An agnostic biosignature is a life-detection strategy that does not require knowing life’s specific chemistry or committing to any single indicator molecule. Instead, it searches for the large-scale statistical footprint that life leaves across a population of planets.
ELSI Method (Smith & Sinapayen, 2026)
harrison-b-smith and lana-sinapayen at the earth-life-science-institute proposed the first practical agnostic biosignature framework in April 2026 (src-panspermia-agnostic-biosignature-2026-04). The method rests on two minimal assumptions:
- Life can spread between planetary bodies (panspermia)
- Life modifies planetary environments over time
Under these assumptions, agent-based simulations show that life-influenced planets cluster statistically by spatial proximity and measurable characteristics. A survey of a large exoplanet population could flag high-probability life-bearing clusters without identifying any specific biosignature gas.
Why It Matters
- Reduces false positives by avoiding single-gas claims (e.g., DMS, O₂) that have known abiotic production routes.
- Does not assume intelligence, unlike technosignatures.
- Chemistry-agnostic: applicable even if life elsewhere uses entirely different biochemistry.
- Scales with survey size: most powerful with large exoplanet catalogs from future instruments like habitable-worlds-observatory.
Contrast with Other Approaches
| Approach | Chemistry assumed? | Intelligence assumed? | FP risk |
|---|---|---|---|
| Gas biosignatures (DMS, O₂) | Yes | No | High (abiotic mimics) |
| Technosignatures | No | Yes | Low (but narrow) |
| Agnostic (ELSI method) | No | No | Low (by design) |