Shock Effects Including Maskelynite Formation in Three Shergottite Meteorites From Mars

Martian meteorites result from large impact events on the surface of Mars that cause intense shock metamorphism. This study examines the shock metamorphic features of three shergottite meteorites, Dho 019, NWA 12241, and NWA 15628, to better understand shock impact events. The research uses petrographic analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) to analyze the meteorites. A key focus of this research is the formation of maskelynite, a glass with plagioclase composition, whose formation mechanism has been the substance of debate among researchers. This study proposes that maskelynite forms through a transient intermediary glass state, exhibiting solid-state transformation and melting characteristics. Shock timescales were estimated by analyzing diffusion profiles in maskelynite grains. The calculated timescales using diffusion timescales are on the order of milliseconds to seconds. In addition, high-pressure phases in melt pockets were studied to trace pressure temperature paths during shock metamorphism. This research provides a more nuanced understanding of shock metamorphism in Martian meteorites, offering new insights into maskelynite formation, shock duration, and the pressure-temperature conditions of impact events on Mars.