IRA FLATOW: This is Science Friday. I’m Ira Flatow. Ever since an asteroid slammed into the Earth, wiping out the dinosaurs, we’ve wondered if there’s another asteroid like that one lurking out there with our name on it. Well, it turns out there might be. It’s called Bennu. And it’s on course to possibly hit us in 2182.

I was reminded of this horrifying possibility in the opening pages of The Asteroid Hunter by Dante Lauretta. His memoir takes us on an awesome journey behind the scenes of a mission in 2016 that sent a probe called OSIRIS-REx all the way to Bennu and brought back a sample six months ago. This mission was a huge success. And scientists have been hard at work picking apart all that space dust.

Dr. Dante Lauretta, author of The Asteroid Hunter– A Scientist’s Journey to the Dawn of Our Solar System, is a planetary scientist at the famed University of Arizona in Tucson. And he joins me now. Welcome to Science Friday.

DANTE LAURETTA: Thank you, Ira. It’s great to be here.

IRA FLATOW: Nice to have you. You called Bennu the, quote, “the most dangerous rock in our solar system.” Tell us why you think so.

DANTE LAURETTA: Well, Bennu is a near-Earth asteroid that’s over 1,600 feet in diameter. That’s taller than the Empire State Building. And as a near-Earth asteroid, its orbit crosses that of our planet. So it has a nonzero chance of impacting the Earth. And that event, if it’s going to occur– and I want to make sure listeners understand, it’s a probability– it will be on September 24, 2182. It has the highest probability of impacting the Earth of any object that we know of in the solar system. That’s why I call it the most dangerous rock.

IRA FLATOW: And how would that collision compare to what killed the dinosaurs?

DANTE LAURETTA: If Bennu were to impact the Earth, it would be a much smaller event than the dinosaur extinction-level event. It wouldn’t be a global catastrophe. It would be a regional disaster.

It would take out a large city. That’s about the scale that we’re discussing. And effects would be felt for hundreds of miles from around the impact site. And it would be an enormous change in terms of the atmospheric composition for a while. It would be dusty, kind of like when a big volcanic eruption goes off.

IRA FLATOW: So why did you choose Bennu for this mission? Was it because of this impending encounter and possibly going there to change its direction?

DANTE LAURETTA: The choice of Bennu as the target of the OSIRIS-REx mission was really driven originally by engineering constraints. We were planning a mission to leave the Earth, rendezvous, and spend a significant amount of time around an asteroid, collect a sample, and bring it back. When you look at the possibilities, you very quickly zero in on the near-Earth asteroids because they’re the most accessible. And the timeline for that round-trip journey is the shortest.

So it was a very practical decision initially. But there were multiple asteroids on the order of a couple dozen that were fitting all of those engineering constraints. Bennu rose to the top of the list because it’s really dark. It’s one of the darkest objects in the solar system.

And for me, the science is really driven not by that impact hazard, which is important, but by the fact that these are ancient rocks from the dawn of our solar system. And when they’re dark and black, we think they’re full of carbon. And I’m particularly driven by understanding the origin of life and the role such carbon-rich asteroids may have played.

IRA FLATOW: Yeah. And you call Bennu the trickster asteroid. What do you mean by that?

DANTE LAURETTA: Asteroid Bennu challenged us every step of the way. It was an amazing journey to a world that nobody had ever been to before. And as we were planning and designing the spacecraft, we were relying on telescopic data to inform us about the nature of the asteroid surface.

And mistakenly, we had assumed or inferred that Bennu’s surface was smooth and sandy and beach like. And it was going to be pretty easy to get down and grab a sample and get out of there. And boy, was that not the case. We were totally spoofed by our interpretations. The surface was rugged and rocky and covered in giant boulders. Quite honestly, it was frightening when we saw the images show up as we approached the asteroid.

Not only that, but as soon as we went into orbit, Bennu started exploding and throwing particles, some of them as big as softballs, off its surface and into orbit. We were really scared and, quite honestly, freaked out for a little while that this was going to be a hazardous environment, and we might not be able to operate safely there.

When we contacted the asteroid surface to collect a sample, it was soft like water or quicksand. And it just flowed away. And we sunk in over 50 centimeters, about the length of my arm, deep into the asteroid. And quite honestly, if we had and fired our rocket engines to back away, I think we would have lost it. It would have just disappeared into the subsurface of the asteroid. None of that is what we expected when we started this journey.

IRA FLATOW: Yeah, because you expected a Mars-like landing, right?

DANTE LAURETTA: Absolutely. We were thinking a hard surface. We had even talked about having a lander that could stay on the surface and do extended operations. We were really thinking of a planetary-like environment.

And what we learned are these relatively small asteroids, they’re like fluid of rubble. They’re just droplets, barely held together by their own microgravity. It’s a whole different realm of astrophysics.

IRA FLATOW: That’s amazing. And now, this isn’t the first asteroid sample ever collected, but what makes this one special?

