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Asteroid Hunting

Season 1Oct 19, 2020

NASA's OSIRIS-REx spacecraft will attempt a daring feat: to briefly reach out its mechanical arm and grab a sample from an asteroid’s surface. Dante Lauretta, Heather Enos, and Ron Mink introduce you to NASA’s asteroid hunter and what this sample return mission means for us here on Earth.

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About the Episode

NASA’s OSIRIS-REx spacecraft will attempt a daring feat: to briefly reach out its mechanical arm and grab a sample from an asteroid’s surface. Dante Lauretta, Heather Enos, and Ron Mink introduce you to NASA’s asteroid hunter and what this sample return mission means for us here on Earth.


NASA's Curious Universe


DANTE LAURETTA: OSIRIS-REx is a grand adventure of exploration in deep space. We built a robotic spacecraft, and we launched it off the earth. And we sent it to a near-Earth asteroid named Bennu.

HOST PADI BOYD: This is NASA’s Curious Universe. Our universe is a wild and wonderful place. I’m Padi Boyd, and in this podcast, NASA is your tour guide!

HOST PADI BOYD: NASA has sent a robotic spacecraft billions of kilometers from Earth to do something we’ve never done before: collect a sample… of an asteroid.

HOST PADI BOYD: In this episode, we’re exploring asteroid Bennu, the target of our OSIRIS-REx mission.

DANTE LAURETTA: October 20, 2020 is the culmination of an enormous amount of work by thousands of people all around the planet. We are getting ready to send our spacecraft down to the surface of Asteroid Bennu to collect our sample.

HOST PADI BOYD: That’s Dante Lauretta, He’s the principal investigator on the OSIRIS-REx mission. He’s been with the team since the very beginning, 2004, preparing for this exact moment.

DANTE LAURETTA: Our goal is to get the treasure off the surface of that asteroid… We’re scientists, and we’re geologists… and our treasure is in the form of rocks.

HOST PADI BOYD: But these aren’t just any rocks…


DANTE LAURETTA: These are very special rocks. These are rocks that are older than the Earth, that date from the formation of the solar system. And they hold clues to why the earth is a habitable planet, why we have oceans here… and maybe why the origin of life occurred.

DANTE LAURETTA: So, we have the amazing objective of bringing those rocks back to the surface of the Earth so we can get them into our laboratories, and study them in great detail.

HOST PADI BOYD: It’s the first time an American spacecraft will attempt to collect a sample of an asteroid… and deliver it to Earth! Scientists hope OSIRIS-REx will bring back the largest cache of dirt from space in half a century–since Apollo-era astronauts visited the Moon in the 1960s and 70s!

HOST PADI BOYD: Like Moon soil from the Apollo era that scientists are still analyzing in their labs today, soil from Bennu will be preserved for decades to come.

HOST PADI BOYD: Future generations will have a chance to analyze it – people not yet born, using techniques not yet invented, answering questions we don’t even know to ask yet.

HOST PADI BOYD: And scientists like Dante can’t wait to get their hands on these samples. Studying asteroids is important for a few key reasons…


DANTE LAURETTA: One is they are the oldest geological samples from the formation of the solar system. Literally, the oldest rocks that formed around the Sun are found in asteroids.

HOST PADI BOYD: So what would NASA want with a bunch of old rocks? Well, Analyzing those ancient rocks will help scientists understand the early solar system in a way that studying Earth rocks can’t.

DANTE LAURETTA: Those rocks don’t exist on the surface of the earth because the earth is a very active geologic body. It’s got volcanoes, it’s got rain, it’s got erosion, it’s got plate tectonics. So these rocks in the asteroids, they’re over four and a half billion years old. There’s nothing that old on the surface of the earth.

HOST PADI BOYD: Bennu is a deep-space time capsule, a leftover fragment from the tumultuous formation of the solar system. It’s been well preserved in the vacuum of space for billions of years.

HOST PADI BOYD: Some of the mineral fragments inside Bennu could be older than the solar system. These microscopic grains of dust could be the same ones that spewed from dying stars and eventually coalesced to make the Sun and its planets nearly 4.6 billion years ago.

HOST PADI BOYD: Bennu’s makeup excites scientists… It’s thought to be rich in organic molecules which are the building blocks of life on Earth. And it’s got the ingredients of another very important molecule locked inside its minerals…

DANTE LAURETTA:…you’d probably be surprised, but it’s water. Water in space is incredibly valuable for a couple of reasons. Primarily, you can break it apart and make liquid hydrogen and liquid oxygen. And that is one of the most powerful rocket fuels that we know of.

