The composition of the early solar system, and by extension the potential for life beyond Earth, is coming into sharper focus thanks to analysis of samples returned from asteroid Bennu by NASA’s OSIRIS-REx mission. Initial findings, published in in Nature and Nature Astronomy, reveal the presence of key molecules for life, alongside evidence of ancient saltwater that could have facilitated their interaction.
While the samples don’t demonstrate the existence of life itself, the discovery significantly strengthens the hypothesis that the building blocks of life were widely distributed throughout the early solar system. This increases the probability that life could have emerged on other planets and moons. As Nicky Fox, associate administrator for NASA’s Science Mission Directorate, stated, “NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our solar system.”
The Bennu samples contain at least 14 of the 20 amino acids used by life on Earth, as well as 19 other amino acids not currently utilized by terrestrial organisms. Amino acids are fundamental organic compounds that combine to form proteins, which are essential for all known life forms. Previously, these amino acids were detected in extraterrestrial rocks, but finding them in a pristine sample collected directly from a space-based object provides stronger support for the theory that asteroids originating far from the sun played a crucial role in delivering these ingredients to Earth.
A recent study led by Penn State scientists, published in the Proceedings of the National Academy of Sciences, adds another layer to this understanding. Researchers focused on glycine, the simplest amino acid, and discovered that its formation within the Bennu samples likely occurred in a previously unexpected environment: an icy-cold, radioactive setting. This challenges the conventional view that amino acids primarily formed in warm, watery conditions near the early sun.
Allison Baczynski, assistant research professor of geosciences at Penn State and co-lead author of the study, explained, “Our results flip the script on how we have typically thought amino acids formed in asteroids. It now looks like there are many conditions where these building blocks of life can form, not just when there’s warm liquid water.” The team utilized custom instruments to measure isotopes – variations in the mass of atoms – within the tiny, teaspoon-sized sample, revealing a greater diversity in the pathways and conditions under which these amino acids could have originated.
The discovery of glycine formation in a radioactive environment is particularly significant. Radioactive decay generates heat, which could have provided the energy needed for chemical reactions to occur even in the frigid temperatures of the early solar system. This suggests that the conditions necessary for the creation of life’s building blocks were more widespread and resilient than previously thought.
The OSIRIS-REx mission delivered the Bennu samples to Earth in . The ongoing analysis of these samples is expected to yield further insights into the origins of the solar system and the potential for life beyond our planet. The pristine nature of the sample is key. unlike meteorites that have been exposed to Earth’s atmosphere and potential contamination, the Bennu sample provides a relatively unaltered snapshot of the early solar system’s chemistry.
This research doesn’t pinpoint the exact mechanism by which life arose on Earth, but it does expand the range of plausible scenarios. The presence of both the building blocks of life and evidence of ancient water on Bennu suggests that asteroids like Bennu may have acted as “broths” where these compounds could interact and combine, potentially leading to the emergence of more complex molecules. The findings support the idea that the raw materials for life weren’t limited to Earth’s unique environment, but were potentially common throughout the early solar system.
The implications extend beyond our understanding of Earth’s origins. If the building blocks of life are indeed widespread, it increases the likelihood that life may exist – or have existed – elsewhere in the universe. Future missions to other asteroids and potentially icy moons in our solar system will likely build upon these findings, searching for further evidence of prebiotic chemistry and the potential for extraterrestrial life.
