Hayabusa2 flies by asteroid Torifune

Sarah Al-Ahmed: Hayabusa2 flies by asteroid Torifune, 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. This week, Paul Abell, NASA's chief scientist for small body exploration at Johnson Space Center, joins us to talk about the Hayabusa2 extended mission flyby of asteroid Torifune. We'll talk about what it revealed about this rare contact binary and what it means for planetary defense. Then Bruce Betts, our chief scientist, is here for What's Up, where we're going to talk about the projectiles that Hayabusa2 fired into asteroid Ryugu. If you love Planetary Radio and want to stay informed about the latest space discoveries, make sure you hit the 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 July 2026, the Japanese Aerospace Exploration Agency, or JAXA's Hayabusa2 spacecraft, added another first to its already remarkable resume. After a year and a half at asteroid Ryugu, collecting samples and blasting an artificial crater into its surface, Hayabusa2 dropped its sample capsule off at earth in December 2020 and just kept going. The extended mission renamed Hayabusa2#, sharp as in the musical notation, set a course for the tiny near earth asteroid called 1998 KY26 with a rendezvous planned for 2031. But on the way, the team lined up something extra, a flyby of an asteroid we now know as Torifune. Torifune is named for Ame-no-torifune, a divine ship from Japanese mythology that carried gods between heaven and earth. JAXA picked the name through a public naming contest, which you know we love here at The Planetary Society after all the ones that we've helped organize.

The flyby happened on July 5th and it was a genuinely difficult piece of flying. Hayabusa2 was never built to do flybys. It was designed to pull up alongside an asteroid and stay for a while, not to thread a needle at high speed. What the spacecraft found was a contact binary, two objects that came together and stuck, kind of like a cosmic snowman.

Joining us today is Dr. Paul Abell, NASA's chief scientist for small body exploration at Johnson Space Center. Paul has been part of the story from the very beginning. He was on the recovery team in the Australian Outback in 2010 when the original Hayabusa spacecraft brought home the first samples ever collected from an asteroid. And after a journey so troubled, it's a minor miracle that that capsule actually made it back to earth at all. Since then, Paul has served as a bridge between JAXA and NASA, helping the Hayabusa2 and OSIRIS-REx teams share some really hard won lessons about landing on boulder-covered worlds. He's been on both of those science teams on the Double Asteroid Redirection Test or DART investigation team, and he has an asteroid named after him, 8139 Paulabell.

Hi Paul. Thanks for joining us.

Paul Abell: Hey Sarah, happy to be here.

Sarah Al-Ahmed: It's such a fascinating realm of study and I think most people, their ideas of studying small bodies and near-Earth objects mostly come from movies and Hollywood. But I mean the fact remains, this is a realm of science where you can make a marked difference in potentially saving the world someday. Do you ever feel that as you're doing this kind of science?

Paul Abell: I mean, yeah. One of the things where originally when I was in astronomy in undergrad, I was looking at things like there were quasars and galaxies and there were many, many hundreds if not millions of light years away. For me, I was like, that's why I got hooked on the near-Earth asteroids because that's something that can be realized now and make an impact today or tomorrow or in the very near future for people, humanity. And so that's one of the things that attracts me about it. We're now to the point where we can go out and "touch," in air quotes-

Sarah Al-Ahmed: Tag.

Paul Abell: Tag and all that and these objects. And my first real experience with the near-Earth asteroid mission was while I was in grad school. I was very fortunate to be part of the NEAR Shoemaker mission-

Sarah Al-Ahmed: Oh wow.

Paul Abell: ... to asteroid Eros. And that's how I cut my teeth on missions. And it was there that one of the lead scientists, I remember his name vividly, and I was sort of his assistant, was Dr. Joe Veverka. And he said, "You should get into this. You should do this more often." And so I was like, "Yeah, sure. Okay." I'm not really thinking. I was like, "Okay, this gentleman is respected." He said that and I had no idea. And yeah, I did. I just followed through with it. But precisely what you said is the near-Earth asteroid population, the small bodies in the inner solar system can really make or break humanity, literally, right?

Sarah Al-Ahmed: We're all going to have a very interesting time in 2029 with Apophis.

Paul Abell: Oh yeah. I can't wait. I can't wait. That's going to be absolutely tremendous. And there's so many of us in the field are just so excited for what we're going to see and experience at that time. So Sarah, I'm originally from Canada. I grew up in a very small town of 500 people, a small town about 120 miles due west of Winnipeg, Manitoba, a place called Wawanesa. And obviously in the middle of the countryside, very rural farming and no lights. We didn't have a stoplight, so very little light pollution. So as a young boy, I used to be fascinated with a night sky. Of course, Canada with no light pollution, but in winter time, skies are dark for much of the evening. It starts getting dark around three, four o'clock and stays dark quite late. And so I used to go outside in my snowsuit and lay in the snow literally and look up at the sky and I was just fascinated because there was so many things to see. I mean, the stars were like diamonds. They didn't twinkle. Everything was so cold it was frozen out.

We had Aurora, we had shooting stars, meteors, satellites, everything. So I was just fascinated. Funny story, my mother would freak out because it would be cold and she'd have to check on me every 20 minutes and yell out the window or the door to say, "Hey, are you still..." And if I didn't respond, she'd come running out. So yes, I had to make sure that I responded to let her know that I had not frozen into death, but I was just so into it. So that has got me started in that whole realm of sky and space. But I got recruited by NASA, NASA Johnson Space Center, six months before I defended my thesis.

Sarah Al-Ahmed: Oh wow, what a time in your life.

Paul Abell: Yeah, it was amazing. It was like I finished, I remember it very vividly because it was kind of a hair of fire experience. I defended my thesis in December of 2003 and January 2004, I started working at the Space Center. So yeah, long story but that's-

Sarah Al-Ahmed: No pressure.

