Abstract EANA2025-152

Direct imaging by the next generation of space telescope instruments is expected to obtain disk-integrated spectra of Earth-like exoplanets in the visible-to-near-infrared. These spectra may capture reflected light from surface materials, potentially including biomass. Photosynthetic life is detectable in Earthshine via the “vegetation red edge” (VRE): a sharp, step-like increase in reflectance with increasing wavelength at ~700 nm. Other forms of biomass display analogous step-like reflectance “edges”. However, some minerals of non-biological origin are also known to show reflectance edges, suggesting a risk of false positives in exoplanet biosignature detection. We investigate edge-like features in mineral reflectance spectra using existing databases. We identify several sulfide and tectosilicate minerals with VRE-like features, as well as the prebiotically important cyanide salt, potassium ferrocyanide. We conclude that the future evaluation of the biogenicity of VRE-like features in exoplanet reflectance spectra may reduce to a judgement about the relative prior probability of a non-Earth-like planetary mineralogy versus Earth-like planetary biology. Current ongoing work involves expanding our understanding of the extent of false positives, testing the potential quantitative relationship between life and non-life, and exploring agnostic biosignatures in future telescope detections.