Welcome back.

Bruce Betts: Thank you Mat. Good to be back. How are you doing?

Mat Kaplan: I'm doing great. I had so many wonderful birthday wishes, that came in from listeners to thank you everybody it was a great birthday.

Bruce Betts: That's amazing. How did they know it was your birthday?

Mat Kaplan: I told them.

Bruce Betts: Good call. I embarrassed you, if it's possible for you to be embarrassed.

Mat Kaplan: It's true, I didn't. You told them about my birthday.

Bruce Betts: Indeed. I was just Josh and night sky, let's talk about it. In the evening, Mars hanging out, hanging in there in the Southwest in the early evening, looking like a kind of fairly bright red star, still hanging out in a triangle with Aldebaran and Betelgeuse the brighter red stars right now. In the pre-dawn, we've got Jupiter looking really bright.

Bruce Betts: And Jupiter and Saturn are now pretty darn easy to see they're up high enough in the East in the pre-dawn, and they will be hanging out with the moon on May 4th. We move on to this week in space history. It was 1990, 1990 the Hubble Space Telescope was deployed. They just put out a release like a day or two ago with new data. It's just amazing.

Mat Kaplan: It's an antique.

Bruce Betts: I think I saw one of them on Antiques Roadshow.

Mat Kaplan: Somebody just had one in their garage. They didn't have room. They had no room for nothing else in their garage but...

Bruce Betts: If I only got it out. Got it to the... Oh, this looks like an antique Hubble Space Telescope. It was originally built. No. Okay. Let's move on. One, two. [inaudible 00:51:01].

Mat Kaplan: Well, that was lovely. But I just can't resist listening one more time to that great barbershop quartet.

Bruce Betts: Oh yeah. That's better. (singing). So constellations, the official IAU 88 approved constellations. A lot of them particularly for us in the Northern hemisphere, we get used to ones that are mythologically named, typically Greek mythology. You go to the Southern hemisphere, you find some that interestingly thanks to Nicolas-Louis de Lacaille, which I butchered because I don't know how to speak French.

Bruce Betts: He named a number of constellations from his observing time in South Africa. And he named them primarily after tools. So we got the air pump, the chisel, the furnace, of course we've got the more fancy names, Antilia, Caelum, Fornax, pendulum clock, microscope, compass, telescope. So it's really a different feel in that neck of the woods.

Mat Kaplan: It's a lot less romantic if you ask me. Look, the air pump is just looking beautiful tonight.

Bruce Betts: Not as nice as Pyxis, the compass.

Mat Kaplan: Yeah, I like that better actually. Yes...

Bruce Betts: Okay. That wasn't very good. There you have it. We'll come back for a little fun in constellations in the trivia contest, but first we have big fun in the trivia contest. I asked you what famous band was so moved by viewing the launch of STS-1, the first space shuttle launch that they wrote a song about it. How did we do Mat?

Mat Kaplan: You're a big fan of this band, aren't you?

Bruce Betts: I am a fan. I am definitely a fan.

Mat Kaplan: You're going to recognize these lyrics quoted for us by Michael [Kaspl 00:53:01] in Germany, not our winner but still excitement so thick you could cut it with a knife technology high on the leading edge of life. You want to identify that song.

Bruce Betts: That is countdown by the band Rush.

Mat Kaplan: The Canadian band, Rush. That is going to become more significant as we continue to talk about this. A couple of people mentioned the great Kate Bush, whose song, hello earth also uses some of the STS-1 comms link audio which was interesting. I did not know that even though I'm a fan of Kate Bush. Here's our winner, [Kathy Koontz 00:53:38] in Florida.

Mat Kaplan: She said, "Yeah, that was Rush." She says, "Sorry, I don't have a poem to talk about Rush and their song countdown." That's okay, Kathy, we don't mind. She says that, "We enjoy listening to your show each week on WMFE in Orlando, and yes, I am a member of The Planetary Society." Kathy, we thank you for that, and we also will be happy to send you a copy of Mars in the Movies: A History by Thomas Kent Miller.

Mat Kaplan: That very authoritative, very comprehensive book which has every movie ever set on the red planet. And a few that weren't necessarily set on the red planet, but still involve Martians of one kind or another. Anyway that's going to come your way Kathy. Congratulations. I got a bunch of other stuff. Nick Bell in Indiana, had to go find my old tape of it, I guess a cassette and then realized he had nothing to play it on.

Bruce Betts: Yeah, it's a bummer.

Mat Kaplan: Charlie Killam in New Hampshire, "I apologize for not responding as a poet." That was the week that we had our little poetry festival I believe from listeners.

Bruce Betts: It's really not required just for future reference.

Mat Kaplan: He says, he's not a poet, he's an engineer. Oh, like those are mutually exclusive Charlie?

Bruce Betts: Yeah, actually... Yeah, they actually are.

Mat Kaplan: They are. By the way I love this album, he says, "I've always been a space geek in the fact that all the members of the band hold PhDs, it's true. They're honorary PhDs. They're awarded by a university in Ontario, Canada.

Bruce Betts: They're a great band. They're very talented in ways far beyond my ability to comprehend.