Paul Abell: Yeah, I know. It was great. And I've just never looked back ever since.

Sarah Al-Ahmed: I've been so excited about all of these sample returns because the stuff that we're finding in some of these missions, starting with Hayabusa and moving on to all of these, we're finding these complex carbon chains, the building blocks of life, all the things that we've seen in things like DNA. We don't have life yet. We haven't actually found full nucleic acids or anything, but it bodes so well for our understanding of where life in the universe came from. So there's this whole other aspect that I think a lot of people in the public don't think about when they think asteroids.

Paul Abell: Right. I mean, the asteroids are so rich, I mean, metaphorically and figuratively speaking in terms of the science that they can provide us, right? They're the leftover building blocks of the early part of the solar system. So they're very ancient materials, but they tell us a lot about things like how the solar system formed, what it was like, how the earth moon system formed, how earth had its water delivered to it. And as you said, how some of the prebiotic molecules may have been delivered to earth and how might life have evolved on earth itself. So they're really, really fascinating from a science point of view. And the sample return missions, the most recent ones, so Hayabusa2 went to, that was the Japanese mission that went to Ryugu and our own mission, the NASA mission OSIRIS-REx, which went to Bennu, both brought back very, very interesting materials from what we call carbonacious type asteroids.

Both Ryugu and Bennu are carbonacious material and very similar to some of these carbonacious meteorites we find on earth. And they're just chock full of these prebiotic molecules and also very rich in some of the volatile materials, especially water. So it actually is a trevor trove of information that really tells us how life may have evolved on earth. So it's an amazing time.

Sarah Al-Ahmed: I know you've actually been to experience one of these samples coming down to earth. What has that actually been like?

Paul Abell: Yeah. So you're referring to the original Hayabusa mission coming back to Woomera, Australia in 2010. And it was an amazing experience. So I was on the contingency recovery team, which basically means you have a prime team, which is designed to take care of everything in the nominal case. Everything works perfectly. The contingency team is a smaller subset of the larger team that is designed to make sure, hey, if something goes wrong, like the parachute doesn't open or the capsule comes in short or long of the intended landing site, but there's someone there that can be deployed quickly to take care of things and just make sure that the scientific integrity of the sample is still maintained. And so that was my job. And so I remember it was a fascinating day. I can still visualize it. It was midnight in the outback. I was up in a place called near Coober Pedy that was sort of our duty station.

And then I was on the end for if the spacecraft came in short from the landing site. Of course, everything went well. It was an amazing mission. I think the capsule came down within half a kilometer of the target point, which is truly amazing. And just seeing it come in and knowing that we had a sample and the confirmation from the base that they had locked on to the capsule, that the helicopters had found the capsule with parachute, landed on the ground, everything looked good. It was an amazing time. It was a very tiring time because we were up all night, but it was just such an exhilarating experience. We were living on adrenaline and knowing that we had those precious samples back here on earth for the first time from a true asteroid sample return was truly amazing.

Sarah Al-Ahmed: Some of my colleagues actually got to go see OSIRIS-REx samples drop down and I wish I could have been there to see it. It just sounds like such an amazing experience.

Paul Abell: It is. It's kind of hard to imagine, but you work so long. These missions are not just quick. They're not just a year or a couple of years. They're multi-year, seven- to eight-year missions from start to finish. And that's just for the launch. I mean, you have a lot more at the pre-planning stages, the proposal stages, everything else. And so a large part of people's careers are spent on these missions. So seeing the capsule come down safely, it's just one of relief and then just pure exhilaration and joy.

Sarah Al-Ahmed: Well, you've worked not only on Hayabusa, but also you've helped support Hayabusa2, and you became kind of this bridge between the JAXA and NASA teams. What is it like building that kind of relationship across two different space agencies with two different cultures and two different missions that are both kind of chasing these same big questions?

Paul Abell: I would say it's rewarding. It was one of those things where I sort of was in the right place at the right time and I realized that there was just an opportunity for someone to be in the room who knew the science, but had a knowledge of some of the other operational issues and things. And also learning a little bit more about the culture and the differences in the culture between how we do things at NASA and how things are done for JAXA, the Japanese Aerospace Exploration Agency. It was there that I decided I'd learned to speak Japanese, right? So I learned Japanese, a little bit self-taught. I had some classes and I'm still learning Japanese, learning about the culture, being there. I usually get over to Japan once or twice a year and maintaining that, but they have a different way of looking at things just like we have a different way of looking at things.

And one of the beauties of working with them and being sort of a liaison in that sense to JAXA, between JAXA and NASA, for these small bodies missions, both Hayabusa and Hayabusa2, you're able to tease out the best of both worlds and help both the science teams and the management teams for the spacecraft missions work together. So specifically, Hayabusa2 got to Ryugu first, and that was planned. That was a separate mission all by itself that JAXA was going to do. We had our own mission, OSIRIS-REx, that we'd planned and get a sample return, different target Bennu. And this was done independently. There was no coordination between the teams. But then of course, I was on Hayabusa2, I was also on OSIRIS-REx, and I saw an opportunity to try and help bring these. And it wasn't just me, there were other people who also saw this opportunity, but I was in a unique position because I had previous experience with Hayabusa and the people involved and a lot of overlap with the Hayabusa2 team. So it was a good situation.

And I remember seeing Ryugu for the first time and like, "Oh wow, there's lots of boulders on there. How's that going to affect our mission of OSIRIS-REx if Bennu is like that?" So there was a lot of crosstalk. There was lots of lessons learned and it truly was an invaluable experience. I will say that the Japanese way of doing things, they take a little bit more risks in terms of how they do it. We're a little bit more cautious, but they tend to really, really go for it. I think it's nice to see that and that they pulled off some amazing results and amazing operational results and it's good to have that. At the same time, we have a way of doing things that is very, very precise. Our instrumentation is really, really good at teasing out information from remote sensing and the amount of sample we got comparatively speaking from OSIRIS-REx with respect to Hayabusa2 was a lot larger.

