Micrograph of a dark Bennu object, about one millimeter long, with a bright phosphate shell. On the right is a smaller fragment that broke away from the object. Image credit: Lauretta & Connolly et al. (2024) Meteoritics & Planetary Science, doi:10.1111/maps.14227
NASA‘s Osiris-Rex The mission recovered a sample from the asteroid Bennu, revealing that it contained key solar system materials and possible signs of past water. This discovery provides valuable insights into the conditions of the early solar system and the possible origins of life.
A deep dive into the sample of rock and dust brought back from near-Earth asteroid Bennu by NASA’s OSIRIS-REx mission, led by the University of Arizona, has revealed some long-awaited surprises.
The OSIRIS-REx sample analysis team found that asteroid Bennu contains the original ingredients that formed our solar system. The asteroid dust is high in carbon and nitrogen, as well as organic compounds, all of which are essential ingredients for life as we know it. The sample also contains sodium and magnesium phosphates, which came as a surprise to the research team because they were not seen in the spacecraft’s remote sensing data on Bennu. Their presence in the sample suggests that the asteroid may have broken off from a small, primitive ocean world that has long since disappeared.
The sample return capsule from NASA’s OSIRIS-REx mission is seen shortly after landing in the desert on Sept. 24, 2023, at the Department of Defense Test and Training Range in Utah. The sample was collected from the asteroid Bennu in October 2020 by NASA’s OSIRIS-REx spacecraft. Credit: NASA/Kegan Barber
Pino sample delivery and trip
The OSIRIS-REx spacecraft launched on September 8, 2016, and began its journey to the near-Earth asteroid Bennu to collect a sample of rock and dust from the surface. OSIRIS-REx was the first American mission to collect a sample from an asteroid. The spacecraft delivered the 4.3-ounce (121.6-gram) sample to Earth on September 24, 2023.
“Finally getting a chance to dig deep into the OSIRIS-REx sample from Bennu after all these years is very exciting,” said Dante Lauretta, OSIRIS-REx principal investigator. Osiris-Rex “This discovery not only answers long-standing questions about the early solar system, but also opens up new avenues for research into the formation of Earth as a habitable planet. The ideas outlined in the overview paper have sparked further curiosity, prompting us to explore further.”
Loretta is a co-author of a research paper published in Meteorology and Planetary Science which details the nature of the asteroid sample. The paper also serves as an introduction to Pino Sample Catalogan online resource where information about the specimen is made available to the public and where scientists can request specimen materials for their own research.
“The publication of the first paper led by Dr. Loretta and Dr. Connolly describing the Bennu sample is an exciting milestone for the mission and for the Lunar and Planetary Laboratory,” said Mark Marley, director of the Lunar and Planetary Laboratory at the University of Arizona and chair of the Department of Planetary Sciences. “Faculty, scientists, and students will continue to study the sample for years and decades to come. For now, we can only imagine the stories of our planet’s origins and life on it that the Bennu grains already in our laboratories will tell.”
An aerial view of one of the containers holding rocks and dust from asteroid Bennu, with instrument scale in centimeters. Credit: NASA/Erica Blumenfeld and Joseph Aebersold
“Aquatic Past” by Pino?
Analysis of a sample from the asteroid Bennu has revealed intriguing insights into the composition of the asteroid. The sample, which is dominated by clay minerals, particularly serpentine, reflects the type of rock found in Earth’s mid-ocean ridges, where material from the mantle, the layer beneath Earth’s crust, meets water.
This interaction between ocean water and materials from Earth’s mantle creates clay and yields a variety of minerals including carbonates, iron oxides and iron sulfides. But the most surprising discovery in the Bennu sample is the presence of water-soluble phosphates, Lauretta said. These compounds are the biochemical components of all known life on Earth today.
Similar phosphates were found in the Ryugu asteroid sample delivered by the Japan Aerospace Exploration Agency’s Hayabusa2 mission in 2020. But the sodium-magnesium phosphates found in the Bennu sample are notable for their lack of impurities, which resemble tiny bubbles of other minerals trapped inside the rock, and their grain size is unprecedented in any meteorite sample, Lauretta said.
