We found a way to spot aliens without needing to know what they look like or what they’re made of—we just look for signs of complexity.
arXiv · March 13, 2026 · 2603.11086
Why it matters
Instead of looking for Earth-like signals like DNA, this method measures the 'complexity' required to build the molecules found in a planet's atmosphere. If the molecules are too complex to have formed by chance, it serves as a 'smoking gun' that an evolutionary process—life—must be present to assemble them.
From the abstract
This white paper introduces a framework for applying Assembly Theory (AT) to planetary atmospheres as a biosignature framework suitable for the Habitable Worlds Observatory (HWO). AT quantifies the minimum combinatorial complexity required to co-construct an observed ensemble of molecular species, providing a measure of how much selection and evolution is encoded in a planetary atmosphere's chemical space, without assuming any specific biochemistry, kinetics nor metabolism. We outline some forth