Using Craters to Study Carbon and Nitrogen Compounds on Icy Worlds
Abstract
Icy worlds have attracted a lot of attention from planetary scientists over the last century because they exhibit an array geophysical and chemical processes that both contrast and mirror those on terrestrial worlds. Nitrogen and carbon molecules drive some of the most unique processes on these icy worlds. The central focus of this thesis is to study the role of carbon and nitrogen rich molecules in different icy body environments, both geologically and chemically. These molecules drive fluvial and aeolian processes on Titan in the form of organic dunes and methane rain, and on Pluto, these molecules are present as volatile ices that go through cycles of deposition and sublimation. On both Pluto and Titan, these molecules also contribute to the formation of prebiotic compounds on the planet surfaces. These prebiotic compounds are often associated with the origin of life on Earth and may have provided the building blocks of life on icy worlds. I investigate both the geologic impact of these molecules and the evolution of the prebiotic chemistry when mixed with liquid water in an impact crater melt lens. Organics that mix into impact crater melt lens are shown to freeze throughout the depth of the melt sheet. The highest concentration is near the center, but it is likely that there will be large enough concentrations for the Dragonfly mission to sample. The concentration will vary, based on the buoyancy of the organic impurity. Hydrolysis can also delay when more complex organic molecules appear, but in most cases, I predict Dragonfly should be able to detect more complex organics within the first meter of the ice. I find that geologic impact of nitrogen and carbon molecules on Pluto creates a range of crater morphologies from entirely degraded to anomalously deep, and there does not appear to be a correlation between the surface age and the level of degradation. There is also a longitudinal relationship with the level of crater degradation, which may hint that Pluto underwent a significant change in conditions in its past (e.g., polar wander).