The Geophysics of Mercury: Current Status and Anticipated Insights from the MESSENGER Mission |
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| Authors: | Maria T Zuber Oded Aharonson Jonathan M Aurnou Andrew F Cheng Steven A Hauck II Moritz H Heimpel Gregory A Neumann Stanton J Peale Roger J Phillips David E Smith Sean C Solomon Sabine Stanley |
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| Institution: | (1) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA;(2) Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA;(3) Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA;(4) The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099, USA;(5) Department of Geological Sciences, Case Western Reserve University, Cleveland, OH 44106, USA;(6) Department of Physics, University of Alberta, Edmonton, AB, T6G 2J1, Canada;(7) Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA;(8) Department of Physics, University of California, Santa Barbara, CA 93106, USA;(9) Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA;(10) Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA;(11) Department of Physics, University of Toronto, Toronto, ON, M5S 1A7, Canada |
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| Abstract: | Current geophysical knowledge of the planet Mercury is based upon observations from ground-based astronomy and flybys of the
Mariner 10 spacecraft, along with theoretical and computational studies. Mercury has the highest uncompressed density of the
terrestrial planets and by implication has a metallic core with a radius approximately 75% of the planetary radius. Mercury’s
spin rate is stably locked at 1.5 times the orbital mean motion. Capture into this state is the natural result of tidal evolution
if this is the only dissipative process affecting the spin, but the capture probability is enhanced if Mercury’s core were
molten at the time of capture. The discovery of Mercury’s magnetic field by Mariner 10 suggests the possibility that the core
is partially molten to the present, a result that is surprising given the planet’s size and a surface crater density indicative
of early cessation of significant volcanic activity. A present-day liquid outer core within Mercury would require either a
core sulfur content of at least several weight percent or an unusual history of heat loss from the planet’s core and silicate
fraction. A crustal remanent contribution to Mercury’s observed magnetic field cannot be ruled out on the basis of current
knowledge. Measurements from the MESSENGER orbiter, in combination with continued ground-based observations, hold the promise
of setting on a firmer basis our understanding of the structure and evolution of Mercury’s interior and the relationship of
that evolution to the planet’s geological history. |
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| Keywords: | Mercury MESSENGER Core Rotational state Magnetic dynamos Thermal history |
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