Unsupervised Classification of Mercury’s Surface Spectral and Chemical Characteristics

Tuesday, 16 December 2014
Mario D'Amore1, Jorn Helbert1, Sabrina Ferrari2, Alessandro Maturilli1, Larry R Nittler3, Deborah Lorin Domingue4, Faith Vilas4, Shoshana Z Weider5, Richard D Starr6, Ellen J Crapster-Pregont7, Denton S Ebel8 and Sean C Solomon9, (1)German Aerospace Center DLR Berlin, Berlin, Germany, (2)DLR, Berlin, Germany, (3)Carnegie Inst Washington, Washington, DC, United States, (4)Planetary Science Institute Tucson, Tucson, AZ, United States, (5)Carnegie Institution, Washington, DC, United States, (6)Catholic University of America, Washington, DC, United States, (7)Columbia University, New York, NY, United States, (8)American Museum of Natural History, New York, NY, United States, (9)Lamont-Doherty Earth Observatory, Palisades, NY, United States
The spectral reflectance of Mercury’s surface has been mapped in the 400–1145 nm wavelength range by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument during orbital observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Under the hypothesis that surface compositional information can be efficiently derived from such spectral measurements with the use of statistical techniques, we have conducted unsupervised hierarchical clustering analyses to identify and characterize spectral units from MASCS observations. The results display a large-scale dichotomy, with two spectrally distinct units: polar and equatorial, possibly linked to differences in surface environment or composition. The spatial extent of the polar unit in the northern hemisphere correlates approximately with that of the northern volcanic plains. To explore possible relations between composition and spectral behavior, we have compared the spectral units with elemental abundance maps derived from MESSENGER’s X-Ray Spectrometer (XRS). It is important to note that the mapping coverage for XRS differs from that of MASCS, particularly for the heavy elements. Nonetheless, by comparing the visible and near-infrared MASCS and XRS datasets and investigating the links between them, we seek further clues to the formation and evolution of Mercury’s crust. Moreover, the methodology will permit automation of the production of new maps of the spectral and chemical signature of the surface.