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A NASA spacecraft successfully touched down

on a skyscraper-sized asteroid 200 million miles away, in order to collect a small amount of rock and dust that can then be returned to Earth.

, is about as big as a 15-passenger van, and it was aiming for a specific spot inside a boulder-strewn crater. The maneuver was tricky and fraught with peril, as the spacecraft had to reach a safe area that's only the size of a few parking spaces.

Because of the coronavirus pandemic, only a skeleton crew was at the spacecraft's operations center at the Lockheed Martin Space Systems Facility in Littleton, Colo., to monitor the probe's progress.

They were only observers during the event, because it took more than 18 minutes for messages from the spacecraft to reach them. They received no images — only a trickle of data came back from the probe as it descended and relied on its on-board systems to survey the terrain and assess the hazards.

The team jumped up and cheered when they learned that the probe had determined that it was safe to proceed to the surface. Moments later, "touchdown" was declared.

"I can't believe we actually pulled this off," said 

 of the University of Arizona, the principal investigator for the mission, who said he was feeling "transcendental."

"It's almost hard to process everything that's happening right now," said Lauretta.

Quickly, word came from the spacecraft that it had safely backed away from the surface, and everyone cheered again. In the coming days, researchers will get images and other data from the spacecraft that will let them assess how much of the asteroid it nabbed.

This spinning top-shaped asteroid, named 

, is one of close to a million known asteroids in our solar system. Scientists want to study it in part to improve our planetary defenses against potentially dangerous space rocks. Bennu, for example, has a small chance of someday striking Earth.

"Our most recent calculations suggest that it has about a one in 2,700 chance," says Lauretta. "The good news is such an impact would not occur for at least 150 years, and part of the OSIRIS-REx mission is to better understand that impact probability."

Scientists also want to study asteroids like this one because they're thought to be nearly pristine time capsules — leftover bits from the early solar system that have gone undisturbed for billions of years.

"Asteroids are relics of the earliest material that formed the planets," says 

, director of NASA's planetary science division. "They hold key information to unlocking our understanding of how the solar system formed and how it evolved."

This mission is NASA's first attempt to collect a sample from an asteroid and bring it back to Earth, but others have tried it before. Japan's space agency has a 

 that's currently on the way home with a small amount of material taken from

"There are some key differences," says Lauretta. He explains that NASA's rock collection equipment can hold onto a larger sample. While Japan's probe might bring home just tens of milligrams of material, OSIRIS-REx is capable of collecting up to 2 kilograms, or almost 4 1/2 pounds.

OSIRIS-REX launched in 2016 and has been orbiting the asteroid since 2018. As soon as it arrived there, scientists got a close-up look at this space object and realized that Bennu was nothing like they thought. They'd expected the surface to be relatively smooth and covered with fine-grained material like sand. Instead, they saw boulders everywhere.

"When I first saw the rugged surface of asteroid Bennu, I knew we were in for a real challenge," says Lauretta.

The team spent a year mapping the asteroid in exquisite detail, finally settling on two craters where it looked possible to touch down: a primary target named 

The spacecraft did low flybys to get high resolution imagery, in order to build 3D maps that can used by its onboard navigation system. In April and August, the probe did two rehearsals, dipping down as close as about 130 feet above the asteroid's surface.

The sample collector is at the end of an 11-foot-long arm and looks "a bit like an air filter you might see in an older car," says Sandra Freund, OSIRIS-REx mission operations manager at Lockheed Martin Space. It's currently unclear how much dust and rock the collector managed to ingest.

The team should have enough information by October 30, however, to determine whether it's an acceptable amount to bring home or whether to go for an additional sampling attempt in January.

Eventually, whatever gets collected will be stowed in a secure return capsule, and the spacecraft will depart for Earth in March of 2021. Once it reaches our planet in September of 2023, it will release the sample return capsule, which will parachute down to Utah.

For Lauretta, who has worked on this mission for 16 years, it feels almost as if the spacecraft is part of the team. "We talk to it on a daily basis. It's kind of our eyes and our sensors, out deep in the solar system," he says. "We're going out there to retrieve this scientific treasure and bring it back to the Earth." 

Science

Nell Greenfieldboyce

Author

on the skyscraper-sized asteroid 200 million miles away, in order to collect a small amount of rock and dust that can then be returned to Earth. The rocks and dust could help us understand potentially dangerous space rocks and the history of the solar system.

A NASA spacecraft successfully touched down on the skyscraper-sized asteroid 200 million miles away, in order to collect a small amount of rock and dust that can then be returned to Earth. The rocks and dust could help us understand potentially dangerous space rocks and the history of the solar system.


A NASA spacecraft successfully touched down on a rocky asteroid

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