DANTE LAURETTA: OSIRIS-REx returned NASA’s first samples of an asteroid. And we targeted an object that was rich in carbon and in water. So it’s driving right towards our origins investigations.

And I think most importantly, we returned a lot of sample, over 4 ounces or 121 grams of material, more than twice what we promised NASA we would bring back. And for sample analysts like myself– I’m trained as a geochemist– that’s a lifetime of material and more. We have so much sample that it will be studied for decades by generations well into the future.

IRA FLATOW: I was surprised when you talked about that on the trip back to Earth, you discovered that the samples were literally leaking out of the spacecraft, leaving a trail behind.

DANTE LAURETTA: Yeah, I think that’s another instance of the trickster Bennu really messing with us. It turned out there was a large stone, about over an inch and 1/2, or 3 and 1/2 centimeters. That was jamming open a protective cover. And particles were leaking out.

Right after our success of pulling off this historic feat of collecting an asteroid sample, we were in panic mode. And it was a crisis. And we had to act rapidly to save as much sample as possible.

IRA FLATOW: Take me back to that day, September 24, 2023, the day the sample came back. And walk me through the events of that day, how you were feeling. What was going on in your mind?

DANTE LAURETTA: Oh my goodness, September 24, 2023, that was the culmination of almost 20 years of effort by me and by an enormous team of people from all over the world to make this a success. I woke up at 1:30 in the morning. I wear a fitness tracker. My heart rate was pounding at 120 BPM, more than twice what I normally see when I wake up. So I knew it was just an anxiety-ridden day.

We had to release the capsule. We were talking to the spacecraft. That’s why I was up that early. And it wasn’t guaranteed that we were going to release it. We might have flown by the Earth and hung on to it, especially if there were safety reasons, i.e. we were off course.

But fortunately, everything went according to plan. The capsule was released about a quarter of the distance to the moon, over 60,000 miles away. And it’s a dumb capsule. It is like a football, an American football. It’s spun up and tossed. And we’re targeting the end zone, which was the Utah Test and Training Range outside of Salt Lake City.

A few hours later, I was in a helicopter. We were heading out towards the anticipated landing site. And I could hear the range command officer making the calls as they were tracking the capsule passing through the atmosphere.

And we reached a critical altitude of 100,000 feet, where the first parachute was supposed to deploy. And no chute was called. And my mind immediately flashed back almost 20 years, to 2004, where we had lost a capsule almost exactly like this one because the parachute didn’t open. And it crashed in the Utah desert.

And for the next three minutes, I was just thinking about, how am I going to handle this? I have to get out of this helicopter. NASA’s got live TV right there flying above us. And I’m going to have to maintain my cool.

And then, thank goodness, three minutes later, the main chute deployed, stopped that downward motion, and we came in for a soft landing. And seeing that capsule on the ground, it was like seeing an old friend, one that I hadn’t seen for seven years, a little charred from its passage through the atmosphere, but pretty healthy and in good shape. It was an amazing moment. I will never forget.

IRA FLATOW: And you write that for the first time in three years, this cosmic vault was unsealed, revealing hints of stories written billions of years ago far from Earth. And that’s really what you were looking for, right?

DANTE LAURETTA: Absolutely. I am looking for the rocks that tell the story of why the Earth is a habitable planet. Why do we have oceans? Why do we have the atmosphere that we do?

And most importantly, how did life take hold here? And did it happen anywhere else in our solar system? And the samples from Bennu formed before any of those planets existed. And we believe, and it’s looking good as we analyze the sample, that it delivered the essential building blocks for life.

IRA FLATOW: Have you learned anything so far?

DANTE LAURETTA: I am really excited by these samples. They’re made of a mineral called serpentine, which is a clay mineral. And when we look on Earth where such minerals are forming, it’s at the mid-ocean ridge, at the hydrothermal vents, especially what we call the white smokers. And that’s pretty exciting because that’s the kind of environment we think may have been essential for the origin of life.

There’s white, crusty material, kind of like salts, adhering to the surface. Those are really rich in phosphorus. And that’s exciting because phosphorus is essential to all life on Earth. It makes the backbone of our DNA, for example. It’s the primary energy-carrying molecule. It’s composed of partly phosphorus. And it makes our bones and teeth. So eventually it ended up in our structure. And it’s the least abundant of the six major what we call biogenic elements.

It looks like an evaporite from a body of liquid water. So I’ve said, maybe we’re dealing with a fragment of an ocean world. When we look at the icy satellites, for example, Enceladus, which is a moon around Saturn, we see geysers erupting from the icy shell, indicating liquid water underneath its surface.

Bennu may actually be fragments of something like that from the early days of our solar system. We’re still evaluating that hypothesis, but it’s looking really interesting. And at least it’s driving a lot of our thinking right now.

