Antonin Affholder

Antonin 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 oxygen-less deep ocean and soils.

Using these models in conjunction with geochemical and geophysical modelling, Antonin 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’s subsurface ocean. Using this modelling, he also constrained the potential for Titan’s ocean to harbour Earth-like life, and estimated the size that hypothetical biospheres in the oceans of icy moons could reach. Some of his other work is focused on the atmospheric evolution of Earth-like planets, researching signatures of habitability and inhabitation in atmospheric spectra that future telescope will acquire. In particular, he researched 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 ETH, Antonin was at the University of Arizona, Tucson, USA, where he focused on the microbial ecology of soil communities and their participation to the Earth’s carbon cycle, specifically on how microbial adaptation affects soil biogeochemistry, and how evolutionary theory can be used to improve models of carbon cycling.

Within the fellowship, Antonin Affholder investigates how complex feedbacks between the abiotic and biotic components of the early Earth system, as well as competition between different metabolisms may have participated to delay 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 particular rather than generic 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 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.