#53 The Hayabusa2 Asteroid Ryugu sample return mission. Space rock expert Greg Brennecka joins us for an incredible up-close look at real life asteroid material.

Our favourite space rock expert Greg Brennecka joins us to talk about the amazing Hayabusa2 mission, the sample return mission to asteroid Ryugu by Japanese space agency JAXA. Greg and his colleagues have been analysing the sample and some of the findings are incredible.
What does Ryugu tell us about the early solar system? What do we learn about water on bodies like asteroids? and could Ryugu be carrying enough of the building blocks of life to potentially populate another habitable planet?

It's a fascinating chat.


 If you want to learn more about rocks from space, check out Greg's book 'Impact' at Harper Collins here

See Hayabusa2's touch and go sample collection on Ryugu https://www.youtube.com/watch?v=4xnInpqMiG4

Hayabusa2 landed back on Earth at the Woomera Rocket Range in South Australia, December 2020 https://www.youtube.com/watch?v=Ek1MRUbJSo8
 

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Transcript

Andrew Prestage: 0:10

This is Cosmic Coffee Time, the place where we take a look at what's happening somewhere in the universe in about the time it takes to have a coffee. It's cosmology in a cup. I'm Andrew Prestage, and join me for a coffee and see where in the universe we're going. This time, meteoriticist and friend of Cosmic Coffee time, Greg Brennecka returns to the podcast to talk about the Hayabusa2 mission. It's a fascinating mission that's already provided new information on the starting composition of the solar system and the origin of water and organic compounds on Earth. Welcome, Greg. It's great to see you again.

Greg Brennecka: 0:52

Yeah, it's great to be back again.

Andrew Prestage: 0:54

I wanted to talk to you today about the Hayabusa2 spacecraft and its mission to asteroid Ryugu. It's an initiative by JAXA, the Japan Aerospace Exploration Agency. Hayabusa1 was the first spacecraft to land on an asteroid and collect a sample, that was back in 2010. Greg, can you give us a bit of background to the Hayabusa2 mission? What sort of spacecraft is it? Where did it go, and how long did the mission take to get this asteroid sample back to Earth?

Greg Brennecka: 1:25

Yeah, sure. Well, as you mentioned, Hayabusa1 or Hayabusa was, was kind of the, the practice mission, you know, going to kind of an ordinary asteroid or, or ordinary chondrite material. Uh, and this was kind of leading up to Hayabusa2 and Hayabusa2 launched in 2014, and then went up to a near Earth orbit asteroid, Ryugu. And, it basically circled it for a while, and then kind of did a, a grab and go, if you will, of some of its surface material. And it brought back a significant amount of material about, I think 5.2 grams of the asteroid, and it landed, I think it was in December of 2020 is when it, came back to Earth.

Andrew Prestage: 2:12

And I wanted to talk to you about it because you and your colleagues are doing analysis on that Ryugu sample. Greg, firstly, that must be a bit of a dream come true for you. And how on Earth did you get to work on such a rare and precious sample of asteroid?

Greg Brennecka: 2:30

<laugh>? You're right. It is pretty cool. We basically were able to apply for the sample from, from JAXA, because they were generous enough to open it up to the international community to work on some of the sample after it came back, we applied and we had some ideas about what we could do with it. So, we got a small bit of material and it was so cool when it arrived in the lab, they just, you know, sent it through the mail and, oh, here are my asteroid's here,<laugh>.

Andrew Prestage: 3:01

Well, that was gonna be one of my questions, like for a six year mission to return that sample to earth and a 10 year project. I was gonna ask, how does it get presented to you? Is there a ceremony or did it get its own seat on a plane, or did it arrive in the mail? It seems it arrived in the mail.

Greg Brennecka: 3:17

It was FedEx, I think, it was, you know, unceremoniously...

Andrew Prestage: 3:21

Wow.

Greg Brennecka: 3:21

...delivered in a cardboard box.

Andrew Prestage: 3:24

And there seems to be a lot of parallels with studying meteorites, uh, which is really your thing. Other scientists on the project, do they have a meteorite background as well?

Greg Brennecka: 3:35

Yeah, we do. Luckily, because there's a lot of us that have been studying meteorites, we've kind of been practicing for when we bring back asteroid material. I mean, meteorites are certainly what we've got on Earth that is the best alternative, but now that we're to the technological stage where we can, as you know, different space agencies go up and collect asteroid material, it's more pristine. But we have the same techniques obviously, that we use for, for meteorites. So, luckily we're the type of people that get to analyze these things.

Andrew Prestage: 4:05

Tell us a bit about Ryugu. Most asteroids are in the asteroid belt between the orbits of Mars and Jupiter, but this one's a little closer to home.

