Asteroid Belt Once Shaken Like a Cosmic Snow Globe: CfA Says

Jupiter may have once been as close to the Sun as Mars is now, and as it migrated through the main asteroid belt to its current position, it played a role is nearly wiping the asteroid belt clean, leaving behind only one-tenth of a percent of the original material in the belt but also bringing in material from the far reaches of the solar system, according to a new report from the Harvard-Smithsonian Center for Astrophysics (CfA).

During the formation of the solar system, the gaseous planets that make up the outer solar system were pulled much closer to the Sun than they are now, causing a jarring cosmic riot in the asteroid belt.

"We found that the giant planets shook up the asteroids like flakes in a snow globe," said lead author Francesca DeMeo, a Hubble postdoctoral fellow at the CfA.

As the planets migrated, it caused a large-scale disruption to the contents of the solar system, the researchers said, noting that objects from as close to the Sun and Mercury and as far out as Neptune all gathered in the asteroid belt.

"The asteroid belt is a melting pot of objects arriving from diverse locations and backgrounds," DeMeo said in a statement.

Astronomers have recognized this cosmic diversity in the asteroid belt for some time, but a new analysis of the asteroids within the belt has revealed that it is more diverse than previously realized, particularly among the smaller asteroids in the belt.

DeMeo and Benoit Carry of the Paris Observatory report the finding in this week's edition of the journal Nature (available Thursday).

"This finding has interesting implications for the history of Earth," the CfA said in a statement. "Astronomers have theorized that long-ago asteroid impacts delivered much of the water now filling Earth's oceans. If true, the stirring provided by migrating planets may have been essential to bringing those asteroids."

The new research brings with it as many questions as it does answers. If, elsewhere in the Universe, an Earth-like exoplanet is forms or exists, would it also require a similar rain of asteroids to make it habitable?

It that is the case, then worlds like our own may be even rarer than we think.