The Re-Os Revolution: Mighty Messages From Two of Earth’s Rarest Elements

The exceptional power and versatility of the Re-Os radioactive decay system for Earth science stems from the distinctive geochemical behavior of its constituent elements. Here, we first explain how the positions of Re and Os in the periodic table are responsible for their highly siderophile, chalcophile, and organophile properties. We then discuss how these properties dictate the distribution of Re and Os within and at the surface of the Earth and other planetary bodies. Lastly, we describe how the analytical challenges posed by the unusual geochemistry of these elements were overcome with major technological advances, leading to a dramatic decrease in the amount of sample material required for Re-Os isotopic analysis, thereby sparking an explosion of new applications.