Elemental abundances at the surface of a rocky planet reflect both the original composition of the body and the various processes that have shaped the surface over billions of years. NASA's MESSENGER spacecraft has been in orbit around Mercury since 18 March 2011, and includes X-ray, gamma-ray and neutron spectrometers designed to characterize the chemical composition of the planet's surface. This talk will discuss how elemental abundances are determined remotely from orbit as well as initial results indicating a planetary surface formed by partial melting of a highly chemically reduced, but not highly volatile depleted, silicate mantle. Implications for models of Mercury's origin and evolution will be discussed.

Argonne Physics Division Colloquium Schedule