Natural and experimental high‑pressure, shock‑produced terrestrial and extraterrestrial materials

Hypervelocity impacts are among the fundamental phenomena occurring during the evolution of the solar system and are characterized by instantaneous ultrahigh pressure and temperature. Varied physicochemical changes have occurred in the building blocks of celestial bodies under such extreme conditions. The constituent material has transformed into a denser form, a high-pressure polymorph. The high-pressure polymorph is also thought to be the constituent of the deep Earth’s interior. Hence, experiments using a high-pressure and temperature generating apparatus have been conducted to clarify its crystal structure, pressure–temperature stability range, and transformation mechanisms. A natural high-pressure polymorph (mineral) is found from terrestrial and extraterrestrial rocks that experienced a hypervelocity impact. Mineralogists and planetary scientists have investigated high-pressure minerals in meteorites and rocks near terrestrial craters over a half-century. Here, we report brief reviews about the experiments producing high-pressure polymorphs and then summarize the research histories of high-pressure minerals occurring in shocked meteorites and rocks near terrestrial craters. Finally, some implications of high-pressure minerals found in impactinduced shocked rocks are also mentioned.