A microscope image of a dark Bennu particle, about a millimeter long, with a bright phosphate crust. On the right is a smaller fragment that broke off. Credit: From Lauretta & Connolly et al. (2024) Meteoritics & Planetary Science, doi:10.1111/maps.14227
NASAS ‘ OSIRIS-REx mission returned a sample from the asteroid Bennu, revealing that it contains key solar system material and possible signs of a watery past. This discovery provides valuable insights into the early conditions of the solar system and the possible origin of life.
A deep dive into the sample of rock and dust returned from the near-Earth asteroid Bennu by NASA’s OSIRIS-REx mission led by the University of Arizona has revealed some long-awaited surprises.
Bennu contains the original ingredients that formed our solar system, the OSIRIS-REx sample analysis team found. Asteroid dust is rich 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 magnesium phosphate, which was a surprise to the research team because it was not seen in remote sensing data collected by the spacecraft on Bennu. Its presence in the sample hints that the asteroid may have broken off from a small, primitive, oceanic world long gone.
The sample return capsule from NASA’s OSIRIS-REx mission is seen shortly after touchdown in the desert on September 24, 2023, at the Department of Defense Test and Training Field in Utah. The sample was collected from asteroid Bennu in October 2020 by NASA’s OSIRIS-REx spacecraft. Credit: NASA/Keegan Barber
Bennu sample travel and delivery
Launched on September 8, 2016, the Origins, Spectral Interpretation, Resource Identification and Security–Regolith Explorer spacecraft, named OSIRIS-REx, began its journey to the near-Earth asteroid Bennu to collect a sample of rocks and dust from the surface. OSIRIS-REx was the first US mission to collect a sample from an asteroid. The spacecraft delivered the sample, weighing 4.3 ounces, or 121.6 grams, to Earth on September 24, 2023.
“Finally having the opportunity to dig into the OSIRIS-REx sample from Bennu after all these years is incredibly exciting,” said Dante Lauretta, principal investigator for OSIRIS-REx and Regents Professor of planetary sciences at the University of Arizona Lunar and Planetary Laboratory. . “This discovery not only answers long-standing questions about the early solar system, but also opens up new avenues of inquiry into the formation of Earth as a habitable planet. The insights outlined in our overall paper have sparked further curiosity, fueling our desire to explore deeper.”
Lauretta is co-lead author of a paper published in Meteoritics and Planetary Science detailing the nature of the asteroid sample. The paper also serves as an introduction to the Bennu specimen catalog, an online resource where information about the specimen is made available to the public and where scientists can request specimen material for their research.
“The publication of the first paper led by Dr. Lauretta and Dr. Connolly describing the Bennu sample is an exciting milestone for the mission and for the Lunar and Planetary Laboratory,” said Mark Marley, UArizona Lunar and Planetary Laboratory director and leader. of the Department of Planetary Sciences. “Our 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 the origin of our planet and life on it that will yet be told by the Bennu grains already in our laboratories.”
A top-down view of one of the containers holding rocks and dust from asteroid Bennu, with hardware scale marked in centimeters. Credit: NASA/Erika Blumenfeld and Joseph Aebersold
A ‘Water Past’ for Bennu?
Analysis of the Bennu sample revealed intriguing insights into the asteroid’s composition. Dominated by clay minerals, particularly serpentine, the sample reflects the type of rock found at mid-ocean ridges on Earth, where material from the mantle, the layer beneath the Earth’s crust, meets water.
This interaction between ocean water and materials from the Earth’s mantle results in the formation of clay and creates a variety of minerals including carbonates, iron oxides, and iron sulfides. But the most unexpected discovery in the Bennu sample is the presence of water-soluble phosphates, Lauretta said. These compounds are components of the biochemistry for all life known on Earth today.
A similar phosphate was found in the Ryugu asteroid sample delivered by the Japan Aerospace Exploration Agency’s Hayabusa2 mission in 2020. But the magnesium sodium phosphate discovered in the Bennu sample is notable for its lack of inclusions, which are bubble-like small amounts of other minerals trapped within the rock and its grain size, unprecedented in any meteorite sample, Lauretta said.
The finding of magnesium sodium 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 phosphates, along with other elements and compounds on Bennu, suggest a watery past for the asteroid,” Lauretta said. “Bennu could potentially have once been part of a wetter world. However, this hypothesis requires further investigation.”
This mosaic of Bennu was created using observations made by NASA’s OSIRIS-REx spacecraft that was in close proximity to the asteroid for more than two years. Credit: NASA/Goddard/University of Arizona
From a new solar system
Despite its possible history of interaction with water, Bennu remains a chemically primitive asteroid, with elemental dimensions closely resembling those of the sun.
“The sample we returned is the largest reservoir of unchanged asteroid material on Earth right now,” Lauretta said.
The composition of the asteroid offers a glimpse into the early days of our solar system, over 4.5 billion years ago. The rocks have maintained their original state, neither melting nor solidifying since their creation, affirming their pristine nature and ancient origins.
This artist’s concept shows the OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security – Regolith Explorer) spacecraft contacting asteroid Bennu with the Touch-And-Go Sampler Arm Mechanism, or TAGSAM. The mission successfully returned a sample of Bennu’s surface mantle to Earth for study. Credit: NASA
Advice on the building blocks of life
The team also confirmed that the asteroid is rich in carbon and nitrogen. These elements are essential to understanding the environments from which Bennu’s materials originated and the chemical processes that transformed simple elements into complex molecules, potentially laying the foundations for life on Earth.
“These findings underscore the importance of collecting and studying material from asteroids like Bennu — especially the low-density material that would normally burn up upon entering Earth’s atmosphere,” Lauretta said. “This material holds the key to unraveling the complex processes of solar system formation and the prebiotic chemistry that may have contributed to the emergence of life on Earth.”
What is expected next?
Dozens of other laboratories in the United States and around the world will receive parts of the Bennu sample from NASA’s Johnson Space Center in Houston in the coming months, and many more scientific papers describing the Bennu sample are expected in the coming years from OSIRIS – REx sample analysis team.
“The Bennu samples are extremely beautiful extraterrestrial rocks,” said the paper’s co-lead 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 research scientist at UArizona. . “Each week, analysis by the OSIRIS-REx Sample Analysis Team provides new and sometimes surprising findings that are helping to place important constraints on the origin and evolution of the terrestrial planets.”
Reference: “Asteroid (101955) Bennu in the laboratory: Characteristics of the sample collected by OSIRIS-REx” by Dante S. Lauretta, Harold C. Connolly, Joseph E. Aebersold, Conel 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, Dionisis I. Foustoukos, Ian A. Franchi, Daniel P. Glavin, Richard C. Greenwood, Pierre Haenecour, 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 Righter, Heather L. Roper, Sara S. Russell, Andrew J. Ryan, Scott A. Sandford, Paul F. Schofield, Cody D. Schultz, Laura B. Seifert, Shogo Tachibana, Kathie L. Thomas-Keprta, Michelle S . Thompson, Valerie Tu, Filippo Tusberti, Kun Wang, Thomas J. Zega, CWV Wolner and, 26 June 2024, Meteoritics and Planetary Science.
DOI: 10.1111/maps.14227