Using Crustal Thickness Modeling to study Mars' Crustal and Mantle Structures

• Main Author: Cheung, Karina Kawing
• Other Authors: Geosciences, King, Scott D., Hole, John A., Tracy, Robert J.
• Format: Thesis
• Language: unknown
• Published: Virginia Tech 2012
• Subjects: Mars; gravitational potential; topography; crustal and mantle structures; Modeling; isostacy; density; South pole
• Online Access: http://hdl.handle.net/10919/32831; http://scholar.lib.vt.edu/theses/available/etd-05152012-123410/

Mars has an intriguing topographic and crustal dichotomy that divides the planet into a Northern Hemisphere and a Southern Hemisphere. The biggest question is to understand how this dichotomy was formed and what are the implications to the interior evolution of the planet. This study uses topography and gravity data obtained from the Mars Global Surveyor satellite observations in a crustal thickness program written by Mark Wieczorek. This program uses an algorithm that incorporates spherical harmonic coefficients of topography and gravity and calculates the Moho topography given a set of user-input parameters; it also generates crustal thickness maps. I modified the code to produce gravity misfit maps for interpretation of crustal and mantle structures. Experiments were performed to test various parameters in the program and observe their effects on the resulting crustal thickness. The algorithm assumes a uniform density for the crust and mantle. A crustal density of 2900 kg/m3 and a mantle density of 3500 kg/m3 were used to represent a basaltic crust and an olivine mantle, derived from petrologic studies of meteorites assumed to have originated from Mars. As the crustal density is held constant while varying the mantle density (and vice versa), it is the total density contrast that changes the crustal thickness; the larger the density contrast, the smaller the crustal thickness. Higher-order terms in the algorithm equation were also tested. Results show that the higher-order terms do not affect the overall crustal thickness by much thus are negligible. In modeling the crustal thickness, a minimum crustal thickness of 5 km was used to anchor the topography so that the resulting crust do not have negative or zero thickness. By using this minimum thickness, there is about 40 km thickness difference between the Northern Lowlands and the Southern Highlands. Crustal thickness and gravity misfit maps show a plume-like track from the South Pole to the Tharsis Rise region, consistent with the theory proposed by Zhong ...