Osiris-Rex probe succeeded in securing its asteroid dust

Artist's impression obtained thanks to NASA of the Osiris-Rex probe approaching the asteroid Bennu.

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Mission almost accomplished: the American probe Osiris-Rex succeeded in securing in an airtight capsule the soil sample of the asteroid Bennu that it had collected last week, NASA announced on Tuesday.

Its return to Earth is scheduled for 2023. “We have successfully completed the operation,” said Rich Burns, project leader on the NASA side, in a conference call.

The collector arm of the probe had collected a large volume of dust and fragments during a contact of a few seconds last Tuesday with Bennu.

But three days later, we learned that the flap of the collection compartment was unable to close, and fragments escaped from into space, endangering the entire mission, launched in 2016. In emergency, the arm this week transferred its cargo in a slow operation (about 36 hours) into the capsule, attached to the center of the probe, and the capsule cover successfully closed.

I've officially closed the Sample Return Capsule!

The sample of Bennu is sealed inside and ready for our voyage back to Earth.

The SRC will touch down in the Utah desert on Sep.

24, 2023. Thanks, everyone, for being a part of my journey #ToBennuAndBack pic.twitter.com/z75ITNiGBf

- NASA's OSIRIS-REx (@OSIRISREx) October 29, 2020

400 grams of secure particles

At that distance, each step took two hours, according to Sandra Freund of Lockheed Martin, as each message took 18.5 minutes to reach Earth, and the team wanted to verify each step before ordering the next.

Osiris-Rex will leave from around Bennu in March 2021, with a landing of the capsule scheduled for September 24, 2023 in the Utah desert in the United States.

The unanticipated valve forced NASA to cancel a weighing operation for the sample.

Scientists therefore do not know exactly how many Bennu particles the probe recovered.

Dante Lauretta, head of the mission, estimates that "tens of grams" were lost as a result of the leak.

But according to him, there remains at least 400 grams secure, according to the images, and probably a lot more.

“We're probably over a kilogram,” added Dante Lauretta.

Very low gravity

He said that the sampling found that the asteroid was covered with a layer of several meters of "cohesive" particles, due to the very low gravity, comparable to a ball pool.

Osiris-Rex probably sank 48 cm into the ground upon contact, without encountering any resistance, and if it hadn't turned on its thrusters to go back the other way, "we would probably have gone to across the asteroid, ”said Dante Lauretta.

“There is almost no force that holds the grains together,” he explained.

If an astronaut tried to step on Bennu, "he would sink to his knees or even deeper," the scientist said, fascinated, adding that these data would allow all the geology models of asteroids to be recalibrated.

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• Space

• Asteroid

• Probe

• Science

• Nasa