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Global Multivariate Spectral Analysis of Mercury and the Identification of Geochemical Terrains: Derived from the MASCS Spectrometer onboard NASA’s MESSENGER Mission
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  • Indhu Varatharajan,
  • Mario D'Amore,
  • Deborah Domingue,
  • Jorn Helbert,
  • Alessandro Maturilli
Indhu Varatharajan
German Aerospace Center (DLR)

Corresponding Author:[email protected]

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Mario D'Amore
DLR
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Deborah Domingue
Planetary Science Institute
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Jorn Helbert
DLR
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Alessandro Maturilli
DLR
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Abstract

The visible-infrared spectra of Mercury’s surface show little variation, displaying no distinct spectral features except for the possible spectral identification of sulfide within the hollows (Vilas et al. 2016). It is essential therefore to define and map any subtle spectral heterogeneity across Mercury’s surface and to correlate these differences where possible to geomorphological features, such as impact craters, volcanic vents, and tectonic features. The Mercury Atmospheric and Surface and Composition Spectrometer (MASCS) instrument onboard MESSENGER spacecraft is the only hyperspectral reflectance spectrometer to date that has mapped Mercury’s surface in the wavelength range 320 nm - 1450 nm. The limitation of MASCS is that it’s a point spectrometer that mapped Mercury’s surface at non-uniform spatial scale. In this study, we resampled the global MASCS hyperspectral dataset to a uniform spatial resolution of 1 pixel per degree. This enabled us to perform global multivariate analyses, including standard spectral parameter maps, k-means clustering, and principal component analysis (PCA) to spectrally characterize Mercury’s surface. Among these techniques, PCA significantly improved the identification of spectral heterogeneities across Mercury correlated to both chemical and physical properties of the surface, enabling us to identify units based on grain size, the presence of amorphous materials, and space-weathering associated alterations. The global MASCS PC color-composite map derived from principal components 1, 2, and 6 effectively distinguishes varying spectro-morphologies across Mercury’s surface, highlighting the spectral properties of various geochemical terrains. We further demonstrate that PCA spectrally differentiates between the two northern volcanic plains’ geochemical regions; the high-Mg and low-Mg terrains.