Major‐element abundances on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

American Geophysical Union (AGU) - Tập 117 Số E12 - 2012
Larry G. Evans1, P. N. Peplowski2, E. A. Rhodes2, D. J. Lawrence2, T. J. McCoy3,4, L. R. Nittler5, Sean C. Solomon5,6, A. L. Sprague7, K. R. Stockstill‐Cahill3,4, R. Starr8, S. Z. Weider5, W. V. Boynton7, D. Hamara7, J. Goldsten2
1Computer Sciences Corporation, Lanham-Seabrook, Maryland, USA.
2The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland USA
3Department of Mineral Sciences, National Museum of Natural History,
4Smithsonian Institution, Washington D.C., USA.
5Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, D.C. USA
6Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA
7Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
8Department of Physics, Catholic University of America, Washington D.C., USA

Tóm tắt

Orbital gamma‐ray measurements obtained by the MESSENGER spacecraft have been analyzed to determine the abundances of the major elements Al, Ca, S, Fe, and Na on the surface of Mercury. The Si abundance was determined and used to normalize those of the other reported elements. The Na analysis provides the first abundance estimate of 2.9 ± 0.1 wt% for this element on Mercury's surface. The other elemental results (S/Si = 0.092 ± 0.015, Ca/Si = 0.24 ± 0.05, and Fe/Si = 0.077 ± 0.013) are consistent with those previously obtained by the MESSENGER X‐Ray Spectrometer, including the high sulfur and low iron abundances. Because of different sampling depths for the two techniques, this agreement indicates that Mercury's regolith is, on average, homogenous to a depth of tens of centimeters. The elemental results from gamma‐ray and X‐ray spectrometry are most consistent with petrologic models suggesting that Mercury's surface is dominated by Mg‐rich silicates. We also compare the results with those obtained during the MESSENGER flybys and with ground‐based observations of Mercury's surface and exosphere.

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American Geophysical Union (AGU)

Tập 117 Số E12

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