Planetary Materials Science and Astrobiology

Planetary materials contain signatures of diverse processes in their mineralogy, chemistry, textures and assemblages. The record contained in planetary materials reflects the complex and commonly overprinting relationships between many processes. Discerning what mechanisms have operated to produce the rocks we observe requires first a careful characterization of various properties. These include the chemical and structural makeup of the rocks (that is, the mineralogy and mineral chemistry), the textural relations within and between rocks (petrology) Therefore, the key to how the studies here hold together is also in the methodology and guiding philosophy: understanding what is there (what atoms and how they are arranged, what their interrelationships are) is the first step to unravelling the record of processes stored in planetary materials of all kinds. In this thesis, the tools of mineralogy and geochemistry/cosmochemistry and petrology have been used along with an understanding of the grand-scale astrophysical constraints on planetary formation to interpret diverse planetary materials: terrestrial rocks and meteorites. In this thesis, detailed mineralogical and chemical study of various planetary materials have enabled some new constraints to be placed on asteroidal melting and shock metamorphic processes, the nature of habitable environments in post-impact hydrothermal systems, and the preservation mechanisms of microbial ichnofossils in basaltic glass. These studies all concern the emergence and development of terrestrial planets and habitable environments within them, and the preservation of records of biological activity through deep geologic time. This work therefore represents, in a broad sense, an exploration of the astrobiological implications of planetary materials including likely precursors to terrestrial planets (enstatite chondrites); and important possible planetary habitats including post-impact hydrothermal mineral deposits and their associated weathering assemblages; and the fossilization of records of an ecosystem based on the microbial leaching of seafloor basaltic glass