Low-Altitude Neutron Measurements at Mercury: New Insights into Volatile Distributions
Tuesday, 16 December 2014
MESSENGER’s low-altitude observing campaign provides an improvement by an order of magnitude in the spatial resolution of neutron measurements compared with previously reported analyses. Those prior measurements revealed the presence of distinct geochemical terranes on Mercury’s surface at the ~1000-km spatial scale. The low-altitude data, in particular measurements acquired below 60 km, provide a spatial resolution of <100 km, facilitating an investigation of the chemical properties of smaller areas of interest. Specific targets include individual polar deposits, fresh impact craters, low-reflectance material, pyroclastic deposits, isolated small expanses of smooth and intercrater plains, and areas with unusual color properties or composition indicated by imaging or other elemental remote sensing observations. Because neutron measurements are particularly sensitive to volatile elements, such as H, Na, and Cl, the low-altitude data provide new insights into volatile transport processes on Mercury, including the sequestration of water ice and other frozen volatile compounds in permanently shadowed craters and volatile-driven volcanism.