NASA’s OSIRIS-REx Brings Bennu Asteroid Sample to Earth

A brown-and-white capsule that spent the last seven years swooping through the solar system — and sojourning at an asteroid — has finally come home. And it has brought a cosmic souvenir: a cache of space rock that scientists are hungry to get their hands on.

On Sunday morning, those scientists waited eagerly as the pod shot through Earth’s atmosphere at thousands of miles per hour. It gently parachuted down into the damp desert landscape of the Utah Test and Training Range, about 80 miles west of Salt Lake City, at 8:52 a.m. local time.

The capsule’s landing is a major win for a NASA mission called OSIRIS-REX, which stands for Origins, Spectral Interpretation, Resources Identification and Security-Regolith Explorer. The spacecraft set out in 2016 to retrieve material from Bennu, a carbon-rich asteroid about 190 feet wider than the height of the Empire State Building. Researchers hope this pristine space dirt will reveal clues about the birth of our solar system and the genesis of life on Earth.

“This is a gift to the world,” said Dante Lauretta, a planetary scientist at the University of Arizona and the principal investigator of the OSIRIS-REX mission, at a news conference last month.

Bill Nelson, the administrator of NASA, said the mission proves the space agency “does big things. Things that inspire us, things that unite us, things that show really nothing is beyond our reach.”

The mission’s scientists endured many twists and turns, including a seven-year struggle to get the project greenlit by NASA. Their perseverance paid off as OSIRIS-REX became the first American spacecraft to retrieve material from an asteroid, bringing back a staggering amount of matter from space for scientists around the world to study. But the victorious final act means much more for the OSIRIS-REX team members, many of whom “grew up on this mission,” according to Dr. Lauretta.

“A little bit of us is on that spacecraft,” said Rich Burns, the OSIRIS-REX program manager at NASA Goddard Space Flight Center. “And a little bit of us is coming home with it.”

Bennu, a near-Earth asteroid, is currently many millions of miles from our planet. Like other asteroids, it is a geological relic of the protoplanetary disk — the swirling mix of gas and dust that eventually coalesced into planets — that surrounded our sun billions of years ago. One theory is that small worlds like Bennu seeded Earth with the prebiotic ingredients for life.

But it is difficult to test this idea using meteorites, pieces of asteroids that reach Earth’s surface, which are heated by the atmosphere and are then contaminated by microbes on the ground, Dr. Lauretta said.

This is not the first chunk of an asteroid brought back to Earth. In 2010, the Hayabusa mission, led by the Japanese space agency JAXA, managed, in spite of technical troubles, to recover less than a milligram of material from a near-Earth asteroid named Itokawa. A decade later, a follow-up mission, Hayabusa2, retrieved a few grams of space rock from Ryugu. With that sample, scientists have found evidence suggesting that asteroids had delivered water to the early Earth, and discovered the presence of uracil — a building block of RNA, a molecule that helps form proteins.

OSIRIS-REX’s delivery will provide an abundant new stock of space rock. The team anticipates about half a pound of unsullied asteroid dirt. Shogo Tachibana, a planetary scientist at the University of Tokyo who led the Hayabusa2 sample analysis and is now a co-investigator on OSIRIS-REX, has “no idea” whether Bennu will be anything like Ryugu — but it’s what he is most looking forward to finding out.

From the beginning, the mission was a marathon. In 2004, a group of American scientists submitted an application for what would become OSIRIS-REX. But NASA returned the project with the lowest ranking: Category 4, or “thanks, but no thanks,” Dr. Lauretta said. “The first proposal just bombed.”

The team tried again in 2007. This time, it scored a ranking of Category 1 — but was too expensive to win funding.

The third time was the charm. NASA selected the project in 2011. “So that began our real journey,” said Harold Connolly, a cosmochemist at Rowan University who joined OSIRIS-REX 15 years ago. The team spent another half-decade “making sure all our little ducks were in a row,” he said, including designing and building the spacecraft, mapping the trek to Bennu and plotting the science campaign.

OSIRIS-REX launched in 2016, embarking on a roundabout series of fuel-efficient loops before arriving at Bennu on Dec. 3, 2018.

The mission repeatedly faced the unexpected. “I call Bennu the trickster,” Dr. Lauretta said endearingly. “Because it has challenged us constantly on this program.”

Mission specialists expected Bennu’s surface to consist of smooth, sandy seas of fine particles. But as the asteroid came into focus, they found it was rocky and rough, with boulders, some 10 stories tall, sprinkled throughout. That made finding a place where the spacecraft could safely retrieve a sample from the surface riskier.

Engineers were troubleshooting that problem when Bennu threw them another loop: It was spewing rubble into space. That was “really exciting scientifically,” said Sandy Freund, the OSIRIS-REX program manager at the aerospace company Lockheed Martin. But “from an engineering standpoint,” the discovery posed a new problem.

The mission scientists frantically churned out calculations to make sure OSIRIS-REX was safe from being struck by the asteroid’s gravelly plumes. The operations team swiftly wrote new navigation software that could compensate for the rugged terrain on Bennu.

The next big hurdle was to select a sample site: a place where the spacecraft could safely fill its canister with fine grain regolith. That was made more difficult by the uneven ground of Bennu. Photos of the asteroid revealed some sandy regions — but only inside bowl-shaped craters. “We got to get inside one of those,” Dr. Lauretta said, to the distress of the operations team. “There’s nowhere else to go.”

The margin for error was small. Touch down wrong, and the spacecraft may have faced a fate like Hayabusa, which crash-landed on its asteroid. Or worse: OSIRIS-REX comes down on a slope and runs into what Dr. Lauretta calls “the banana peel scenario,” where it slips and falls into a crater.

