Planetary Radio • Mar 17, 2021

Return From Ryugu: The Hayabusa2 Leader on His Mission’s Success

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On This Episode

Yuichi tsuda portrait

Yuichi Tsuda

Project Manager, JAXA Hayabusa 2 asteroid sample return mission

Bruce betts portrait hq library

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

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

Hayabusa2 project manager Yuichi Tsuda and his team learned a lot from Hayabusa1, Japan’s troubled-though-successful mission that returned a sample from asteroid Itokawa. Now they are celebrating the recovery of a much larger sample from a different world: asteroid Ryugu. Dr. Tsuda joins Mat Kaplan for a fascinating, exclusive conversation about the mission’s 5-billion-kilometer journey and the great science to come.

Hayabusa2 Sample Return Capsule Recovery
Hayabusa2 Sample Return Capsule Recovery Hayabusa2 team members recovered the intact sample return capsule from the Australian outback on 6 December 2020. Each particle of material from asteroid Ryugu is now being cataloged.Image: JAXA
Global view of Ryugu (Urashima crater perspective)
Global view of Ryugu (Urashima crater perspective) Urashima crater is at center. Taken on 30 June 2018.Image: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST
Ryugu's Surface from MASCOT, in Color
Ryugu's Surface from MASCOT, in Color This color view of Ryugu's surface at night was created from images captured by MASCOT using red, green, and blue LEDs for illumination.Image: MASCOT/DLR/JAXA
Hayabusa2 SCI impact (DCAM3 digital camera)
Hayabusa2 SCI impact (DCAM3 digital camera) Hayabusa2's deployable DCAM3 digital camera caught this view of debris spreading from Ryugu approximately 3 seconds after the SCI experiment detonated on 5 April 2019.Image: JAXA

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The spacecraft that went the farthest out in the solar system after a Venus gravity assist was the Cassini Saturn orbiter.


Mat Kaplan: Five billion kilometers to earth this week on Planetary Radio. Welcome. I'm Mat Kaplan of the Planetary Society with more of the human adventure across our solar system and beyond. Some of you got that science fiction reference, right?

Mat Kaplan: We're not talking about oldie but goodie British sci-fi films. Our topic is the gloriously successful asteroid sample return accomplished by Hayabusa2, the Japanese mission that is now voyaging to two other asteroids. Hayabusa2 project manager Yuichi Tsuda is here to tell us about his spacecraft and the great science it has enabled. Then, we'll travel even further across the void to Saturn for the answer to this week's space trivia contest, courtesy of Bruce Betts. Bruce will also give us another What's Up? review of the night sky.

Mat Kaplan: I can't feel much better than I do when I see fresh wheel tracks on the Red Planet, so I'm a happy Mars camper looking at this week's edition of the Downlink. It's topped by an image taken by the Perseverance rover of its own mark on Mars. Just below are these headlines, beginning with a big sigh of relief: The 30-year-old Hubble Space Telescope is back in full operation after a software glitch put it in safe mode for a few days. Hang on, old friend. The JWST is coming soon.

Mat Kaplan: Speaking of old friends, NASA's SOFIA observatory, the big infrared telescope carried by a 747, has discovered carbon in a comet. If you're going to have carbon-based lifeforms, you probably need several good helpings of element number six. There seems to be plenty out there.

Mat Kaplan: Northrop Grumman will be developing the small two-stage rocket that will carry samples of Mars back to Earth. The NASA contract is another step in the sample return process begun by Perseverance. Want more? You'll find it every week at

Mat Kaplan: There are only a few days left to become part of the Planetary Society's 2021 virtual Day of Action. Chief advocate Casey Dreier needs everyone onboard before the online training session on March 28. You can learn more at

Mat Kaplan: Back to those five billion kilometers. That's roughly how far Hayabusa2 had to travel to reach Ryugu and return. It was only when it had almost reached the asteroid that Yuichi Tsuda and his team saw how difficult sample return would be. Almost all of Ryugu is covered with boulders, big ones that could seriously damage the spacecraft as it approached. This was just one of the challenges met as Hayabusa2 managed to grab not one, but two samples from the surface. It also dropped similarly successful mini rovers, including one built by Germany and France. And, as you're about to hear, it blew its own 18-meter wide crater in Ryugu so that it could look below that messy surface.

Mat Kaplan: There was plenty of reason for celebration when, after six years in space, the probe finally sent its sample return capsule streaking through Earth's atmosphere to the Australian Outback. And it's not done yet, so neither is Yuichi. He joined me a few days ago from JAXA, the Japanese space agency.

