Abstract_EANA2026-1

Abstract EANA2026-1

Mapping abiotic atmospheric diversity together with environment-dependent disequilibrium gases as indicator for potential non-Earth-like biosignatures

Lena Noack (1), Caroline Brachmann (1), Tim Lichtenberg (2), Haiyang Wang (3) and Sean Jordan (4)

(1) Freie Universität Berlin, Germany; (2) University of Groningen, The Netherlands; (3) University of Copenhagen, Denmark; (4) ETH Zurich, Switzerland

The search for life on planets beyond the solar system relies on the identification of robust biosignatures in exoplanetary atmospheres that can be detected with current or future space and ground observatories (such as JWST, ELT, HWO or LIFE). However, for a correct interpretation of the potential sources of biosignatures (specifically including abiotic sources), we first need a solid understanding of the potential range of abiotically created atmospheres over a wide range of planetary parameters, including planetary composition, redox state, and atmospheric pressure and temperature conditions [1,2].

Based on the wide range of potential abiotic baseline atmospheres that we already identified [2], we now focus on determining the gases that would be maximally out of equilibrium with the entire baseline atmosphere.

For this, we developed a new chemical reaction model in Python that allows us to first define the chemical elements (so far limited to COHNSP, but arbitrarily extendable to more elements) and molecules of interest, and automatically derives the according network of all possible chemical reactions in the atmosphere together with the Gibbs energies of the equilibrium reactions. This allows on the one hand to calculate the equilibrium atmosphere based on the atmospheric elemental composition, and leads on the other hand to an automatic marking of gases that are most out of equilibrium with that atmosphere – i.e. potential biosignatures.

In the next step, we will compare the identified potential biosignatures and their diverse baseline atmospheres with non-equilibrium reactions models to estimate their potential to be false positive signatures due to kinetics/photochemistry [3].

The final goal of the project is to constrain the observability of the identified biosignatures for each baseline atmosphere with the proposed LIFE (Large Interferometer For Exoplanets) mission [4].

[1] Liggins, P., Jordan, S., Rimmer, P.B., Shorttle, O. (2022). Growth and evolution of secondary volcanic atmospheres: I. Identifying the geological character of hot rocky planets. J. Geophys. Res.: Planets 127 (7), e2021JE007123.

[2] Brachmann, C., Noack, L., Baumeister, P.A., Sohl, F. (2025). Distinct types of CHON atmospheres and surface pressures depending on melt redox state and outgassing efficiency. Icarus, 429, 116450.

[3] Liggins, P., Jordan, S., Rimmer, P.B., Shorttle, O. (2023). Growth and evolution of secondary volcanic atmospheres: II. The importance of kinetics. J. Geophys. Res.: Planets 128 (3), e2022JE007528.

[4] Quanz, S. P., Ottiger, M., Fontanet, E., et al. (2022). Large Interferometer For Exoplanets (LIFE)-I. Improved exoplanet detection yield estimates for a large mid-infrared space-interferometer mission. Astronomy & Astrophysics, 664, A21.