When especially interesting new planets are discovered in the cosmos, scientists around the world begin the process of identifying their characteristics — their orbit, their mass and density, their composition, their thermal properties and much more. It’s all part of a drive that seems to be innate in humans to learn about the workings of the world (or worlds) around us.
This began millennia ago when our distant ancestors started to learn about the make-up and processes of Earth. We now know enormous amounts about our planet, but I was recently introduced to a domain where our knowledge has some substantial holes. The area of the Earth least well understood is, not surprisingly, what lies deep below us, in the mantle — the inner 2,900 kilometers (2000 miles) of the planet between the outer crust and the iron core.
The on-going exploration of this vast region — made up substances including some which cannot remain intact on the Earth’s surface — struck me as in some ways comparable to the study of exoplanets. It’s also a realm where scientific observation is limited, but what knowledge is gained then leads through induction, deduction, modeling and exacting lab work to a gradual expansion back of our knowledge.
And in the case of some high-temperature, high-pressure minerals, this has led to a most unusual technique for identifying and naming key components of our inner planet. Unable to reach or preserve some of the most important components of the mantle, geochemists and other deep Earth scientists go to incoming meteorites to learn about what’s beneath (deeply beneath, that is) our feet.
With this in mind, here is a look at the discovery and recent naming of the mineral hiroseite, an unusual but quite widespread component of the very deep Earth.
It was two decades ago when Kei Hirose – a Japanese geochemist expert in high-pressure, deep-Earth phenomena, then at the Tokyo Institute of Technology – began researching a long-standing problem in understanding the working of the lower depths of our planet’s enormous mantle: the last 300 kilomiles above the boundary with the scalding iron core.