In a sense, they were different missions. There was a lot of overlap. The teams were embedded. We had membership from Hayabusa2 and OSIRIS-REx and vice versa. There were lots of lessons learned, especially from the curation side, the sample storage side and how to store samples, what are the lessons learned from storing those samples, keeping those samples pristine, how to handle those types of samples. So it was really rewarding to see that all come to fruition. I'd like to think that I helped play a role in making both missions be more successful, but also actually, if you think about it, getting the most, getting in another level of information out of both missions, so working together. And you'll see that even now we're still cooperating and having this whole new realm of curation on small bodies and the knowledge that we were gaining because we're going to do this again, maybe not NASA per se right away or maybe not JAXA right away, but there's going to be plans.

People are going to send spacecraft to asteroids. We're going to get more samples. And so all these lessons learned are going to be really invaluable.

Sarah Al-Ahmed: That spacecraft almost buried itself in that rubble pile when it tried to grab that sample. So who knows what could have gone even more wrong without that collaboration?

Paul Abell: Well, I will tell you with the collaboration it helped. I mean, I helped facilitate a team meeting between the Hayabusa navigation team and the close operations team, when I say nav, navigation, right? And the OSIRIS-REx team. And it was in Sagamihara in JAXA Planetary Science Institute, so ISAS. And it was to discuss what did they do to get down to the surface because you had all those boulders. If you look at the asteroids, people originally when you had Hayabusa, they had this image of Itokawa, right? And so you had these vast areas, I say vast, but 60 meter area of small, smooth, pebbly beach sand type, great place to touch down for a spacecraft, no obstacles in the way. Great. And so that was the sort of the mental image that people had that there were going to be these areas on these objects that you go to.

And then of course we got to Ryugu and it was like, "Uh-oh." And then Bennu was like, "Oh, okay, this is even worse." And so the Japanese obviously went in first, they figured it out. And then we with this meeting were able to learn a lot from them. And it was at that meeting that the PI, Dante Lauretta, decided, "Nope, we got to change things up." So this is what we're going to do and we're going to change it up. And it was because of that decision was made, it was instrumental in making sure that we could get down to the surface and get the sample that we did. So yeah, it's super, super important to have this international collaboration.

Sarah Al-Ahmed: Well, you co-authored a white paper for the Planetary Science Decadal Survey that laid out these characterization priorities for near-Earth objects. Basically, what do we have to know about these things in order to potentially deflect them? And I think one of the things that really kind of stuck out to me is this fact that we can only learn so much from the ground with our telescopes. There's a lot that is really difficult to glean from this kind of distance. So how well can we answer those questions from the ground and why are these flybys so useful?

Paul Abell: If you're just talking about planetary defense, which we're talking about right now, there's only limited amount of information you can get from the ground. And that's true for some of the science, and this goes back to some of the conversations we had about Bennu and Ryugu. I mean, the information that we got from our remote sensing from the ground on Bennu was that all the infrared data and thermal modeling suggested there's going to be some smooth areas on there. Turned out not to be for a variety of reasons. And so yeah, surprise. And so I've been on some other missions. Every time we've gone somewhere, we've been surprised, right? When we get up close to the asteroid, there's a surprise. And that's great because that's what it's all about. It's all about science discovery.

When you're dealing with planetary defense, you do not want any surprises, right? That's the last thing you want. And I had a mentor who retired the last couple of years from JPL, actually two, both Don Yeomans and Paul Chodas, and they drilled into me one of the mantras. There's a couple other mantras, but this one in particular that stuck with me is when you're dealing with planetary defense, you don't get to choose the asteroid. The asteroid chooses you, and that's why you need to know as much as you can about the target. That's why these flybys, what I wrote in that white paper, that's why the flybys are one aspect are really important. Again, those flybys are more important when you don't have a lot of warning time, right? You want to get out there quickly and see what you're dealing with. If you have lots of time, 50 years or more, oh, then sure, you can send a rendezvous spacecraft and you get a lot more detailed information, but you got time to deal with it. Sometimes you don't always have the time.

Sarah Al-Ahmed: Well, thankfully with our actual missions, we do get to pick the asteroid, right?

Paul Abell: Right. Yeah.

Sarah Al-Ahmed: Which allows us to look at just the diversity of all of these different objects out there. And Hayabusa2 is really interesting because it went and it got this sample and then it came back to earth, deposited in December 2020. We got our mission accomplished, but the spacecraft was still healthy, so that allowed JAXA to continue its lifetime and go on to these other objects. But I am wondering between dumping the samples back on earth and this recent flyby of Torifune, what was Hayabusa2 doing during that time?

Paul Abell: Yeah, it's actually a good story. The difference between Hayabusa and Hayabusa2. So Hayabusa as it was coming back, as you know, was not healthy, right? That was a really a tense time, right? The spacecraft was eventually pretty much crippled. We were coming back in some ways sort of a wing on a prayer, but it hung in there and the Japanese team, the engineering team was amazing. I mean, I refer that to sort of like the robotic version of Apollo 13. It was really amazing that they managed to get the capsule delivered with the sample. It was amazing. Hayabusa2, completely different, much more healthy spacecraft, as you mentioned. So you got a healthy spacecraft, you've done your prime mission, what else can you do with it? And so the idea was, hey, we can carry on and look at some other asteroids, right? It's a solar-powered spacecraft, really should stay in near-Earth space, near the sun for operational purposes. Here's our trajectory. Let's look and see what other targets we can get to.

