Through my research history of more than 50 years, I have adhered to three main themes such as age, terrestrial noble gases and mantle to clarify the origin and evolution of the Earth, with special reference to reveal the chemical structure and evolution of the Earth’s interior. In this paper, I introduce some of them and how such themes are related one another in my mind. On the basis of accumulated information, I have a belief that in the lower mantle there should be some region (s) which retain primordial components associated with relatively un-fractionated and un-degassed characters.
Continuous developments in inorganic mass spectrometry techniques, such as the combination of an ICP ion source and a magnetic sector-based mass spectrometer equipped with a multiple-collector array (MC-ICPMS), have revolutionized the precision of the isotopic ratio measurements, and the applications of the inorganic mass spectrometry in geochemistry, cosmochemistry, and biochemistry are beginning to appear over the horizon. The analytical community is actively solving problems, such as spectral interferences, correction of mass bias effect, high-yield chemical separation and purification processes, or reduction of the contamination of analytes. With the state-of-art techniques developed in the past decade, isotope ratio data of the elements are not specially for geochemical or cosmochemical studies.
Natural variations in isotopic ratios of the heavy elements can provide new insights into the past and present of various geochemical and biochemical processes. Stable isotope tracers are now increasingly being used in studies of elemental metabolism, bioavailability or toxicity of nutrients, as well as evaluating the elemental turnover time. The metabolism of higher organisms can be transcribed as stable supply of the most essential elements through transfer, absorption, and storing processes, which form the basis of homeostasis function. Variations in the isotopic composition of the elements induced through dietary or metabolism processes have potential to become novel biochemical markers for assessing impairments in metal metabolism or nutritional status of the elements.
We are still struggling to create new research fields in the stable isotope geochemistry through instrumental developments using the inorganic mass spectrometer, covering the isotopic analysis of nanoparticles in meteorites, high-speed 3D imaging analysis of biological tissue samples, as well as merging of metallomics with traditional -omics studies. Our goal is to realise the words by Walter Bagehot that “The great pleasure in life is doing what people say you cannot do”.
The search for life on planets beyond the solar system has become a subject of intense public interest, with heightened expectations for the detection of atmospheric biosignatures using the next generation of space and ground-based telescopes. However, significant gaps remain in our mechanistic understanding of Earth’s chemical evolution, and in particular the cause-and-effect relationships with evolving biosphere. Here, I discuss the coupled evolution of life and the atmosphere through Earth history based on the results obtained from biogeochemical models.