In this project, experiments on planetary materials were performed on compositions and under conditions that had never been investigated before. The new data provided by the MESSENGER spacecraft provide unique opportunities for significant breakthrough on Mercury. A major originality is to combine experimental petrology, geochemical analyses and spacecraft measurements. Specifically, this project is the first to attempt experiments aimed at understanding the evolution of volatiles in Mercury’s mantle by determining the solidus of the entire mantle, investigating the partitioning of radioactive elements between sulfides and silicate melt under extremely reduced conditions, and exploring whether a diamond layer might exist in the deep mantle. Experiments were performed at pressure and temperature conditions relevant to the entire Mercurian mantle. This is highly challenging and requires the development of new approaches and methods that are not commonly used in experimental petrology. The results of this project provided the following new insights into primitive silicate liquids depleted in FeO: 1) the solidus of the entire Mercurian mantle, 2) the speciation and solubility of sulfur and carbon, 3) the distributions of volatiles and radioactive elements in the mantle, and 4) the structure of the Mercurian deep mantle.
This project was rooted in igneous petrology and in the combination of experimental petrology, geochemical analyses, numerical and thermodynamic modelling, and spacecraft measurements of the surface of Mercury acquired by MESSENGER. The experimental strategy and the interpretations of data also strongly rely on geophysical measurements for the internal structure of Mercury. Our experiments can also be used for the calibration of the MERTIS instrument (Mercury Radiometer and Thermal Imaging Spectrometer) installed on the Mercury Planetary Orbiter of the BepiColombo spacecraft (to be launched to Mercury in October 2018). We discussed with the Principal Investigator Harald Hiesinger (University of Münster, Germany) and co-Principal Investigator Jörn Helbert (DLR Institut für Planetenforschung, Berlin, Germany) and shared our experiments' data that have relevant compositions and mineralogy for the surface of the planet. MERTIS is an infrared imaging spectrometer and these wavelengths have a high potential for mineral identification because it is in this region where the major rock-forming minerals have their fundamental vibration bands.
