Shock-related processes in planetary materials: Earth and beyond

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This research will explore the interaction of shock waves with solid materials via three approaches: (1) laboratory experiments using light gas gun technology; (2) terrestrial impact structures; and (3) extraterrestrial samples from the Moon, Mars and asteroids (i.e., meteorites and Apollo lunar sample returns). The interaction of shock waves with solid media remains relatively poorly understood, especially for polyphase materials. Shock processes have been fundamental in building our Solar System via hypervelocity impact; they remain an important contributor to the surface condition of many planetary bodies today. It is especially at the microscopic scale that heterogeneities in shock wave structure are manifest as modifications to rock texture and mineralogy. The proposed research will explore these effects using natural and synthetic samples and laboratory experiments. In the last 6 years, the applicant has established a high-speed impact facility at the University of New Brunswick. It comprises two light gas guns, which can achieve velocities of 8 km/s. This enables us to replicate shock effects under controlled conditions to >60 GPa (the shock melting pressure for most materials). We will use shock recovery apparatus to retrieve shocked samples, and optimize shock duration by using the reverberation technique. The experiments will be designed to evaluate the effects of increasing shock pressure on feldspar structure, especially plagioclase, which is a major rock- and crust-forming component of many solid planetary bodies. This will represent a major advance in correlating shock microtexture to shock pressure, with the goal of building a new shock scale for plagioclase. Experiments will include an evaluation of maskelynite formation, as well as phase transformations to high pressure polymorphs, and fusion. In addition, synthetic and lunar powders (regolith) will be shocked to better understand agglomeration, melting and breccia formation: an important rock-forming process on many solid planetary bodies. This will build on previous experimental work performed over the last 40 years in North America and Europe. The research will broaden our understanding of materials behaviour under extreme conditions (e.g., hypervelocity impact), which is relevant to developing next-generation protective systems for the benefit of society (e.g., armour for space infrastructure to defeat orbital debris and micrometeroid collision threats). Shocked products will be analyzed using electron microscopy and Raman spectroscopy. Samples from the Moon, Mars and asteroids, as well as contextually well-constrained samples from select terrestrial impact structures, will be deployed to ground-truth experimental work. The research will provide excellent, unique training opportunities for undergraduate and graduate students, and the post-doctoral and research scientist members of my team.