NASA’s OSIRIS-REx nabbed over 120 grams of space rocks from asteroid Bennu

It’s official: NASA’s OSIRIS-REx spacecraft snagged 121.6 grams of pristine space rocks when it bopped the asteroid Bennu four years ago, more than double the mission’s official science goal, the agency confirmed February 15.

Launched in 2016, OSIRIS-REx is NASA’s first mission to collect samples from an asteroid and return them to Earth so scientists can study our solar system’s origins. After performing its grab-and-go procedure from the diamond-shaped Bennu, the spacecraft dropped its canister into our atmosphere last year (SN: 9/22/23). Engineers swiftly shuttled it off to a specially designed sample curation center at the Johnson Space Center in Houston, where it was placed in a hermetic glove box to prevent contamination by terrestrial material.

While researchers have been able to analyze some rocks and dust already, weighing the full sample has been delayed by a couple stuck screws that prevented anyone from accessing the entire contents of the capsule (SN: 10/11/23). Some clever workarounds finally unlocked the full sample on January 10, and it will now be distributed to scientists around the world for study.

To learn how engineers got the canister open, as well as what kinds of science the sample will teach us, Science News spoke with Harold Connolly, a geologist at Rowan University in Glassboro, N.J., who oversees analysis of the material from Bennu. The conversation has been edited for clarity and brevity.

SN: Shortly after retrieving the OSIRIS-REx canister, you were able to collect some sample, right?

Connolly: There was lots of dust on the outside of the canister. That was the first material we got, approximately 1 to 1.1 grams or so of fine dust particles.

SN: What kinds of problems did you face before you could fully open the main sample container?

Connolly: There’s a bunch of fasteners or screws holding the container closed, approximately 32 of them. And two of them we couldn’t loosen enough with the equipment we had. But there’s a mylar flap that moves, which trapped the sample in a container. The curation team at the Johnson Space Center figured out it could just push down the flap. Without removing the plate that was stuck, the team could get sample out from inside the TAGSAM [Touch-and-Go-Sample-Acquisition-Mechanism] head by literally pushing down the mylar flap and scooping it out very gently. We got 70 grams of sample — a lot.

But to access the rest of the sample, they had to create a new kind of ratchet wrench screwdriver. The previous screwdriver was starting to flex a little bit, so you might be breaking the screwdriver.

SN: Can you tell me anything about what you’ve found from the sample you have so far?

Connolly: It’s a serpentinite. It’s an altered rock where the original rocky material has interacted with water, and that original rocky material must have been rich in olivine and pyroxene and some other common rock-forming minerals on Earth, but changed and altered in a beautiful way. That is a geologic puzzle to figure out.

SN: What have we suspected about the history of Bennu that the sample is helping to confirm?

Connolly: Oh, there’s a lot.

Bennu itself is in a configuration that is not what it originally was. Once upon a time, the pieces that became Bennu were in a much different object, probably a heck of a lot bigger. We’re talking soon after the solar system formed, 4.5 billion years ago.

When that object formed, material came together, brought ices with it — and not just water ice, but carbon monoxide and ammonia ice — which means it had to accrete somewhere out past what we call the snow line, out past Mars in the outer solar system. At that distance from the sun, temperatures are low enough for those ices to form.

Eventually, the interior of the larger, original object started to heat up because of radioactivity that’s naturally in the material, and that began to melt the ice and become fluid. Fluid began to interact with the parent body to form new minerals — like serpentinite — from the material that accreted.

We’ll be teasing out how much of it was altered, how much is relic from the pre-accretion stage, how much is actually from stars that died and injected dust into our solar system.

SN: It sounds like a dynamic and complicated history.

Connolly: We’re interested in what happened: How did that original parent body change? Was it impacted by another body and smashed apart to create the larger boulders that eventually came together to form Bennu? And how long has Bennu been in this current configuration? How much had it experienced interaction with the sun or with cosmic rays? All these kinds of processes we can tease out by analyzing teeny tiny little bits of sample.

SN: Do we have any answers to any of these questions?

Connolly: Stay tuned.