“Bonus sample” in OSIRIS-REX canister

UNITED STATES // Even though the heart of the OSIRIS-REx sample return canister, called the TAGSAM, has not yet been opened, its exterior contained an unexpected gift.

Nicole Lunning, NASA’s OSIRIS-REx curation team leader, refers to it as an extra “bonus sample”.

It’s a big enough bonus that in and of itself, would be the second largest sample ever returned from an extraterrestrial body other than the Moon.

Technically, of course, there’s only one sample, because OSIRIS-REx only touched down once, collecting all of its material in a single grab.

But this material was sitting on the lid of the TAGSAM, from which it had escaped when other rocks blocked the flap that was supposed to seal the inner container shut. And with 1.5 grams of the sample already weighed and catalogued, it’s already more than a quarter the size of the sample returned from asteroid Ryugu three years ago by Japan’s Hayabusa2 mission – a hint to the treasure trove to be found when the TAGSAM itself is opened.

Visually, it’s nondescript – just a collection of small pebbles and dust not unlike what you might dump from your shoes after walking on a rocky path, but notable mostly for being almost black in colour. It’s the first material scientists have seen from the surface of asteroid Bennu, from which Osiris Rex returned the canister late last month, and the scientists wasted no time taking their first look.

The most exciting find, NASA Administrator Bill Nelson announced today at a press conference at the Johnson Space Center in Houston, Texas, is that the material tested so far proved to contain abundant water in the form of hydrated clay minerals. It also turned out to be nearly 5% carbon by weight, he said, adding “carbon and water are exactly the kinds of material that we wanted to find”.

The water, said principal investigator Professor Dante Lauretta, was in a clay mineral called serpentine, which was spotted by electron microscopy from its distinctive fibrous structure. “They look like serpents or snakes inside the sample,” Lauretta says, “and they have water locked inside their crystal structure.”

That’s important, because one of the most important questions in planetary science is how the Earth obtained its water.

“The reason the Earth is a habitable world is that we have oceans and lakes and rivers and rain,” Lauretta says, and they exist only because “minerals like the ones we’re seeing from Bennu landed on Earth 4 billion to 4½ billion years ago. So, we’re seeing the way that water got incorporated into the solid material and then ultimately into planets—not just Earth but probably Venus and Mars as well.”

The carbon is important because carbon is also essential for all life on Earth, and one of the things scientists want to determine is whether asteroids like Bennu could have not only delivered water for our oceans but also seeded the Earth with prebiotic chemicals – the building blocks of life.  

So far, the main thing scientists know is that the samples are carbon-rich. “The actual number is 4.7%,” says Daniel Glavin, OSIRIS-REx sample analyst.

Minerals like the ones we’re seeing from Bennu landed on Earth 4-4.5 billion years ago.

Professor Dante Lauretta

This, he adds, is truly a big deal. “At the time this data came back,” he says, “there were scientists on the team going, ‘Wow, oh my God,’ and when scientists say that ‘Wow,’ that’s a big deal.”

In fact, he says, “the lab that did the analysis said that this was the highest abundance of carbon they’d ever measured in any extraterrestrial sample – and they’d analyzed close to 250 meteorites. So, this is a unique sample that we’re dealing with.”

Furthermore, he says, much of the carbon appears in the form of blob-like organic globules. “The analyst who made this measurement,” Glavin adds, “said, ‘This thing is loaded with organics.’” 

The next step is to find out what exactly those organics are composed of, a process that can’t be done with the non-destructive scans used to date. Instead, that will require crushing bits of the sample and extracting the organics for examination with the types of instruments used by analytical chemists. “That’s personally something I’m excited about,” Glavin says. “We’ll be making what we call Bennu tea and extracting these compounds. Stay tuned.”

Also important, Lauretta says, was the discovery of minerals containing sulphur, as well as ores called magnetites. That’s because sulphur is critical not only for planetary evolution (by its effect on the way rocks melt) but also for its role in producing the disulphide bonds that give proteins their three-dimensional shapes.

Magnetites are important because they can catalyze organic reactions, making them another possible key player in the origin of life.

All of this makes the scientists feel particularly fortunate. “We picked the right asteroid,” Glavin says. “And not only that, we picked the right sample. This stuff is an astrobiologist’s dream.”

Meanwhile, the process of sample retrieval continues. The first goal, says Francis McCubbin, astromaterials curator for NASA’s Johnson Space Center, will be to continue cautiously unpacking the sample and developing a catalogue of the rocks in it, from which scientists around the world can make requests for materials to study. It’s a process that McCubbin estimates will take six months, because it has to be done slowly and meticulously, working inside a glove box in a clean room built specifically to house the OSIRIS-REx sample.

“As you can imagine, working with hands inside a glove box within a clean lab is hard, challenging work, and it does not go quickly” McCubbin says. “[But] those glove boxes are necessary to keep these samples as pristine as the day [they] landed in Utah.”

Overall, at least 70% of the sample will be retained for study in years or decades to come, as was done with the Apollo program’s Moon samples, a decision that has allowed it to continue yielding exciting results 50 years after its completion. Most will remain at Johnson Space Center, but portions will also be curated by JAXA and the Canadian Space Agency.

Three samples will also be given to museums, so the public can have an opportunity to see them in person—but only after the scientists ensure that they aren’t giving away a critically important sample.

“Basically we’re looking for things that we have more than one of, McCubbin said. “Usually, we want at least four of any type of thing before we start using it for something else.” But, he says, “I can’t wait to have the public get an opportunity to look at these beautiful samples.”

Not that any are likely to wind up in Australia. Right now, they are scheduled to go to the Smithsonian, the Johnson Space Center, and Arizona State University.