And so they actually came up with a trajectory. They wanted to go to a smaller target. So their prime rendezvous target is an asteroid called 1998 KY26. It's a very small target. It could be only a few tens of meters across or maybe a little bit less rapidly spinning, but very unique and interesting. And we don't have much information on this type of the small body population, like really, really small asteroids up close and personal. So they targeted that one. And on that trajectory where they were going to do it, again, the samples were dropped off in 2020. The rendezvous is not until 2031. And so they've got time in between and they looked and it's like, "Hey, we're going to be able to fly by this other asteroid, 2001 CC21 or asteroid Torifune is it now named?" And the flyby they did was amazing.

That already occurred. But they had all that time, but still between 2020, the drop off of the sample, you've got the flyby of Torifune, which is 2026, which just happened. So there's six years there. And then you've got another five years between going to the other target. So what do you do? So the Japanese are amazing. They've done some amazing work. And first thing they're doing is they're checking the health of the spacecraft, right? It's still an older spacecraft. They're checking all the ion engines. They're checking how the instruments are working from the touchdown on Ryugu, all the material that has been liberated. There is some degradation of the sensors just because there's material adhered from when they actually touch down in the pluming, but they still work. So they do all that. There's a lot of health checkout, trying to figure out how the systems are working, how long a spacecraft can exist in space, but they also have some key sensors.

One of their key sensors is their optical camera that they use for navigation, which they used heavily in this flyby. And two things that they did because they have time and they're in crews. One is they looked at exoplanets. They actually did some exoplanet transits and they looked a couple candidates. The plans, I think they're still looking at doing that in the future. So why not? Why not see what you can see? So they did some exoplanet research. They also did another project with zodiacal dust. This is the dust that's mainly in the ecliptic plane with all the planets in the earth, thought to come from comets, but primarily asteroids. And you have these dust zones and zodiacal light, and it's very useful to know. These are small bits of dust that cause a background glow. You can actually see some of it at sunset, you can see some of the effects of it.

And it's useful to know because it adds to the background light. And this is going to be important for our understanding, especially for our own mission that's coming up, the NEO Surveyor mission, which is a planetary defense early warning system, as you will. It's an infrared telescope looking for asteroids. It'll be situated between the earth and the sun. It doesn't look at the sun, but near somewhere the side. But anyway, understanding the zodiacal light and the contribution, especially in the infrared, that will help you understand your sensitivity of your detectors and what you can actually see. So some of this sort of in cruise serendipital science that they're doing is actually really important for future, not only science, but for future operational reasons as well.

Sarah Al-Ahmed: Man, we're in such an exciting time for learning more about these objects. I love that they did some exoplanet observations too, because getting time on telescopes is so difficult. I'm sure that the people who got to take that data were really excited to have one more tool in the toolbox.

Paul Abell: Oh, they were. They were ecstatic. And keep in mind that telescope on the spacecraft, yeah, you're out so you don't have to worry about weather and things like that, but it's very small, right? It's not very big. So much smaller than the telescopes we have here on earth.

Sarah Al-Ahmed: Yeah, maybe see some hot Jupiters or something.

Paul Abell: Yeah, exactly.

Sarah Al-Ahmed: Well, it was only recently about a month ago on July 5th that Hayabusa2# actually flew by Torifune and it was going maybe about five kilometers per second and got pretty close, about 800 meters. And it actually turned out to be pretty scientifically interesting. Can you tell us about what type of asteroid this is?

Paul Abell: Yeah. So we have some good indications from the ground, ground-based, in terms of the composition that this is an asteroid very similar to asteroid Itokawa. So the original target of the Hayabusa mission, right? And so it is what we call an ordinary chondrite type asteroid or after the ordinary chondrite type meteorite. So it's a very common type of material that we find on earth in our terrestrial meteorite collections. We see this in some of the materials from our own DART mission that went to Didymos and Dimorphos. It's very similar to the type of material type that is thought to be making up the asteroid Apophis, which is going to pass by here in 2029, so that people are excited about. So this is a very, very common type material.

What was interesting about the asteroid itself was we thought it was... We had some indications from the ground-based observations of the light curve. We knew the rotation rate pretty well. We had some indication that it was a bit elongated, but we weren't sure. There may be some speculation about a contact binary, but this actually confirms it. It's actually really interesting. If you look at the images, which I encourage everybody to go online and find that you should be able to see them, they're two lobes and they're almost. I wouldn't say they're almost equal, but not quite, but much more equal than say the two lobes of Itokawa, which sort of more resembles an otter. Itokawa looks like an otter with its head and smaller head and larger body.

Sarah Al-Ahmed: It kind of does.

Paul Abell: And Torifune has these two sort of spherical balls that are stuck together. The other thing is the size of the object is a little bit bigger. And again, that's just from spacecraft, we get that better information. So it turned out the average dimension is about 540 meters in length. We were thinking maybe around 450, 500 from the ground. So again, having that spacecraft up close personal look, you refine that dimension and you actually get an idea of what the surface is like. And of course there's two lobes or the two parts of the asteroid covered in boulders, lots of big boulders, so it looks like a rubble pile. One of the interesting things to point out is, hey, there's some smooth areas on there. I don't know if you noticed that, Sarah, in looking at some of the images, but there's some smoother areas down near the southern part of the object.

So that's really interesting and be really interesting to see what the material is like near the neck between where the two objects meet. We haven't got good imagery of that yet. I'd like to point out that the data is still being analyzed from the mission. During the flyby, we took... When I say we, it's the mission, right? I'm part of the mission, but we. The spacecraft got about 300 megabytes of data. Because of the way the flyby worked, we only had three days to download that data because they had to operate the ion engines to get to the next target, which was KY26. So we only had a three-day window to download some of the data. So we got 25 megabytes of data downloaded. The rest is going to be downloaded later from the spacecraft once it stops its ion engine operation to have the first maneuver to KY26.

