Discovery of High-Pressure Minerals in HED Meteorites(Press Release)
- Release Date
- 15 Jul, 2014
- BL10XU (High Pressure Research)
Hiroshima University
Tohoku University
National Institute of Polar Research
A research group discovered the high-pressure polymorphs*1 of silica (SiO2), coesite, and stishovite, in a Howardite–eucrite–diogenite (HED) meteorite, which probably originated from the asteroid 4 Vesta. The group was led by Masaaki Miyahara (associate professor) of the Graduate School of Science, Hiroshima University, Eiji Ohtani (professor) and Shin Ozawa (assistant professor) of the Graduate School of Science, Tohoku University, and Akira Yamaguchi (Assistant Professor) of the National Institute of Polar Research. NASA’s spacecraft Dawn revealed that there are many impact basins on 4 Vesta, indicating that 4 Vesta experienced heavy impact events. However, high-pressure polymorphs had not been discovered in HED meteorites although they should be formed under ultrahigh pressure and temperature conditions induced by an impact event. The research group succeeded in discovering high-pressure polymorphs of silica (SiO2) in one of HED meteorites, Béréba (Fig. 1) using nanoscale analysis techniques such as electron microscopy and a focused ion beam machining device*2. Publication |
《Figures》
《Glossary》
*1 High-pressure polymorphs
Minerals are naturally occurring solid substances that are uniform in chemical composition and crystal structure. Their crystal structure changes depending on the surrounding conditions such as pressure and temperature. Minerals that are stable at a pressure higher than the pressure at the earth’s surface (1 atmosphere) are called “high-pressure polymorphs.”
*2 Focused ion beam machining device
A device in which a finely focused ion beam is scanned over a sample for the observation or micrometer-scale machining of the sample surface. In this study, such a device was used for cutting out a part of the samples and preparing thin films for electron microscopy.
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