Mat Kaplan: Dr. Tsuda, congratulations. I say that on behalf of myself, all the members of the Planetary Society and all the listeners to this show. It has been absolutely wonderful to see the tremendous success of the Hayabusa2 mission. Welcome to Planetary Radio.

Yuichi Tsuda: Thank you for inviting me to this radio. The Hayabusa2 is a really great success, even for us. I'm very proud of that.

Mat Kaplan: You should be. Six years, five billion kilometers out there to the asteroid and back. Where were you on December 6 of last year, 2020, when the sample returned capsules streaked across the sky and came to rest in the Australian Outback? Were you in Australia?

Yuichi Tsuda: Unfortunately, no. I wanted to be there, but I was actually in the Sagamihara Space Operation Center. That's the control room of this spacecraft, located in the center of Japan. I was controlling the spacecraft so that the spacecraft worked perfectly to the end to separate the reentry capsule precisely to Australia. Also, after that, spacecraft had to continue the flight to an extended mission, so I have to be on the control room to take care of the spacecraft itself.

Mat Kaplan: Obviously, someone had to stay at home and drive the spacecraft. But I know that there was a very excited reaction when you learned that the sample return capsule had arrived on the ground in one piece. That must've been absolutely thrilling.

Yuichi Tsuda: Yes, yes. Exactly. When I saw the fireball in the sky of the Australia actually through the internet, the time was exact, within one second of error. Also, the direction was perfect.

Yuichi Tsuda: For us, Hayabusa2 team, it was a time we physically viewed the appearance of the spacecraft. Before that, we just watched the status of Hayabusa2 through the telemetry and data displayed in the computer, so like [inaudible 00:05:59]. At that moment, we could watch physically the spacecraft. That's the wonderful moment also for me and the team.

Mat Kaplan: Almost as exciting as being there in the Australian Outback, I'm sure. It was a perfect ending to a essentially perfect mission. The capsule came back, I read, in excellent condition. Was it in better condition than you expected?

Yuichi Tsuda: Yes. The capsule's condition was perfect and almost as expected. We found the landed capsule actually a few hours after the landing. Then after that, we brought the capsule back to the facility and opened it immediately. Everything was as planned. The condition of the capsule was very clean. We could not almost imagine that that capsule traveled more than five billion kilometer. It definitely feel very, very clean. Like new.

Mat Kaplan: Truly amazing. I did just read that as we speak, the capsule may be put on display in a museum there in Japan so that the members of the public can see it. Is that still happening?

Yuichi Tsuda: Yeah. We are planning that. In a few days from now, we are going to display that to the public. But we are still watching the situation of COVID-19. We will decide soon.

Yuichi Tsuda: But in the Hayabusa1 era in 2010, we did the same things. We displayed the return sample to public. At that time, many, many people came to see the capsule from all over the Japan. That was surprising for me, the space science community, that so many people are interested in space missions.

Mat Kaplan: I'm not a bit surprised because we at the Planetary Society know how the public is often extremely excited to be able to participate in these successes. Speaking of participating in these successes, I saw an image on the Hayabusa2 website of those two micro SD cards that contained the names and messages of members of the Planetary Society and many, many other people, and that apparently they came back in good condition. You were able to read the data off of those?

Yuichi Tsuda: Oh, yes. I have to thank the Planetary Society to collaborate with us. There are many names and message in the micro SD card contained in the return capsule. That was already opened and the data was retrieved. To tell the truth, I was expecting some errors because of the cosmic radiation effect.

Mat Kaplan: Sure.

Yuichi Tsuda: But in reality, what we confirmed that there was no error. All the names and message are contained as it was installed six years ago. It works like a time capsule. Many of you may already forget what you put as a message to the SD card, but you will be able to remember soon.

Mat Kaplan: I look forward to looking up my own message. I know my name was carried by Hayabusa2 to the asteroid and back.

Yuichi Tsuda: Oh, you also did that?

Mat Kaplan: Oh, yes. Absolutely. Well, I'm a member of the Society, for one thing, but I wouldn't have missed the opportunity. There were some other messages, messages of congratulations. I promise we're going to talk more about the science and the spacecraft, but if you'll allow me to celebrate a little bit more with you for a moment or two here, there are messages on the Hayabusa2 website, the mission website, from a number of leaders of space agencies around the world.

Mat Kaplan: There is a colleague of yours, Dante Lauretta... I know you know Dante well. He's been a guest of ours on Planetary Radio several times. Of course, he is the principal investigator for OSIRIS-REx, the other asteroid sample return mission out there.

