Timothy L. Grove, Professor, Department of Earth, Atmospheric & Planetary Sciences, MIT
Abstract: The MESSENGER spacecraft obtained x-ray fluorescence spectra of the surface lavas on Mercury. We used these data to calculate the absolute element abundances of Mercury’s lavas, recreated synthetic analogs of the lavas and subjected them to high pressure – high temperature melting experiments in the laboratory. We selected the end members of compositional variation observed among the surface lavas. These correspond to the oldest lavas and the youngest lavas present on the surface. The results of the melting experiments allow us to infer mantle-melting processes, melting conditions and the composition of the mantle sources from which the lavas were derived. Melting of Mercury’s mantle began at ~400 km depth (near the core-mantle boundary) at very high temperatures. As Mercury’s mantle cooled, melting moved to shallower depths and lower temperatures. Mercury’s surface lavas thus provide the first snapshot of early planetary differentiation processes on any of the terrestrial planets. They also provide an opportunity to compare the composition of Mercury’s mantle to that of the rest of the rocky planets in our solar system.