NASA MESSENGER team has provided two new maps of mercury’s surface which shows unidentified regions.

MESSENGER an acronym for mercury surface, space environment, geochemistry, and ranging is the NASA spacecraft orbiting mercury. It has entered mercury’s orbit on March 2011. It is designed to study the chemical composition of surface, geological history, magnetic field, size and state of core.

The maps were created using the X-Ray Spectrometer (XRS) and the Gamma-Ray Spectrometer (GRS) of the MESSENGER and they also provided information on the concentrations of potassium, sodium, chlorine, and silicon, thorium, uranium, as well as ratios relative to silicon of magnesium, aluminum.

The new maps show unidentified regions of mercury known as “geochemical terranes” which has different composition than the surrounding crust. These terranes provide insights into the formation of the outer surface of Mercury.

“The consistency of the new XRS and GRS maps provides a new dimension to our view of Mercury’s surface, the terranes we observed had not been previously identified on the basis of spectral reflectance or geographical mapping.” said the study’s lead author Shoshana Weider, of the Carnegie Institution of Washington.

Geochemical maps for some of the rations and elements were limited to one hemisphere and had poor spatial resolution. But a different methodology called the X-Ray fluorescence technique by which X-Rays emitted from the sun’s atmosphere will help examine the planets composition.  This technique has been used to produce global maps of aluminum/silicon and magnesium/silicon abundance ratios from the data provided by XRS. This is the first global geochemical maps of Mercury and the first maps of global extent for any planetary body by using this technique.

The global aluminum and magnesium maps are paired with the less spatially complete maps of calcium/silicon, iron/silicon and sulfur/silicon to study the geochemical characteristics of the surface.

The most visible of these geochemical terrane is a large feature covering over 5 million square kilometers. This terrane “exhibits the highest magnesium/silicon, sulfur/silicon, and calcium/silicon ratios, and some lowest aluminum /silicon ratios on the planet’s surface” said Shoshana Weider from the Carnegie Institution of Washington. This high magnesium region could be because of an impact long ago. This indicates that the exposed mantel could have aided in the formation of this large feature.
The second map which is the geochemical terranes of mercury’s northern hemisphere by MESSENGERS GRS shows the absorption of the low-energy thermal neutrons across the surface. By this the distribution of the neutron absorbing elements like iron, sodium can be identified. This information combined with MESSENGERS XRS information helped to identify four geochemical terranes on mercury

“Earlier MESSENGER data have shown that Mercury’s surface was pervasively shaped by volcanic activity, the magmas erupted long ago were derived from the partial melting of Mercury’s mantle. The differences in composition that we are observing among geochemical terranes indicate that Mercury has a chemically heterogeneous mantle.” said Peplowski.

“The crust we see on Mercury was largely formed more than three billion years ago,” said Carnegie’s Larry Nittler.

“The remarkable chemical variability revealed by MESSENGER observations will provide critical constraints on future efforts to model and understand Mercury’s bulk composition and the ancient geological processes that shaped the planet’s mantle and crust.”