Antonin Affholder is a NOMIS–ETH Fellow at the Centre for Origin and Prevalence of Life at ETH Zurich (Switzerland). He is conducting his research in the Department of Environmental Systems Science under the mentorship of Loïc Pellissier.
Affholder became an evolutionary ecologist at École Normale Supérieure in Paris, France. During his PhD there, he applied tools from the theory of ecosystems to tackle inference of habitability and biosignatures. He developed models for the atypical microbial ecosystems, which may have dominated the biosphere of Earth’s young years and now populate the oxygenless deep ocean and soils.
Research Focus
Using his models in conjunction with geochemical and geophysical modeling, Affholder was able to infer the likelihood of data gathered from space by the Cassini mission under the hypothesis of Earth-like hydrothermal microbes in Enceladus’ subsurface ocean. Likewise, he also constrained the potential for Titan’s ocean to harbor Earth-like life and estimated the potential size of hypothetical biospheres in the oceans of icy moons. Focusing on the atmospheric evolution of Earth-like planets, Affholder researched signatures of habitability and inhabitation in atmospheric spectra that future telescopes might observe. In particular, he explored how a future telescope probing the atmosphere of Earth-like planets could infer whether an Earth-like carbon cycle is required to sustain a temperate climate over geological timescales.
Prior to his NOMIS–ETH Fellowship, which begins in September 2025, Affholder is conducting postdoctoral research at the University of Arizona (Tucson, US), where he is investigating the microbial ecology of soil communities and their participation in the Earth’s carbon cycle — specifically, how microbial adaptation affects soil biogeochemistry, and how evolutionary theory can be used to improve models of carbon cycling.
As a NOMIS–ETH Fellow, Affholder will investigate how complex feedback between the abiotic and biotic components of the early Earth system, as well as competition between different metabolisms, may have participated in delaying the oxygenation of Earth’s atmosphere by hundreds of millions of years after oxygenic photosynthesis emerged. This inherent system complexity raises the possibility that the timing of the oxygenation of Earth’s atmosphere is a unique outcome of geochemical and biological processes interacting together on a rocky, Earth-sized, habitable-zone planet with life. Detection of O2 in exoplanet atmospheres is seen as a relatively achievable goal in the coming decades. But unless we gain a deeper understanding of how the presence or absence of this gas in the atmosphere relates to the presence or absence of a biosphere at the planet’s surface, interpretation of these future observations will remain challenging.