Impact cratering is one of the most fundamental geologic processes in the Solar System. Mars is an excellent natural laboratory for exploring cratering processes, as its thin atmosphere allows for the investigation of both impact processes and atmospheric effects. The objective of this study is to describe the formation of enigmatic streaks radiating from some, but not all, well-preserved craters on Mars. Thermal Emission Imaging System (THEMIS) camera images reveal that these streaks are long and thermally bright at nighttime, and they typically occur as double tails extending from topographic obstacles. We propose that these bright features represent scour zones generated from intense, impact vapor-driven winds, i.e., “impact-wind streaks.” This dissertation incorporates laboratory experiments, numerical simulations, and planetary observation in order to test the impact winds model. Chapter 1 explores the relationship between vapor expansion and wind development through a series of experiments performed at the NASA Ames Vertical Gun Range (AVGR). Only vapor that expands within an atmosphere will generate long-lasting winds. Chapter 2 documents impact-vapor generation on Mars based a suite of 3D planetary-scale impact simulations and tests the effect of target and impactor properties (composition, impact angle, and impact speed) on vaporization and wind development. Results reveal enhanced vaporization (compared to a typical asteroid impact) can occur from fast impact speeds, thick volatiles (ice) within the target, or an icy impactor. Additionally, the models demonstrated that topographic obstacles are necessary to bring winds to the surface. Chapter 3 inventories the distribution of impact-wind streak craters across Mars. Among other similar age craters, only 12 examples exhibit impact-wind streaks, and they occur in a wide range of terrains and lithologies. As a result, the development of impact-wind streaks is most consistent with vapor derived from fast, icy impactors (comets), rather than target ices. Finally, Chapter 4 synthesizes the range of work presented in the dissertation and investigates the effect of volatile-rich impactors at the AVGR. It also tests the impact winds model with case studies of two craters (Jijiga and Mojave) where abrupt changes in topography separate the effects of vapor-driven winds from basal ejecta flows.
Bouchey, Stephanie Nicole Quintana,
"The Impact Winds of Mars"
Earth, Environmental and Planetary Sciences Theses and Dissertations.
Brown Digital Repository. Brown University Library.