Mathematics – Logic
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.u21a0016m&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #U21A-0016
Mathematics
Logic
5430 Interiors (8147), 5475 Tectonics (8149), 6235 Mercury
Scientific paper
The lobate scarps of Mercury bear witness to the history of contraction of a cooling planet. Previous models of the contraction of Mercury were for a one-dimensional mechanical model in which outermost crust of the planet is assumed to be elastic. However, the time-averaged surface temperature of Mercury varies strongly with both latitude and longitude due to the pattern of solar insolation over the planet, influenced by the planet's 3:2 spin-orbit resonant state, near-zero obliquity, and eccentric orbit about the Sun. The variation in surface temperature produces variations in lithospheric thickness and viscosity structure that may affect the patterns of deformation and faulting due to contraction. We explore this issue using a semi-analytic, spherical viscoelastic model that incorporates lateral variations of viscosity. Results suggest that temporal and spatial variations in lithospheric thickness during contraction affect the response of the planet. In particular, for contraction occurring relatively late in the presence of a thick lithosphere, the lithosphere deforms at the longest wavelengths, bowing outward where it is thinnest -at low latitudes for Mercury, particularly the areas around the equatorial "hot poles" that face the Sun at perihelion. We couple this model to thermal evolution calculations to simulate the effects of different core evolution scenarios. Topographic data returned by the Mercury Laser Altimeter (MLA) from MESSENGER's first flyby of Mercury in January demonstrate the existence of a long-wavelength slope along the equator, and many new lobate scarps were documented from MESSENGER images. After MESSENGER's second flyby in October, nearly the entire planet will have been imaged by spacecraft. Information on the long-wavelength shape of the planet, the distribution and orientation of lobate scarps, and their relation to other geological features, together with model results, will provide new constraints on the timing of global contraction and the heterogeneous response of the planet to interior cooling.
Hauck Steven A.
Johnson Clifton L.
Mohit Pundit Surdas
Neumann Gregory A.
Phillips James R.
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