New geochemical maps of Mercury
Two studies that were published recently, they produced, for the first time, global maps of the geochemical composition of the first planet of the Solar System.
Like never before we can now know in detail the chemical composition of Mercury’s surface, primarily thanks to two recent studies conducted by the scientific team working at the mission MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) of NASA. The researchers were able to create maps on a global scale of geochemical characteristics that reveal previously undetected regions, as large terrains that have different compositions from their surroundings. And the presence of these large regions has important implications for studying the history of the planet.
The probe was launched in 2004 to answer several important scientific questions, including the geological history of Mercury. The probe has reached the orbit of the first planet of the Solar System in March 2011 and since then the data from the X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) have provided information on the concentration of potassium, thorium, uranium, sodium, chlorine and silicon, as well as data related to the magnesium silicide, aluminum, sulfur, calcium and iron.
Until now, however, the geochemical maps for these elements are limited to analyzing only one hemisphere and in any case with a poor resolution. In one of the two new studies, “Evidence for geochemical terrains on Mercury: Global mapping of major elements with MESSENGER’s X-Ray Spectrometer” published in Earth and Planetary Science Letters, the authors used a new method to produce global maps on the relationship of abundance of magnesium / silicon and aluminum / silicon on the surface of Mercury.
Those obtained by researchers are the first global geochemical maps of Mercury acquired using the technique of X-ray fluorescence, with which the X-rays emitted by the atmosphere of the Sun let us examine the composition of the planet’s surface. The global maps of magnesium and aluminum have been combined with less complete information on ratios of abundance of sulfur / silicon, calcium / silicon and iron / silicon. From the maps that have been created, it can be observed that to an even greater extent it is obvious that the complex geochemical covers more than 5 million square kilometers and has the highest ratios observed in magnesium / silicon, sulfur / silicon and calcium / silicon, as well as the ratio of aluminum / silicon lowest on the planet’s surface, said Shoshana Weider, planetary geologist and a Visiting Scientist at the Carnegie Institution, and first author of this study. He and his colleagues suggest that this “region high in magnesium” may be an ancient basin born of an impact, and that would mean that its distinctive chemical signature reflects in large part the composition of the mantle exposed during the collision.
The second study, “Geochemical terrains of Mercury’s northern hemisphere as revealed by MESSENGER neutron measurements” published in the journal Icarus, shows the first maps of the absorption of low-energy neutrons over the entire surface of the planet. The data of this research were obtained with the instrument GRS, which is sensitive to the emission of neutrons from the surface of Mercury. “From these maps we can infer the distribution of the elements-thermal-neutron which are absorbed across the planet, including iron, chlorine and sodium,” wrote lead author of this study Patrick Peplowski the Johns Hopkins University Applied Physics Laboratory. “This information was combined with other measures geochemical from MESSENGER, including new measurements made with XRS, to identify and map four distinct geochemical terrains on Mercury.”
“The data collected previously with MESSENGER showed that Mercury’s surface has been shaped by volcanic activity, ‘” added Peplowski. “The magma that erupted long ago, it came from partial melting of the mantle of Mercury. The dissimilarities in the composition that we are looking in different regions geochemical indicate that the planet has a chemically heterogeneous mantle. ” Weider also underlined: “The maps made with XRS and GRS provide a new dimension to our knowledge of Mercury’s surface. The regions that we are seeing, they have not been identified before on the basis of spectral reflectivity or geological mapping. ”
Larry Nittler, Vice-Principal Investigator of the mission and co-author of both studies, said: “The crust that we see on Mercury was mainly formed more than three billion years. “The chemical variability observed by MESSENGER will provide constraints on future efforts to model and understand the composition of Mercury and the ancient geological processes that shaped the planet’s mantle and crust.”