Most of Earth gets a nameThis is a section of the Tenham meteorite, which fell in Queensland Austral

Most of Earth gets a nameThis is a section of the Tenham meteorite, which fell in Queensland Australia in 1879, and it just forever changed how we will describe the interior of the Earth.The Earth is composed of several layers; a deep iron core, a thin crust, and a thick mantle. That mantle is fairly homogeneous in composition, made mostly of the elements magnesium, silicon, iron, and oxygen, but there’s a complication. Geologists determine minerals by how the molecular structure of a crystal is arranged and there are lots of different ways to assemble the same elements; think about how many different ways there would be to assemble 4 different colored Lego blocks. There are some rules for how they fit together, but lots of arrangements are possible.Shallow in the mantle at low pressures, the most abundant mineral is called olivine. This mineral even appears at the Earth’s surface sometimes, in lavas or even making up a green sand beach in Hawaii (https://www.facebook.com/TheEarthStory/posts/511311338929915). But, when olivine is squeezed deep within the Earth, its structure changes.About 660 kilometers below your feet, the olivine structure undergoes a massive change. It breaks down into 2 different minerals, one of which has the formula (Mg,Fe)SiO3. That mineral is stable for a huge pressure range, from 660 kilometers deep all the way to the core-mantle boundary. That mineral is literally the most abundant thing in the Earth; there’s more of it than there is iron in the core, it probably makes up over 30% of the planet by volume.That mineral has the same structure as the mineral “perovskite”, but finding a name for it has been complicated. You see, a mineral can only receive an official name when it is found in a naturally occurring location and characterized in that setting, but one has ever gotten a fresh piece of this mineral from inside the Earth. It is incredibly deep, 10 times deeper than where the magmas that feed normal volcanoes are sourced, and when it is occasionally brought up by eruptions called “kimberlites”, it is unstable and never reaches the surface without breaking down.Thus, until now, the most abundant phase in the Earth has never had a name. We generally called it “magnesium silicate perovskite” – the structure of perovskite but with the normal elements in that mineral replaced by magnesium and silicon. Complicated enough?This meteorite has solved the problem. Dr. Chi Ma from Caltech has spent years examining meteorites in detail and characterized literally dozens of new minerals from them. Meteorites are special; they can preserve conditions that occurred only briefly because they’re cooled down quickly. This meteorite also saw extreme pressures; sometime early in the solar system’s history it was involved in a huge impact that created pressures comparable to the inside of the Earth today.This meteorite, therefore, saw high enough pressures to create magnesium silicate perovskite, and it also was cooled down rapidly, so quickly that the mineral didn’t have time to react away like it does any time it is brought to the Earth’s surface.Dr. Ma, working with Oliver Tschauner from UNLV, was able to identify surviving magnesium silicate perovskite in this meteorite and characterize its structure, all the requirements to give the mineral a name at long last.In 1946, Dr. Percy Bridgman was awarded the Nobel Prize in physics for work on the properties of materials at high pressure and on crystallography. Because of the relevance of this work to high pressure phases, Dr. Ma and Dr. Tschauner suggested that the most abundant phase in the Earth, magnesium silicate perovskite, should be named bridgmanite.Thanks Dr. Ma. This will make writing about the lower mantle so much easier since I don’t have to explain what magnesium silicate perovskite means any more.-JBBImage credit: Chi Mahttp://blogs.agu.org/geospace/2014/06/06/earths-abundant-mineral-finally-gets-name/Dr. Bridgman:http://www.nobelprize.org/nobel_prizes/physics/laureates/1946/bridgman-bio.html -- source link

More pics about