HOST PADI BOYD: The presence of water ingredients on Bennu means that one day, we may be able to use asteroids like space gas stations…

DANTE LAURETTA: And so the idea is that you could turn these asteroids into space gas stations, you could have a spacecraft that’s using liquid hydrogen and liquid oxygen, and then it could stop at Bennu and get refueled. Or you could bring that fuel back even to around the moon or near Earth orbit and you could use it to refuel vehicles there.

HOST PADI BOYD: Studying Bennu will also help scientists understand the hazards of near-Earth asteroids…

DANTE LAURETTA: Bennu is also what’s called “potentially hazardous”, which means it has a reasonably high probability of impacting the earth in the future, creating a widespread natural disaster.

DANTE LAURETTA: But I don’t want anyone to panic… because the impact would be not for at least 150 years.. Still, it’s something I feel as a species we should be studying.

HOST PADI BOYD: Bennu is one of the most potentially hazardous near-Earth objects currently known. It’s as wide as the Empire State Building in New York City is tall, and it has about a 1 in 2,700 chance of impacting Earth sometime between the years 2175 and 2199.

HOST PADI BOYD: Our ability to make a detailed study of the asteroid now helps us prepare for the future, should Bennu stay on a course towards Earth in the next century.

DANTE LAURETTA: It’s kind of a gift to the future to go out and characterize this object, particularly to understand its orbit, and its chemical and physical properties. Because it’s likely that at some point in the future, maybe within the next hundred years, some group of people are going to have to figure out how to deflect this asteroid and prevent it from impacting the Earth.

HOST PADI BOYD: There’s a lot of information locked up in the rocks and dirt on Bennu’s surface. But before scientists on the ground get the opportunity to study those samples, OSIRIS-REx has to collect them. The spacecraft launched in 2016 from NASA’s Kennedy Space Center in Florida with this goal in mind…


HOST PADI BOYD: Since launch day, OSIRIS-REx has had it’s eyes set on asteroid Bennu. For two years it made its way to the asteroid and has been in orbit ever since, circling the asteroid, and mapping its surface in great detail… all in preparation for October 20, the day it will attempt to grab a sample from the surface…

HOST PADI BOYD:…On the ground, OSIRIS-REx engineers like Ron Mink have been preparing, too.


RON MINK: As a systems engineer, part of my job is to identify the bad things that could happen and to prepare for them. And so I’m thinking about risk all the time..

RON MINK: Now Bennu, the asteroid. Hasn’t been very compliant with what we need its surface to be…

DANTE LAURETTA: We first saw the asteroid in August of 2018. And that was one of the most exciting days of my life. Something I’ve been planning for well over a decade was finally coming into focus, literally, I could see the target…


DANTE LAURETTA: And then the asteroid got more and more resolved. And I just had this sinking feeling in my stomach because .. the surface looked really rough, rugged, and rocky, and not what we were expecting…

RON MINK: Our sample collector, we need to have particles that aren’t much more than an inch in size to be collected. And there aren’t very many places on Bennu that have grains that small. And so we think we found the sweetest spot on the asteroid… and we’re going to go there.

RON MINK:…But, Bennu may not want to give up her secrets. And that’s probably my biggest concern. We’ve done everything we can, but that’s part of exploration.

HOST PADI BOYD: Space exploration means being vulnerable… and sometimes trying things that no one has tried before. The OSIRIS-REx team has done everything they can to prep the spacecraft for its sample collection. They’ve even gone through rehearsals for the big day.

HOST PADI BOYD: Finding the right spot — one that’s clear of boulders — is key. It wasn’t easy, but the team found such a spot: they called it “Nightingale.” It’s a 52-foot-wide, relatively clear area inside a crater — a rare sighting on Bennu.

HOST PADI BOYD: And, if Nightingale doesn’t work out, the mission team picked a backup site, dubbed Osprey, where they can try for the second and final time to pick up a sample. These sites have the most evidence of fine grain material on the asteroid and give OSIRIS-REx the best shot at collecting a sample.


HOST PADI BOYD: After years of hard work, the big day is here. If OSIRIS-REx succeeds in its mission, scientists will get the opportunity to unlock secrets of the early solar system.

HOST PADI BOYD: Even though the talented team is prepared beyond question, in space, there’s always a risk that things might not go according to plan…

DANTE LAURETTA:…Even though we found a nice spot where we think there’s lots of material that we can collect a sample from, there’s still some pretty big rocks around that site. The biggest one I call Mount Doom, it’s about 10 meters tall, and it’s just off to the east of the crater. And we absolutely do not want to fly into that.

