4bn year old Bennu dust lands gently in the Utah desert

It might have been a scene from a science fiction movie. Helicopters converging on an object fallen from outer space into a stark, desert landscape. People in gas masks cautiously approach, checking to see if it’s safe.  

But science fiction it wasn’t. This was the long-awaited return of NASA’s OSIRIS-REx mission, which launched in 2016, rendezvoused with asteroid 101955 Bennu in 2018, delicately scooped perhaps 250g of material from one of the few flat spots it could find, then made its way back to Earth to deliver its cargo to waiting scientists.  

Not that the object in the desert was the OSIRIS-REx spacecraft itself. It was simply a 45kg capsule released by the mother ship as it sped by Earth at 45,000km/h, already on its way to its next destination, a hoped-for rendezvous in 2029 with another asteroid, 99942 Apophis.  

But the capsule was by far the most important part of the mission, a precious payload that entered the Earth’s atmosphere like a fiery meteor, deployed its parachute, and gently plopped onto the mud flats of America’s Utah Test and Training Range slightly before 9am local time on 24 September, about 8km east of its target landing zone.  

That might look like it was a bit off the mark but, actually, the offset had been predicted in advance, based on weather forecasts of landing-day atmospheric density and wind speed.

“I was really excited,” says Mike Moreau, NASA’s deputy project manager for the mission. “[The forecasters] told me exactly where it was going to land, and that’s where it ended up.”  

Furthermore, it really did come down light as a feather, barely denting the soft desert surface, perfectly upright waiting to be collected…and rather amazingly right near a road that provided a convenient helicopter landing zone. “Boy did we stick that landing,” says Dante Lauretta, the mission’s principal investigator. “It didn’t roll, didn’t bounce, it just made a tiny little divot in the Utah soil.” 

The only glitch was that the first parachute, a small drogue designed to pull out the main chute, may have been a bit slow to fully deploy. But it worked, and more importantly, the main chute functioned perfectly.  

When Lauretta heard the main chute had deployed, he says, “I literally broke into tears because that was the moment I knew we made it home.” 

The caution in approaching the capsule wasn’t because scientists were afraid of the sample itself. Since the Apollo Moon landings, 3 countries – the US, Japan, and China – have all brought back material from other bodies in our solar system. Scientists knew that material from asteroid Bennu would be safe, in fact, Bennu is close enough to Earth that chips blasted off of it by collisions with smaller asteroids have probably reached us numerous times during the course of our planet’s history. The concerns were more prosaic. The Utah Test and Training Range is an active military base, where dangers might lurk near the landing site.  

“We are operating on a munitions range, so the first order of business is to ensure that the area around the capsule is safe and free of any hazards that such a range may pose,” Rich Burns, NASA’s program manager for the mission, said at a press conference 2 days before the landing.  

In addition, the canister had recently entered the atmosphere at a very high velocity. The heat shield that protected the sample from burning up would have hit a peak temperature in the vicinity of 2800°C (5,000°F), Burns said, and while it should have cooled substantially during the remainder of the descent, the retrieval team had brought along heat sensors and insulated gloves, just in case.  

Another concern was that the capsule contained a battery that might have ruptured. If so, it could have released toxic gases that would take a while to dissipate.  

As it was, it all went swimmingly. Nobody was blown up, nobody was burned, nobody was poisoned. Within minutes a member of the team had given the thumbs up and removed his gas mask, and an hour after that, one of the helicopters was carrying the capsule away to a clean room where it was flushed with nitrogen to drive out Earth air and soon being disassembled to retrieve the sample container proper, deep inside it.  

Once retrieved, the sample container will go to the Johnson Space Center in Houston where, if all goes well, it will be opened in a few days and preliminary results studies will begin perhaps as early as a week from Tuesday.  

One of the first tasks will be to weigh the sample. Right now, Lauretta says, the best estimate for how much material the spacecraft got is 250g, plus or minus 101g. That means there’s a chance there might be as much as 350g, but even if there is only 150g, that’s more than twice the 60g the mission promised to bring back. It’s also vastly more than any other sample retrieval mission has ever brought back from anywhere other than the Moon. “Even at the low end of the estimate, we’re well above our mission requirements,” Lauretta says.  

Portions of the sample will then be parcelled out to a wide range of scientists in the U.S. and elsewhere. “We have over 200 researchers using 60 different analytical techniques to interrogate this material,” Lauretta says. But much of it will be saved for study in years and decades to come with methods undreamed of today.  

“The curation team knows the importance of getting samples out as quickly as possible,” says Lauretta, who admits that he himself is itching to get into the lab and see what Bennu has to show us. “But it’s also about the legacy, and the legacy is that long-term collection.”

“Those are going to be a treasure for scientific analysis for years and years to come, to our kids and our grandkids, and people that haven’t even been born yet,” says Lori Glaze, Director of NASA’s Planetary Science Division. “They are truly gifts that keep on giving.”  

Those are going to be a treasure for scientific analysis for years and years to come

Lori Glaze

The mission, she adds, is part of a larger NASA project to study asteroids and other small bodies throughout the Solar System, looking for clues to how our Solar System formed – clues she describes as relating to various chapters of “our origin story.” In the case of the Bennu, she says, “Scientists believe that [it] is representative of the Solar System’s oldest material, forged in large, dying stars and supernova explosions” – that is, our origins all the way down to the atomic level. 

The one fly in the ointment is the threat of a US government shutdown on 1 October if Democrats and Republicans fail to agree on urgently needed funding measures. Right now, that looks likely to many Americans, but NASA isn’t going to let it threaten the safety of a sample that took 7 years and nearly $1 billion to obtain. If the shutdown happens, Glaze says, it might disrupt the schedule, but won’t endanger the sample. “This sample has waited for more than 4 billion years for humans to study it,” she says, “and if it takes a little longer, I think we’ll be OK.”