The new findings from NASA’s OSIRIS-REx mission have changed how we think about the origins of life. The asteroid Bennu, which OSIRIS-REx returned samples from in September 2023, contains at least 14 types of amino acids that are essential to life on Earth. What makes this discovery exciting is that it also includes 19 other amino acids that aren’t used in life as we know it.
Traditionally, scientists believed these amino acids formed in warm, wet environments close to the early sun. However, recent analysis suggests they might have come from much colder conditions, possibly further out in the solar system, where ice was present. “This confirms that life’s building blocks can be formed in various settings across the universe,” says Allison Baczynski, an organic chemist at Penn State University and co-lead author of the study.
To understand where these amino acids came from, Baczynski and her team studied their isotopic composition, particularly focusing on glycine, the simplest amino acid. On Earth, glycine is produced when hydrogen cyanide, ammonia, and organic compounds react in warm water. For comparison, they examined the Murchison meteorite, which fell in Australia in 1969 and contains amino acids formed in warmer settings. Surprisingly, Bennu’s glycine showed a different isotopic pattern than Murchison’s, suggesting it formed through a different process in a frozen environment.
This aligns with historical theories about the early solar system, notably the “snow line.” Inside this line, water was liquid, and reactions unfolded differently than in the icy regions beyond it. Current evidence hints that Bennu likely originated from material that formed beyond this snow line, further expanding our understanding of where life’s building blocks appear.
A fascinating twist emerged during their analysis: traditionally, scientists thought that left- and right-handed versions of amino acids would display identical nitrogen isotopes. Yet, upon studying glutamic acid from Bennu, they found significant differences. Although this specific amino acid is not used in life, these findings pose a tantalizing question. Could this variation help explain why all known life uses only left-handed amino acids?
“It was surprising to discover the variation in nitrogen isotopes. This could be a clue to understanding life’s preference for left-handed forms,” says Baczynski. As scientists continue to explore this mystery, the implications are enormous. If amino acids can form in varied settings, it opens up the possibilities for discovering life in places previously deemed unlikely.
This fascinating research was published on February 9 in the journal Proceedings of the National Academy of Sciences.
Overall, the findings present a broader picture of how life’s building blocks might exist throughout the universe, potentially in environments we’ve yet to explore.