Mat Kaplan: If you'll indulge me, I'd like to play that message that he sent to congratulate you and your team. Here it is. It's very brief.

Dante Lauretta: To Tsuda-san and the Hayabusa2 team, [Japanese 00:10:34]. I'm incredibly proud of the accomplishments of the Hayabusa2 team. This mission has been groundbreaking in so many areas. Exploration of asteroid Ryugu has shed new light on our understanding of formation of our solar system and the properties and future of near-Earth asteroids.

Dante Lauretta: I'm particularly proud of our ongoing collaboration, where we have worked together to understand both asteroid Bennu and asteroid Ryugu, interpret the results in terms of understanding the history of our planet, why Earth is a habitable world and how the origin of life occurred here. I'm particularly excited to get those Hayabusa2 samples into our laboratories to perform detailed investigations and further our understanding of the properties of asteroid Ryugu, and looking forward to comparing those to the samples from asteroid Bennu in just a few short years.

Dante Lauretta: Congratulations again on a historic, amazing accomplishment. Everybody here has been cheering for you and rooting for you. We're very proud of the amazing sample return from asteroid Ryugu. [Japanese 00:11:42].

Mat Kaplan: So Dante Lauretta, leader of the OSIRIS-REx mission, he has talked on our program a number of times about this collaboration between your team with Hayabusa2 and his. I think this is an important component of both missions. Do you feel that way?

Yuichi Tsuda: Yes, yes. Sure. Yeah. Dante is a good friend of mine for around 10 years. We have been discussing how to do the exploration of the unexplored asteroids both from engineering point of view and also from the scientific point of view. We have been shared that the same type of problems and same type of difficulties for long time so for me, he is a very long-time special friend.

Yuichi Tsuda: Because of this type of collaboration, the both missions are mutually stimulated and motivated. I sometimes explain to JAXA's upper level or to the government that, "Hey, O-REx is doing it this way, so we have to be more smart." In that way, we can propose more challenging things or sometimes more budget.

Mat Kaplan: Oh, that's good. Dante has also told me how much his team was able to learn from Hayabusa1 because of the information that was shared there. I know that you have also talked about that mission, which was also successful. In fact, there is a news item just recently about some science that has come from the sample returned by Hayabusa1.

Mat Kaplan: But it was a troubled mission. Did you learn a lot? Did it help prepare you for Hayabusa2?

Yuichi Tsuda: Yes, yes. Actually, I learned a lot. My career as a space engineer started from the Hayabusa1. Hayabusa1 was launched in 2003. At that time, I joined the JAXA and I joined the Hayabusa1 team. Since then, the Hayabusa1 faced many, many troubles. The landing was not perfectly success, but just faintly retrieved the samples of asteroid Itokawa.

Yuichi Tsuda: After that, the spacecraft lost communication for a few tens of days. Very fortunately, we could reestablish the communication. The fuel was lost after that because of the leakage in the pipe. By using the another other back up strategy, then we could finally bring the spacecraft back to Earth.

Yuichi Tsuda: Each moment, the Hayabusa1 team worked very hard to solve the problem. I watched the way the team was solving the problem not always depending on the preplanned way, but sometimes the team solved the problem in a totally different way using the equipment that was not expected to be used for that specific function. In that way, we could finally bring the spacecraft back to the Earth.

Yuichi Tsuda: From that experience, we learned a lot. For the Hayabusa2 mission, I am the lead of engineering of the spacecraft so I tried to reflect all the lessons learned from Hayabusa1. I didn't want to experience again the bad experience of the Hayabusa1. In that sense, the Hayabusa1 was a good teacher for the Hayabusa2.

Mat Kaplan: It is a very inspiring story, really. Success grabbed from the jaws of defeat, as we might say. I don't know if you had heard this story. It came out just a couple of days before our conversation that this one tiny bit of dust, and it was given the name Amazon because apparently it looks like the continent of South America, has been revealed to contain water and organics. What an amazing science result to get from this spacecraft that almost didn't make it back to Earth.

Yuichi Tsuda: Actually, I haven't noticed about that news, so you know better than me.

Mat Kaplan: Oh, I'm glad to tell you about it.

Yuichi Tsuda: Yeah, thanks. Sometimes, earlier than that years, there was, I think, another research finding, the clue of water in the sample of Itokawa. The surprising things is that Hayabusa1 returned 10 years ago. After 10 years, the research is still continuing. So the return sample is really a treasure for scientists. Like sample of moon from Apollo missions, the research continues for several decades.

