Bridgmanite captured for the first time... on a meteorite

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Bridgmanite captured for the first time... on a meteorite

Posted by sciencetech-blog on Tuesday, December 2, 2014 Label:

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Perovskite crystal may be the most abundant material on Earth, but for centuries scientists have failed to get their hands on this elusive mineral.

The mysterious substance makes up more than a third of the volume of Earth and is mostly found in the planet's lower mantle 410 to 1,796 miles (660 to 2890 km) beneath the planet's surface.

Now, for the first time, US researchers have been able to get a sample of the mineral, and have finally given it a formal name: bridgmanite.

The mineral was found by Oliver Tschauner of the University of Nevada, Las Vegas, and his team in the Tenham meteorite, which had experienced intense pressures over a short period of time

The mineral, which thought to make up roughly 36 per cent of the planet, was named after Percy Bridgman, a US physicist who won the 1946 Nobel Prize in Physics for pressure physics.

It was found by Oliver Tschauner of the University of Nevada, Las Vegas, and his team in the Tenham meteorite, which had experienced intense pressures over a short period of time.

'Despite appearing for decades in numerous experimental and theoretical studies, characterisations of possible natural samples have not been sufficient to meet International Mineralogical Association criteria for naming new minerals,' Professor Tschauner wrote in the journal Science.

The mysterious substance makes up more than a third of the volume of Earth and is mostly found in the planet's lower mantle (pictured) 410 to 1,796 miles (660 to 2890 km) beneath the planet's surface

According to International Mineralogical Association rules, a mineral cannot be given a formal name until a specimen has been found that can be studied first hand.

'Consequently, any detailed chemical, structural, and petrographic analysis of natural [bridmanite] has remained impossible,' Professor Tschauner added.

The Tenham meteorite hit Australia in 1879 after experiencing temperatures of 2000°C and pressures of 24 gigapascals – conditions similar to those deep inside the Earth.

Due to the massive pressures, bridgmanite essentially 'froze' in place before it could decay, forming crystallites within the meteorite.

MOST OF EARTH'S CARBON MAY BE HIDDEN IN THE PLANET'S INNER CORE

As much as two-thirds of Earth's carbon may be hidden in the inner core, making it the planet's largest carbon reservoir.

This is according to a new model that even its backers acknowledge is 'provocative and speculative'.

University of Michigan researchers suggest that iron carbide, Fe7C3, is a good match for the density and sound velocities of Earth's inner core.

T"The model of a carbide inner core is compatible with existing cosmochemical, geochemical and petrological constraints, but this provocative and speculative hypothesis still requires further testing," said Professor Jie Li.

'Should it hold up to various tests, the model would imply that as much as two-thirds of the planet's carbon is hidden in its center sphere, making it the largest reservoir of carbon on Earth."

It is now widely accepted that Earth's inner core consists of crystalline iron alloyed with a small amount of nickel and some lighter elements.

However, seismic waves called S waves travel through the inner core at about half the speed expected for most iron-rich alloys under relevant pressures.

Some researchers have attributed the S-wave velocities to the presence of liquid, calling into question the solidity of the inner core.

The mineral was named after Percy Bridgman (right), a US physicist who won the 1946 Nobel Prize in Physics for pressure physics. It was found in the Tenham meteorite hit Australia in 1879 (left)

Scientists had looked at likely meteorites in the past, but by using electron microscopes to study the material, they ended up inadvertently destroying it.

This time, the team used a less destructive test using a micro-focused X-ray beam alongside with electronmicroscopy to keep the sample intact.

Its discovery not only allows scientists to finally name the abundant mineral, but also better analyse it to understand how the deep mantle behaves.

The researchers claim that the sample has more sodium and ferric acid than they had been expected.

They say it might even hold clues about what goes on when rocky bodies in space when they collide, which may offer insights into how the universe formed.

Scientists say mineral might hold clues about what goes on when rocky bodies in space when they collide

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