A time capsule of supplies bearing witness to its origin and transformation over billions of years

Asteroid Bennu—the goal of NASA’s OSIRIS-REx pattern return mission, led by the University of Arizona—is a combination of supplies from all through, and even past, our photo voltaic system. Over the previous few billion years, its distinctive and different contents have been remodeled by interactions with water and the tough house setting.

These particulars come from a trio of newly revealed papers based mostly on evaluation of Bennu samples delivered to Earth by OSIRIS-REx in 2023. The OSIRIS-REx pattern evaluation marketing campaign is coordinated by the U of A’s Lunar and Planetary Laboratory (LPL) and includes scientists from all over the world. LPL researchers contributed to all three research and led two of them.

“This is work you just can’t do with telescopes,” stated Jessica Barnes, affiliate professor on the U of A’s Lunar and Planetary Laboratory and co-lead creator on one of many publications.

“It’s super exciting that we’re finally able to say these things about an asteroid that we’ve been dreaming of going to for so long and eventually brought back samples from.”

Bennu is made from fragments from a bigger “parent” asteroid that broke up after it collided with one other asteroid, seemingly within the asteroid belt between the orbits of Mars and Jupiter.

The mother or father asteroid consisted of fabric with various origins—close to the solar, removed from the solar, and from different stars—that coalesced greater than 4 billion years in the past as our photo voltaic system was forming.

These findings are the topic of a paper, revealed in Nature Astronomy, collectively led by Barnes and Ann Nguyen with the Astromaterials Research and Exploration Science Division at NASA’s Johnson Space Center in Houston.

“Bennu’s parent asteroid may have formed in the outer parts of the solar system, possibly beyond the giant planets, Jupiter and Saturn,” Barnes stated.

“We think this parent body was struck by an incoming asteroid and smashed apart. Then the fragments re-assembled and this might have repeated several times.”

By trying on the samples returned by the OSIRIS-REx spacecraft, Barnes and her colleagues had been capable of get probably the most complete snapshot of its historical past to this point. Among the findings was an abundance of stardust, materials that existed earlier than our photo voltaic system fashioned, Barnes stated.

The discovery of those most historical supplies was made potential, partly, by the NanoSIMS instrument on the U of A’s Kuiper-Arizona Laboratory for Astromaterials Analysis, which might reveal a pattern’s isotopes—variants of chemical parts—at nanometer scales. The tiny grains of stardust are identifiable by their uncommon isotopic make-up in comparison with supplies fashioned within the photo voltaic system.

“Those are pieces of stardust from other stars that are long dead, and these pieces were incorporated into the cloud of gas and dust from which our solar system formed,” Barnes stated.

“In addition, we found organic material that’s highly anomalous in their isotopes and that was probably formed in interstellar space, and we have solids that formed closer to the sun, and for the first time, we show that all these materials are present in Bennu.”

The chemical and isotopic similarities between samples from Bennu and the same asteroid, Ryugu, which was sampled by the Japanese Hayabusa 2 mission in 2019, and probably the most chemically primitive meteorites discovered on Earth recommend their mother or father asteroids might have fashioned in a shared area of the early photo voltaic system.

Yet the variations researchers are observing within the Bennu samples might point out that the beginning supplies on this area modified over time or weren’t as well-mixed as some scientists have thought.

The analyses present that a number of the supplies within the mother or father asteroid survived numerous chemical processes involving warmth and water and even the energetic collision that resulted within the formation of Bennu.

Nevertheless, many of the supplies had been remodeled by hydrothermal processes, as reported in a second paper, revealed in Nature Geoscience. In reality, that research discovered, minerals within the mother or father asteroid seemingly fashioned, dissolved and reformed over time as a consequence of interactions with water.

“We think that Bennu’s parent asteroid accreted a lot of icy material from the outer solar system, which melted over time,” stated Tom Zega, director of the Kuiper-Arizona Laboratory who co-led the research with Tim McCoy, curator of meteorites on the Smithsonian.

The crew discovered proof that silicate minerals would have reacted with the resultant liquid water at comparatively low temperatures of about 25 levels Celsius, or room temperature.

That warmth might have both lingered from the accretion course of itself, when Bennu’s mother or father asteroid first fashioned, or was generated by impacts later in its historical past, presumably together with the decay of radioactive parts deep inside it. The trapped warmth might have melted the ice contained in the asteroid, in accordance with Zega.

“Now you have a liquid in contact with a solid and heat—everything you need to start doing chemistry,” he stated. “The water reacted with the minerals and formed what we see today: samples in which 80% of minerals contain water in their interior, created billions of years ago when the solar system was still forming.”

The transformation of Bennu’s supplies didn’t finish there. A third paper, additionally revealed in Nature Geoscience, reviews microscopic craters and tiny splashes of once-molten rock on the surfaces of Bennu particles—indicators that the asteroid has been peppered by micrometeorite impacts.

These impacts, along with the results of photo voltaic wind, are often called “space weathering” and happen as a result of Bennu doesn’t have an environment to guard it. This weathering is occurring so much sooner than typical knowledge would have it, in accordance with the research, which was led by Lindsay Keller at NASA Johnson and Michelle Thompson at Purdue University.

As the leftover supplies from planetary formation 4.5 billion years in the past, asteroids present a document of the photo voltaic system’s historical past. But many of those remnants could also be completely different from what meteorites recovered on Earth would recommend, Zega stated, as a result of various kinds of meteors (fragments of asteroids) might deplete within the environment and by no means make it to the bottom.

“And those that do make it to the ground can react with Earth’s atmosphere, particularly if the meteorite is not recovered quickly after it falls,” he added, “which is why sample return missions such as OSIRIS-REx are critical.”