Yuichi Tsuda: Equipment on ground evolved time by time. Once we got the sample from the other celestial body, then we can make research with the latest instruments on ground, accessed by many worldwide scientists. They can do their own research in their own labs. That's the important thing.

Mat Kaplan: It's also a great lesson, considering the much larger sample that has now returned by Hayabusa2 which I'm sure will be delivering the same sort of science for many, many years to come. Before we talk more about the sample return, I hope that you can talk a little bit about the science that Hayabusa2 conducted at Ryugu even before. I mean while it was at the asteroid still. What did we learn about the asteroid even before that journey back to Earth began?

Yuichi Tsuda: First of all, before we arrive at the Ryugu, only thing we know is from the light spot observed through the ground-based telescope. That's only information we have to plan a mission. After we arrived at the Ryugu, we are surprised that the shape is so odd. It looks like a top shape, what we call top shape. Actually, the top shape is the popular shape among the asteroid scientist. For example, the Bennu, which is the target of O-REx mission, was known to have the top shape from the later observation.

Yuichi Tsuda: But for the Ryugu, we didn't have such a later observation due to the geometrical constraint between Earth and the Ryugu. So we are surprised that the Ryugu is also a top shape. Just by chance, we became the first of mankind to visit a top shape, just before the O-REx mission.

Mat Kaplan: Yes, yes.

Yuichi Tsuda: The next thing we are surprised is that the surface of Ryugu was bumpy and covered with numerous rocks all over the [inaudible 00:19:19]. We thought that there were no safe place to land the spacecraft.

Mat Kaplan: Again, that's much like Bennu.

Yuichi Tsuda: Yeah, yeah. That terrain feature is also found in Bennu. In that sense, we share that same headache both in Bennu and Ryugu. Because of that, we had to completely change our strategy to make a successful landing. We delayed our original schedule by four months to change the strategy and make more fine observation of the asteroid and to reprogram the spacecraft to do the more precise landing. There were many, many difficulty. For me, after we succeeded in that, I thought that's the best experience for me as a engineer.

Yuichi Tsuda: Finally, we succeeded in landing to the surface of asteroid with a landing accuracy of one meter. The asteroid itself is 3,000 million kilometer away from the Earth. With that distance, one meter accuracy landing, so that's more than satisfactory.

Mat Kaplan: Oh, I think it's quite satisfactory, yes.

Yuichi Tsuda: Yes, yes.

Mat Kaplan: Now, Hayabusa2 project manager Yuichi Tsuda. He has more to share, including a brief look ahead toward a Japanese mission to the moons of Mars. Stay with us.

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Yuichi Tsuda: Can I explain the whole history within the...

Mat Kaplan: Sure.

Yuichi Tsuda: The proximity of mission Ryugu?

Mat Kaplan: A brief history would be great.

Yuichi Tsuda: Just briefly, okay. After the first landing was successful, that was February of 2019, one and a half months later we did new challenges, which was to dig a hole or make an artificial crater on the surface of the asteroid by the kinetic impacting. For that, we developed the novel device called the Small Carry-on Impactor. That was very successful. Finally, we could make the 18-meter diameter and three-meter depths big hole on the surface of asteroid. Through that, we could obtain the subsurface information. Not only the surface information, but also the subsurface information of the asteroid, or the internal structure of the asteroid.

Yuichi Tsuda: After that, one thing we wanted to do is bring the subsurface material back to Earth. So for that purpose, we attempted to do the second touchdown about three months later. There was actually a huge discussion whether we should do the second touchdown or not. But after the thorough discussion and the technical and scientific investigations, we decided to do that.

Yuichi Tsuda: On July 11 in 2019, we did the second touchdown. That was also very successful. At that time, the landing accuracy was small as 60 centimeter. We expected get the subsurface material.

Yuichi Tsuda: After that, we returned to the Earth. We already opened the contents of the capsule and we already confirmed that the samples from two sites are included in the samples. I hope we can say something about the ingredient of Ryugu soon.

Mat Kaplan: Absolutely. Yes. And as you said, laboratories around the world looking forward to getting portions of that sample. Before you go on to that, though, I have to mention this amazing image. We have a copy of it on the Planetary Society website that was taken, I read, about three seconds after Hayabusa2 fired that impactor for the Small Carry-on Impactor experiment at the surface of Ryugu. You could actually see the material being blown off of the surface of the asteroid. It is truly one of the most amazing images I've ever seen come from elsewhere in the solar system.

Yuichi Tsuda: Yeah, yeah. It's really a dynamic image or movie. We're also surprised that that kind of very drastic reaction occurs. Actually, we had the worst-case scenario and the best-case scenario. Always, we try to be based on the worst-case scenario. In that case, we expected to have one major or two major crater would be generated.