Greg Brennecka: 4:16

Yeah, it's what we call a near Earth asteroid. So it's like you said, it's not in the typical asteroid belt, which makes it a little bit easier to get to and collect. I mean, if you do an asteroid collection, in the asteroid belt, then you have to spend a lot more time, and a lot more fuel actually. So, we're going to collect near Earth asteroids for the moment, because this is a little bit easier and closer,

Andrew Prestage: 4:39

Ryugu seems to be an unusual shape. It has a bulge at the equator, which seems like it's not uncommon for asteroids and some descriptions call it the shape of a spinning top. How does it get to be that shape?

Greg Brennecka: 4:54

Well, I'm certainly not an expert on the dynamics of, of asteroids, but I believe it's because it's kind of a rubble pile, and as it's spinning, it kind of, it bulbouses out at the middle, you know, kind of equator area, because it's not really a cemented rock. It's just kind of a glomeration of dust and, small pebbles and things. So it's not really a rock that's floating up there. It's just a pile of dust essentially.<laugh>

Andrew Prestage: 5:20

And Hayabusa2 is still in space, but it dropped off a landing capsule to Outback South Australia in 2020, as you mentioned. What was inside that capsule when it arrived?

Greg Brennecka: 5:32

Well, it was it was the most pristine material of the solar system we've ever been able to sample, actually. It was about a little bit over five grams of basically exactly what the sun is made of from what we can tell, which is really, really cool. We've got meteorites that are pretty close that we always kind of considered to be the same composition as the sun, because we can measure that with spectral lines. But this is as close as it's ever been, to exactly what we see in the sun

Andrew Prestage: 6:04

Until the moon landings, all the space material we had to study was meteorites. And I think it was you that told me that, meteorites survive a fiery plunge through the Earth's atmosphere and an impact with the ground at supersonic speeds. When you're studying for the chemical composition of a meteorite, does that bias the sample toward more robust material?

Greg Brennecka: 6:29

It does, and it's actually seen a lot in our meteorite collection. We have so many metal asteroids or, you know, iron meteorites, and they're not that common probably in space, but because they survive the transition from space to Earth that they're just overrepresented in our collection. We have very few of these very pristine and, very primitive meteorites, you know, like we were sampling with Ryugu

Andrew Prestage: 6:54

And meteorites aren't always picked up as soon as they land. I mean, sometimes they can be kicking around for hundreds or even thousands of years. And what difference does it make to someone like you to have that pristine sample completely isolated and presented to you in an airtight container?

Greg Brennecka: 7:13

Well, it is really important because while we try to sample the interiors of meteorites that have less alteration, if something kicks around on the surface of the earth for a while, it's gonna get rained on. It's gonna get, you know, heated up, like you said, as it enters the atmosphere, what we have with Ryugu is something that was completely protected as it came through the atmosphere. So it really is something that represents what it was in space, and that allows us to study some really interesting things that we have a harder time to do with meteorites, so we can look for, you know, organics that may break down with either, you know, aqueous alteration on the Earth or with the heat produced as it enters. So it really does represent something that's a very scientifically valuable, you know, piece of material.

Andrew Prestage: 7:57

And all the meteorites and asteroids in the solar system, they're all around about 4.5 billion years old, but the Ryugu sample, it's been described as being primitive. What's that difference between primitive and old

Greg Brennecka: 8:13

<laugh>? That's, that's a good question. So primitive usually just kind of refers to how pristine it is. So primitive asteroids, and primitive meteorites, they haven't seen a lot of alteration, they haven't seen a lot of heat, I think in the case of Ryugu, it's, you know, gotten to maybe 150 degrees, something like this Celsius as about as hot as it's ever been, so it really hasn't seen a lot of alteration, and that's kind of what we mean by primitive or pristine

Andrew Prestage: 8:43

And a lot of study of material like this. It seems to gravitate toward the organic material and the building blocks of life to hopefully understand a bit about how life came to Earth. Is there organic material in the Ryugu sample?

Greg Brennecka: 8:57

There is, there's quite a bit, and it's, we're finding more every day, you know, if you, if the listeners are following the news, which I'm sure they are, there was some recent reports of uricil, which is, you know, definitely one of the building block amino acids of you know, of life. So we've recently found that, and I'm sure we're gonna be finding more as time goes on.

Andrew Prestage: 9:21

And what does that, what does that material mean to the origin of life? Is this organic material, it's sprinkled all over the solar system, does that mean life will begin on any body that's got the right condition? I mean, one thing that bothers people who are interested in looking for life beyond Earth is that the more we look it seems, the less we find, but the building blocks are everywhere.

Greg Brennecka: 9:43

Yeah. The building blocks do seem to be everywhere, and there's no reason why a habitable planet wouldn't be able to develop, you know, life. It should have the ingredients because meteorites would be delivering them. Of course, we don't know what those exact conditions are, to start life, we know what life exists right now and has for the last couple million years or, you know, couple hundreds of million years on earth, but, yeah, it's a real difficult question to know what is needed to get, you know, from those building blocks to actual life, so that's a, that's a whole other set of podcasts, I think<laugh>.

