OSIRIS-REx Principal Investigator Dante Lauretta discusses the NASA mission to near-Earth asteroid Bennu.
NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx), the first U.S. mission to successfully collect a sample from an asteroid, is on its way back to Earth with an abundance of rocks and dust from Bennu.
OSIRIS-REx is the third mission in NASA’s New Frontiers Program, managed by NASA’s Marshall Space Flight Center for the agency’s Science Mission Directorate. Goddard Space Flight Center provides overall mission management, systems engineering, and safety and mission assurance for the mission, and the University of Arizona, Tucson, leads the science team and the mission’s science observation planning and data processing.
In this episode of Small Steps, Giant Leaps, you’ll learn about:
- OSIRIS-REx challenges and surprises
- The asteroid with the highest probability of impacting Earth
- The possibility of extending the OSIRIS-REx mission to another asteroid
Dante Lauretta is Principal Investigator of NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) mission and a Regents Professor of Planetary Science at the University of Arizona’s Lunar and Planetary Laboratory. Lauretta heads the OSIRIS-REx research team at the University of Arizona working on the mission, which has included more than 200 undergraduate and graduate students. He fosters the advancement of the next generation of scientists, engineers and other space leaders through mentorship and taught coursework which apply his expertise in planetary science and spacecraft mission design and implementation. His research interests focus on the chemistry and mineralogy of asteroids and comets. Lauretta is an expert in the analysis of extraterrestrial materials, including asteroid samples, meteorites, and comet particles. He holds bachelor’s degrees in mathematics and physics and oriental studies from the University of Arizona and a doctorate in earth and planetary science from Washington University.
Dante Lauretta: OSIRIS-REx is a great adventure. We’re going off to explore an unknown world.
It’s a menacing world because it’s what we call a potentially hazardous asteroid. In fact, it is now the most potentially hazardous asteroid, meaning it has the highest probability of impacting the Earth of any known asteroid in our solar system.
Deana Nunley (Host): Welcome to Small Steps, Giant Leaps, a NASA APPEL Knowledge Services podcast where we tap into project experiences to share best practices, lessons learned and novel ideas.
I’m Deana Nunley.
June 30 is International Asteroid Day. And we’re in conversation with Dante Lauretta, the Principal Investigator for NASA’s OSIRIS-REx asteroid sample return mission, which is on its way back to Earth with samples from the asteroid Bennu.
Dante, thank you for joining us today on the podcast.
Lauretta: My pleasure.
Host: Let’s start with a summary of the mission objectives.
Lauretta: Sure. OSIRIS-REx, the mission name itself is an awesome acronym that captures the objectives of the mission. The O is for origins. And this is what really drives me in my scientific career, is to understand how did Earth form, how did it become a habitable planet and how did the origin of life take hold here? Our other investigations involve spectral interpretation, that is using telescopes and the way that they reflect light to try to infer their composition of asteroids and other planetary bodies; resource identification, looking at asteroids as potential near-Earth resources that could further our exploration of the solar system; and security, which is looking at these near-Earth asteroids as potential impact hazards, and trying to understand the ways that we might be able to mitigate those in the future.
Host: Would you take us through the OSIRIS-REx journey and your involvement with the mission?
Lauretta: I got involved in this program all the way back in 2004, when I was a young assistant professor here at Arizona. And I got a phone call from my boss, the director of the lab, Mike Drake. And he was working with Lockheed Martin to develop an asteroid sample return mission concept to propose to NASA, and invited me to come on board as the deputy principal investigator and really as the lead science investigator. So, my job was to define the science program for this whole mission. And as you can imagine, that was an awesome moment, to be invited by your boss to be part of this major program, and then to be the one that gets to define the mission. So when I got that assignment, I went home that evening and I wrote down four words that capture the major themes of asteroid science: origins, spectroscopy, resources and security.
