Last month, researchers from the Geological Survey of India collected some meteorite fragments near the town of Katol in Nagpur in 2012. Studying this, IIT Kgp researchers have unravelled the composition expected to be present in the Earth’s lower mantle which is at about 660 km deep.

Katol L6

• Initial studies revealed that the host rock was mainly composed of olivine, an olive-green mineral.
• Olivine is the most abundant phase in our Earth’s upper mantle.
• Our Earth is composed of different layers including the outer crust, followed by the mantle and then the inner core.

Key findings: Presence of Bridgmanite

• The study reported for the first time, presence of veins of the mineral bridgmanite, which is the most abundant mineral in the interior of the Earth, within the Katol L6 Chondrite meteorite.
• Bridgmanite consists of magnesium, iron, calcium aluminium oxide and has a perovskite structure. It is the most volumetrically abundant mineral of the Earth’s interior.
• It is present in the lower mantle (from 660 to 2700 km), and it is important to understand its formation mechanism to better comprehend the origin and evolution of planetary interiors.

What is the hypothesis of moon-formation?

The discovery of Bridgmanite in Katol L6 adds evidence to the Moon-forming giant impact hypothesis.

• The Moon-forming giant impact hypothesis occurred nearly 4.5 billion years ago.
• The Earth collided with a planet the size of Mars named Thela.
• The force of this impact was so huge as to melt the Earth down from the surface to a depth of 750 km to 1,100 km.
• The hypothesis goes that this caused the Earth to be bathed in a magma ocean, and the ejecta from the collision led to the formation of the Moon.

Note: Earth was an ocean of magma in the past.  The heavier iron and nickel went to the core while the lighter silicates stayed in the mantle.

Future prospect of the study

• This finding could help investigations of high-pressure phase transformation mechanisms in the deep Earth.

Back2Basics: Interior of Earth

​​The earth is made up of three different layers: the crust, the mantle and the core.

The crust

This is the outside layer of the earth and is made of solid rock, mostly basalt and granite. There are two types of crust; oceanic and continental. Oceanic crust is denser and thinner and mainly com​posed of basalt.  Continental crust is less dense, thicker, and mainly composed of granite.

The mantle

The mantle lies below the crust and is up to 2900 km thick.  It consists of hot, dense, iron and magnesium-rich solid rock. The crust and the upper part of the mantle make up the lithosphere, which is broken into plates, both large and small.

The core

The core is the centre of the earth and is made up of two parts: the liquid outer core and solid inner core. The outer core is made of nickel, iron and molten rock. Temperatures here can reach up to 50,000 C.

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