‘Missing’ element is clue to planet formation

Friday, February 25, 2011

WASHINGTON - A new study has shown that early in the formation of the Earth, some forms of the element chromium separated and disappeared deep into the planet’s core.

The finding will help scientists understand the early stages of planet formation, said Qing-Zhu Yin, of the UC Davis and coauthor of the paper.

The researchers used specialized equipment at UC Davis to make very exact measurements of chromium isotopes in meteorites, compared to rocks from the Earth’s crust, and use modern high performance computers to simulate early Earth environment.

They studied a class of meteorites called chondrites, which are leftovers from the formation of the solar system over four and half billion years ago.

As well as adding shiny, rust-proof surfaces to metalwork, chromium adds color to emeralds and rubies. It exists as four stable (non-radioactive) isotopes with atomic masses of 50, 52, 53 and 54.

It has been known for decades that chromium isotopes are relatively underrepresented in the Earth’s mantle and crust, said Yin. That could either be because they were volatile and evaporated into space, or got sucked into the Earth’s deep core at some point.

By making very accurate measurements of chromium isotopes in the meteorites compared to Earth rocks and comparing them to theoretical predictions, the researchers were able to show for the first time that the lighter isotopes preferentially go into the core. From this the team inferred that some 65 percent of the missing chromium is most likely in the Earth’s core.

The findings have been published in the journal Science. (ANI)

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