And I looked at those four words and I was like, ‘Well, that’s pretty close to Osiris.’ And I’m a mythology buff, and I knew about Osiris as the ancient Egyptian deity, probably the first Pharaoh of ancient Egypt, and establishing agriculture and the Egyptian civilization. But Osiris became the god of the underworld, and was there to judge you when you passed and determined if you had lived a worthy life. So, Osiris had this dual nature, of the bringer of life and bringer of death, very much like asteroids do. So I like to say, I bought a couple of vowels, where spectroscopy became spectral interpretation, and resources became resource identification, and voilà, we had OSIRIS. And that was our mission name for quite a while. For about four years, we worked on that concept, and we ended up going to a different program at NASA called New Frontiers, which had a larger budget, which we needed in order to pull this mission off.
And we added the REx to the mission name at that point to keep the Osiris theme, but make it bigger and stronger, New Frontier’s level of mission. And then I call REx my backronym because I made it the Regolith Explorer. And regolith is what we call the loose blanket of rock that surrounds airless bodies in the solar system.
Host: Where are we now on the timeline?
Lauretta: OSIRIS-REx has had a phenomenal almost now five years in space. We launched in September of 2016, and we arrived at our target asteroid Bennu in December of 2018. We spent all of 2019 mapping the surface in great detail, selecting a site that we dubbed Nightingale. And then on October 20, 2020, we sent the spacecraft down to make contact with the asteroid surface for a very short duration. We were on the surface for a little over 16 seconds, accumulating and collecting a large amount of the regolith from the surface, and then safely backing away. We then went back in April of 2021 for a final look at the asteroid, to see what the surface looked like after our collection event. And then on May 10, 2021, we departed Bennu and we are now in what we call the return cruise phase. Basically, we’re on cruise control for the next two-and-a-half years until those samples arrive back on Earth in September of 2023.
Host: What do you think it is that gets people excited about this mission?
Lauretta: OSIRIS-REx is a great adventure. We’re going off to explore an unknown world. It’s a menacing world because it’s what we call a potentially hazardous asteroid. In fact, it is now the most potentially hazardous asteroid, meaning it has the highest probability of impacting the Earth of any known asteroid in our solar system. But people also love the wonder of thinking back four-and-a-half billion years in time to the dawn of our solar system, when we were just a spinning disc of dust and gas surrounding our young growing protosun. So it gives us that sense of awe and wonder of the scale of the universe and how long this planet has been here, and the history that’s entailed in these asteroids.
Host: Why was Bennu selected?
Lauretta: Bennu was chosen as the target of the mission because of its orbital characteristics. We needed an asteroid that was basically in an Earth-like orbit, and one that crosses the orbit of the Earth so that we could launch off our planet, rendezvous with the asteroid, spend a significant amount of time there and then come back to our home. And because of that orbital characteristic, which enabled the sample-return aspect of the mission, we ended up going to an asteroid that has a large probability of impacting our Earth. So part of our investigation is to understand that likelihood. And it turns out these small asteroids, Bennus’s relatively small, it’s about 500 meters in diameter, which is about the height of the Empire State Building. Nevertheless, it would be a major natural disaster for it to impact our planet. And these asteroids, when they wander through the solar system, they’re not just influenced by gravity.
In fact, sunlight plays a significant role in their orbital trajectory. Bennu, which we targeted because of its composition, is very dark, meaning it has a lot of carbon on its surface. But that darkness means it absorbs most of the sunlight that hits it. And it emits that energy back into space later in the day as thermal radiation. And that emission of heat acts like a thruster and it actually slows the asteroid down and decreases its orbit, making it move inward into the solar system. So if you don’t account for the interaction of the asteroid and sunlight, then you’re not going to accurately predict where the asteroid is going to be in the future. And therefore, you’re not going to understand the likelihood if and when it’s going to hit the Earth. So a big part of our mission is about understanding the thermal properties of the asteroid surface.
We can do that with remote sensing, using our spectrometers, but we’re bringing material back and we’re going to get into our laboratories and we’re going to analyze those thermal properties in great detail, so we can really understand the phenomena and ultimately decide what are the odds that Bennu’s going to hit the Earth in the future.
Host: Does that factor into the interest toward asteroid mining?