Yuichi Tsuda: But in reality, what we found is that more than 18-meter diameter. The huge ejecta was blown up in the air to as high as like 40 meter or so. So it's a very drastic response.

Mat Kaplan: You make quite an impression, quite an impact on asteroid Ryugu, one might say. We will get to the samples, but I also want to mention these passengers that you were carrying on Hayabusa2 that you also delivered to Ryugu. In particular, that little lander called MASCOT that was built by the DLR, the German space agency, in collaboration with JAXA and CNES, the French agency. That resulted in even more stunning images from right there at the surface of the asteroid.

Mat Kaplan: I hope that people will either visit our website or yours. We'll provide these URLs, the web addresses, on this week's show page at But you must've been pleased by the success of MASCOT and the other little spacecraft that you carried.

Yuichi Tsuda: We had three Japanese rovers called MINERVA-II and also the MASCOT lander by the German and the French partners. They are all successful. As you said, the images... There were other science data, but especially images are very exciting to see.

Mat Kaplan: Stunning.

Yuichi Tsuda: It's the scenery just in front of the robot on the surface. The resolution of that image is less than one millimeter. It's a color image. It's just wonderful to see the scenery of the other celestial body. It's a new world.

Mat Kaplan: It really is, literally. Okay, those samples. Are portions of the sample now in laboratories in Japan? Have they started to make their way across the world?

Yuichi Tsuda: Yes. After we opened the container of the capsule, then we first measured the weight of the sample, the mass of the samples, and which was 5.4 gram. Our criteria or mission requirement was 0.1 gram. So compared to that, 54 times heavier than that.

Mat Kaplan: Very good return on [crosstalk 00:27:50].

Yuichi Tsuda: More than satisfied. Yes, yes. We have three chambers, chamber A, B, C. Chamber A contained the sample from the first touchdown. Chamber C contained the samples from the second touchdown. The chamber B was open between touchdown number one and the number two. We saw some very fine grains in the chamber B. That will be also interesting to investigate.

Yuichi Tsuda: Now, in the curation facility in Sagamihara, we are picking up the each sample from the chamber one by one. Each grain sizes from less than one millimeter to up to one centimeter. One-centimeter sample looks like a stone. We are now making a catalog of what we got.

Yuichi Tsuda: Soon, in early summer, we will start to analyze the compounds of the material, so what we call the initial analysis. Through that, we want to confirm how much especially carbon-related material and also the water-related material are contained in that sample. Because for the Hayabusa2 mission, carbon and water is the theme of our science.

Mat Kaplan: The scientists, I'm sure, cannot wait to get these particles into their spectrometers and start to look for these organics, because I know this was a carbonaceous asteroid largely consisting of carbon compounds and water. It's a cliché to say so, but we are talking here, aren't we, about the building blocks of life?

Yuichi Tsuda: Yes, yes. We are focusing on the organic compounds, also the [inaudible 00:29:55] minerals. We already estimated from the in situ observation in Ryugu that the sample is estimated to contain some organic material and also the [inaudible 00:30:10] minerals.

Yuichi Tsuda: But we did not know exactly what type of compounds we have. Especially for the molecular number of the organic compounds, if we have very large molecular number, that means that material is composed of series of carbon atoms.

Mat Kaplan: Very complex molecules.

Yuichi Tsuda: Very long chain of the carbon atom. That's right, that's right. So the molecules can be related to the life. It's easier through investigating that way, so we may know how complicated material exist in the universe outside the Earth.

Mat Kaplan: So important, I'm thinking, because also, while we have all the meteorites that have covered the surface of Earth for billions of years, these are exactly the sorts of complex molecules and volatile compounds which don't last more than, in some cases, minutes or hours or days or weeks in a meteorite that hits Earth. Isn't this part of why it's so important to pick up these pristine samples from asteroids and bring them home?

Yuichi Tsuda: That's right. All the meteoroids came through the atmospheric reentry, so at least the surface information was buried or changed due to the very high temperature. Also, because the meteoroid stays very long on the surface of the Earth, so the contents should be changed.

Yuichi Tsuda: But the direct sample from the asteroid, the sample itself is contained within the very tightly sealed chamber in the reentry capsule. The contents inside the capsule has never experienced the Earth's atmosphere, even though the capsule itself experienced the reentry. The contents was directly transported to the curation facility, which are clean and the environment of control and isolated from Earth's environment. So now, we have a very pure, pristine material as it was in space. That's important scientifically.

