Detectability of Atmospheric Biosignatures in Earth Analogs with Varying Surface Boundary Conditions: Prospects for Characterization in the UV, Visible, Near-infrared, and Mid-infrared Regions

Abstract The search for potentially habitable exoplanets centers on detecting biosignature molecules in Earth-like atmospheres, making it crucial to understand their detectability under biologically and geologically influenced conditions. In this study, we model the reflection and thermal emission spectra of such atmospheres in the UV/VIS/near-IR and mid-IR regions and simulate their detectability using future mission concepts such as the Habitable Worlds Observatory (HWO) and the Large Interferometer for Exoplanets (LIFE). We employ numerical weather prediction model data, based on Earth’s atmosphere, to derive temperature–pressure profiles and integrate a 1D photochemical model to assess the detectability of these molecules in Earth analogs located 10 pc away. We investigate the dominant reaction pathways and their contributions to the atmospheric composition of an Earth analog, with a focus on how they shape the resulting molecular signatures. We also examine the role of surface boundary conditions, which indirectly trace the effects of biological and geological processes, on the detectability of these molecules using HWO- and LIFE-type mission concepts. Our findings indicate that O 3 is detectable with both mission concepts, while H 2 O requires specific surface humidity levels for detection with LIFE and shows only potential detectability with HWO. CO 2 is detectable with LIFE. Both N 2 O and CH 4 require continuous outgassing for potential detection with LIFE, and CH 4 further requires low surface humidity to prevent masking by water features. Our work highlights the feasibility of characterizing the atmospheres of Earth analogs in the UV/VIS/near-IR and mid-IR domains using HWO- and LIFE-type mission concepts and provides valuable insights for the development of future missions operating in these spectral regions.