Pieces of the near-Earth asteroid Bennu are ready to return to Earth.
The OSIRIS-REx spacecraft successfully stowed the sample collector head, which is full of surface material gathered from Bennu on October 20, in the sample return capsule on Wednesday. This will prevent any more of the sample from leaking into space.
The mission team received images sent by the spacecraft on October 22 that revealed the sample collection head was full of surface material — so much so that a flap was wedged open by rocks, allowing particles to escape into space.
A camera on the spacecraft helped the NASA mission team confirm that the sample was safely stowed on Wednesday. This marks the end of one of the most challenging phases of the mission, according to NASA.
“This achievement by OSIRIS-REx on behalf of NASA and the world has lifted our vision to the higher things we can achieve together, as teams and nations,” NASA Administrator Jim Bridenstine said in a statement.
“Together a team comprising industry, academia and international partners, and a talented and diverse team of NASA employees with all types of expertise, has put us on course to vastly increase our collection on Earth of samples from space. Samples like this are going to transform what we know about our universe and ourselves, which is at the base of all NASA’s endeavors.”
Before securely sealing the sample in the return capsule, the spacecraft had to cut a tube that helped carry nitrogen gas to the surface of the asteroid. This gas helped stir up material on the asteroid’s surface so it could be collected. The spacecraft was also commanded by the mission team to separate the collector head from the robotic arm it was attached to for the Touch-and-Go, or TAG, collection event.
The arm was also used to tug on the collector head and make sure it was securely latched in place.
The spacecraft closed the lid of the sample return capsule and fastened its internal latches late Wednesday.
The art of stowing an asteroid sample
Researchers are confident that the spacecraft collected well over the mission’s requirement of 2 ounces, or 60 grams. They believe the spacecraft was able to collect at least 1 kilogram of material, if not more, and estimate that tens of grams were lost before the sample was stowed.
Due to the success of the sample collection, the team worked over the weekend to expedite preparations for stowing the sample, which was originally scheduled for November 2. The stow process took about 36 hours overall.
The asteroid and the spacecraft are currently more than 200 million miles from Earth. This creates a one-way, 18.5-minute communication delay between OSIRIS-REx and its mission team on Earth.
Each stage of stowing the sample required oversight and commands sent by the team. Basically, every time the spacecraft completed a step, it sent back data and images to the team. Once the researchers received them, they assessed OSIRIS-REx’s progress and sent another command. Because of this, the stowing process spanned multiple days.
“Given the complexity of the process to place the sample collector head onto the capture ring, we expected that it would take a few attempts to get it in the perfect position,” said Rich Burns, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement. “Fortunately, the head was captured on the first try, which allowed us to expeditiously execute the stow procedure.”
The sample return capsule will protect material gathered by the spacecraft during its brief and historic roughly six-second touchdown on Bennu last week.
This is NASA’s first mission to land on and collect a sample from an asteroid, and it will be returned to Earth in September 2023.
The spacecraft won’t depart for Earth until March 2021 when the asteroid is in alignment with Earth to provide a more fuel-efficient trip home.
Returning a sample to Earth
When OSIRIS-REx passes by Earth in September 2023, it will drop the capsule containing the sample in the Utah desert. A team will be ready to retrieve the sample from an aircraft hangar that will serve as a temporary clean room.
The sample will then be whisked away to labs that are currently under construction at Johnson Space Center in Houston.
The labs will be managed by NASA’s ARES, or Astromaterials Research and Exploration Science division. This division includes the study of an array of materials that originated in space, including meteorites, moon rocks, solar wind particles and comet samples.
In order to properly prepare for protecting the sample returned from Bennu while also studying it, ARES will also have new cleaning facilities, tools and storage areas in addition to the new labs in development. This will allow scientists to study Bennu’s surface material without damaging it.
The ARES team has been planning for this return for more than 15 years.
Kevin Righter, curator of the Antarctic meteorite collection at Johnson Space Center, and OSIRIS-REx deputy curators and scientists Keiko Messenger, Nicole Lunning and Christopher Snead will be some of the first to see and handle the sample.
The scientists, along with other ARES staff, will characterize, prepare and divide the sample so it can be studied by other scientists. It will also be digitally cataloged.
“I’m really excited to see the sample and interact with it,” Lunning said in a statement. “Before it arrives, we’ll be preparing in many ways, such as holding sample return capsule retrieval and disassembly rehearsals to make sure the actual event goes as smoothly as possible and the sample is protected.”
The OSIRIS-REx science team will study the sample initially to learn more about the asteroid’s chemistry and minerals. These will be the basis of the first studies released about the sample from Bennu.
The team at NASA will also build a separate lab to house the Ryugu samples collected by Hayabusa2, provided by the Japan Aerospace Exploration Agency in exchange for some of the Bennu samples.
And the Canadian Space Agency, which contributed an instrument to the OSIRIS-REx mission, will also receive some of the Bennu sample. About 75% of the sample will be sealed and reserved for future generations to study.
“I’m very thankful that our team worked so hard to get this sample stowed as quickly as they did,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson, in a statement. “Now we can look forward to receiving the sample here on Earth and opening up that capsule.”