Mat Kaplan: So really, the best part of the mission may be yet to come because it will come from the science that is performed using these samples. And, as we mentioned earlier, Hayabusa2's work is not done either. Where is it headed now? Is the spacecraft in good condition for the years ahead and its next targets?

Yuichi Tsuda: Yes. After the capsule was separated to head to Earth, the main spacecraft diverted from the reentry cradle and flew away from Earth again. Now, as the next mission extension, or we can say it's a bonus mission, we are aiming at basically two new asteroids. One is named 2001 CC21. Another is 1998 KY26. Those two are new to humankind and also very scientifically interesting.

Yuichi Tsuda: The first target, 2001 CC21, we will do the flyby in 2026, five years from now. For the 1998 KY26, we will rendezvous there in 2031, 10 years from now. The spacecraft condition is currently very healthy. The fuel left aboard the spacecraft is more than 50%.

Mat Kaplan: Excellent.

Yuichi Tsuda: Which means that we can do the similar type of travel as round trip mission to Ryugu to the new target. So we want to make full use of it to pursue extra science.

Mat Kaplan: 2031. As we have heard many times on this program, exploring the solar system requires a great deal of patience.

Yuichi Tsuda: That's right, that's right. 10 years. 10 years is short for space engineer and the space scientist. At least, we have to think it like that.

Mat Kaplan: I also read that these other asteroids which Hayabusa2 will visit, they play a part in another area of research which I know is important to you and is important to a lot of us who live here on Earth and that is planetary defense. Is that element of the mission an important one to everyone on the Hayabusa2 team?

Yuichi Tsuda: Yes, that's right. The planetary defense is actually also a small part of our mission objective in the original Hayabusa2 mission. But for the extended mission, we put the planetary defense as one of the big pillar of our objectives because we are going to visit two asteroids.

Yuichi Tsuda: The first one, 2001 CC21, we will do the first flyby which is going to be a very precise, controlled, very close flyby, which means that if we can do in the same strategy, we'll be able to impact the asteroid. But instead of that, we will try to fly the spacecraft very close to the asteroid. It's like an impact experiment of the spacecraft. From an engineering point of view of the planetary defense, the orbit of deflection is one of the key technology to be studied to avoid the impact of the asteroid to the Earth. This technology is expected to connect to that future technology.

Yuichi Tsuda: And also, the second target, 1991 KY26, that's really an interesting asteroid. Its size is only around 30 meter, so it's very small. The rotation period is as fast as 10 minutes. It's very fast-rotating asteroid. Many of these asteroid exist around the Earth's orbit. Sometimes, they came into the Earth's atmosphere once in a million years or once in 10 million years and make a vast disaster. So that kind of very small and fast-rotating asteroids are the good target to investigate scientifically to know more about the target of the planetary defense.

Mat Kaplan: Another very important step as we learn how to defend our planet in ways that the dinosaurs weren't able to. It is good to hear that it has this element as well.

Yuichi Tsuda: That's right.

Mat Kaplan: Before we close our conversation, I hope that you can say something about another very exciting mission which is coming up from JAXA. That is the Martian Moons eXploration, or MMX mission, to Phobos and Deimos launching, I believe, in 2024. Aren't these, in a way, also asteroid missions? Because I know the thinking is that those two moons, once upon a time, were asteroids.

Yuichi Tsuda: Yes, yes. The MMX is planned to be launched in 2024 and explore the martian moon. The mission was originally inspired by the Hayabusa2 mission. Actually, I was one of the proposer of that mission, initially.

Yuichi Tsuda: The focus is about 10 times larger than Ryugu. The environment is little bit different from the asteroid. And also, the Phobos is trapped in the Mars gravity, so the spacecraft has to first go to Mars orbit and then reach Phobos. In the return phase, we have to leave Phobos and then escape from the Mars gravity and then return to the Earth. So it's more complicated with a bigger propulsion system. The strategy are actually very different from the Hayabusa2 mission.

Yuichi Tsuda: But we know how to deal with the sample return mission. After we arrive at the targeted celestial body, then we can apply our technology to land or access to the surface of that body. In that sense, the MMX is strongly based on the technical heritage of Hayabusa2. I am very personally looking forward to that. From my perspective, I hope this descendant of Hayabusa2 will do will in its mission.

Mat Kaplan: That would be a descendant to be very proud of. And with those samples return from Phobos, which is the target for sample return I know, it is just possible that we will be getting back a sample from Mars itself, isn't it? I mean, because there is material from Mars that has ended up on Phobos. MMX could be a Mars sample return mission.