So there's a lot more data to come. I know that we have spectroscopic data from the spectrometer on the mission. We have thermal data that is being analyzed. We actually got LiDAR data, so laser ranging, which is going to be super, super cool. And one of the amazing things to me that blows me away is that the spacecraft got within 400 meters of the surface. That is the closest we have ever purposely flown by something, a small object like that. And keep in mind, it's sub-kilometer object and we were screaming in at five kilometers per second. And this was not designed as a flyby spacecraft. This was designed for rendezvous. So hats off to the Japanese engineering team, hats off to the JPL navigation team. They had a lot to help and play in that role as well, but they got within 400 meters roughly. And they're still tweaking the numbers, but that's the latest number that we have on the science team. So that's tremendous, right? It shows just how close we can get and target these very small objects.

Sarah Al-Ahmed: That is really amazing. But this object is very small and dark. And my understanding is the team couldn't pin down the exact trajectory until a few days before the flyby. So how nerve wracking was that for everyone?

Paul Abell: Yeah, it's a little interesting. There's a couple times I remember being on the team and then we're like, "Well, if we get too close, we actually might hit it." So there was an email that was sent out to the observing communities like, "Hey, can you watch this asteroid around time of impact? Let us know if it gets brighter because we may have hit it." Unfortunately, that didn't happen. But yeah, no, there's always that concern. It's a little bit nerve wracking. You want to get as close as possible, but not too close. Because it was a rendezvous spacecraft, the way the instrument deck was located, you had to basically come straight at the object in order to get your instrumentation in the right field of views. There was no way of slewing effectively. It just wouldn't work. You wouldn't get anything. Again, this was a rendezvous spacecraft, not a flyby spacecraft.

So completely different design than some of the other spacecraft that you may have known that were purposely made to fly by. And so yeah, there's a little bit of nervous energy. Everybody was super pumped though and of course it pulled off and we got the images and yeah, it was again, one of those big relief moments, making sure we still had telemetry, knowing that the spacecraft obviously didn't hit, but got very, very close. It was a tremendous feeling.

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

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Sarah Al-Ahmed: Well, surface, as you said, is covered in a bunch of these different boulders. Does the data tell us what these boulders are made of or are we still waiting for more of that spectroscopic data?

Paul Abell: So when you look at it from the ground, and this is one of the, I think getting back to the questions of what can you tell from the ground, what can you tell from the spacecraft? From the ground, you just sort of get a general whole hemisphere, what's facing, what's reflecting the light off the asteroid back to the telescopes on earth. And we think that's ordinary chondritic material, and that's the overall signal. The way to bet is just from me looking at the data and what I've seen so far is that that's probably a good bet that everything there looks to be ordinary chondritic. The spectra, we haven't had a chance to. There's a lot of calibration. They're still working on it. Do you have to worry about blurring? Some portion of the asteroid may be a little bit closer to you as again, you're coming in at five kilometers per second.

So some of your exposure times, it's interesting to see what you get even with a spectrometer, what the area of coverage is that field of view. So there's a little bit of calibration, but my assessment is it's probably still going to be ordinary chondritic.

I guess from the data that's been downloaded, I don't see anything that would suggest, hey, there's different types of material. And again, it's dependent on the resolution that we have. It's different from a rendezvous. If you remember from the data from Hayabusa2 at Ryugu and OSIRIS-REx at Bennu, they actually discovered different types of materials on the surface that were different, either really bright materials or some of the little bit darker materials. And so that tends to lend credence that there's some impact processes and some of these asteroids collect different types of materials on the surface. We don't see that yet from Torifune. Again, it may be a resolution issue. We did see that a little bit on Itokawa. There's the black boulders. Again, don't know if those are different materials or if there were different shock types, maybe the same material, but just shocked. There's some different theories.

But again, that's the nice part about having a spacecraft. Again, with a rendezvous, you can take your time and focus in. On a flyby, it's like that quick snapshot, so you just sort of get what you get. Keep in mind, there's still a lot of data on the spacecraft that we have yet to download, so who knows? But my sense is from what we've seen so far, pretty much everything is probably going to be an ordinary chondritic type of composition.

Sarah Al-Ahmed: Based on how fast it's rotating, can we tell anything about how this contact binary formed?

Paul Abell: It's a good question. So the rotation rate is about five hours. It's relatively slow. Basically, we do know not so much from the rotation rate, a little bit more from what we think in terms of the model, the shape model, the structure, the boulders. This looks like a classic rubble pile, right? It looks like what we've seen on Itokawa, not identical, but similar. Again, not identical, but similar to Dimorphos and Didymos. This looks like rubble pile, right? So basically the idea is you have two asteroids collide together, catastrophic disruption, and then pieces fly off at low relative velocity to each other. So you have pieces that are sort of clumped and grouped together, and then through mutual gravitation or interactions, these pieces come back and form together.

One of the interesting things is, and if you look at images from Dimorphos, Didymos, Itokawa, and Torifune is you see lots of boulders. And you see this also with Ryugu and Bennu, you see lots of boulders on the surface, but what we don't know is, is the interior the same? In other words, what we see on the surface is indicative of what's in interior or are there larger blocks or larger coherent chunks inside? So for example, in Torifune, those two main lobes, are there bigger pieces making up those lobes themselves? My sense is, again, from talking with some of the dynamicists who work on this and model this, it looks like these two lobes may have come into contact at low relative velocity to each other to form Torifune. So then basically you have pieces that come together and they formed one lobe, had formed a separate lobe, and then those two lobes actually came in together at low relative velocity and then sort of just stuck there.

And then the object evolves over time and you get these rotation rates. But in terms of the actual rotation rate, it doesn't tell us, it can tell us something about the formation, but more likely it's the actual surface, the shapes, the number of boulders, the density of the boulders and things like that, that really tell us a lot about the interior structure.