Mat Kaplan: Robert Cohen Massachusetts, "I guess we could say the first major Canadian contribution to the space shuttle, since the Canada arm didn't fly until STS-2."

Bruce Betts: Oh, nice trivia, nice random space fact.

Mat Kaplan: Robert Klein in Arizona. "If you play Mars party by The Amoeba People backwards," he swears he hears them say, "Turn me on Mars helicopter." I'm not sure what that has to do with STS-1 or Rush but I thought I was entertained by it. And of course The Amoeba People that's the house band of Planetary Radio. He goes on to ask, "Weren't you and Bruce in a rock band in the old days?" He said, "I thought for sure, I saw you guys at Woodstock."

Bruce Betts: That would have been so wrong for me to be at Woodstock at so many levels.

Mat Kaplan: Even I was not old enough to be in a band at Woodstock, I was though a roadie for Country Joe and the Fish.

Bruce Betts: You are just an enigma wrapped in a conundrum, wrapped in a joke.

Mat Kaplan: Wrapped in a fish. Jenny Murray King in Colorado, she got it right of course, countdown by Rush. "Proving that my claim, that nerds and rock and roll go together like Bruce Betts and weird noises." [inaudible 00:56:43].

Bruce Betts: [inaudible 00:56:47].

Mat Kaplan: The song contained samples of Bob Crippen and John Young speaking to mission control. She says that during Ingenuity's pre-flight briefing at JPL, she was surprised and pleased to hear Mr. Mat Kaplan call in to ask a question as if he's a normal human, rather than the king of Planetary Radio. I like to put on commoner clothes and mix with the peasants now and there Jenny, so yeah.

Bruce Betts: You should see his usual clothes.

Mat Kaplan: This goes on and on. There were so many good ones. Martin Hajovsky in Texas, he says, "It's also possible the three other songs in that same Rush album could have Planetary Radio associations. Mat Kaplan, as the analog kid, Bruce Betts, as the digital man and Casey Dreier as new world man." I got a poem for you, from Dave Fairchild, our poet laureate.

Mat Kaplan: The band was there the day the shuttle was supposed to fly, the countdown scrub they had to rush to make their airport time. They played in San Antonio, then flew back full of life, where Rush felt the excitement you could cut it with a knife.

Bruce Betts: Nice.

Mat Kaplan: And there's one more. You got that one?

Bruce Betts: I do. I first saw a comment that indeed it apparently because the launch delay, they had to go play a concert and then fly back in time for the launch, which they did because they're into it. Here is a poem from Jean Lewin in Washington. Inspiration comes in many forms, and moves a mortal's soul. Sometimes it's captured in a song, this time it was rock and roll.

Bruce Betts: Lifeson, Peart and Geddy Lee used rhythm to convey the launch of the first STS, they witnessed on that day. Audio from the crew has heard countdown to the dragon's flames, brings to life this awesome force, and Rush is the band's name.

Mat Kaplan: Nicely done. You and Jean. You're a good team.

Bruce Betts: We go way back.

Mat Kaplan: Let's go way forward. What do you got for next time?

Bruce Betts: Way forward, back to constellations. What is the only IAU constellation? So one of the 88 official constellations whose name is derived from a geographical feature on earth, a feature or place on earth. The only one derive from it, go to It's a little tricky but I have faith.

Mat Kaplan: I do too. And if you want to satisfy our faith in you, you need to get us that response by Wednesday, April 28th at 8:00 AM Pacific time to enter in this round of the space trivia quiz. And we will once again give away this gorgeous Mars pocket atlas, assembled, edited by Henrik Hargitay. Also from Europlanet, the Central European Hub, it is gorgeous, it is just the most amazing little publication.

Mat Kaplan: I believe that Henrik will include a little overlay, with the nation or state or whatever that you're from. That is to scale and you can lay it over the maps of Mars in the beautiful Mars pocket atlas, we're done.

Bruce Betts: All right, everybody go out there and look up in the night sky and think about what tool you would name a constellation after. Actually, how about household appliance? Thank you, and good night.

Mat Kaplan: I would choose a microwave oven. Because it could actually be detected by radio telescope, the microwave oven constellation.

Bruce Betts: There you go. It has a modern feel to it. I was thinking more of something that slices, dices, chops and smashes, but a microwave oven is a very nerdly, wonderful answer.

Mat Kaplan: Thank you. Thank you. Did Popeil make microwave ovens? I don't think so. That's Bruce Betts, he's the chief scientist of The Planetary Society. He joins us every week here for what's up, [inaudible 01:00:53].

Bruce Betts: I couldn't think of a funny... What's a funny kitchen appliance?

Casey Dreier: Blender.

Bruce Betts: Blender was the first thing that came to my...

Mat Kaplan: Blender was... That was the first thing that came to my mind.

Bruce Betts: But I was thinking something... Wow, all three of us thought blender first. But I was thinking something that Ron Popeil would sell, the George Foreman grill.

Mat Kaplan: At great barbershop quartet, they call themselves sound wave. Planetary Radio is produced by The Planetary Society in Pasadena, California, and it's made possible by its members naturally. You can begin to understand their nature at Mark Hilverda is our associate producer, Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser. Ad astra.