Yuichi Tsuda: Yes, yes. Going to Mars' surface is very challenging. NASA is already been doing so, but returning the sample from Mars is even difficult. But yeah, as you said, some of the particles or samples of Mars may exist in the surface of the Phobos. That's something that we are aiming at by the Phobos sample return.

Mat Kaplan: Dr. Tsuda, you have painted a very bright picture of the future, both for Hayabusa2 and MMX. We know that JAXA has many other plans underway, but of course our purpose here is largely to congratulate you again on the tremendous success of this mission that you have led as the project manager. Thank you so much for spending this time with us today to tell us about Hayabusa2. Best of success to you and your team and JAXA with all of these great plans for the future.

Yuichi Tsuda: My pleasure. Thank you very much. I'm very happy to introduce about the Hayabusa2 to the public and the world and also in the US. Thank you very much for this opportunity.

Mat Kaplan: Yuichi Tsuda leads the Hayabusa2 team that has successfully returned material from asteroid Ryugu. I think I need to apologize before we turn to What's Up?. By the time I discovered a problem with my audio track, it was too late to rerecord this week's segment with Bruce. Maybe you can pretend I'm talking to you in a Zoom session? On second thought, I'd hate to subject you to another of those.

Mat Kaplan: Hey, it's time for What's Up? on Planetary Radio. The chief scientist of the Planetary Society is here. He's here every week to tell us about the night sky and bring us a contest and random space facts. There's just so, so much. Welcome back.

Bruce Betts: Thank you. Joy will be had.

Mat Kaplan: By all.

Bruce Betts: Well, most people.

Mat Kaplan: Almost all. There's a couple people over there in the corner who look kind of sad. Hey, over there. Cheer up. Bruce is here.

Bruce Betts: Hey, I'm here. And hey, night sky still cool after all these years and millennia and, well, you get the idea. Evening sky, still got Mars and Aldebaran in Taurus looking very similar, like twins in the southern, southwestern sky pretty high up. Mars will be to the upper right of Aldebaran in the early evening or mid-evening. They are similar in brightness, similar in color. On the 19th, they will be near the moon as well. In a few days after that, they'll be at their closest point together, about seven degrees. That's about 14 moon diameters, for those playing the home game.

Bruce Betts: In the predawn sky, getting higher all the time are Jupiter and Saturn, Jupiter looking super bright, Saturn looking yellowish up above it. They are low in the east, very low, in the predawn. Will be getting higher in the coming months.

Mat Kaplan: Have to admit they're getting higher, they're getting higher. I just saw a Ringo Starr interview by Stephen Colbert.

Bruce Betts: I did, too. It was so cool.

Mat Kaplan: Wasn't that great? He looks like he's much younger than us. He looks like he's about... Maybe not much younger than you, actually, but a lot younger than me.

Bruce Betts: I think he looks good.

Mat Kaplan: He does, yeah.

Bruce Betts: He's the Ringo man. Onto this week in space history, it was 10 years ago that MESSENGER went into orbit around Mercury, the first Mercury orbiter. Going back further to 1965, this week the first spacewalk occurred by Alexei Leonov of the Soviet Union. Moving forward to a dark day that was hidden from much of the world for a long time, in 1980, 50 workers died at the Soviet launchpad in a rocket explosion. On to random space fact.

Mat Kaplan: Not the way the Beatles would do it, but not bad.

Bruce Betts: Not good, not Beatles.

Mat Kaplan: Maybe Wings. Maybe Wings would do it.

Bruce Betts: I would love to speculate with you on this, but I think we'll need a different podcast. Instead, I will tell you about something you've been hearing about, Hayabusa2. They had what they call a solar sail mode. I don't know if you know it, Mat, but I'm kind of into solar sailing.

Mat Kaplan: A little?

Bruce Betts: It wasn't a solar sail, but they use solar radiation pressure, this push of light used by solar sails for propulsion. They used it to help control the spacecraft orientation during several months of the mission and were able to use just one reaction wheel to change the orientation of the spacecraft on axis rather than having to use all of them. It was designed, in part, using lessons learned from their solar sail mission, IKAROS.

Mat Kaplan: I did not know this. Had I known, I might've brought it up with Dr. Tsuda. But I'm very glad that you have.

Bruce Betts: He published papers talking about it. All right, we move on to the trivia question I asked you. Of the spacecraft which used Venus for a gravity assist maneuver, which went farthest out in the solar system? How'd we do, Mat?

Mat Kaplan: A moderate, but very nice response this time around. We got this poem, which is really quite impressive, from [Gene Lewit 00:45:39] in the state of Washington. I'm going to let him answer the question, and you can confirm.

