Mars has been a target for space exploration for decades. Exploring the interior of the red planet could reveal information about its formation and evolution. In this thesis, the crustal structure of Mars is investigated by a power spectra analysis of both topographic and gravitational data. With models of flexural isostasy, the best-fitting lithospheric (crust + uppermost mantle) thickness is found to be between 136 km and 158 km globally. Possible values for the thickness of the lithosphere range from 120 km to 580 km. In addition, a 3D flat Finite Element Method (FEM) model is created for Mars. The FEM Mars model incorporates the above-mentioned crustal profiles and calculates the surface stresses in the regions of interest. The calculated stresses are compared to observed faults in Tharsis, Hellas, and Utopia to reveal information about the evolution of these regions.