The Building Blocks of Life Can Be Found Anywhere—Including Space
By Leo Kelly
Are we alone? It’s the oldest question we have. And recently, a rock might have answered.
In 2020, NASA’s OSIRIS-REx mission landed on asteroid Bennu, a 500-metre-wide lump of space debris older than the Earth itself, and scooped up 121 grams of dust and rubble. When that sample returned to Earth in 2023, scientists got to work. What they found has raised intriguing questions about the chemical building blocks of life beyond Earth. [1]
Bennu carries amino acids, the building blocks of proteins; nucleobases, the chemical letters that write DNA and RNA; and sugars including ribose. Not traces. Not hints. The complete toolkit, on a rock that has been drifting through space since before our planet existed. [2]
What makes this different from previous asteroid finds is how clean the sample is. Meteorites that hit Earth burn through the atmosphere and spend years exposed to the elements. Bennu’s sample came back sealed, pristine, and uncontaminated. What we’re seeing is genuinely 4.5 billion years old. [3]
Here’s where it gets strange. The amino acids found on Bennu come in equal left and right-handed forms, mirror images of each other. Life on Earth uses almost exclusively left-handed amino acids. Something, somewhere, tipped the scales. Nobody knows what. The fact that Bennu’s are balanced suggests that when the first molecules of life formed on Earth, they started from this 50/50 mix, and something nudged them toward one side. We still don’t know what. [2]
There’s also the panspermia question — the idea, increasingly taken seriously, that the raw ingredients for life didn’t originate on Earth at all. That asteroids like Bennu, crashing into early Earth billions of years ago, delivered the starter pack. Life on Earth as a cosmic import. It sounds like sci-fi, but the evidence is starting to make it look less far-fetched. [4]
None of this is evidence that life exists elsewhere. But it does mean the building blocks aren’t rare. They’re out there, on ancient rocks, distributed across the solar system, waiting. The real question now isn’t whether the ingredients exist. It’s why, out of all the places they landed, only one place seems to have done anything with them. [2]
[1] NASA. “OSIRIS-REx.” NASA Science. https://science.nasa.gov/mission/osiris-rex/
[2] NASA. “NASA’s Asteroid Bennu Sample Reveals Mix of Life’s Ingredients.” NASA, February 2025. https://www.nasa.gov/news-release/nasas-asteroid-bennu-sample-reveals-mix-of-lifes-ingredients/
[3] Furukawa, Y. et al. “Bio-essential sugars in samples from asteroid Bennu.” Nature Geoscience, December 2025. https://doi.org/10.1038/s41561-025-01838-6
[4] Glavin, D. et al. “Prebiotic organic compounds in samples of asteroid Bennu.” PNAS, November 2025. https://www.pnas.org/doi/10.1073/pnas.251246112