Lauretta: Asteroid mining is related to that in the sense that you’re going to be targeting similar orbital characteristic objects. You need things that are close to us in space. And some of these near-Earth asteroids, they’re the most accessible objects in the solar system, even easier than landing on the surface of the Moon, from an energy perspective. So absolutely, when we think about asteroid mining, and I worked on this for quite a while over the past decade or so, the commodity that we feel is the most viable right now from an economic perspective is kind of surprising, but it’s actually water. And a lot of people think, ‘Why would you go into space to get water? There’s plenty of water here on Earth.’ Well, we’re not going to bring this back to the surface of the Earth. What we’re going to do is we’re going to process it in space and we’re going to break it apart and make liquid hydrogen and liquid oxygen, which is a really powerful rocket fuel.
So, the idea with asteroid mining is you go to an object like Bennu, which in addition to the carbon that I mentioned earlier, also has abundant water locked up inside minerals called clays, and you can extract that, and you basically have a gas station in space.
Host: Such intriguing possibilities. How has OSIRIS-REx measured up against expectations?
Lauretta: Well, I’m a little biased, but I think that OSIRIS-REx is awesome, and it’s done an amazing job. And all kidding aside, the team that runs this mission, and I have the honor of leading the team, but really it’s this group of people that do all these amazing adventures in space, they are absolutely phenomenal. And we have hit our marks on every performance aspect of this program that we were hoping to achieve.
We were challenged by Bennu. When we arrived, we saw that the surface was really frightening, that it was covered with these giant boulders, which looked really menacing and challenging to get the spacecraft down to the surface and maintain its safety. So we had on the fly to redesign our guidance system to not only target much smaller areas on the asteroid surface for sample collection, but also to make the spacecraft autonomous so that it could recognize any potential hazards as it was descending down to collect that material, and if it decided it was going to hit an area that was unsafe, it could stop its descent and move away from the asteroid, and as we said, live to sample another day.
Host: Were there other surprises along the way?
Lauretta: Bennu is a trickster, so it’s always full of surprises. It’s made our lives fun, but challenging. And that’s why we’re in the business. We’re explorers and we love to be surprised in good ways, especially science ways. So, one of the biggest surprises after the initial shock of the rough surface, was almost immediately after the spacecraft went into orbit around Bennu, which happened on New Year’s Eve of 2018, we saw that Bennu’s surface was literally exploding, that is rock fragments were flying off the surface. These looked like eruption events in the first images that we captured of this phenomena. And as you can imagine, we started to get a little worried. It’s like, ‘Wow, are these hazardous to the spacecraft?’ We were immediately thinking, ‘This surface looks rough and we’re worried about the safety of the spacecraft when we get down to it, but now the hazards might be coming at us, like Bennu might literally be throwing curve balls.’
So, we did an immediate safety assessment and analyzed the data in great detail and realize that these events, they’re not all that energetic. And this is a great example of how your intuition fails you in these microgravity environments, right? Bennu has a surface acceleration that’s just a few millionths of that on the Earth. You would barely even notice it. It’s about comparable to what the astronauts on the space station experience. So it doesn’t take a lot of energy to eject these particles off the surface. And so it went from being something that we were concerned about safety, to being this phenomenal scientific opportunity.
Bennu is erupting like this constantly. We’ve seen hundreds of these ejection events during our encounter with the asteroid. Some of them leave Bennu and they become part of the inner planetary dust population. Some of them fall right back onto the surface. But a significant fraction of them actually went into orbit around Bennu. And we were able to track them for days and days as they moved around the asteroid’s gravity field. And then this turned out to be a phenomenal scientific opportunity. A good analogy is, we wanted to map out the gravity field. If you ever played in a sandbox with a magnet, you know that the magnetic field becomes apparent if you have particles like iron filings, they’ll actually map out the field lines of the magnetic field. We did the same thing with these particles in the gravity field, by watching how they moved around the asteroid, they were moving through the gravity field and we were able to track them and do an amazing job of understanding the way the mass is distributed in the inside of the asteroid.
Host: What was the initial reaction or response when you discovered the unexpected ruggedness of the asteroid surface?
