Mercury’s Surface Composition and Character as Measured by Ground-Based Observations |
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Authors: | A Sprague J Warell G Cremonese Y Langevin J Helbert P Wurz I Veselovsky S Orsini A Milillo |
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Institution: | (1) Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA;(2) Department of Astronomy and Space Physics, Uppsala University, 75120 Uppsala, Sweden;(3) INAF-Osservatorio Astronomico, vic.Osservatorio 5, 35122 Padova, Italy;(4) Institut d’Astrophysique Spatiale, CNRS/Univ. Paris XI, 91405 Orsay, France;(5) Institute for Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany;(6) Physics Institute, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland;(7) Skobeltsyn Institute of Nuclear Physics, Moscow State University, 119992 Moscow, Russia;(8) Space Research Institute (IKI), Russian Academy of Sciences, 117997 Moscow, Russia;(9) Istituto di Fisica dello Spazio Interplanetario (IFSI), via del Fosso del Cavaliere, 100,00133 Rome, Italy;(10) Istituto Nazionale di Astrofisica (INAF), via del Fosso del Cavaliere, 100,00133 Rome, Italy |
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Abstract: | Mercury’s surface is thought to be covered with highly space-weathered silicate material. The regolith is composed of material
accumulated during the time of planetary formation, and subsequently from comets, meteorites, and the Sun. Ground-based observations
indicate a heterogeneous surface composition with SiO2 content ranging from 39 to 57 wt%. Visible and near-infrared spectra, multi-spectral imaging, and modeling indicate expanses
of feldspathic, well-comminuted surface with some smooth regions that are likely to be magmatic in origin with many widely
distributed crystalline impact ejecta rays and blocky deposits. Pyroxene spectral signatures have been recorded at four locations.
Although highly space weathered, there is little evidence for the conversion of FeO to nanophase metallic iron particles (npFe0), or “iron blebs,” as at the Moon. Near- and mid-infrared spectroscopy indicate clino- and ortho-pyroxene are present at
different locations. There is some evidence for no- or low-iron alkali basalts and feldspathoids. All evidence, including
microwave studies, point to a low iron and low titanium surface. There may be a link between the surface and the exosphere
that may be diagnostic of the true crustal composition of Mercury. A structural global dichotomy exists with a huge basin
on the side not imaged by Mariner 10. This paper briefly describes the implications for this dichotomy on the magnetic field
and the 3 : 2 spin : orbit coupling. All other points made above are detailed here with an account of the observations, the
analysis of the observations, and theoretical modeling, where appropriate, that supports the stated conclusions. |
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Keywords: | Mercury Planetary surface composition Mercury’ s surface composition Remote sensing Ground-based observations Spectroscopy |
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