Meteorite: Hint For Earth’s Mantle

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A new study has now shown that by studying a meteorite and its minerals we may find new clues about the Earth’s lower mantle. 

About

• A meteorite, which belonged to the Asteroid Belt, fell in Assam in 2015, holds clues to Earth’s deeper layers and its formation.
• A team of students and researchers from the Indian Institute of Technology (IIT) Kharagpur have analysed the meteorite.
• The Earth has different layers: 
  • the upper, very thin crust 
  • Followed by the intermediate silicate mantle which starts from 30km to 2,900 km depth, and 
  • then the centre iron nickel alloy core. The mantle faces high temperature and pressure. 
• While we know about crust (the outermost layer) formation and composition, very little is known about the mantle and the core, which are located below the crust.

Image Courtesy: GeologicalSurvey

Key Findings

• L6 Chondrite:
  • The meteorite was classified as an L6 chondrite, a variety of stony meteorite.
  • This meteorite has gone through high-pressure and high-temperature conditions due to an impact event. It will help in concluding that it has a similar chemical composition as found in Earth’s lower mantle.
  • It provided the research team with samples of naturally occurring high-pressure minerals like those believed to make up the Earth’s deep mantle.
• Similarity with Earth’s lower mantle:
  • 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, pyroxene, plagioclase and chromite.
  • Olivine is also found in Earth’s upper mantle. 
  • Olivine is a rock-forming mineral found in dark-coloured igneous rocks and has a very high crystallisation temperature compared to other minerals. 
• Evidence of the complex chemical reaction: 
  • 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. 
  • They 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 breakdown may occur where the olivine remains in the solid state or may also form by melting of the olivine. 
  • The breakdown assemblage of bridgmanite and magnesiowüstite formed by both of these mechanisms has been reported in few Martian meteorites.
• Found in the asteroid belt:
  • This particular kind of meteorite is found in the asteroid belt
  • Formed by 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.
• Similar Pressure:
  • The meteorite 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. 

Significance

• This research could help in better understanding of the formation of Earth.
• The samples found in the meteorite are similar to those observed on plate tectonics and could prove useful in studying earthquakes and volcanic activities.
•  Life on Mars can also be better examined with the help of this meteorite.

Conclusion

• The results suggest what processes and reactions may be involved in the formation of Earth’s lower mantle. 
• By studying different meteorites, we can understand in detail about their parent body and in the process understand our own planet and its formation.
• The Mechanism needs to be verified in natural terrestrial samples in future studies.

Source: TH