Abstract EANA2026-118

Oxygen-rich atmospheres are widely considered promising indicators of life, yet Earth’s own oxygenation history shows that biological oxygen production and atmospheric oxygen accumulation can be separated by hundreds of millions of years (Runge et al., 2025; Vulpius et al., 2026). Several authors have pointed out in their models that atmospheres containing appreciable amounts of O2 can be produced abiotically (e.g. Wordsworth and Pierrehumbert, 2014; Harman et al., 2016). Processes thought to influence atmospheric O2 values abiotically include serpentinization, changes in crustal thickness and composition, subduction initiation, an evolving mantle redox state, and photochemistry. However, the strength of the influence of these processes on atmospheric composition remains poorly constrained.

In our new project, we aim to develop a quantitative, geologically grounded framework to understand when and how photosynthetic life can actually imprint an oxygen signal on a rocky planet’s atmosphere, and when purely abiotic processes might mimic or obscure that signal. Our main aim is to link the redox evolution of a planet’s interior and surface to the timing and extent of atmospheric oxygenation. We will test three related hypotheses: (1) early core formation and magma ocean solidification set long-lived redox “initial conditions” that control volatile storage and outgassing for billions of years; (2) subsequent geological and chemical processes, as mentioned above, can strongly delay or promote atmospheric oxygen buildup; and (3) under some conditions, abiotic processes alone can create oxygen-rich atmospheres that resemble biological Great Oxidation Event (GOE) analogues.

To address these questions, we will couple two-dimensional numerical models of mantle convection and volatile cycling with simple atmospheric evolution models. The interior models will track the storage and release of key volatile species (including hydrogen-, carbon-, nitrogen-, and sulfur-bearing gases) under different redox conditions, and will be extended to follow iron oxidation states in melts as volatiles degas. The atmospheric component will use these outgassing histories to calculate the evolving balance of oxygen sources and sinks, including the potential for strong hydrogen escape. By varying planetary parameters, we will simulate Earth, Venus, Mars, and a broader population of rocky exoplanets. We also plan to connect to existing and upcoming observations of exoplanet systems, such as TRAPPIST-1, where numerical interior–atmosphere models already suggest nitrogen–oxygen atmospheres may arise without biology.

Here, we present first results for several of the above processes studied in isolation, with a strong focus on redox-dependent outgassing. We show that the redox state of the melt not only influences the gases released, but that, conversely, the gases may also change the redox state of the melt, both in a magma ocean and in volcanic settings. We furthermore show that the initial volatile budget has a strong influence on a planet’s evolutionary path and may determine whether a planet ends up habitable, Mars-like, or Venus-like.