The Earth’s surface Fe cycle is very important for biogeochemical systems that regulate planetary climate, nutrient availability, marine primary productivity, and the Earth’s habitability. Firstly, as a redox sensitive element, Fe availability is sensitive to atmospheric O2 concentration and the redox landscape of the ocean. Earth's surface redox evolution in deep time has been widely investigated using palaeoredox proxies, including Fe speciation and Fe isotopes. Secondly, Fe is essential for life, engaged in various physiological functions, such as cell proliferation and differentiation, gene regulation, and steroid synthesis, but excessive free Fe ions are also toxic. Thirdly, diverse Fe-related metabolisms, e.g., anoxygenic photosynthesis, the metabolisms of Fe-oxidizing bacteria, and dissimilatory iron reduction by microorganisms, may be recorded in Banded iron formations or sedimentary pyrite, which may yield information on biosignatures of early Earth or extraterrestrial planets, such as Mars. Importantly, the sedimentation processes are strongly influenced or even driven by iron cycles in the past. As such, microbial iron cycle related sediments are important archives of iron cycles in deep time.

This session aims to provide a platform to communicate recent progress on Fe biochemical processes in cells/organisms, biogeochemical cycles in the Earth System, both present and deep time, and Fe biosignatures on extraterrestrial materials, particularly various sedimentary records of Fe cycles. We welcome contributions that document diverse approaches, including but not limited to modern environmental chemistry, geobiology, sedimentology, geochemistry, laboratory experiments, and numerical simulations/models that add insight into the Fe cycle on Earth and beyond, from deep time to present.