A research group led by Assistant Professor Tatsuya Sakamaki and Professor Eiji Otani of Tohoku University has found that "hydrogen, silicon, and sulfur" are included as promising candidates for light elements contained in the inner core of the earth.This research result, which was carried out in collaboration with Assistant Professor Hiroyuki Fukui of the University of Hyogo, Senior Researcher Tomoji Tsutsui of the High Brightness Optical Science Research Center, and Associate Senior Researcher Alfred Baron of the Institute of Physical and Chemical Research, is the result of the American scientific journal "Science Advances". Published in.
It has become possible to bring back samples from extraterrestrial celestial bodies, but it has not yet been possible to obtain samples from inside the earth.The core that exists in the center of the earth is mainly composed of metallic iron, and is composed of a solid inner core and a liquid outer core.Regarding the chemical composition of the inner core, which is the deepest part of the earth, it is suggested that nickel is present in addition to iron, which is the main component, and that light elements such as hydrogen, carbon, oxygen, silicon, and sulfur are also contained. It was not clear which element was contained.
"Elastic waves", which show different propagation velocities depending on the chemical composition of a substance, are an index to know the properties of a substance.In this study, we tried to estimate the chemical composition of the deepest part of the earth by using the characteristics.Focusing on the longitudinal wave velocity among elastic waves, pure iron is placed in the same environment as the inside of the earth (ultra-high pressure and high temperature state), and the density and longitudinal wave elastic wave velocity are measured at the same time to measure the inner core of the earth. The chemical composition of was estimated.
When the results obtained in the experiment were directly compared with the seismic wave observation data, it was found that the light elements contained in the Earth's inner core are likely to be "hydrogen, silicon, and sulfur."This is an important research result in constraining the composition of the Earth's inner core.
Understanding the inner core of the earth is indispensable for thinking about the origin of the earth, but this research provides a great guideline for advancing its elucidation.It is expected that further research and experiments will be carried out based on this result, and the composition of the Earth's inner core will be elucidated.