Constraints on Mercuryâs surface composition from MESSENGER and ground-based spectroscopy
Warell, J. and Sprague, A. and Kozlowski, R. and Rothery, D.A. and Lewis, N. and Helbert, J. and Cloutis, E. (2010) Constraints on Mercuryâs surface composition from MESSENGER and ground-based spectroscopy. Icarus: International Journal of Solar System Studies, 209 (1), pp. 138-163. ELSEVIER. DOI: 10.1016/j.icarus.2010.04.008.
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The composition and chemistry of Mercury’s regolith has been calculated from MESSENGER MASCS 0.3–1.3 μm spectra from the first flyby, using an implementation of Hapke’s radiative transfer-based photometric model for light scattering in semi-transparent porous media, and a linear spectral mixing algorithm. We combine this investigation with linear spectral fitting results from mid-infrared spectra and compare derived oxide abundances with mercurian formation models and lunar samples. Hapke modeling results indicate a regolith that is optically dominated by finely comminuted particles with average area weighted grain size near 20 μm. Mercury shows lunar-style space weathering, with maturation-produced microphase iron present at ˜0.065 wt.% abundance, with only small variations between mature and immature sites, the amount of which is unable to explain Mercury’s low brightness relative to the Moon. The average modal mineralogies for the flyby 1 spectra derived from Hapke modeling are 35–70% Na-rich plagioclase or orthoclase, up to 30% Mg-rich clinopyroxene, <5% Mg-rich orthopyroxene, minute olivine, ˜20–45% low-Fe, low-Ti agglutinitic glass, and <10% of one or more lunar-like opaque minerals. Mercurian average oxide abundances derived from Hapke models and mid-infrared linear fitting include 40–50 wt.% SiO2, 10–35 wt.% Al2O3, 1–8 wt.% FeO, and <25 wt.% TiO2; the inferred rock type is basalt. Lunar-like opaques or glasses with high Fe and/or Ti abundances cannot on their own, or in combination, explain Mercury’s low brightness. The linear mixing results indicate the presence of clinopyroxenes that contain up to 21 wt.% MnO and the presence of a Mn-rich hedenbergite. Mn in M1 crystalline lattice sites of hedenbergite suppresses the strong 1 and 2 μm crystal field absorption bands and may thus act as a strong darkening agent on Mercury. Also, one or more of thermally darkened silicates, Fe-poor opaques and matured glasses, or Mercury-unique Ostwald-ripened microphase iron nickel may lower the albedo. A major part of the total microphase iron present in Mercury’s regolith is likely derived from FeO that is not intrinsic to the crust but has been subsequently delivered by exogenic sources.
|Title:||Constraints on Mercuryâs surface composition from MESSENGER and ground-based spectroscopy|
|Journal or Publication Title:||Icarus: International Journal of Solar System Studies|
|In Open Access:||No|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 138-163|
|Keywords:||Mercury, Surface; Mineralogy; Radiative transfer; Regoliths; Spectroscopy|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Space|
|HGF - Program Themes:||W EW - Erforschung des Weltraums|
|DLR - Research area:||Space|
|DLR - Program:||W EW - Erforschung des Weltraums|
|DLR - Research theme (Project):||W - Vorhaben BepiColombo (old)|
|Institutes and Institutions:||Institute of Planetary Research > Terahertz and Infrared Sensors|
|Deposited By:||Ulrike Stiebeler|
|Deposited On:||12 Jan 2011 10:40|
|Last Modified:||20 Mar 2013 19:43|
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