DANTE LAURETTA: We don’t know what’s going to happen when the spacecraft touches the asteroid surface, one of the things that might happen is it might tip over and start to move in another direction. And then it fires its engines to leave the asteroid surface, it could fly right into Mount Doom… if it tipped over too much.

HOST PADI BOYD: If the team can safely capture samples from Bennu, there’s a huge payoff.

HOST PADI BOYD: For Dante and the team, there’s a lot riding on this moment. It’s the culmination of many years of hard work for an entire team. On sample collection day, the stakes are high.


DANTE LAURETTA:…We are getting ready to send our spacecraft down to the surface of asteroid Bennu to collect our sample. As you can imagine, there’s a lot of excitement.

DANTE LAURETTA: There’s a lot of anxiety. And there’s a lot of nervousness to make sure everything goes according to plan.

DANTE LAURETTA: I’ve been working on this program since 2004. Almost 17 years of my career has been focused on this one day… to make sure everything goes according to plan.

DANTE LAURETTA: We have thought through everything that could go wrong on that day. And we’ve done our best as the team of engineers and scientists and managers, to make sure in NASA parlance, we’ve mitigated all. known. risks.

DANTE LAURETTA: That doesn’t mean that things can’t go wrong still, because there’s always the unknown nature of the asteroid surface, and what’s going to happen when we make contact… [fade out]

HOST PADI BOYD: On the day of the sample collection, OSIRIS-REx will go through a series of carefully-choreographed moves to prepare to secure rocks and soil from the surface of Bennu…

HOST PADI BOYD: OSIRIS-REx was designed with these steps in mind.

DANTE LAURETTA:…OSIRIS-REx is a robotic spacecraft, and it is designed to operate around an asteroid and eventually go down to the surface to collect those rocks. So there’s some very special features about the spacecraft that allow us to do that.

HOST PADI BOYD: OSIRIS-REx has a number of science instruments on board that will do things like map the surface of Bennu and provide information about the minerals it finds there.

HOST PADI BOYD: It’s also got cameras and sensors to help it navigate, and an “arm” that will collect rocks and dirt from the asteroid’s surface. Even though OSIRIS-REx has the right tools to get the job done, sample collection can be pretty tricky…

HEATHER ENOS: We need to get onto the surface into parking spot sized space with our spacecraft in order to collect a sample. And when you’re doing that from 200 million miles away. It takes a lot of practice…

HOST PADI BOYD: That’s Heather Enos, she’s the Deputy Principal Investigator for the mission, and will walk you through the steps of OSIRIS-REx’s sample collection… a process called TAG:

HEATHER ENOS: So Tag is “touch and go.” What we mean by that is literally we’re reaching out with the arm of our device, and we are touching and going. We don’t land on Bennu, we actually literally kiss the surface with the end of the arm.

HEATHER ENOS: We’re kissing the surface somewhere between about 6-16 seconds. So, after all these years, it really all happens in less than 20 seconds.

HOST PADI BOYD: But leading up to that moment, Heather and the team will observe as OSIRIS-REx swoops closer and closer to the asteroid’s surface… preparing to make contact.

HEATHER ENOS: The day of TAG… it’s about a four and a half hour sequence..

HEATHER ENOS: We will leave orbit. Currently, we’re in a safe home orbit, we call it, around Bennu. And we will command the spacecraft to get out of its orbit and start to slowly descend onto the spacecraft onto the surface of Bennu…

RON MINK: The spacecraft is going to fire its thrusters and leave orbit and very slowly, approach the surface of Bennu… taking images along the way.

HOST PADI BOYD: OSIRIS-REx will use those images and compare them to an existing catalog of the site. This helps the spacecraft make sure it’s headed in the right direction!

HOST PADI BOYD: The whole time, OSIRIS-REx is going through the steps on its own. There’s no one controlling OSIRIS-REx in real time from the ground.

HEATHER ENOS: All of this is preloaded, autonomous and so we were not joy sticking it. We have literally uploaded the night before that morning of the sequence that tells the spacecraft and the instruments what to do. So once we hit go, everything becomes autonomous.

RON MINK: We’re going to send up a set of commands that basically tell the spacecraft what to do from leaving orbit until leaving the surface. So it’s all it’s on all automated commands. We don’t have a joystick, you know, or, uh, or an Xbox controller here on the ground to tell the spacecraft what to do, because there’s going to be at about a 15 to 20 minute, uh, delay in our signal. So we can’t talk to the spacecraft in real time that way.

HOST PADI BOYD: It’s all pre-planned…OSIRIS-REx is fully autonomous. It begins to descend closer to the asteroid’s surface..

