Mercury s crust possibly made of magnesium rich basalt
Using spectrometric measurements taken by MESSENGER and laboratory analyzes of Mercury surface-analogue samples, researchers have determined that the upper layers of the planet’s crust most closely resemble magnesian basalt terrestrial rocks, though with lower iron concentrations.
With both x-ray and gamma-ray spectrometers, the MErcury Surface, Space ENvironment, GEochemistry and Ranging probe (MESSENGER), which entered orbit around Mercury in 2011, is well equipped for carrying out a detailed compositional analysis of Mercury’s crust, the understanding of which could help determine the nature of the planet’s formation, and of its volcanic past.
To make their determination, the researchers used a software package known as MELTS to simulate the cooling and crystallization of potential Mercurian lavas with different chemical compositions, estimating the temperatures at which minerals would crystallize out of the molten lava and the abundances of different mineral species. Similarly, they simulated the cooling of magnesium-rich terrestrial rocks and of meteoritic samples.
Based on their chemical compositional analysis, they infer a number of properties for an early lava on Mercury. They suggest that the lava would have had a very low viscosity, streaming across the surface in widespread but thin layers.
Further, they calculated that the temperatures required to produce the magnesium-rich lava would have been much higher than for terrestrial rocks not enriched in magnesium.
The researchers said that the low-viscosity lava would leave telltale marks on the planet’s surface that could be identified through further MESSENGER observations.
The study was published in the Journal of Geophysical Research-Planets.