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

The search for potentially habitable exoplanets centers on detecting biosignature molecules in Earth-like atmospheres, which makes it essential to understand their detectability under biologically and geologically influenced conditions. In this study, we model the reflection and thermal emission spectra of such atmospheres across the UV/VIS/NIR and mid-IR regions and simulate their detectability with future mission concepts such as the Habitable Worlds Observatory (HWO) and the Large Interferometer for Exoplanets (LIFE). We employ Numerical Weather Prediction (NWP) model data, based on Earth’s atmosphere, to derive temperature pressure profiles and couple them with a 1D photochemical model to assess the detectability of these molecules in Earth analogs located 10 parsecs 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 O3 is detectable with both mission concepts, while H2O requires specific surface humidity levels for detection with LIFE and shows only potential detectability with HWO. CO2 is detectable with LIFE. Both N2O and CH4 require continuous surface outgassing for potential detection with LIFE, and CH4 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/NIR and mid-IR domains using HWO- and LIFE-type mission concepts and offers guidance for the development of future missions operating in these spectral regions.

💡 Research Summary

This research presents a rigorous assessment of the detectability of atmospheric biosignatures in Earth-analog exoplanets, focusing on the capabilities of future mission concepts such as the Habitable Worlds Observatory (HWO) and the Large Interfer验ferometer for Exoplanets (LIFE). The study addresses the fundamental challenge of identifying biological and geological markers—specifically O3, H2O, CO2, N2O, and CH4—within the complex chemical environments of potentially habitable worlds located at a distance of 10 parsecs.

The methodology employs a sophisticated modeling approach, integrating Numerical Weather Prediction (NWP) data from Earth’s atmosphere to derive highly accurate temperature-pressure profiles. These profiles were coupled with a 1D photochemical model to simulate the reflection and thermal emission spectra across a broad spectral range, encompassing the Ultraviolet (UV), Visible, Near-Infrared (NIR), and Mid-Infrared (MIR) regions. This approach allows for a realistic representation of how surface boundary conditions, which reflect biological and geological processes, influence the observable atmospheric composition.

The findings provide critical insights into the feasibility of future spectroscopic characterization. The study confirms that Ozone (O3) is a robust biosignature, detectable by both HWO and LIFE. Carbon dioxide (CO2) is also identified as a detectable component via the LIFE mission. However, the detectability of other key molecules is highly contingent upon environmental variables. For instance, the detection of water vapor (H2O) with LIFE is sensitive to specific surface humidity levels, while its detectability with HWO remains marginal. Furthermore, the detection of Nitrous Oxide (N2O) and Methane (CH4) via LIFE requires continuous surface outgassing to maintain detectable concentrations. A particularly significant finding is the “masking effect” of water vapor; high humidity can obscure the spectral features of CH4, suggesting that low-humidity environments are more favorable for methane detection.

In conclusion, this work demonstrates the high potential of HWO and LIFE-type missions to characterize the atmospheres of Earth-like planets. By quantifying the impact of surface-atmosphere interactions and the role of geological outgassing, the study provides essential scientific constraints and strategic guidance for the design and operational planning of future space-based observatories aimed at the search for life in the universe.