© ESO/L. CALÇADAMeteorites suggest that a proto-Jupiter separated two sets of asteroids in the solar system's disk of dust.
The stately solar system of today was in turmoil in its first several million years, theorists believe, with giant planets sowing chaos as they strayed far from their current orbits. But corroborating evidence has been thin-until now.
Scientists have found a new window into the early dynamics: a curious chemical divide in the dozens of species of meteorites. The picture has emerged over several years, but in work presented last week at the Lunar and Planetary Science Conference here, a group of German geochemists reported clinching evidence.
They tested 32 meteorites representing nearly all known types and found that "any meteorite you take, it belongs to either one of these groups," says Thorsten Kleine, a geochemist at the University of Münster in Germany who led the work.
Those divergent chemistries imply distinct origin stories for asteroids, the parent bodies of most meteorites.
One group formed from grist that began near the current location of the asteroid belt. The others coalesced much farther out, beyond a proto-Jupiter, near where Saturn orbits today. Only later, pushed and pulled by the wandering giant planets, did these immigrant asteroids find their home in today's asteroid belt. Bill Bottke, a planetary dynamicist at the Southwest Research Institute (SwRI) in Boulder, Colorado, thinks the chemical divide holds other clues to the timing and formation of the planets. "It really seems to be a powerful mechanism for understanding our solar system."
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