IRA FLATOW: You say that among the numerous lessons, paramount were persistence and resilience. What do you mean by that?

DANTE LAURETTA: The first seven years of this program were spent writing proposals and getting rejected to NASA.

IRA FLATOW: Really? You couldn’t convince anybody that this was important?

DANTE LAURETTA: Eventually we did, but it took persistence. Every year, we would pick ourselves back up, work on another proposal, get farther, get better, build that team cohesion. It wasn’t until May of 2011 that we got formal approval from the agency to fly the program.

IRA FLATOW: Wow.

DANTE LAURETTA: And then that’s five more years of designing, building, and then ultimately launching the spacecraft, and seven years in flight from launch to that sample landing on the Earth. It’s amazing to me to think I’ve been working on this for 20 years because I never imagined that when I first signed on to the program way back in 2004.

IRA FLATOW: This is Science Friday from WNYC Studios. Your book reads like a love letter to the universe, to our solar system, to exploration. How did you come to study space in the first place?

DANTE LAURETTA: When the book starts, I’m a young undergraduate student here at the University of Arizona and really looking for a path in life. And I was incredibly fortunate to get a NASA undergraduate research space grant and to get assigned to the search for extraterrestrial intelligence.

And that was such an eye-opening moment for me because I realized, first of all, there are other people like me who are thinking about who’s out there? What is the solar system made out of? How did it come to be? And are there other places like the Earth where life may have taken hold? And so I got really excited by the idea that you could have a job thinking about and making progress towards answering those questions.

IRA FLATOW: You write this as a memoir. It’s very interesting. And you write about your feelings. And I can tell from reading as you write about two twin atoms that were flung apart billions of years ago, tell me that story and why they have to do with you.

DANTE LAURETTA: The story of the two carbon atoms is the underlying cosmic imperative that I feel inside me. I was driven to do this, to fly this mission, to lead this program, to get those samples. And I personify that as there’s a carbon atom that’s inside me, and there’s a carbon atom in Bennu. And they’re driven to reconnect because they were formed together in the same star well before our solar system existed.

And it’s a way to bring the readers through that long history. For 4 and 1/2 billion years, all of the carbon atoms in me, in you, Ira, in all of the listeners, they all were formed inside stars. They’ve all gone through the history of life on Earth for billions of years. And I wanted to give people that sense of connection to the cosmos and to all of the components that come together to make this amazing habitable world that we live in.

IRA FLATOW: Any way to sum up what this entire mission has meant to you in a larger scale?

DANTE LAURETTA: For me, the mission really shows the power of unity and cooperation when humans get together and dream up what sounded impossible. When we were talking about this mission in 2004, it sounded crazy. And I was like, we can do this if we agree, we’re motivated, we’re unified, and we’re focused. We can do amazing, positive things. And I hope that’s a lesson that resonates out into the world because we sure need that attitude right now.

IRA FLATOW: Now, there are two parts to the spacecraft. There is the return of the sample, but the spaceship itself is still out there in space, right? Is it headed anyplace else?

DANTE LAURETTA: Yeah, we built a really good spacecraft. It’s a satellite. It’s got solar power. It’s got rocket engines and some fuel left over and a fantastic array of cameras and other instruments for analyzing asteroid surfaces.

And you’re right, the capsule carrying the sample landed on Earth. But most of the vehicle is in outer space. And it’s in orbit around the sun. And we found a path to get to another near-Earth asteroid, one that is also potentially hazardous, called Apophis.

And one of the things I’m most proud of is I stepped down as the leader of the extended mission, which is now called OSIRIS-APEX, and handed that over to an early-career scientist, Professor Dani DellaGiustina. She’s one of the heroes in my book. I met her in 2005 as a freshman. And she grew up on this program and is now leading the next generation off into the future to study a new asteroid and improve humanity’s chances of dealing with an asteroid impact should that be necessary.

IRA FLATOW: You’re saying “the asteroid impact.” Is it possible, now that we’ve had a dry run to Bennu, that we could go back and maybe nudge it off its path?

DANTE LAURETTA: Well, think, we’ve got over 160 years to deal with it. And so yeah, absolutely. Humanity is entirely capable of moving the asteroid.

Or I think another area and part of the mission is resources. You could mine it. And there’d be nothing left by the time it crossed the orbit of the Earth in 2182.

IRA FLATOW: Wow. I hadn’t thought about that. That’s very interesting. Well, we’ll get on to that in another show, OK, Dante?

DANTE LAURETTA: Sure.

IRA FLATOW: Thank you for taking time to be with us today. It is a wonderful book.

DANTE LAURETTA: Thank you so much, Ira. It was a real pleasure.

IRA FLATOW: Dr. Dante Lauretta, planetary scientist at the University of Arizona and principal investigator of the OSIRIS-REx mission, based in Tucson, Arizona. You can read an excerpt from his new book, The Asteroid Hunter, at sciencefriday.com/asteroid.

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