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NASA’s OSIRIS-REx survived its risky mission to grab a piece of an asteroid


NASA's OSIRIS-REx spacecraft is a collector of cosmic rocks. Cheers erupted from mission control at 6:12 p.m. EDT on October 20, when Earth scientists got the news that the spacecraft had gently slammed an asteroid close to Earth called Bennu and picked up some of its rocks to return to Earth.

“The spacecraft did everything it was supposed to do,” mission lead researcher Dante Lauretta of the University of Arizona in Tucson said on a NASA television program. "I can't believe we really got this out."

OSIRIS-REx arrived in Bennu in December 2018 and spent almost two years making detailed maps of the characteristics and composition of the asteroid’s surface 500 meters wide (SN: 10/8/20). Earth observations suggested that Bennu should be smooth and sandy, but when OSIRIS-REx arrived, he found a treacherous, rocky landscape.

The team selected a relatively soft patch on a crater called Nightingale. However, the place was not without dangers: the team was so worried about an especially large rock nearby that they named it “Mount Doom” (SN: 12/12/19).

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Luckily, the spacecraft did not need to land completely in the crater to complete its mission. When positioned just above the surface, OSIRIS-REx extended a robotic arm with an instrument called a TAGSAM at the end, for the Touch-And-Go sample acquisition mechanism. The instrument lightly touched the asteroid for several seconds and launched an explosion of nitrogen gas to disturb surface dust and pebbles. Once those little rocks were lifted, some of us waited for them to go to the sample collector.

Because the Earth's signals took 18 and a half minutes to reach Bennu, the spacecraft performed the sampling sequence autonomously. When the mission team received the signal that the spacecraft had finished its work and withdrew at a safe distance from Bennu, the team members pumped their arms in the air, cheered and sent each other away and hugs.

OSIRIS-REx is not the first spacecraft to take samples from an asteroid. That distinction corresponds to the Hayabusa mission of Japan, which brought back grains from the asteroid Itokawa in 2010 (SN: 14/06/10). An encore to that mission, Hayabusa2, collected samples from the asteroid Ryugu last year and is on its way to landing in Australia in December (SN: 22/02/19).

But OSIRIS-REx tried to collect much more material than Hayabusa2 did. Hayabusa2 hoped to collect 100 milligrams; OSIRIS-REx targets a minimum of 60 grams, or just over two ounces.

Hayabusa2 scientists have no way of knowing how much material he collected until the spacecraft returns to Earth. But the OSIRIS-REx team plans to discover it using the spacecraft itself. On October 24, the ship will extend its arm and rotate its entire body. The difference in the way it rotates before and after sample collection will reveal the mass of the sample.

OSIRIS-REx will return to Earth in 2023, where scientists will analyze the rocks in hopes of unlocking details of the history of the solar system and the origins of water and life on Earth (SN: 15/1/19).



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