Mat Kaplan: In order to travel the planets afar and sometimes out of our galaxy's hood, the assistance of forces provided by mass are used and results are quite good. Approaching the planet, and sometimes the sun, can serve as a way to change speed and adjust the velocity to such a point that lets us get to the place that we need. Cassini employed this racket we know, and traveled the furthest than those on this list. Even Serena, the noted queen of the court, in doubles needed a Venus assist.

Bruce Betts: Surprise ending. Didn't see it coming.

Mat Kaplan: No, neither did I and I was reading it. Gene, hey. Congratulations and thank you. Is he correct? Is it Cassini?

Bruce Betts: It is indeed Cassini. Multiple spacecraft have used Venus for gravity assist. Cassini went the farthest out, all the way to Saturn.

Mat Kaplan: Our winner, and he's a first-time winner once again, [Ben Drought 00:46:43] who said, "Yep, Cassini performed two gravity assist flybys just to Venus and then those others, Earth and Jupiter." Ben, who is in Dubuque, Des Moines, [inaudible 00:46:55], Marshalltown, Mason City, Keokuk, Ames, Clear Lake... Ought to give Iowa a try. I'm not saying which of those he lives in, but it's one of those. Congratulations, Ben. We are going to send that copy of The Lion of Mars by the award-winning children's author Jennifer Holm. It's a terrific book for young adults. We'll throw in a Planetary Society rubber asteroid as well.

Mat Kaplan: [Darren Richie 00:47:23], he says, "We're full of music today. Well, a cheer, anyway. Give me a V. Give me a V. Give me an E. Give me a J. What does it spell? Saturn."

Bruce Betts: Yes, the initials were often used to describe the seemingly crazy orbital mechanics maneuvers used to fly by planets to get out there to Saturn.

Mat Kaplan: From [Laura Die 00:47:47] in Northern California, "Now, I wonder if Cassini also traveled the greatest number of miles during its mission to and around and around Saturn," which I doubt. Wouldn't Voyager 1 have an edge just for traveling for so many years?

Bruce Betts: Oh, yeah. Voyager 1 and Voyager 2.

Mat Kaplan: [Olla Franzen 00:48:07] in Sweden, "Although I understand the principle, it always fascinates me that going the "wrong way" first makes for the best journey." And finally from our poet laureate [Dave Fairchild 00:48:19], "When our Galileo went to Jupiter to play, it got a gravity assist from Venus on the way. Cassini said, 'That's good for you, but I can do better. I'm headed out to Saturn where I'll be the new pacesetter.'" Thank you all.

Bruce Betts: Here's a question for you for next time. What was the Hayabusa2 Small Carry-on Impactor's projectile made of? This is the SCI. There are more than one projectile on the Hayabusa2, or there were, so pay attention. Small Carry-on Impactor's projectile, what was it made of? Go to

Mat Kaplan: And I did come across this in my research, but it did not come up in the conversation with Dr. Tsuda.

Bruce Betts: Yes.

Mat Kaplan: Go for it, folks. You have until the 24th, that's March 24, Wednesday, at 8:00 AM Pacific Time. You know what I discovered? We have a lot of great books piling up at the office. I mean, these are great, great space books. I think we're going to give away a series of things, beginning with this extra copy got, one we gave away sometime ago, by Wade Roush, a great science writer, called Extraterrestrials from MIT Press. It's a fun little book. It goes through the various answers people have given to that question from Enrico Fermi, where is everybody?

Mat Kaplan: It could be yours if you were chosen by and hit us with the right answer for this one. Keep those cards and letters coming. Well, no we don't need cards and letters. But if you want to send us a nice card, why not? I think we're done.

Bruce Betts: All right, everybody. Go out there. Look up at the night sky and think about what object in the solar system you'd like to hit with a two kilometer per second projectile. Thank you. Good night.

Mat Kaplan: It's that asteroid out there that has my hometown's name on it. I want to hit it with, what'd you say? Two kilometers a second? I think I want to hit it about 400 years before it impacts. Will that do?

Bruce Betts: That should do, depending on how big it is. We'll have to look into your hometown.

Mat Kaplan: It's a good size town. That's Bruce Betts, the chief scientist of the Planetary Society who is here every week for What's Up?.

Mat Kaplan: I'm back in full voice. Planetary Radio is produced by the Planetary Society in Pasadena, California. It is made possible by its members throughout the world. Mark Hilverda is our associate producer. Josh Doyle composed our theme, which is arranged and performed by Pieter Schloser. Ad astra.