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Why is the Dense Polymorph of Silica Present in Lunar and Martian Meteorites? Understanding the Collisional History of Asteroids and Formation process of Planets Recorded in Shocked Meteorites

Why is the Dense Polymorph of Silica Present in Lunar and Martian Meteorites? Understanding the Collisional History of Asteroids and Formation process of Planets Recorded in Shocked Meteorites

2015.05.11

Research ResultsPhysics & Chemistry

　In a joint study carried out with Yuji Higo and Ken-ichi Funakoshi, research fellow and visiting fellow respectively at the Japan Synchrotron Radiation Research Institute, Associate Professor Tomoaki Kubo and Professor Takumi Kato of the Kyushu University Faculty of Sciences discovered that seifertite, one of the high-pressure polymorphs of silica (SiO2), formed at much lower pressures than previously reported.

　This is an important discovery that solves the seifertite puzzle in lunar and martian meteorites and can be a unique shock indicator for understanding the collisional process of asteroids in the early solar system.

　The results were published online on May 8, 2015 in the international journal Science Advances.

The Kawai-type high-pressure apparatus at the synchrotron radiation facilities of SPring-8 (BL04B1), Japan. We conducted in situ X-ray diffraction experiments at high pressures using this apparatus to solve the seifertite puzzle.

Phase relation of silica at high pressure. We found that seifertite, thermodynamically stable at more than ~100 GPa (blue), metastably appears at pressures as low as ~11 GPa (red).

The time-temperature-transformation curves constructed based on the experimental results. The temperature-insensitive but time-sensitive kinetics for the formation of seifertite constrains that the critical shock duration and size of the impactor are at least ~0.01 s and ~50 m, respectively, from the presence of seifertite.

Journal Reference

Curious kinetic behavior in silica polymorphs solves seifertite puzzle in shocked meteorite, ,Tomoaki Kubo, Takumi Kato, Yuji Higo and Ken-ichi Funakoshi, Science Advances, 10.1126/sciadv.1500075

Research-related inquiries

Tomoaki Kubo, Associate Professor, Faculty of Sciences

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