Sarah Al-Ahmed: It's really cool getting more data on more of these objects and just the diversity of what we're seeing out there is really startling. But I do wonder if that diversity complicates our planetary defense efforts.

Paul Abell: Yeah, it's sort of job security. I mean, when you've got lots of objects out there, you've just got a sheer number of objects that we have yet to discover. Again, I sleep well at night, your listeners should sleep all at night, you should sleep well at night. We're doing it, but we're here just in case, just in case, insurance. But there's lots of objects out there, but there's lots of different types, right? We have contact binaries, we have true binaries, we have ternary systems, we have carbonacious material, we have metal material, we have ordinary chondritic material. So there's lots of different types. And it goes back to the whole thing of there's a wealth of diversity and that's great for science. It does complicate things a little bit in planetary defense in terms of you really have to know what you're dealing with.

We have done DART. We have one data point on how we can deflect a certain type of asteroid. I would like to try and be ready for a few other alternatives, maybe three other scenarios, just to be ready. It's just like you practice for a play, you practice for a concert, you practice for a sporting event if you're on a sports team. We do planetary defense and we have to practice for that because we don't want to have to do it right the very first time. We need to practice and know. So DART was an amazing mission. I was on that. It was tremendous, but that's just a start, that's one data point. We need to try and expand our portfolio and look at things. Maybe we want to try and see if we can deflect things in different ways. There may be different techniques to deflect or stop an asteroid, maybe a different size of asteroid.

How would you target something that's 50 meters? Torifune is about 500 meters, average 540 meters across. How do you target something that's 50 meters? DART hit Dimorphos that was 150 meters, but now you're talking about something that's 50 meters. So you're stepping up the challenge in terms of dealing it with it operationally, but 50-meter objects, if we're going to get hit again, that's probably the size that's going to give us the next problem that we'll have to deal with. So anyway, just something that we tend to think about here in Planetary Defense.

Sarah Al-Ahmed: Is there some concern that if we're hitting something like a contact binary that we might break it into two pieces and basically make one threat into two threats or are we not concerned?

Paul Abell: Well, I mean, you always have that in the back of your mind, right? And again, that's why you want to know everything you can about the object. And that's why you're not going to, hopefully, unless you're left with no other choice and it's a last minute thing, but that's why we have the systems that we have. We have the ground-based survey systems that track and find all these objects that we have right now. Why we're planning to launch the near-Earth object surveyor mission, the infrared telescope, is to find all these damaging targets or a lot of them and be prepared. And then if we do see something coming, we have the time.

The other mantra that I will tell you, so the two mantras, the one was you don't get to choose the asteroid, the asteroid chooses you, but the other one mantra is find them early, find them early, find them early. So you got to find them early and then you have time and then you have time to deal with them. And then having time to deal with them helps you being able to send spacecraft out there and know what you're dealing with, tailoring the specific mitigation method, whether you have to deflect or disrupt on the basis of what you find for an asteroid or maybe even a comet.

So those are the type of things that we want to be able to do. And if you have the time, if it is a contract binary, obviously hitting it on the very edge is not great. It's not great for even a monolithic type. You want to be able to know everything about the target and where's the best place to deflect it, not only in terms of on the asteroid itself, but also in the time of orbit, the location in the orbit. You basically want to slow it down or speed it up. You just want to make sure that it misses that conjunction point with Earth. Or if it's really, really hazardous and last minute and it's small enough, then maybe you can disrupt it. But that's risky and we haven't done that yet.

So there's always things that you worry about, but again, having that time, having that information, gathering it so you can tailor the technique to the specific object is always the best way. And that's how I'd like to think about it.

Sarah Al-Ahmed: Well, between NEO Surveyor, we've got Vera Rubin and all of the other asteroid hunters out there. I do. I'm beginning to sleep much better at night knowing how many of these things that we've cataloged, but it is those small ones that are harder to detect that we really have to worry about. And I think that's what's so interesting about the next target for Hayabusa2, this 1998 KY26. It's tiny and it's rotating really, really fast. Is that what makes it worth this trip?

Paul Abell: So we don't have a lot of information about the small body, really, really tiny small body population, the 20 meters and less. And so going to these very small objects, having them rotate really quickly, there's some question of is this a solid piece of something or does it have some internal cohesion or strength or something that we don't understand that even though it's a rubble pile, it allows to spin that quickly. Most people think it's got to have some type of internal strength so it's a solid object to spin that fast. But knowing how these smaller objects are like, how they're put together, what's their composition, how do they interact, this is something that Hayabusa2 is going to find out.

One of the neat things about Hayabusa2, two aspects that I will share with you is we still have a tantalum projectile from the sampling system on the spacecraft. So this is a 300-gram, of all intents and purposes, think of a bullet. And so they're talking about going up and rendezvousing with the target and then shooting that tantalum projectile into it and forming a crater and seeing what happens. And so that'll be really interesting from a scientific experiment. The other thing they're going to do is towards the end of the mission, after they rendezvous and get all the information they possibly can, they're going to try and land on it.

And so, something that's spinning once every 11 minutes, that's going to be really challenging doing that robotically. So they're going to have to try and do that from on the pole. On the pole, you can get away with it, but that's something they're going to try and do. So we have all this data that we still have yet to analyze, but I'm really looking forward to KY26 and the rendezvous opportunity and the science that we may get. Again, I got to be patient because I got to wait another five years. The team has to wait another five years. But yeah, it's a very exciting time. And in the meantime, we've got all these other fantastic missions that are going on. We've got our own launch of NEO Surveyor maybe sometime next year. We've got Hera arriving at the Didymos-Dimorphos system later this year.

