Studying the Thermal and Structural Evolution of Planetary Bodies

The focus of this research is to study the thermal and structural evolution of three planetary bodies, Mars, Venus and the asteroid Vesta. The almost uniform spatial distribution of craters on the surfaces of planets makes them excellent candidates to examine the evolution of planets as a whole. By modeling the viscoelastic deformation of craters at the surface and subsurface with the Finite Element Method (FEM), this study investigated the role of lower crustal flow in crater relaxation, and since lower crustal flow is sensitive to the thermal state, it serves as a probe into the thermal evolution of planets. The thermal history of Mars was explored by modeling the evolution of large craters and Quasi-Circular Depressions (QCDs) in the Southern Highlands and Northern Lowlands, respectively. Because of the spatial distribution of craters, this study yielded a thermal map for Mars that is more complete and less biased regionally relative to other studies. The results revealed a higher background heat flux for the Northern Lowlands relative to the Southern Highlands during the most ancient Noachian epoch, which suggests a thermal fingerprint to whatever process that formed the hemispherical crustal dichotomy, the oldest and most prominent geomorphic feature on Mars. Next, the largest crater on the surface of Venus, Mead, also appears to have undergone significant lower crustal flow. Modeling the viscoelastic deformation of Mead puts constraints on the thermal state of our sister planet in the vicinity of the basin. The background heat flux of Venus estimated here is higher than globally average values predicted by previous thermal models. Moreover, this study showed that Venus’s crust and mantle seem to be dry relative to those of the Earth. Last, modeling the evolution of two large craters in the south polar region of Vesta (Rheasilvia and Veneneia) showed that the shallow topography and large central peak of these craters are likely the products of a planetary scale impact, and not relaxation. Additionally, the possibility of relaxation of the rotational bulge was tested for the asteroid and showed that True Polar Wander (TPW) is not a likely scenario for Vesta.