Lauretta: Well, we rolled up our sleeves and we said, ‘We’ve got a problem to solve, but we’ve got a talented group of scientists, engineers and managers, and we’re going to figure this out.’ So, we looked at where do we think we could get to on the asteroid surface, that was the first job. It’s like, ‘OK, it’s not what we expected, but we still have to get this material. So where could we go? What is the best place on the asteroid?’ And that’s how we went through a very rigorous and quantitative assessment of the surface. We used our cameras to take images with pixel scales of centimeter sizes. We used our lasers to map out the topography of the asteroid surface at the same kind of resolution. We used our spectrometers to determine the chemistry and the mineralogy of the surface. And we spent a year processing all of that data, meanwhile, updating and upgrading the spacecraft’s flight software to get into tighter and tighter locations.
And by the end of 2019, we settled on our primary sample site that we call Nightingale. We also had a backup site in case something didn’t work right at Nightingale, that we called Osprey. So well over a year after first seeing Bennu with the spacecraft instruments, we had selected our location and we had upgraded the flight software and we felt like we were ready to go and plan the sample collection event.
Host: Could you take us inside some of the conversations and how engineers compensated to overcome the challenges?
Lauretta: Well, you know these engineers. They love a good problem, and we definitely gave them that. So they were excited. I could tell, they were like, ‘OK, this is why we’re in this business.’ It’s kind of an engineering dream to be working on a spacecraft, that’s flying around an asteroid and having a real problem to solve in flight. And as you know, there’s no repair stations or anything like that in space. The only thing you can fix on a spacecraft after you’ve launched it is the software, because you’re talking to the spacecraft constantly through the radio antennas, and you can upload new code. So that was the solution that we started to focus on. It’s like, ‘What can we do with software to improve the spacecraft’s guidance accuracy?’ And that really turned into, ‘The spacecraft needs a better way to know where it is relative to the asteroid surface.’
So, we zeroed in on a technology called natural feature tracking. And what this is, is it requires an extensive collaboration between the science and the engineering teams, because the engineers say, ‘OK, you want to go get a sample here. The spacecraft’s going to fly over this section of the asteroid surface. We need a catalog of a series of natural features that the spacecraft can recognize and then use that recognition to calculate not only its position, but its motion relative to the asteroid surface.’ So, our science team rolled up their sleeves and they said, ‘OK, we’re building features all the way across the swath of the asteroid.’ It was this great iterative cycle between the engineering team as they received the inputs from the scientists and said, ‘Yeah, this worked great. Or actually this one’s not working in our code for some reason.’
And we ended up building features, some of them as small as a centimeter, a fraction of an inch on the surface of the asteroid, that we not only mapped with our cameras, but in three dimensions. So that if the spacecraft took an image and that feature was in it, it would automatically identify it, and then it would use that information to say, ‘Am I on track to get to the sample site, or have I wandered off course?’ And if it’s wandered off course, it can fire its thrusters and get it back onto the safe trajectory to sample the surface.
Host: As the principal investigator, what have you learned from the mission?
Lauretta: Wow, I’ve learned a lot from this mission. I’ve been on this program for 17 years. So I’ve learned a lot about myself, what it means to be a leader, to set an example, what you can do wrong in a position of authority like this, what you do right, and how to motivate your team and how to inspire your team. Those are the real challenges of the principal investigator. And one of the things I realized early on was that we had a culture clash because we were bringing a group of people from a university, from a NASA government center and from an industry partner. And each of those groups have their own cultures, their own motivations, their own interests. And I had to build a culture that was OSIRIS-REx. It’s like, ‘We are not Arizona, we are not Goddard, we are not Lockheed, we are OSIRIS-REx. And you give us that identity.’ And you say, ‘We’re on a mission.’ And that word is really powerful. Being on a mission gives you purpose, gives your life meaning.
And everybody embraced that, absolutely, we’re doing something that’s really important, we’re doing something that’s really hard and we’re doing it really well, and we’re doing that because we are OSIRIS-REx.
Host: And now there’s consideration of a potential extended mission to another asteroid after returning the sample capsule to Earth, right?
