An eco-evolutionary modeling framework to constrain microbial energetic limits and evaluate life environmental impact at planetary scale - Implications for habitability and biosignatures.

Abstract:

Ecosystem models have played a major role in elucidating how our planet’s biosphere has shaped Earth’s key characteristics (e.g., atmospheric composition, climate) throughout its history and helped interpreting geological evidence to constrain the evolutionary history of life on Earth (e.g., Kasting et al 2001, Kharecha et al 2005, Catling et al. 2007). These models can be extended beyond Earth to help predict planetary biosignatures that could be used to search for signs of life on other planets, given current or foreseeable technologies, and to reduce uncertainties in discriminating lifeless and inhabited planets (Krissanson-Totton et al 2018, Catling et al 2018).

Existing models can represent abiotic planetary processes in much detail. In contrast, the way they resolve life feedbacks to the planetary environment remains usually extremely simplified. An oversimplification of biological processes may result in inaccurate or flawed predictions regarding planetary features that might be candidate biosignatures. Here we present a new planetary modeling framework which explicitly includes the physiological, ecological and evolutionary processes of chemotrophic microbial biospheres to address both their energetic limits and their feedback to the planetary environment. We show how this framework can be applied to a variety of important topics regarding early Earth atmosphere and climate and life beyond Earth. This framework produces new and refined predictions on habitability, biomass production, biological regulation of climate, and planetary biosignatures.