Earth, Mars, Moon Have Different Origin, Study Says

March 19, 2008

A new study is challenging the long-standing notion that the whole solar system formed from the same raw materials.

Until now most scientists had believed that the inner solar system bodies—Mercury, Venus, Earth, its moon, and Mars—had the same composition as primitive meteorites called chondrites.

But, problematically, Earth's chemistry doesn't quite match.

Now, French researcher Guillaume Caro, from Centre de Recherches Pétrographiques et Géochimiques in France, and his colleagues say that the makeup of Mars and the moon don't correspond either.

It turns out the three bodies may be more similar to each other than the chondrite-rich asteroids located between Mars and Jupiter.

Caro and his team say scientists may now have to revisit the idea that chondrites represent the building blocks for the whole solar system.

"What our results suggest is that the sorting of the elements that make up these planets may have happened at a much earlier stage than had been believed," said Alex Halliday, a study co-author from Oxford University.

"The composition of these worlds is inconsistent with them simply forming out of large 'lumps' of stony meteorites like those we see today in the asteroid belt."

The study appears in this week's issue of the journal Nature.

Earth Askew

Chondrites are the most common class of meteorites, and, at an estimated 4.5 billion years old, believed to be the oldest.

Because the objects chemically resemble the sun, it is widely believed that they represent the basic materials for the entire solar system.

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