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

TL;DR

This study models the spectral detectability of biosignature gases in Earth-like exoplanet atmospheres across multiple spectral regions, assessing how surface conditions influence their observability with future space missions.

Contribution

It provides a comprehensive analysis of biosignature detectability considering surface boundary effects and evaluates the capabilities of upcoming mission concepts like HWO and LIFE.

Findings

Ozone is detectable with both missions.

Water detection depends on surface humidity levels.

CO2 is detectable with LIFE.

Abstract

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.