The evolution of biological hydrogen oxidation as a key mechanism to prevent planetary water loss

Objective

Water is essential to planetary habitability, and Earth’s long-term water stability depends on mechanisms preventing hydrogen escape to space. Hydrogen on Earth is continually produced through geological and biological processes. While hydrogen production from water photolysis in the upper atmosphere is largely prevented by Earth’s magnetic field and atmospheric cold traps, hydrogen generated in the crust or near the planetary surface would escape to space unless oxidation processes act on it quickly. AQUA hypothesises that biological hydrogen oxidation is one of the major processes preventing planetary water loss and that it played a key role during Earth's evolutionary history. Biological hydrogen oxidation is an ancient and ubiquitous metabolism that spans all major branches of life and is prominent across Earth's environments. Simple calculations suggest that without biological hydrogen oxidation Earth would have lost a significant fraction of its oceans over time. By integrating microbiology, evolutionary biology, geochemistry, and planetary science, AQUA aims to unravel the role of biological hydrogen cycling in Earth’s water retention and its implications for the search of life in the universe. The project will focus on: (1) Quantify hydrogen oxidation in microbial communities using novel in situ and laboratory methods; (2) Decipher biological imprints on geological hydrogen across diverse settings; (3) Trace the evolution and biochemical basis of microbial hydrogen metabolism; and (4) Model biological hydrogen cycling’s role in planetary water retention and its potential as a biosignature for extraterrestrial life. Fieldwork in diverse geological settings, cutting-edge analytical techniques, and computational modeling will allow AQUA to reconstruct Earth's biological hydrogen cycling history. Insights from this project promise transformative advances in understanding Earth's redox balance, microbial ecology, clean energy prospects, and planetary sciences.