NASA’s OSIRIS-REx spacecraft successfully landed gently on the surface of the asteroid Bennu last week and scooped up a sample of pristine material from the early solar system. It’s an incredible accomplishment for all involved, but OSIRIS-REx might end up a victim of its own success. NASA reports the probe grabbed so much regolith from the asteroid that it’s leaking out of the collector. The team is now working to determine how best to keep the precious cargo from escaping.
OSIRIS-REx launched in 2016, reaching the near-Earth asteroid known officially as 101955 Bennu in late 2018. After painstaking examination of the space rock, NASA selected several possible landing zones that avoided the worst of the craggy terrain. Last week, the spacecraft descended from orbit around the asteroid, tapped the surface, and used a burst of compressed nitrogen to blow material into the sample container.
NASA hoped to collect about 60 grams of dust and gravel from the surface of Bennu. If the first attempt didn’t work, the probe had the resources to make another attempt at the secondary landing zone. However, NASA believes the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) worked a bit too well. The initial images from the sampling site showed a significant divot in the surface following the maneuver, and sure enough, the TAGSAM is so overloaded that asteroid particulates have wedged open the container’s mylar lid.
Yesterday, the OSIRIS-REx team received images of the spacecraft’s sample collector head brimming with regolith. So much sample was collected that some of it is actually slowly escaping the sampling head. More details: https://t.co/ufUXdotgsO pic.twitter.com/2wINd1Tk2g
— NASA's OSIRIS-REx (@OSIRISREx) October 23, 2020
The team initially planned to conduct a sample measurement last weekend to see how much material was in the collector and assess whether another run was needed. Examinations of the TAGSAM head (above) show the sample is leaking out through the gaps in the lid, and there’s some concern any unnecessary movements could cause more of the sample to fall out. There might be hundreds of grams of asteroid debris already inside OSIRIS-REx, so NASA has decided to focus on transferring the remaining material into the Sample Return Capsule (SRC), which will keep it secure on the return journey to Earth.
OSIRIS-REx will depart from Bennu in March of next year when the asteroid’s orbit brings it close to Earth. The SRC is expected to return to Earth in September 2023, giving scientists an unprecedented opportunity to study material from the birth of the solar system. Even if OSIRIS-REx only hits the planned 60g threshold, that will be much more than similar missions. The Japanese Hayabusa probe scooped up less than one gram from 25143 Itokawa in 2005, and Hayabusa2 should return to Earth with 100mg of dust from 162173 Ryugu late this year.
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NASA is making plans for OSIRIS-REx to head back to Earth with its precious cargo. According to the team, OSIRIS-REx will begin that journey on May 10th.
NASA’s OSIRIS-REx Probe Reaches Asteroid Bennu
Eventually, OSIRIS-REx will graze the surface of Bennu to pick up a tiny bit of material to send back to Earth.
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Not only is the surface remarkably rugged, but the asteroid is also regularly ejecting puffs of dust and rock into space. This is a phenomenon never before observed on an asteroid.
NASA Chooses Asteroid Landing Zone for OSIRIS-REx Probe
It'll be a delicate operation to collect samples from Bennu and return them to Earth, but we could learn a great deal from the pristine material on the asteroid.