After two years of surveying the asteroid, the mission team chose a spot it named Nightingale, near the asteroid’s north pole. In October 2020, OSIRIS-REX punched the surface of Bennu using a tool that was supposed to bounce off Bennu like a pogo stick.

But it did not exactly bounce as planned. Dr. Connolly recalled that he was shocked at how deep the instrument penetrated into the asteroid — about one and a half feet.

“We thought it would be a little more firm,” he said. “But it turns out gravity is basically the only thing that’s holding it together.”

The blow excavated a 30-foot-wide crater and blasted dusty debris into space.

The surprises didn’t end there. When the team checked to make sure it had collected a large enough sample, it found the chamber overflowing with regolith.

“We had overachieved,” Ms. Freund said. “It was wedged open and leaking into space.” Every movement of the spacecraft led to greater loss of Bennu’s dust, like the way salt comes out of a shaker.

The team immediately halted all planned maneuvers to prevent losing any more of its precious cargo. Instead, the crew rushed to stow what remained in the leaky chamber within the return capsule.

Six months later, OSIRIS-REX captured one last look at Nightingale and then began the two-year journey back to Earth. “It was definitely an adventure,” Dr. Lauretta said.

In the days leading up to the sample’s plunge into Earth’s atmosphere, Dr. Lauretta was having trouble sleeping. He tried to push away “all of the doom scenarios” like what happened with NASA’s Genesis probe that collected plasma from the solar wind. In 2004, it crashed into a Utah desert when the parachute for its return capsule failed to deploy. (Despite the rough landing, researchers were able to recover and analyze the sample.)

“And that felt like a gut punch then,” Dr. Lauretta said while squeezing a stress ball shaped like the OSIRIS-REX capsule. Approaching the latest sample return was “unlike anything I’ve ever felt before,” he added. “I feel like there’s an electric wire at the base of my spine, just tingling.”

Michael Puzio, an engineering major at North Carolina State University, also felt “a bit terrified” leading up to the sample’s return. In third grade, Mr. Puzio won a contest to name the asteroid Bennu. It ignited in him a love of space and a dream to be an astronaut.

“But I think it’s in good hands,” Mr. Puzio added. The mission team “is pretty good at math, so I’ve heard.”

At 2 a.m. local time on Sunday morning, the OSIRIS-REX command team in Littleton, Colo., evaluated the landing conditions and voted to order OSIRIS-REX to release the capsule at 4:42 a.m.

Four hours later, it entered Earth’s atmosphere. A high-altitude camera on a NASA plane captured the fireball streaking across the lavender sky as the capsule’s heat shield protected the cargo from temperatures of more than 5,000 degrees Fahrenheit.

The first, smaller parachute should have inflated 19 miles above the surface, though engineers have not yet been able to confirm that it did. The larger main chute deployed at a higher altitude than planned, which led to a landing three minutes earlier than expected.

The capsule, charred from its journey through the atmosphere, landed on its nose. About half an hour after the landing, a mission team reached the capsule and began the procedures to recover it.

“We scored the first touchdown today,” said Tim Priser, an engineer at Lockheed Martin, at a news conference following the capsule’s landing.

Dr. Lauretta was tuned in to the “pulse-pounding” final moments while riding in a helicopter to the landing site when he heard confirmation that the main chute had deployed.

“I literally broke into tears,” he said at the post-landing news conference. “That was the moment I knew we made it home.” Approaching the capsule felt like “seeing an old friend that you haven’t seen for a long time,” he added.

For Dr. Lauretta, the safe return is both a professional achievement and a personal one: Michael Drake, the first principal investigator of OSIRIS-REX, died only five months after the mission was funded. “You need to be the one that finishes the dream,” Dr. Lauretta said Dr. Drake told him. “And so I did.”

The capsule and its contents were stowed in a temporary clean room near the Utah landing site and are to be transferred on Monday to Johnson Space Center in Houston. Scientists plan to crack open the capsule on Tuesday for what Dr. Connolly calls a “quick look” analysis. In October, the sample team will reveal the first results to the world, including Bennu’s composition and how it compares with material brought back from the asteroids studied by the Japanese missions. (A potential government shutdown on Oct. 1 may delay those plans.)

“It’s the end of a journey and the beginning of a new one,” Dr. Lauretta said. “We’re going into the atomic realm.”

Dr. Connolly struggled to express what it meant to him that the mission had come back to Earth.

“I feel like a little kid again,” he said. “I’m just so happy to be able to tell the story that these rocks contain.”

Scientists will spend the next two years conducting a more robust investigation of the asteroid. Small portions of the sample will be handed off to JAXA and the Canadian Space Agency.

Up to 75 percent of Bennu’s regolith will remain in storage so that scientists in the future can “work on the sample with new techniques that we don’t even know exist yet,” Dr. Connolly said.

“These samples are an amazing treasure trove for generations,” said Eileen Stansbery, a chief scientist at NASA’s Johnson Space Center, at the post-landing news conference.

The OSIRIS-REX mission may have come to an end, but the spacecraft remains fully operational in space. It will next visit Apophis, another near-Earth asteroid that was once seen as a major threat to crash into Earth. More recent measurements determined that the asteroid will pass by Earth in 2029, within one-tenth of the distance to the moon.

The new project is named OSIRIS-APEX, where APEX means Apophis Explorer, and may provide information for mitigating more hazardous encounters with asteroids.

The leader of OSIRIS-APEX will be Dani Mendoza DellaGiustina, a former undergraduate student of Dr. Lauretta’s who is now a planetary scientist at the University of Arizona. It is another example of how the journey to Bennu and back has raised a generation of scientists in the field.

“I’ve been working on some incarnation of this mission basically my entire adult life,” Dr. DellaGiustina said. She added that while she was “super stoked” about OSIRIS-REX’s return, “for me, it’s definitely not the last hurrah.”