Bennu Asteroid Sample Reveals Organic Compounds That May Hint at Life Beyond Earth

A sample from asteroid Bennu, delivered to Earth by NASA's OSIRIS-REx mission in 2023, has revealed a collection of molecules and minerals that play a fundamental role in biological processes. Organic compounds such as amino acids, nucleobases, and ammonia, along with minerals formed in saltwater, have been identified. The findings suggest that the necessary conditions for life may have been present in various regions of the early solar system, raising the possibility that life could have developed beyond Earth.

Key Findings from the Study

According to the study published in Nature and Nature Astronomy, 14 of the 20 amino acids essential for protein formation and all five nucleobases found in DNA and RNA were detected in the Bennu samples. The presence of ammonia and formaldehyde was also noted, both of which are significant in the formation of complex organic molecules. These compounds, previously identified in meteorites, were found in an uncontaminated sample collected directly from space, reinforcing the idea that asteroid material could have contributed to the emergence of life's building blocks.

As reported by NASA, Danny Glavin, senior sample scientist at NASA's Goddard Space Flight Center and co-lead author of the Nature Astronomy paper, stated that the pristine nature of the Bennu sample allowed researchers to detect compounds that would have been easily altered or destroyed upon exposure to Earth's environment.

Traces of Water and Ancient Chemistry

Mineral analysis of the sample revealed the presence of evaporite minerals such as calcite, halite, and sylvite—indicative of prolonged water activity. The study, led by Tim McCoy of the Smithsonian's National Museum of Natural History and Sara Russell of the Natural History Museum in London, suggests that these minerals formed as saltwater evaporated over time. Similar brines have been observed on celestial bodies such as Ceres and Saturn's moon Enceladus.

McCoy noted that while evaporites have been found in meteorites, this is the first time a complete mineral set preserving an extended evaporation process has been identified in extraterrestrial material. The discovery of trona, a mineral never previously observed in samples from space, adds further significance to the findings.

Unanswered Questions and Future Research

One of the key questions that remain is why amino acids on Earth predominantly exhibit a left-handed molecular orientation, while the Bennu samples contained an equal mixture of left- and right-handed forms. Jason Dworkin, project scientist for OSIRIS-REx and co-lead author of the Nature Astronomy paper, pointed out that the data contributes to a broader understanding of the solar system's chemistry but leaves open the question of why life has only been observed on Earth so far.

The OSIRIS-REx mission, managed by NASA's Goddard Space Flight Center, was a collaborative effort involving multiple institutions, including the University of Arizona, Lockheed Martin Space, and international partners such as the Canadian Space Agency and Japan's JAXA. The sample continues to be studied at NASA's Johnson Space Center, where further research is expected to provide additional insights into the origins of life's essential components.