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NASA's 'OSIRIS-REx' Preparing For Touchdown On Asteroid

NASA's OSIRIS-REx will attempt to touchdown briefly on the asteroid Bennu in order to collect samples Monday.

Monday afternoon, NASA will attempt its first-ever sample collection from an asteroid in hopes of learning more about the origin of life on Earth. The daring mission is gathering worldwide attention. WAMC’s Jesse King spoke with NASA scientist Danny Glavin for a rundown.

The hype is real for NASA today, as OSIRIS-REx prepares to tap the surface of the rocky asteroid Bennu. It’s a long-awaited and precarious mission, in which the van-sized spacecraft already spent two years lying in wait in the asteroid’s orbit, flying low for high resolution photos and the occasional touchdown rehearsal. Glavin says the main event, however, will only last a few seconds.

"We're gonna touch the surface for about five seconds, we're gonna fire a bottle of pressurized nitrogen gas to stir up the dirt and the soil on the asteroid, and then collect it in this sample collector which kind of looks like an old 1957 Chevy air filter," Glavin explains. "So that material will get collected in the collector, and then we'll back away — fire some thrusters on the spacecraft to back away from the asteroid to a safe distance — and then assess how much material we have. We're hoping to collect about 2 ounces, so think 30 packets of sugar. But if we fill the collector, we might get lucky and get like a 4-pound bag of flour. So we're hoping we fill that container up and really capture some of this precious material from the earliest stages of the solar system."

How difficult is a mission like this? OSIRIS-REx arrived at Bennu in 2018, so I imagine there's a lot of planning going on here. 

Oh, there's a ton of planning. The navigation folks are just amazing in what they've had to do. When we first imaged the asteroid, we thought it would be very sandy and smooth, kind of like a beach. But as we got closer and the images became more clear — oh my God, there were building-sized boulders strewn out about the surface. Which, of course, makes it very challenging to get down to the surface — we want to protect the spacecraft. We've identified a spot today called Nightingale, which is a crater in the northern hemisphere. There are a lot of rocks around this crater — I'm not gonna lie, one of them is called Mount Doom, which is a two-story-high boulder — and we're trying to get in to a 26-foot-wide tag zone. That's what we're aiming for here. So imagine trying to take this 15-passenger van spacecraft and parking it in three parking lot spaces. That's about the room we have, [there's] not a lot of room for error here. 

And this entire sequence has to be autonomous, because there's an 18.5-minute delay for the signal to get from the spacecraft to the Earth, we're over 200 million miles away. But we've got the software on board that will navigate us safely to the surface, and if we detect any hazards or boulders, we'll do a backaway burn just to keep the spacecraft safe and live for another sampling attempt. 

Tell me a little about why NASA has chosen this asteroid for this mission. What's special about Bennu? 

You know, there are a lot of asteroids out there — there's over a million asteroids in the asteroid belt — but only a handful of them really have orbits that are similar to the Earth, that we can access with spacecraft, so we can get to the asteroid easily and get back. Bennu is one of those. What excites me most about Bennu is that it's carbon-rich. Carbon is — you know, all life on Earth is made up of carbon — it's a fundamental building block of life, if you will. So we think that by collecting samples from Bennu and getting them back to labs on Earth, we can really learn about how the solar system formed, how the planets formed — but even, potentially, how life on Earth started. 

Did I read right, that Bennu also has the possibility of colliding with Earth one day? 

Yeah, so this is another reason that Bennu was selected. It is a potentially hazardous asteroid. NASA defines these potentially hazardous asteroids as asteroids that have orbits that are similar to the Earth's, that cross the orbit, and that are large — so over 140 meters in diameter. And Bennu is about 500 meters in diameter, so it certainly fits that bill. We've looked at this carefully, and it turns out the risk is pretty low. There's a very small probability beginning in 2175, so a long time from now, that Bennu could hit the Earth — but that probability is very, very small, it's only like [a] 1 in 2,700 chance.

We want to go to these asteroids to learn how they're made up, so we can plan. If there's a future asteroid that's on a trajectory to Earth, we want to be able to understand how to move them, and to do that you really need to understand how they're made up and put together. And OSIRIS-REx is gonna give us a lot of that very important information. 

NASA is planning a mission called DART — the Double Asteroid Redirect — which will launch next year [and] go to an asteroid called Didymos. And actually, for the first time, we're gonna intentionally crash it into one of the asteroids of the Didymos system, to see how it perturbs the other asteroid. So we are thinking about the future, this is part of our security. If there is an asteroid that's on a trajectory to hit the Earth, you know, how are we gonna go out there and deflect it so it doesn't? 

OK, so today you're hoping to grab a sample. How long is that probably going to take, and when will you know whether you've gotten anything? 

The entire TAG sequence, the touch-and-go sampling, takes about 4.5 hours. As I mentioned earlier, the actual time that we're touching the surface is very short, so five to 10 seconds or so. We're not gonna know today whether or not we collected sample. We'll get confirmation from the spacecraft that it's safe, that we touched the asteroid, but it'll take a day or two to figure out how much material we actually collected. So hopefully by this weekend, maybe early next week, we'll know whether or not we collected those 30 sugar-packet-sized sample, or if its something much larger, like a 4-pound bag of flour. I'm hoping for a larger sample, more is definitely better. 

What are you most looking forward to learning about this mission? 

You know, I made a career out of studying meteorites looking for the building blocks of life. For decades I've been doing this, and one of the big frustrations is that all of these meteorites are contaminated. As soon as they hit the atmosphere and get heated up and hit the Earth they get contaminated with all the organics and bacteria on the Earth, and that makes it difficult to look at the chemistry that led to life — it complicates that science. So the samples returned from Bennu by OSIRIS-REx will provide us with the first samples that are prestine. So prestine samples of the asteroid that have never seen the Earth, right, and haven't been contaminated. And I'm hoping that we're gonna be able to finally answer these questions about how life started by looking at this really primitive and prestine material.


NASA will air live coverage of OSIRIS-REx’s descent to Bennu on its website starting at 5 p.m. ET today, with the touch-and-go maneuver scheduled for just after 6 p.m. Danny Glavin is an astrobiologist with NASA's Goddard Space Flight Center in Maryland. 

Jesse King is the host of WAMC's national program on women's issues, "51%," and the station's bureau chief in the Hudson Valley. She has also produced episodes of the WAMC podcast "A New York Minute In History."
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