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OSIRIS-REx mission sample contained organic material, stardust. What that means, and what's next

By Mark Brodie
Published: Tuesday, January 30, 2024 - 11:11am

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The return to Earth this past fall of the capsule containing a sample of the asteroid Bennu was a cause for celebration among many — especially at the University of Arizona — which led NASA’s OSIRIS-REx mission. But now, scientists are combing through the tiny particles, looking for clues about what they contain.

While a percentage of the sample will be saved for future generations — and their presumably more sensitive equipment — researchers are making interesting discoveries in what they’re looking at now.

Tom Zega is one of those researchers — he’s a professor of Planetary Science at the Lunar and Planetary Laboratory at UA. He joined The Show to talk more about what key findings they've discovered so far.

Picture of the sample collector with Bennu material inside
Erika Blumenfeld and Joseph Aebersold/NASA
A view of the outside of the OSIRIS-REx sample collector. Sample material from asteroid Bennu can be seen on the middle right. Scientists have found evidence of both carbon and water in initial analysis of this material. The bulk of the sample is inside.

Full interview

What to you are some of the key takeaways from what you found so far?

TOM ZEGA: So among the, the goals of the OSIRIS-REx mission was to bring back 60g or more of material from a carbonaceous asteroid. And of course, as you know that asteroid is asteroid Bennu. And we've, we've met those level one requirements now. So we returned over 70g of, of material from asteroid Bennu.

And so far, our preliminary measurements have been, have been very exciting, and they've revealed that the return sample contains organic compounds and other materials that contain what we refer to as structural water in them. And those were among the goals for the mission, to bring back material from an asteroid that had carbon bearing organic material in it as well as material that we know forms by reaction with liquid water.

Well, so what does that tell you that this material has organic material and evidence of, of some kind of at least reaction with water?

ZEGA: So, obviously, we know that life here on earth requires both carbon and it requires water. And so those of us that are interested in understanding origins of life, perhaps the prebiotic molecules that could have been delivered to the early earth, we have to sample primitive bodies that may contain these kinds of these kinds of materials. And, and researchers have been studying meteorites for, for decades and and longer, which are fragments of asteroids. They are, they are pieces of asteroids.

But with meteorites, we don't actually know what asteroid they come from. And so that's why sample return missions are really, really important. Whereas with meteorites, we're sort of at the mercy of what falls from the sky. But with a sample return mission like OSIRIS-REx, we're going directly to the asteroid. We're gonna go into orbit around it for a period of time. We're gonna image it at very high resolution, we're going to measure its composition on the surface with sophisticated spectrometers, and we will know exactly where we're going to sample that asteroid and bring back that material to Earth. So we have all of that context that we really would like to have with any kind of study of a meteorite, but unfortunately, we don't because because they're random, right.

Does that kind of context maybe help you put some of the other meteorites into context? Like are you able to say, OK, this is what we found from the source. So if you find something similar from, you know, something, a piece of rock just falling from the sky, that maybe we can infer or, or confirm something else about that.

ZEGA: Yeah, that's a great question. And so there's those of us that study meteorite samples in the laboratory, then we also have colleagues that study asteroids out in space using telescopes. It'd be great if we could do both, we could point a telescope and asteroid, we could take pictures of it, we could image it, we could measure its composition and then we could send a spacecraft to it or get in our, I don't know our Battlestar Galactica or our Millennium Falcon and fly out to the asteroid belt and grab a sample of, of that asteroid, but that's not quite how it works yet, right?

So we try to piece the two together, right. We try to connect what we see spectroscopic remotely using telescopic observation with what we can actually measure in the laboratory by studying meteorites, which are again, are these samples of asteroids. But now that we actually have a sample that's been returned from an asteroid that we've actually surveyed in detail, absolutely, it helps us make that connection and further explore the the asteroid classifications that have been developed over many, many decades of, of research.

OK. So you mentioned that obviously life on earth requires two of the things that you have found in this sample in terms of organic matter and, and evidence of reactions that require water. So, are you able at this point to make any determinations or does this give us any clues about whether there is any kind of life beyond earth?

ZEGA: Also an excellent question. And I think the short answer right now is that we wouldn't, we wouldn't take that leap of faith. We don't, we don't have that kind of evidence about life beyond earth. What we can say is that carbonaceous asteroids certainly have fallen on earth over its 4.5 billion year history. In all likelihood, and the kinds of compounds that carbonaceous asteroids contain a mix of organic compounds, including things like amino acids, certainly have been delivered to earth as meteorites from these asteroids have fallen on our planet.

And so often scientists will say that the Earth, the early Earth was seeded with material that was raining down on the, on the early Earth and has rained down on the Earth since since the Earth formed some 44 billion years ago or so. As to life outside of the solar system, we're still very intrigued by, of course, that possibility. But that's not something that at this point we could say anything about based on our, our, you know, our sample analysis.

Sure. Well, so what then are you most excited to study next? Like what what, what are you really hoping to find out based on what you have found out so far?

ZEGA: So we we know that certain types of materials are contained within the sample. Now, now the the the focus is is on the details of, you know, what is the range or the diversity of these materials? So take organic compounds, for example, right. Carbon can form all kinds of organic compounds. And so now the focus is on how many types of organic compounds do we find in the sample? What is their diversity? What is their molecular structure? What types of isotopes are contained within these organic compounds as well as the inorganic materials that occur in the sample as well?

So I mentioned earlier that there were minerals in the sample that we know form characteristically by reactions with liquid water, but it's, it's several different types that can form that way. And so the focus is on, what is the diversity of those minerals? And what does that tell us about the the chemistry that must have happened on or inside this large asteroid for those things to have formed.

One of the things that we're also interested in is looking at whether or not the return sample contains preserved stardust. And by stardust, I quite literally mean samples of preserved ancient stars that formed outside of our solar system. Yeah. And so it turns out that meteorites contain at low abundances actual pieces of stardust. And so we're, we're interested in looking to see whether or not that stuff occurs in the return sample as well.

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