Sarah Al-Ahmed: I cannot wait.

Paul Abell: It's going to be amazing. And then we've got in 2029, we'll have three spacecraft to encounter Apophis, right? We've got DESTINY+, which Japanese is going to fly by Apophis in early February 2029. Then we have Ramses, which is sort of a European space agency mission following on the guidelines of Hera that we'll rendezvous with Apophis in late February of 2029. And then we have our own spacecraft, OSIRIS-APEX, that will get there in June. So it's going to be an exciting time and 2029 is the International Year of Asteroid Awareness and Planetary Defense. Lots of amazing things are going to happen starting very soon leading up to that international year and during that international year. So it's an exciting time for small body science and planetary defense.

Sarah Al-Ahmed: Well, as we're looking ahead to all the things that are coming up in the future, what are you most hopeful that these missions are going to enable us to do in the future?

Paul Abell: That's an amazing question and it's something that I think about and there's so many aspects to that, right? I mean, for science, I just hope that it's not practical to go to every asteroid and get a sample of it, but I'd love to be able to do that, but you can't do that. But one of the things these missions do, especially NEO Surveyor, will be able to help us find a lot of what we call low delta V targets, low-energy targets that come close to earth that are easier to get to from the standpoint of a spacecraft trajectory. We just don't know where to look. So having that capability will be an amazing boon, not only for planetary defense, you get to see what's coming at you, but you actually get to see what's coming close to you and that provides opportunities for spacecraft missions.

And that's not only science missions, but that's also for mining missions, ISRU missions. There's companies out there that are looking at trying to see if they can extract resources from these asteroids. And the information that we've got from Hayabusa and OSIRIS-REx suggests that there are lots of material there that's very interesting. And then you've got the whole planetary defense aspect, but then you've got the exploration aspect. Wouldn't it be cool if we're trying to shake down missions to Mars, right now we're focused on the moon. We just did Artemis II. We did a flyby around the moon. And wouldn't it be cool to test out our expiration systems? Mars is a long way away, but here's some nearest asteroids that are in between us and Mars. We could go out and have a human mission to an earth asteroid and then come back. And at the same time, you're testing your operational capabilities, your spacecraft systems, life support systems as you're stepping away from the earth moon system and then starting to explore the solar system with the idea of getting out to Mars and then other destinations.

But at the same time, learning about these really valuable objects, not only from the standpoint of science, but mining and planetary defense. That's my hope. That's my desire.

Sarah Al-Ahmed: You're calling up all these science fiction future ideas in my brain from For All Mankind or The Expanse, right? People in the future are using these as resources. It's just amazing what this kind of science could enable us to do in the future and what it could do for humanity, not just for planetary defense, but for resources that we might need for our technology and who knows what else, right? So it's really cool knowing someone like you who's seen the entire arc of this. I cannot wait, not just for us, but for you when we get to KY26 and when we see OSIRIS-APEX, all of these things, I'm sure it's going to be such a culmination of everything you've done in your career.

Paul Abell: It's going to be tremendous and I'm super excited about the future and I just can't wait.

Sarah Al-Ahmed: Well, thank you so much for joining us, Paul. You're absolutely fascinating. And I think this conversation is just a great example of why this kind of rendezvous science with asteroids is so important.

Paul Abell: Well, thank you, Sarah. I appreciate it.

Sarah Al-Ahmed: Fun Sarah fact. I actually studied Japanese in college, so I've always had this soft spot for JAXA missions. They're constantly defying the odds of what's possible, whether it's nursing an injured spacecraft home on ion engines alone or pulling off a flyby that their spacecraft was never designed to do. They also have a bit of a habit that I personally appreciate. They really like firing things into asteroids, which brings us to What's Up with Dr. Bruce Betts, our chief scientist here at The Planetary Society. Hey, Bruce.

Bruce Betts: Hi, Sarah. How are you doing?

Sarah Al-Ahmed: Doing well. I survived NIAC, the NASA's Innovative Advanced Concept Symposium. We'll hear more about that over the next two weeks, but glad to be back in California.

Bruce Betts: It's supposed to be a challenge, but it sounds like you had quite the trip that I assume people will hear something about.

Sarah Al-Ahmed: Yeah, it's quite an adventure, but I'm not going to tell the story right this moment. But in any situation, anytime I have the joy of getting to be at one of these conferences, I think I talk to so many people and I hear so many stories. By the time I get home, I am so full of new science knowledge that I just need to veg out. So my plan this week is to talk about Hayabusa2 and get a little chill.

Bruce Betts: Well, I don't know that it was really that chill emission. I mean, chill while traveling through space, but it shot an asteroid a couple times.

Sarah Al-Ahmed: Right. Take that one for the dinosaurs. No, I actually noted that though as I was talking with Paul Abell about this. He mentioned the different projectiles that are on Hayabusa2, and there's two different kinds. There's the small carry-on impactor, and then there's the tantalum one. And he mentioned that they have a spare tantalum one that they might be using on their next target, 1998 KY26.

Bruce Betts: Sweet.

Sarah Al-Ahmed: We need a cuter name for that, but I wanted to talk a little bit about the SCI, the small carry-on impactor, because this is such a cool story. And the fact that we're just going around shooting asteroids for science is just amazing.

Bruce Betts: For science.

Sarah Al-Ahmed: For science, if you could tell us a little bit about what happened there, because why are we shooting asteroids?

Bruce Betts: Well, here, there are different reasons. So the DART mission was shooting asteroids primarily to practice planetary defense and changing orbits of asteroids in case one comes for us. Whereas this was to do things like uncover the material that hasn't been as modified by the space environment underneath so you can study it. And even in the case of their sampling, they used kind of a big funnel sample horn thing that actually collected the sample by shooting the asteroid when they were up in contact, and then the material flew up into their sample horn, and that's how they collected at least one of their samples.

