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Abstract
Fracturing on small planetary bodies is controlled by low gravity, which differs from what is observed on Earth and other large planets. Studying the tectonics of small bodies is crucial for understanding the planetary evolution of recent and past lithospheres, from large to small, rocky to non-rocky bodies in the Solar System. Asteroid 4 Vesta displays a remarkably large set of troughs, Divalia Fossae, encircling the asteroid around the equator, while planetary-scale impact basins occupy most of the southern hemisphere. These structures provide vital clues for understanding the growth and origin of large fractures on small bodies. Moreover, the fractures hidden beneath the regolith layer or invisible in spacecraft imagery can be revealed using the planform shape of impact craters and provide insight into the planetary evolution that has not been studied before. Furthermore, studying the evolution of fractures in extensional tectonic regimes on Earth allows us to compare to the structures on low-gravity planetary bodies, which is crucial to understand the geologic processes on extraterrestrial worlds.This research investigates several topics related to the growth and origin of fractures on low-gravity planetary bodies, drawing a comprehensive understanding of the deformation of planetary lithospheres. The study of the structure and tectonics of the Divalia Fossae on Vesta involved structural mapping, rock mechanical calculations, crater counting, and geomorphologic characterizations. A series of geologic constraints are inconsistent with the leading hypothesis that the Divalia Fossae were directly formed by the large impact in the southern hemisphere via normal faulting, but rather had a spinning-related origin as a long-term consequence of large impacts, accommodating opening-mode displacements. The planform shape of impact craters on Vesta and the dwarf planet Ceres reveals regional and global tectonic patterns. Modeling predictions specifically tied to the low gravity and associated rock properties of these bodies are needed to evaluation of the origins of these patterns. A field investigation of the Koa’e Fault System, Hawaii studied an analog process to that of the Divalia Fossae. The conceptual model and fracture scaling capture the transition from jointing to faulting, which is comparable to the proposed fracturing process on low-gravity bodies.