HEATHER ENOS: At that point, we’re about 125 meters from the surface. And that’s our first opportunity to do our position and velocity checking and to make sure that our trajectory is on target.

HEATHER ENOS: So then we would continue to go down a little bit slower even yet, and when we do another check, which we call matchpoint. And that will be about 40 meters above the surface.

HEATHER ENOS:. And then we start to continue to slowly descend. We have what we call our “TAGSAM” arm, the touch and go arm, that is, we have then deployed and we slowly descend to the surface.

HOST PADI BOYD: OSIRIS-REx will aim to collect at least 60 grams of dirt and rocks, equal to about 30 sugar packets. It does that by stirring up the asteroid’s surface. Think about a reverse vacuum cleaner.

HEATHER ENOS: It’s a microgravity environment. So that is why we actually, we actually use a gas bottle, a very high purity nitrogen, to blow down on the surface in order to get the soil to move into the agitated because otherwise, with no gravity, things don’t move around. And so we’re forcing movement by blowing it down with the high purity nitrogen.

HEATHER ENOS: It’s a very clean, pristine gas, so we’re not also not contaminating the surface with anything we’ve brought along.

HOST PADI BOYD: After stirring up the surface, the samples will float up into a chamber. Once OSIRIS-REx successfully secures them, the spacecraft will slowly drift away from Bennu until it reaches a safe distance. And, it will stay there until its departure in March 2021, preparing for its return back to Earth.

HOST PADI BOYD: When OSIRIS-REx reaches Earth in 2023, it will drop the capsule with the samples packed inside into Utah’s west desert, where scientists will be waiting to collect it.

HEATHER ENOS: We really refer to it as the mission that keeps on giving. And the reason that we call it that is, we’re bringing back this precious material back to Earth, and it’s going to then be analyzed in laboratories. It, you know, at the macroscopic scale that we cannot do remotely in space…

HOST PADI BOYD: And getting these samples back to Earth will be a huge deal. It could literally change what we know about the history of our solar system.

HOST PADI BOYD: That’s why the day of TAG will be an emotional one for the whole team…


HEATHER ENOS: To get here? It really has taken a lot of time and a lot of people’s passion and a lot of sacrifice. So… it’s… you become personally attached to the spacecraft. It becomes human. The instruments become human. And, it’s not just a team after many years of sharing this hard work and sacrifices and common passion with your team that really becomes your family.


RON MINK: We hear a lot about the planets, Mars and Venus and Mercury, there’ve been fabulous missions to all those objects and some pretty incredible science and some incredible pictures, but what I love about asteroids and comets is that each one of them is their own unique, small world.

RON MINK: And there are, you know, literally tens of thousands or depending how, how small you want to look at millions of them in the solar system that we can explore.

RON MINK: And so, I look at Bennu as not just a, you know, a space rock, or the flotsam leftover from the formation of the solar system… but rather a unique world, all of its own that has its, its own beauty and its own secrets.

RON MINK: And also, in the case of Bennu, it’s its own dangers…

DANTE LAURETTA: OSIRIS-REx… It’s an extension of me in so many ways. It’s hard to explain. And it sends chills down your spine because you’re like, wow, we are an amazing species of human beings built this robot and we sent it out on this seven-year, billion kilometer journey to get this material so that we can study in our laboratories.

DANTE LAURETTA: OSIRIS-REx is all about inspiring the next generation of scientists and engineers and leaders to go after something big. Whether in space exploration or in any field that you’re passionate about…

DANTE LAURETTA: You can make it happen. And when it does happen, it makes your whole life worthwhile..


HOST PADI BOYD: This is NASA’s Curious Universe. The Curious Universe team includes Maddie Arnold, Micheala Sosby, Margot Wohl and Vicky Woodburn. Our executive producer is Katie Atkinson.

HOST PADI BOYD: Special thanks to Ryland Heagy, Rani Gran, Nancy Neal Jones, Lonnie Shekhtman, and the University of Arizona.

HOST PADI BOYD: If you liked this episode, please let us know by leaving us a review, tweeting about the show @ NASA, and sharing this episode with a friend… and, make sure you’re subscribed so you’ll get new episodes directly in your podcast feed.


HOST PADI BOYD: You can follow OSIRIS-REx as it completes it’s TAG attempt in real time. Go to To learn more about NASA’s asteroid hunter, follow @OSIRISREx on twitter.


HOST PADI BOYD: Still curious about NASA? You can send us questions about this episode or a previous one and we’ll try to track down the answers!

HOST PADI BOYD: You can email a voice recording or send a written note to Go to for more information.