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Support of long‐wavelength topography on Mercury inferred from MESSENGER measurements of gravity and topography
Author(s) -
James Peter B.,
Zuber Maria T.,
Phillips Roger J.,
Solomon Sean C.
Publication year - 2015
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/2014je004713
Subject(s) - geology , mantle (geology) , geophysics , gravity anomaly , mercury (programming language) , crust , stratification (seeds) , geoid , wavelength , structural basin , geomorphology , paleontology , physics , computer science , programming language , seed dormancy , botany , germination , optoelectronics , dormancy , oil field , biology , measured depth
To explore the mechanisms of support of surface topography on Mercury, we have determined the admittances and correlations of topography and gravity in Mercury's northern hemisphere from measurements obtained by NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. These admittances and correlations can be interpreted in the context of a number of theoretical scenarios, including flexural loading and dynamic flow. We find that long‐wavelength (spherical harmonic degree l < 15) surface topography on Mercury is primarily supported through a combination of crustal thickness variations and deep mass anomalies. The deep mass anomalies may be interpreted either as lateral variations in mantle density or as relief on compositional interfaces. Domical topographic swells are associated with high admittances and are compensated at 300–400 km depth in the lower reaches of Mercury's mantle. Quasi‐linear topographic rises are primarily associated with shallow crustal compensation and are weakly correlated with positive mass anomalies in the mantle. The center of the Caloris basin features some of the thinnest crust on the planet, and the basin is underlain by a large negative mass anomaly. We also explore models of dynamic flow in the presence of compositional stratification above the liquid core. If there is substantial compositional stratification in Mercury's solid outer shell, relaxation of perturbed compositional interfaces may be capable of creating and sustaining long‐wavelength topography.