Morphological Characterization of Quasi-Circular Features Across the Solar System

Abstract

The interior dynamics and geologic activity of a planetary body are linked. Due to instrumentation limitations, probing or studying the interior of planetary bodies directly is difficult. I argue that by studying surface features whose formation mechanism is linked to the material exchange between the interior and crust, I can gain information on the evolution and dynamics of the planetary body. For this dissertation, I have chosen to study microfeatures on Europa, coronae on Venus, and calderas on Earth.New methods were developed to determine the orientation and circularity of surface features across three planetary bodies. Three circular statistical tests were conducted to test the distribution of the orientation data for the quasi-circular features. A new definition of misorientation based on spherical geometry was defined for the Venus and Earth studies. On Europa, the orientation of microfeatures is not uniformly distributed and does not depend on latitude. Microfeatures are found to have formed episodically and under various stresses. Chaos and hybrids have a more extended formation period than pits and domes. These findings support formation mechanisms dependent on a diapir or liquid water body interacting with crustal horizontal stresses. A new digital map of 525 coronae was created for Venus. Orientation results show that coronae have a non-uniform orientation distribution. Their orientation is not dependent on size, formation location, or circularity. Comparing the orientation of coronae to implied stress orientations shows that coronae are likely to be elongated in the direction of maximum horizontal compressional stress. These results align with coronae formation models that show a preferential injection of melt in the direction of maximum horizontal compressional stress or a rising plume that pools along a step in lithospheric thickness. I compared the orientation of calderas on Earth to direct stress measurements. These findings show that calderas are more likely to be elongated perpendicular to the direction of maximum horizontal compressional stress. These results suggest that local stresses and preexisting structures influence calderas’ orientation. I advocate for caldera formation models based on the deformation of magma chambers or the preferential injection of magma along preexisting fault structures.