Lauretta: Yeah, that’s right. As you can imagine, we build these spacecraft to be very reliable, they’re going off into deep space and they have to operate for years and years. So, OSIRIS-REx continues to remain in excellent health. There was no effect at all from the sample collection event in terms of spacecraft performance, which surprised me. I thought there might be some dust on the solar rays. I was just reading this morning how the Insight Mars lander is struggling with dust accumulating on its solar panels, and it can’t generate as much electricity as it used to. We thought that would be the case with OSIRIS-REx after the sample collection, because we kind of made a mess on this asteroid surface. But it’s great. There’s no sign at all that there’s any dust on the solar rays or on the radiators, which keep the spacecraft cool. And so, we were like, ‘OK, what are we going to do after we dropped the capsule off? We’re going to have this great vehicle with all these amazing science instruments.’
And our flight dynamics team sat down. And this is the group that looks at pathways through the solar system. And it’s really an art. It’s wonderful to watch this team work through all these different trajectory solutions. And they came back to me and they said, ‘Hey, we can get to another asteroid.’ And I was thinking this would be a fly-by. That’s kind of common in NASA extended missions. You can fly by another asteroid or a comet, and within a window of a few hours, you can collect some data, and then it’s like, ‘Hello, goodbye.’
But in this case, we can actually rendezvous with another asteroid, and not just any asteroid, but a very famous asteroid called Apophis. Apophis became well-known in 2004, when it was discovered, it seemed like it had a really high probability of impacting the Earth, scary high probability in the year 2029. Turns out that that’s not going to happen, it’s going to do a very close approach to our planet. And that position of the asteroid deep within the Earth’s gravity well provides a unique opportunity. We can send the spacecraft to arrive there at the same time, and it will also use Earth’s gravity field to change its trajectory. And then a few weeks later, the spacecraft will actually be able to go into orbit around this asteroid, and we’ve got a whole new asteroid mission.
Host: Wow. How does information gleaned from this misison influence future missions and planning?
Lauretta: It’s great to see the legacy of OSIRIS-REx as it feeds forward. And I kind of consider NASA’s next asteroid mission, called Lucy, to be like our progeny because first of all, I talk to the principal investigator, Hal Levison, quite a bit. We’re good friends and we share experiences and ideas. But a lot of the instruments that we built for OSIRIS-REx, they also put similar ones on the Lucy spacecraft. So, OSIRIS-REx took all those scientific instruments, and we analyzed the data and we said, ‘OK, it looks like we have clay minerals. It looks like we have organic compounds. We see different kinds of minerals like iron oxides and calcium carbonates.’ But all of that is inferred from the spectral properties. Our mission is unique in that we’re bringing that material home, back to the Earth.
So first off we’re going to say, ‘Did we do a good job? Did our instruments accurately measure the composition of the surface?’ Because we now ground truth that data with the sample. And then we go back to the Lucy team and we say, ‘Hey, we did a great job. And we got everything right. And you can confidently apply these instruments to your asteroids to determine what they’re made out of.’ Or actually, ‘We were fooled.’ I mentioned that Bennu is a trickster, so it’s not going to surprise me if there’s some different compound that we didn’t detect or didn’t understand in the spectral data. And we can then go back to the Lucy team and say, ‘Aha, we learned that our instruments, when it has this kind of signal, it actually means that this mineral is present on the surface. And now you can do an even better job characterizing your asteroids because of our knowledge.’
Host: So fascinating. Dante, it has been an absolute pleasure to have you on the podcast. Thank you for joining us.
Lauretta: Oh, it was my pleasure too. It’s always fun to talk about the great science of OSIRIS-REx.
Host: Any closing thoughts?
Lauretta: It’s a real honor and a privilege to be able to lead a program like this for NASA. It’s a dream come true. When I was a kid, I always looked up to the agency and the awesome missions. And so I’m really proud of everything we’ve accomplished, and I really appreciate the opportunity to lead a program like this.
Host: You can learn more about the mission in this episode’s Related Resources on our website at appel.nasa.gov/podcast. Dante’s bio and a transcript of today’s show are also available.
We’re always interested in your feedback and would like to hear your ideas for future episodes. Connect with us on Twitter at NASA APPEL – that’s APP-el – and use the hashtag Small Steps, Giant Leaps.
Thanks for listening.