The existence of magnetization signatures and landform modification antipodal to young lunar impact basins is investigated further by (a) producing more detailed regional crustal magnetic field maps at low altitudes using Lunar Prospector magnetometer data; and (b) examining Lunar Reconnaissance Orbiter Wide Angle Camera imagery. Of the eight youngest lunar basins, five are found to have concentrations of relatively strong magnetic anomalies centered within 10° of their antipodes. This includes the polar Schrödinger basin, which is one of the three youngest basins and has not previously been investigated in this context. Unusual terrain is also extensively present near the antipodes of the two largest basins (Orientale and Imbrium) while less pronounced manifestations of this terrain may be present near the antipodes of Serenitatis and Schrödinger. The area near the Imbrium antipode is characterized by enhanced surface thorium abundances, which may be a consequence of antipodal deposition of ejecta from Imbrium. The remaining three basins either have antipodal regions that have been heavily modified by later events (Hertzsprung and Bailly) or are not clearly recognized to be a true basin (Sikorsky-Rittenhouse). The most probable source of the Descartes anomaly, which is the strongest isolated magnetic anomaly, is the hilly and furrowed Descartes terrain near the Apollo 16 landing site, which has been inferred to consist of basin ejecta, probably from Imbrium according to one recent sample study. A model for the origin of both the modified landforms and the magnetization signatures near lunar basin antipodes involving shock effects of converging ejecta impacts is discussed.

<p dir="ltr">Impact cratering is the most pervasive geologic process to have shaped our Solar System. At the largest scales, impact basins provide a window into the primordial structure of the impacted body as the mechanics governing their formation and evolution are dependent on the planet's surface structure at the time the basin was formed and for several tens of millions of years thereafter. This dissertation focuses on Mercury's Caloris basin, its largest best-preserved impact basin, to aide in characterizing the internal and surgical structure of a young Mercury.</p><p dir="ltr">Mercury has been visited by two spacecraft over the past several decades, providing us with a wealth of information about its surface morphology, its unique internal structure, and chemical makeup. Views of Caloris basin show that it preserves evidence of Mercury's early volcanic history both within its interior and in an annulus surrounding the basin, though they mask our ability to determine whether Caloris formed as a culturing basin. The plains units within the basin record the evolution of the regional stress field and its interplay with Mercury's persistent global contraction in the form of brittle deformation features and linear long-wavelength topographic undulations. </p><p dir="ltr">This dissertation attempts to unravel the sequence of events that led to Caloris basin's present-day configuration to aide in characterizing Mercury's thermomechanical structure and how it has evolved over geologic time. Impact simulations are used to reproduce Caloris basin's crustal structure which is indicative of Mercury's thermal state at the time of its formation. Results from these models are used as initial conditions in subsequent finite element models that explore how the basin evolved over geologic time. Here, it will be shown that Mercury's thermal structure and the large impact velocities experienced on the planet inhibit its formation as a multiring basin. Further, Mercury's thin silicate shell causes Caloris to undergo a unique postimpact evolution compared to other large impact basins, potentially resulting in its formation as a mascon basin without the need for the emplacement of its interior volcanic plains.</p>