About Kei Hirose

Kei Hirose, Recipient of the 2011 Science Innovation Award, named after Ted Ringwood

Kei Hirose is a professor of high-pressure mineral physics and petrology at the Tokyo Institute of Technology. He was originally interested in the generation of basaltic magmas and conducted experiments using piston-cylinder apparatus on partial melting of peridotites in the uppermost mantle. As a PhD project at the University of Tokyo, he and his former adviser Professor Ikuo Kushiro succeeded in the determinations of the chemical compositions of magmas directly formed by equilibrium partial melting of natural mantle peridotite up to 3 GPa (Hirose and Kushiro, 1993 EPSL). Subsequently he carried out a series of experiments to quantify the effects of water and carbon dioxide on partial melting in the uppermost mantle (e.g., Hirose and Kawamoto, 1995 EPSL; Hirose, 1997 Geology).

His main interest was then shifted to the lower mantle after he moved to Tokyo Tech as an assistant professor. During his stay at the Geophysical Laboratory, Carnegie Institution of Washington in 1996-1998, he precisely determined the post-garnet phase transition in MORB and its melting curve in the lower mantle (Hirose et al., 1999 Nature). After returning back to Tokyo, he established a laser-heated DAC laboratory at the Tokyo Tech. Similar system at the beamline BL10XU of SPring-8 synchrotron facility was also renewed by his group. In 2004, together with his former PhD student Motohiko Murakami, he discovered MgSiO3 post-perovskite phase based on the XRD measurements at SPring-8 (Murakami, Hirose et al., 2004 Science). Post-perovskite is now believed to be a main constituent of the Earth’s lowermost mantle and has been studied extensively in recent years. He and his colleagues determined the stability, Clapeyron slope, equation of state, sound velocity (Iitaka, Hirose et al., 2004 Nature), Fe partitioning, and transport properties of this new phase. The exceedingly high electrical conductivity of post-perovskite has profound implications for electromagnetic coupling between the core and mantle (Ohta, Onoda, Hirose et al., 2008 Science).

He is now working at multi-megabar pressure range to study Fe and Fe-alloys. Very recently, he and his colleague Shigehiko Tateno reported that hexagonal-close-packed (hcp) structure is a stable form of iron at the Earth’s inner core, based on the static laser-heated DAC experiments up to 377 GPa and 5700 K, which is beyond the condition at the center of the Earth (Tateno, Hirose et al., 2010 Science). Such high-pressure experimental technique now enables us to synthesize any materials inside the Earth.

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