The Exo-Life Finder (ELF) telescope: New strategies for direct detection of exoplanet biosignatures and technosignatures

The Exo-Life Finder (ELF) will be an optical system with the resolving power of a ≥20m telescope optimized for characterizing exoplanets and detecting exolife. It will allow for direct detection of Earth-size planets in commonlyconsidered water-based habitable zones (WHZ) of nearby stars and for generic exolife studies. Here we discuss capabilities of the ELF to detect biosignatures and technosignatures in exoplanetary atmospheres and on their surfaces in the visual and near infrared. We evaluate sensitivity limits for mid- and low-resolution spectral, photometric and polarimetric measurements, analyzed using atmosphere models and light-curve inversions. In particular, we model and estimate integration times required to detect O₂, O₃, CO₂, CH₄, H₂O and other biosignature gases and habitability markers. Disequilibrium biosignature pairs such as O₂+CH₄ or CO₂+CH₄–CO are also explored. Photosynthetic and nonphotosynthetic pigments are other important biosignatures that ELF will search for in atmospheres and on resolved surfaces of exoplanets, in the form of bioaerosols and colonies of organisms. Finally, possible artificial structures on exoplanet surfaces and in near-exoplanet space can be detected. Practical instrument requirements are formulated for detecting these spectral and structural biosignatures and technosignatures. It is imperative that such a study is applied first to characterize the nearest exoplanet Proxima b, then to search for exo-Earths in the Alpha Cen A and B system and other near-Sun stars, and finally to explore larger exoplanets around more distant stars.