Asteroid Bennu Samples Reveal Life's Building Blocks Formed Throughout Universe

Space Rock Delivers Ancient Secrets

NASA's OSIRIS-REx spacecraft, which launched in 2016, scooped up bits of dust, soil and rocks from the asteroid Bennu and then brought them to Earth in 2023. The 4.5-billion-year-old asteroid is thought to have formed in the first 10 million years of the solar system's existence. What scientists discovered in those pristine samples has fundamentally changed our understanding of how life's essential ingredients spread throughout the cosmos.

An analysis of that collected asteroid material, published Wednesday in the journal Nature, indicates that the samples included thousands of organic compounds and 14 of the 20 amino acids that life on Earth uses to form proteins. The samples also contained four "nucleobases" — the main components of DNA and RNA, which store and transmit genetic blueprints within our cells. Unlike meteorites that have been contaminated during their fiery journey through Earth's atmosphere, these samples are pristine , offering an unaltered glimpse into the early solar system.

The discovery has profound implications for astrobiology. "This confirms that life's building blocks can be formed in a diversity of environments throughout the universe," Allison Baczynski, an organic chemist at Penn State University and co-lead author of the new study, told Space.com. The findings suggest that the chemical precursors to life are far more widespread than previously imagined.

Cold Origins Challenge Previous Theories

It had been thought that these amino acids had formed in warm, watery conditions close to the infant sun 4.5 billion years ago. However, a new analysis of the isotopes contained within the amino acids points to a much colder origin for the compounds: in the presence of ice far away from the young sun, beyond what scientists call the "snow line."

"Our isotopic data indicates that the amino acids formed in a cold, icy environment and other data acquired by the OSIRIS-REx mission suggests that the parent body of Bennu formed beyond the snow line," said Baczynski. This revelation rewrites the textbook on where and how life's building blocks can emerge, expanding the potential habitable zones where such chemistry might occur.

A second paper, in the journal Nature Astronomy led by Scott Sandford at NASA's Ames Research Center in California's Silicon Valley and Zack Gainsforth of the University of California, Berkeley, reveals a gum-like material in the Bennu samples never seen before in space rocks – something that could have helped set the stage on Earth for the ingredients of life to emerge. The surprising substance was likely formed in the early days of the solar system, as Bennu's young parent asteroid warmed. Once soft and flexible, but since hardened, this ancient "space gum" consists of polymer-like materials extremely rich in nitrogen and oxygen.

Ancient Water and Chemical Factories

Perhaps most intriguingly, scientists found evidence of ancient saltwater environments within Bennu's parent asteroid. Ranging from calcite to halite and sylvite, scientists identified traces of 11 minerals in the Bennu sample that form as water containing dissolved salts evaporates over long periods of time, leaving behind the salts as solid crystals. These briny pools would have provided ideal conditions for complex chemical reactions to occur.

"This is all very exciting because it suggests that asteroids like Bennu once acted like giant chemical factories in space and could have also delivered the raw ingredients for life to Earth and other bodies in our solar system," said Glavin, lead author of a study on the samples published Wednesday in the journal Nature Astronomy. The combination of organic molecules, water, and mineral environments creates a compelling case for how asteroids might have seeded early Earth with life's prerequisites.

Expanding the Search for Life

If life's building blocks can form in a wide variety of conditions, it increases the number of locations where we could potentially look for life. The discovery that amino acids can form in cold, icy environments far from stars dramatically expands the potential real estate for life throughout the universe. Similar brines have been detected or suggested across the solar system, including at the dwarf planet Ceres and Saturn's moon Enceladus.

Yet mysteries remain. And there is also the puzzle of why life didn't form inside Bennu itself, given that most of the raw ingredients needed were present, Glavin said. Understanding this gap between having the ingredients and achieving life itself represents the next frontier in astrobiology research. As we continue analyzing these ancient samples, each grain of space dust brings us closer to answering one of humanity's most profound questions: are we alone in the universe?