NASA's OSIRIS-REx spacecraft is returning with its first-ever asteroid sample

Regolith scraped from the surface of Bennu will reach Earth on 24 September

NASA is preparing to nab its first-ever asteroid sample as the OSIRIS-REx spacecraft drops a capsule containing fragments of the potentially hazardous object Bennu onto Earth.

Launched in 2016, OSIRIS-REx, which stands for the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, took two years to reach Bennu. When it rendezvoused with the rhombus-shaped asteroid, it spent two years studying its surface to choose a perfect place to land and collect regolith.

In 2020, it descened to the asteroid and scooped up more material than expected. The granules were carefully stowed away in its sample return capsule, and the spacecraft headed for home. Now, after seven years, it is finally delivering its scientific payload. 

Evidently NASA does not have an Amazon Prime account.

On September 24, OSIRIS-REx will eject its sample return capsule as it passes above our home planet. The device will barrel towards Earth and reenter the atmosphere at 0842 MDT (1542 UTC), reaching 27,650 miles per hour. After about two minutes, it will deploy a parachute to slow down to touch down in the desert in Utah.

On Wednesday, leaders from NASA working with the US military performed the final dress rehearsal for the return mission, dropping a dummy sample capsule from an aircraft to test its ability to land at a drop zone within the Department of Defense's Utah Test and Training Range. 

"We are now mere weeks away from receiving a piece of solar system history on Earth, and this successful drop test ensures we're ready," Nicola Fox, associate administrator of NASA's Science Mission Directorate, declared in a statement. "Pristine material from asteroid Bennu will help shed light on the formation of our solar system 4.5 billion years ago, and perhaps even on how life on Earth began."

When the capsule, estimated to be holding as much as 250 grams of regolith, lands on Earth, it will be carefully retrieved and flown to a clean room on the military range. The pod will be disassembled and shipped to NASA's Johnson Space Center in Houston, where the sample will be documented, stored, and distributed to scientists around the world. 

OSIRIS-REx is NASA's first asteroid return mission. Japan's Aerospace Exploration Agency was the first to collect space rocks in its Hayabusa mission to 25143 Itokawa from 2003 to 2010.

Asteroids are thought to be chunks of leftover material forged during the planets' formation in the solar system. Astronomers believe that understanding their properties and chemical makeup will reveal secrets of how the planets and even life on Earth formed. 

After OSIRIS-REx jettisons its capsule, it will begin a new chapter. The spacecraft's second mission, dubbed OSIRIS-APEX, has a new target: Apophis, another potentially hazardous object that is expected to make a close approach to Earth in 2029. OSIRIS-APEX will not collect a sample this time – it will instead spend 18 months observing Apophis up close.

"Apophis is one of the most infamous asteroids," said Dani DellaGiustina, an assistant professor at the University of Arizona and principal investigator of OSIRIS-APEX. "When it was first discovered in 2004, there was concern that it would impact the Earth in 2029 during its close approach. That risk was retired after subsequent observations, but it will be the closest an asteroid of this size has gotten in the 50 or so years asteroids have been closely tracked, or for the next 100 years of asteroids we have discovered so far."

"It gets within one-tenth the distance between the Earth and Moon during the 2029 encounter. People in Europe and Africa will be able to see it with the naked eye, that's how close it will get. We were stoked to find out the mission was extended," she said. ®

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