Andrew Prestage: 10:20

It is. And I was never gonna miss an opportunity to ask you if, are we any closer to understanding how that can happen? How non-living material, rocks, minerals, how that can come to life? I mean, there is an answer. I'm just dying to know what it is.

Greg Brennecka: 10:38

<laugh>. Alright, me too, Andrew. I don't have anything for you. I just know it, I'm glad it happened. How's that

Andrew Prestage: 10:45

<laugh> Yeah, me too. I mean, and developed to a point where two specimens like us can sit around talking about how we came to be.

Greg Brennecka: 10:53

Exactly a couple, a couple thousand miles away, or a couple thousand kilometers away.

Andrew Prestage: 10:59

And how about water? We've spoken before about the origin of water on Earth and water couldn't have survived that intense heat of the early molten Earth. Does Ryugu tell us anything about the history of water in the solar system?

Greg Brennecka: 11:14

Well, we know that the water in the solar system is pretty common. So Ryugu, it's a very primitive meteorite. It has about 7% water, and we have meteorites that actually have more than that. I think they go up to maybe 20%. And then of course, comets are almost, you know, 90 plus percent. Some of'em are almost full water ice, so water is pretty ubiquitous in the solar system and in the universe, how that got to Earth is, you know, kind of still debated. We may have actually started with the water were kind of born with, we don't necessarily need water added to the earth.

Andrew Prestage: 11:49

It makes sense to me that water is a good medium for mixing, on dry land you can have a substance here and you can have a different substance a meter away, and they'll never meet. In liquid water, everything's mixing and mingling around creating new compounds, and that generally helps the process along. Is there any evidence to link water with more diverse organics or just more organics on a body like Ryugu?

Greg Brennecka: 12:15

That's a, that's a really great question, and it's one we don't really have the answer to, but we can certainly speculate, so as I mentioned earlier, there are other meteorites like Murchison that actually that fell very near where you are now...

Andrew Prestage: 12:27

Yes.

Greg Brennecka: 12:28

...that is kind of the poster child for a lot of organics in meteorites, and it also has a little bit more water and it saw slightly higher temperatures. So one can speculate that some of that organic material was actually helped out by those slightly higher temperatures, and maybe a little bit more water. So, you know, that it, I think you're right that it's, it's possible that a little bit more aqueous alteration and a little bit more active water in a body is gonna help it produce more organic materials and more diverse organic materials.

Andrew Prestage: 13:02

And are there any indications of how Ryugu formed? It seems in the solar system, we've got the planets, moons, and then asteroids and a bunch of leftover rocks. Where does Ryugu fit in? Has it had much of a life cycle?

Greg Brennecka: 13:17

Yeah. Well, so we know from its content, it's chemical and isotopic kind of fingerprints, we know that it formed in the outer solar system, so probably beyond the orbit of Jupiter. We also know that because it has a considerable amount of water, and you wouldn't get that amount of water somewhere closer to the sun. So we know it started in the outer solar system at some point it moved in the inner solar system, probably during the shifting of the giant planets and things like this. And we also know that it was broken up at some point in the relatively recent past, and then probably what happened is, was hit by a projectile, another asteroid most likely, and then it kind of reformed so it kind of busted it up and then reformed on its own gravity, so we've got it. And you know, that could have been what knocked it into a near Earth orbit as opposed into the, into the main asteroid belt, but that again, is a lot of speculation. We just know that it did break up at some point and has reformed.

Andrew Prestage: 14:14

Hayabusa2 is heading off now to fly by two other asteroids in 2026 and 2031. Hopefully we get some more incredible data and images from those asteroids. And JAXA has another sample return mission planned for Phobos, a Moon of Planet Mars launching 2024 and returning to Earth in 2029. You think you might get an opportunity to work on that one as well?

Greg Brennecka: 14:40

I was just talking with some colleagues about that last week, at a NASA meeting. And one of the cool things about that is I think with just a few measurements we can tell if that moon of Mars is actually from Mars or if it was captured by Mars. So I think, you know, that's one of the things I'll definitely hope to propose when we have those samples coming back.

Andrew Prestage: 15:02

And in the near future, we've got the OSIRIS-REx spacecraft landing a sample of asteroid Bennu back on earth later in 2023. So there's a lot to look forward to, but I'm sure we'll learn more about Ryugu even before that. What an incredible thing to be involved with Greg. It's been a real treat to talk to you about some of the findings, and I know I'm looking forward to learning even more as well. Will you come back and talk to us again another time?

Greg Brennecka: 15:30

Absolutely. Sounds great.

Andrew Prestage: 15:32

And thanks again Greg. It's been great to talk with you on Cosmic Coffee Time. If you want to learn more about rocks from space, check out Greg's book'Impact'. There's a link in the show notes. Remember, if there's something in the universe that you want us to take a closer look at, send us an email at cosmiccoffeetime@gmail.com. Thanks for joining me. I'm Andrew Prestage and I'll see you again soon for another Cosmic Coffee Time.