The discovery of sodium and magnesium phosphates in the Bennu sample raises questions about the geochemical processes that brought these elements together, and provides valuable clues about Bennu’s historical conditions.
“The presence and condition of phosphate, along with other elements and compounds on Bennu, suggests a watery past for the asteroid,” Lauretta said. “It is possible that Bennu was once part of a wetter world, although this hypothesis requires further investigation.”
This mosaic of Bennu was created using observations made by NASA’s OSIRIS-REx spacecraft, which has been close to the asteroid for more than two years. Credit: NASA/Goddard/University of Arizona
From the young solar system
Despite its possible history of interaction with water, Bennu remains a chemically primitive asteroid, with elemental ratios very similar to those of the Sun.
“The sample we returned is the largest reservoir of unaltered asteroid material currently on Earth,” Lauretta said.
The asteroid’s composition offers a glimpse into the early days of our solar system, more than 4.5 billion years ago. The rocks have been preserved in their original state, and have not melted or solidified again since their formation, confirming their pristine nature and ancient origins.
This artist’s concept shows the OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security – Regolith Explorer) spacecraft touching down on the asteroid Bennu using the Touch-And-Go Sample Arm Mechanism, or TAGSAM. The mission successfully returned a sample of Bennu’s surface paint to Earth for study. Credit: NASA
Hints on the building blocks of life
The team also confirmed that the asteroid is rich in carbon and nitrogen. These elements are essential for understanding the environments from which Bennu’s materials originated and the chemical processes that transformed simple elements into complex molecules, which could lay the foundation for life on Earth.
“These results underscore the importance of collecting and studying materials from asteroids like Bennu — particularly the low-density materials that typically burn up as they enter Earth’s atmosphere,” Lauretta said. “These materials hold the key to unraveling the complex processes of solar system formation and the biochemistry that may have contributed to the emergence of life on Earth.”
What then
Dozens of other laboratories in the United States and around the world will receive portions of Bennu’s sample from NASA’s Johnson Space Center in Houston in the coming months, and more scientific papers describing the Bennu sample are expected in the next few years from the OSIRIS-REx sample analysis team.
“The Bennu samples are stunningly beautiful exoplanetary rocks,” said study co-author Harold Connolly, the mission’s sample scientist who leads the sample analysis team, a professor at Rowan University in Glassboro, New Jersey, and a visiting scholar at the University of Arizona. “Every week, the OSIRIS-REx sample analysis team provides new and sometimes surprising results that help place important constraints on the origin and evolution of Earth-like planets.”
Reference: “Asteroid (101955) Bennu in the Laboratory: Characterization of the Sample Collected by the OSIRIS-REx Spacecraft” by Dante S. Lauretta, Harold C. Connolly, Joseph E. Aebersold, Connell M. O. D. Alexander, Ronald L. Ballouz, Jessica J. Barnes, Helena C. Bates, Carina A. Bennett, Laurinne Blanche, Erika H. Blumenfeld, Simon J. Clemett, George D. Cody, Daniella N. DellaGiustina, Jason P. Dworkin, Scott A. Eckley, Dionysis I. Foustoukos, Ian A. Franchi, Daniel P. Glavin, Richard C. Greenwood, Pierre Haenecourt, Victoria E. Hamilton, Dolores H. Hill, Takahiro Hiroi, Kana Ishimaru, Fred Jourdan, Hannah H. Kaplan, Lindsay P. Keller, Ashley J. King, Piers Koefoed, Melissa K. Kontogiannis, Loan Le, Robert J. Macke, Timothy J. McCoy, Ralph E. Milliken, Jens Najorka, Ann N. Nguyen, Maurizio Pajola, Anjani T. Polit, Kevin Reiter,Heather L. Roper, Sarah S. Russell, Andrew J. Ryan, Scott A. Sandford, Paul F. Scofield, Cody D. Schultz, Laura B. Seifert, Shogo Tachibana, Cathy L. Thomas-Kiberta, Michelle S. Thompson, Valerie Tu, Filippo Tosperti, Kun Wang, Thomas J. Zega, C. W. V. Woolner, June 26, 2024, Meteorology and Planetary Science.
DOI: 10.1111/maps.14227