Science

A meteorite fall in Assam holds clues to Earth’s formation

The meteorite offers insights into the Earth's deeper layers and how it was formed.

UPDATED: June 23, 2021 15:48 IST

The Earth’s surface is composed of three layers — the crust, mantle and core. While we know about crust (the outermost layer) formation and composition, very little is known about the mantle and the core located below the crust. Researchers have now analysed a meteorite that could hold clues about the composition of the mantle and offer insights into how Earth was formed.

A team of students and researchers from the Indian Institute of Technology (IIT) Kharagpur have analysed a shocked meteorite — one that has gone through high-pressure and high-temperature conditions due to an impact event — to conclude that it has a similar chemical composition as found in Earth’s lower mantle. The meteorite, which belonged to the asteroid belt located between Mars and Jupiter, fell near a village in Assam in 2015.

The researchers’ findings were published in Geophysical Research Letters. The findings state that Earth’s mantle was formed from a similar material that constitutes the Assam meteorite, which is mostly made up of a substance known as Olivine. Olivine is a rock-forming mineral found in dark-coloured igneous rocks and has a very high crystallisation temperature compared to other minerals. It is considered an important mineral in Earth’s mantle.

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“This is the first time that researchers have found compositions in a meteorite that is found when Olivine is melted at high temperatures and pressures, confirming that the chemical found in the mantle is also present in the asteroid belt,” Dr Sujoy Ghosh told IndiaToday.in.

The Kuiper Belt is a disc-shaped region is populated with hundreds of thousands of icy bodies larger than 100 km (62 miles) across and an estimated trillion or more comets. (Photo: Nasa)
The Kuiper Belt is a disc-shaped region is populated with hundreds of thousands of icy bodies larger than 100 km (62 miles) across and an estimated trillion or more comets. (Photo: Nasa)

A METEORITE FROM THE ASTEROID BELT

Researchers from IIT Kharagpur studied the shocked meteorite that had struck Kamargaon village of Assam on November 13, 2015. The meteorite was classified as an L6 chondrite. “It provided our team with samples of naturally occurring high-pressure minerals like those believed to make up the Earth’s deep mantle,” Ghosh added.

Researchers used a high-resolution electron microscope to image and scan the meteorite and conduct a set of complex analyses on a nanometer scale to find evidence of the complex chemical reaction that forms the Earth’s mantle. Researchers found that Olivine breaks down into Bridgmanite and Magnesiowustite in the Earth’s lower mantle, which is one of the most important reactions that largely control the properties in the Earth’s interior.

This particular kind of meteorite is found in the asteroid belt — formed by the accumulation of solid particles during the formation of planets — located between the orbits of Jupiter and Mars. These materials are at times pulled out from the belt due to collision and gravitational forces. “These meteorites have survived high-pressure and high-temperature events during their formation and fall on Earth due to the planet’s gravitational pull,” Ghosh added.

Earth's mantle extends from 660 kilometres. (Photo: Getty)
Earth’s mantle extends from 660 kilometres. (Photo: Getty)

UNDERSTANDING EARTH’S MANTLE

The mantle is the second layer of Earth that begins at nearly 660 kilometres under the surface and extends up to 2,700 kilometres. With the centre of Earth around 6,360 kilometres from the surface, the only way to study material from such immense depths is through volcanic eruptions and magma samples.

The meteorite found in Kamargaon experienced the kind of pressure found in Earth’s mantle — around 24 Giga Pascal, which is 2,50,000 times more than the atmospheric pressure that we experience on the surface. The layer also sees temperatures ranging up to 2,500 degrees Celsius. The samples found in the meteorite are similar to those observed on plate tectonics and could prove useful in studying earthquakes and volcanic activities.

Scientists are now looking to prove the breakdown of Olivine through lab experiments.

Source-https://www.indiatoday.in/science/story/earth-formation-assam-meteorite-iit-kharagpur-1818414-2021-06-23

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