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Artist’s concept of the OSIRIS-Rex spacecraft reaching out to scoop rocks from the surface of asteroid Bennu.
A view of the sample collection site for OSIRIS-REx spacecraft on Bennu, the asteroid. The crater where sample site Nightingale is located can be seen near the top, center of the image – it is a small region containing dark, fine-grained material.
Image shows the TAGSAM over the surface of Bennu as scientists conduct a last dress rehearsal of OSIRIS-REx collecting a sample before October 20.
For many driving to work on a soggy Monday morning, it’s enough of a challenge to find parking and avoid pedestrians. Parking a spacecraft on an active asteroid hundreds of millions of miles from Earth to scoop up a sample of surface dust seems impossible.
Yet on Tuesday, Oct. 20, that’s exactly what a team of scientists at NASA will attempt to do.
The mission will see the OSIRIS-REx land on a 52-foot diameter site inside what is thought to be a well-preserved crater on the asteroid Bennu. For up to 10 seconds, the spacecraft will collect 60 grams of surface dirt and then immediately launch from the asteroid on a three-year journey back to Earth.
OSIRIS-REx , which was launched from Earth in 2016, and reached Bennu in 2018, has been circling the 1,600 metre-long asteroid for two years now, sending back observations to scientists on its chemistry and geology. Researchers now know the asteroid is active — it loses mass by chucking debris into space. It also probably used to have huge rivers of water flowing inside it. Data from the spacecraft has also debunked beliefs that the asteroid surface is like a sandy beach; instead it is covered in rough, rocky and rugged boulders.
“Bennu is a time capsule,” Thomas Zurbuchen, the head of NASA’s Science Mission Directorate, told the MIT Technology Review . “It has been out there for 4.5 billion years and carries the history of that environment with it.”
While this would be the first attempt to collect dirt from Bennu, asteroid sample collection isn’t new.
So far, Japan is the only country to successfully complete such a mission, after collecting a sample from the asteroid Itokawa in 2005, and then from asteroid Ryugu in 2018. However, while Japan’s spacecraft Hayabusa 2 collected dust by firing high speed space bullets into the surface, NASA scientists are opting for another method, called TAGSAM — short for “touch-and-go acquisition mechanism.”
The plan, which will take 4.5 hours to orchestrate, will see scientists carefully nudge OSIRIS-REx out of its orbit toward the asteroid’s surface. They will use a natural feature tracking system that ensures the right location for landing and thrusters to match the spacecraft’s speed with the asteroid’s rotation to ensure it lands with correct contact and velocity.
As the spacecraft is directed towards the crater, the TAGSAM, a 3.35 metre-long arm with a collection head fitted on the end, is deployed. It will fire nitrogen gas onto the surface to stir up material toward the head for it to scoop — ideally particles that are two centimetres or smaller.
If the arm detects danger, it will execute an abort burn, launching the spacecraft away from the surface.
“So, for some perspective, the next time you park your car in front of your house or in front of a coffee shop and walk inside, think about the challenge of navigating Osiris-Rex into one of these spots from 200 million miles away,” NASA’s deputy project manager Mike Moreau told Sky News .
There is a 30 per cent risk that not enough sample could be collected and, so, scientists have planned for a second attempt in January at a separate site on the asteroid, called Osprey. This means the spacecraft might bring back samples from two different sites on the asteroid, leaving it up to scientists to separate the samples and study their origins.
The OSIRIS-REx is scheduled to leave Bennu in later 2021 and deliver the samples to Earth by Sept. 24, 2023.
Copyright Postmedia Network Inc., 2020