Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002jgre..107.5136m&link_type=abstract
Journal of Geophysical Research (Planets), Volume 107, Issue E12, pp. 19-1, CiteID 5136, DOI 10.1029/2002JE001854
Physics
75
Planetology: Solar System Objects: Mars, Planetary Sciences: Heat Flow, Planetary Sciences: Gravitational Fields (1227), Planetary Sciences: Interiors (8147), Tectonophysics: Dynamics Of Lithosphere And Mantle-General
Scientific paper
From gravity and topography data collected by the Mars Global Surveyor spacecraft we calculate gravity/topography admittances and correlations in the spectral domain and compare them to those predicted from models of lithospheric flexure. On the basis of these comparisons we estimate the thickness of the Martian elastic lithosphere (Te) required to support the observed topographic load since the time of loading. We convert Te to estimates of heat flux and thermal gradient in the lithosphere through a consideration of the response of an elastic/plastic shell. In regions of high topography on Mars (e.g., the Tharsis rise and associated shield volcanoes), the mass-sheet (small-amplitude) approximation for the calculation of gravity from topography is inadequate. A correction that accounts for finite-amplitude topography tends to increase the amplitude of the predicted gravity signal at spacecraft altitudes. Proper implementation of this correction requires the use of radii from the center of mass (collectively known as the planetary ``shape'') in lieu of ``topography'' referenced to a gravitational equipotential. Anomalously dense surface layers or buried excess masses are not required to explain the observed admittances for the Tharsis Montes or Olympus Mons volcanoes when this correction is applied. Derived Te values generally decrease with increasing age of the lithospheric load, in a manner consistent with a rapid decline of mantle heat flux during the Noachian and more modest rates of decline during subsequent epochs.
Aharonson Oded
Head James W.
McGovern Patrick J.
Neumann Gregory A.
Phillips Roger J.
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