First Look at Material from Asteroid Bennu on the Ground

It has been worth the wait: NASA gave the public a first look today at what’s inside the sample return capsule, newly arrived from the small carbonaceous asteroid 101955 Bennu. The sample represents the largest collection of asteroid material to date, and it will offer researchers a first-hand look at pristine material from the primordial solar system. Today's reveal previews some of the science that's in store.

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Though the Origins, Spectral, Interpretation, Resource Identification and Security Regolith Explorer (Osiris-REX) took seven years to journey from Earth to Bennu and back again, the final leg of the journey was terrestrial. The Sample Return Capsule successfully came to rest on the ground at the Utah Test and Training Range on September 24, 2023. The sample container then made its way to NASA’s Astromaterials Acquisition & Curation Office at the Johnson Space Center, flying aboard a U.S. Air Force C-17 Globemaster III aircraft. An ongoing flow of inert nitrogen gas kept the sample pure from earthly contamination.

While the sample is undergoing its first tests and measurements, the final weight estimate is not yet in. The team had estimated the sample mass in flight by measuring the TAGSAM arm's motion as it stowed the sample, and comparing it against the momentum imparted against the spacecraft reaction wheels. That calculation indicated a sample mass of some 250 grams, or 8.8 ounces. Team members were overjoyed, as the sample far exceeded the 60-gram goal set by the mission. However, a more precise mass estimate awaits the opening of the head of the Touch and Go sample Acquisition Mechanism (TAGSAM).

What’s Inside the Container

The TAGSAM itself has not yet been opened. The team is taking their time, as it turns out that there’s a wealth of material to collect and examine just inside the canister, around the TAGSAM. This "bonus" material, which had overflowed the TAGSAM as the probe was lifting off from the asteroid, comes in the form of dark particles coating the inside of the canister lid.

Fourteen round "witness plates" on the top of TAGSAM and 24 surface contact plates appear to have trapped fine-grained material as well. By the third day, the curation team had cleaned the particles off the interior deck, revealing a diverse assortment that ranges from fine dust to pebbles. More material is suspected just underneath the TAGSAM closure flap.

The team at the Johnson Space Center has thus far worked on the sample for 10 days.

The first look inside the canister revealed additional fine dust as well as intermediate particles, roughly the size of grains of rice. These diverse, carbonaceous, and organic-containing rocks are just what the team was hoping the find. A first measurement made by the Carnegie Institute of Science found 4.7% carbon in a small test sample. Ultraviolet analysis also revealed organic globules in the dust grains.

Electron microscope analysis has revealed water-bearing clay minerals, sulfur, and iron particulates. X-ray computed tomography analysis also revealed sulfide minerals. The existence of water-bearing clays is especially intriguing, because scientists think that asteroids such as Bennu might have played a key role in bringing water and organics to early Earth.

“We definitely picked the right asteroid,” says Daniel Glavin (NASA-GSFC), highlighting the wealth of science already seen in the first tests.

What’s Next for the Sample

Over the next six months, the team plans to assemble a sample catalog, available for researcher requests.

“Our labs were ready for whatever Bennu had in store for us,” says Vanessa Wyche (NASA-JSC) in today's press release. “We’ve had scientists and engineers working side-by-side for years to develop specialized gloveboxes and tools to keep the asteroid material pristine and to curate the samples so researchers now, and decades from now can study this precious gift from the cosmos.”

International partners will obtain their share of material from the sample collection. Specifically, the Canadian Space Agency will receive 4% of the overall sample, and Japan’s Aerospace Exploration Agency (JAXA) will get 0.5%. Both agencies will also receive one contact pad each. In all, some 200 researchers and 35 international intuitions will study the material in the years to come.

Three museums will also be given samples for the public to see. These are the Alfie Norville Gem and Mineral Museum at the University of Arizona in Tucson, the Smithsonian National Museum of Natural History in Washington D.C., and the Houston Space Center in Texas.

The sample from Bennu joins a host of other celestial samples housed at the Astromaterials and Research Science (ARES) collection at the Johnson Space Center, including Apollo lunar samples, Stardust comet samples, samples from JAXA's Hayabusa 1 and 2 asteroid missions. Over the coming decade, it may eventually host material from Mars, currently being collected by the Perseverance Rover.

Even as scientists study the asteroid sample on Earth, the mission continues on, with the spacecraft now in a heliocentric orbit and renamed Osiris-APEX, short for Apophis Explorer. Remaining fuel will bring the probe to rendezvous with asteroid 99942 Apophis in 2029 shortly after to that asteroid's near-Earth flyby.

Today’s exciting first peek inside the canister is just a hint of things to come, as the team works toward opening TAGSAM itself.