Sarah Al-Ahmed: So that was the first tantalum projectile that did the sample thing. Now we got one more of those.

Bruce Betts: Tantalum, that's exotic.

Sarah Al-Ahmed: Tantalum. But before they even took that sample, right, they shot it with something else.

Bruce Betts: Cheese. I think it was hyper velocity cheese. Yes, they shot it with the small carry-on impactor. They shot it with that first to expose material. So I think they went and sampled that material, but they certainly did spectroscopy of it because you do oddly in the vacuum of space because of things like solar wind and cosmic rays, you do modify the surface. And so if you want to get a less modified surface, you want to clear off the top stuff. That's less true than if you're on the earth and you have water and humans and plants and stuff that gets in the way of the geologists, but still that's it. So, they made a crater.

Sarah Al-Ahmed: So when we talk about DART, we had that situation where we can't actually. They're waiting for the Hera follow-up mission because they had to give it some time to chill out after they blasted that object. So how did Hayabusa2 deal with the fact that they blew a bunch of debris off of this object?

Bruce Betts: Yeah, this is very cool. They have the best gadgets, and so they had a separate camera that they let loose to try to capture the impact. And then the spacecraft went and hid on the other side of the asteroid, so none of the material would come flying at it. It was quite the clever and difficult to do thing, which worked. And so the spacecraft is all happy.

Sarah Al-Ahmed: Although it's going to be a different situation when they make it to 1998 KY26, that object is so tiny that what if you just shoot it and the whole thing flies apart?

Bruce Betts: Then just make sure you take pictures.

Sarah Al-Ahmed: Valid.

Bruce Betts: And actually, and we would learn something, I don't think that's going to happen. But if it did, we'd sure learn something about the structural integrity of that particular asteroid.

Sarah Al-Ahmed: Right.

Bruce Betts: But we also learned things from the impact. So you get an idea of structural integrity, perhaps not of the whole asteroid, but are you dealing with. Because asteroids come in all these different flavors, it turns out, from iron, nickel things that were inside a proto planet and then got ripped apart again, where you've got basically metal asteroids. And then at the other end of the spectrum, you've got these fluff balls, I think. And then you've got the boulder piles, the rubble piles, which we've been encountering a lot of with recent spacecraft like Bennu and OSIRIS-REx that are just gravity fairly loosely holding together a bunch of rubble.

Sarah Al-Ahmed: There are those things that you know you shouldn't do, but your brain wants to do them. If I could jump out of an airplane and go right through a cloud, that would be a terrible idea, but would be really cool. I just want to jump into one of these asteroid ball pits and see what that's like. Terrible idea.

Bruce Betts: I'm sorry, asteroid ball pits?

Sarah Al-Ahmed: Yeah, rubble piles.

Bruce Betts: We'd have to fire you into it, though.

Sarah Al-Ahmed: Valid. Yeah. Sarah as a projectile.

Bruce Betts: Larger carry-on impactor.

Sarah Al-Ahmed: Right?

Bruce Betts: Sarah, it can still be SCI, Sarah carry-on impactor, perfect.

Sarah Al-Ahmed: Yes.

Bruce Betts: This is a brilliant, brilliant idea. Another one, chalk up another brilliant idea for the team of Sarah and Bruce. Well, that was exciting. I don't want to get you too excited, but random space fact. Rewind. So space, humans, the world record holder for the most time in space is Oleg Kononenko at 1,111, yes, that's four 1s, days over five ISS missions. That's three years and about 15 days that he spent in space.

Sarah Al-Ahmed: That is so long.

Bruce Betts: Yeah.

Sarah Al-Ahmed: Imagine how that changes your brain and your body being in space that long. That's cool or terrifying, one or the other. Keep coming back to this space. Terrifying.

Bruce Betts: Not that he's in space, it's the fact that his brain changed. That's cool.

Sarah Al-Ahmed: Yeah. I mean, it's just one more reason why we need to study more of these things, but also another reason to appreciate earth because we're kind of made to be here.

Bruce Betts: Well, it's true. It's true. Okay, everybody go out there, look up the night sky and think about spending your time in space. Firing Sarah into an asteroid. Yay.

Sarah Al-Ahmed: Wee.

Bruce Betts: Thank you and goodnight.

Sarah Al-Ahmed: As a heads up, keep your eye out next month in October for the launch of JAXA's MMX mission. That's the Martian Moon Explorer. It's headed toward Mars's Moon Phobos to bring back the first samples from the Martian system, other than meteorites, of course. We'll be covering that here on Planetary Radio, in part because it's amazing science, but also because Planetary Society members helped fund Honeybee Robotics PlanetVac sampling instrument, which is on board. We did that through our STEP grant program, so thank you to everyone who helped donate to that campaign.

We've reached the end of this week's episode of Planetary Radio, but we'll be back next week with more space science and exploration. If you love the show, you can get Planetary Radio t-shirts at planetary.org/shop, along with lots of other cool spacey merchandise. Help others discover the PB&J, the passion, beauty, and joy of space science and exploration by leaving a review or rating on platforms like Apple Podcasts and Spotify. Your feedback not only brightens our day, but helps other curious minds find their place in space through Planetary Radio. You can also send us your space thoughts, questions, and poetry at our email, [email protected]. Or if you're a Planetary Society member, leave a comment in the Planetary Radio space and our online member community app.

Planetary Radio is produced by The Planetary Society in Pasadena, California. Rae Paoletta is our producer. Kate Howells and Mark Hilverda are our associate producers. Casey Dreier is the host of our monthly space policy edition, and Mat Kaplan hosts our monthly book club edition. Andrew Lucas is our audio producer. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. My name is Sarah Al-Ahmed, the host and producer of Planetary Radio. And until next week, ad astra.