Research
The Experimental Mineral Physics group applies high-pressure and high-temperature experimental approach mainly using a laser-heated diamond anvil cell technique to reproduce the deep Earth's condition in the laboratory.
With this method, the group is trying to clarify the issues including the determination of density, crystal structure, elasticity and chemistry of the deep Earth's materials to understand the mineralogical model and evolution of the Earth's deep interior.
The new development of spectroscopic measurement system combined with the laser-heated diamond anvil cell technique is an important part of the work of the group. Over the last 15 years, Motohiko Murakami was strongly involved in the new development of the in-situ high-pressure and high-temperature synchrotron X-ray diffraction measurement system with multiple spectroscopic measurement techniques such as Brillouin & Raman scattering using double-sided infrared laser heating diamond anvil cell. With those newly developed measurement systems, Motohiko Murakami has first succeeded to achieve the in-situ X-ray diffraction measurement under lowermost mantle P-T condition, and revealed a number of phase transformations of the lower mantle phases including the MgSiO3 post-perovskite phase transition occurred at the very base of the mantle, and to achieve the sound velocity measurements of the lower mantle minerals down to the core mantle boundary condition.
Outlook
The group focuses on the following three fundamental research objectives:
- establishment of the mineralogical model of the Earth's whole mantle (upper mantle, transition zone, and lower mantle)
- clarification of the differentiation process of the early Earth from fully molten state
- exploring the internal structure of giant planets such as super-Earth, ice giants, and gas giants
Ultimately, by combining all the knowledge from those research outcomes, the group wants to propose the universal internal evolution model of the planets.
One of the most important keys to achieve this goal would be the new development of the experimental techniques related to the stable generation of ultrahigh-pressure and high-temperature, and the probes to extract the essential physical properties from the tiny samples. Within this framework, the group plans to pursue the development of new heating method to achieve the long and stable high-temperature condition above 2000 K (less than plus-minus 50 K) alternative to the conventional laer heating method which has less stability. The group will also explore opportunities to expand its state-of-the-art experimental techiniques to the rheological studies to understand the dynamics of the deep Earth over the last 4.5 billion years, which will enable it to put tighter constraints on the evolution of the Earth.