The Nature of the Mars Crust from Low-altitude MAVEN and MGS MAG Data and Elastic Thickness Variation from High Resolution Gravity and Topography Models across Northern Lowlands and other Crustal and Magnetic Dichotomy Boundaries

The goal of this study concerns understanding the tectonic history, and regional variations in the magnetic property and elastic variations of the crust, including the crustal dichotomy boundary and other magnetic and gravity boundaries on Mars. Analysis and interpretation of magnetic field anomaly data, when co-analyzed with gravity, geology, and topography, will improve our understanding of the processes occurring within the crust of Mars. We have been doing initial processing of low altitude subset of data from MAVEN MAG instrument (< 300 km from the mean planetary surface). These data have sufficiently dense coverage to map and analyze Northern Lowlands and the crustal dichotomy boundary and other magnetic contrast boundaries in unprecedented detail. We now have the capability of stably downward continuing magnetic field data to the surface of the planet aiding the resolution and interpretation of magnetic anomalies. Mars? planetary dynamo and the movement of its paleopole which implies several episodes of tilting of the planet in its early geologic history. Changes in the tilt of a planet due to reorganization of masses within is an important research area for understanding planetary evolution. The tilting and reorientation has implications on the past climatic zones of the planet and have implications on the origin and habitability of life. The tilting history comes indirectly from only a few kinds of information: the analysis of the magnetic field anomalies in the crust and the epochs of their formation constitutes a major part of this evidence. Without precise knowledge of the magnetization vector causing the anomalies and the association of magnetic regions to geology and geologic ages, incorrect inferences can be made regarding the changing orientation of the rotational axis of the planet. Using magnetization direction invariant methods for detection of edges of magnetic sources (the Analytic Signal field for 2D features) and new digital geologic/surface age maps in GIS, we will analyze association of geology and magnetic sources without having to pre-suppose their magnetization direction. Thus, this analysis will lead to a more robust understanding of the timing of the dynamo. The recent availability of global high-resolution topography and gravity data from MGS and MRO missions have provided ample opportunity to map the subsurface structure of the Martian crust and upper mantle. Joint analysis of gravity and topography can be used to estimate effective elastic thickness (Te), which parameterizes the inherent mechanical strength of a lithosphere derived from a theoretical equivalent elastic plate?s flexural rigidity (i.e., a measure of the resistance of a lithosphere to flexure in response to loading). Te primarily depends on age, thermal gradients, composition, and plate flexure curvature caused by deviatoric stresses acting on the lithosphere. Therefore, spatial variations and gradients in Te can be used as powerful diagnostic to understand the lateral variability in the deep structure of the lithosphere and its degree and style of deformation. Previous geophysical studies on Mars, estimated global models of lateral variations of Te and crustal thickness (Tc) using different techniques (e.g., coherence and admittance computation) that operate in spectral domain. In contrast, this research will employ the convolution method based flexure inversion technique which operate in space-domain to compute the spatial variation of Te and Tc data using window based techniques to derive high-resolution variations over the contrasting Martian lithospheric provinces. The analysis and interpretation of Te and Tc data sets with other constraints including the geodynamic history assessed from magnetic anomaly models, geology, and heat flow data/models, will ultimately give a better understanding on the processes involved in the geodynamic and/or tectonic evolution of the Martian lithosphere.