Ironing Out Biosphere Oxidation

摘要

Iron is the most abundant element on Earth. It plays a critical role in a wide range of Earth system processes, from generation of the magnetic field in Earth's outer core to the production in the cell of a variety of compounds essential for life. Investigations into the biogeochemical behavior of other elements have benefited from slight differences in the chemical behavior of different stable isotopes of the same element. Yet, despite iron's importance, almost nothing was known about the natural variability of the stable iron isotopes until about a decade ago (1) and only now are researchers beginning to use iron isotopes in biogeochemical and Earth-system evolution studies. The latest application of iron isotopes to major questions in Earth history appears on page 1088 in this issue, in which Rouxel and colleagues (2) show that a progressive change in iron cycling during the Precambrian (from 3.5 to 0.5 billion years ago) was associated with the establishment of an oxy-gen-rich biosphere.