Where Asteroids Come From

Over the past millions of years, Earth has taken some major hits from asteroids. Where do these huge boulders come from and why are they in orbits near the Earth? Scientists now think the sun is to blame.

Asteroids most likely come from the dense area of gigantic, spinning rocks that exists between Mars and Jupiter. But scientists have a hard time explaining what might have dislodged so many of them from their stable asteroid belt and sent them hurtling towards Earth.

A U.S.-Czech team, led by William Bottke of the Southwest Research Institute in Boulder, Colorado, says there may be an unexpected cause — the absorption and re-absorption of sunlight over millions or billions of years. This slow process could gently nudge asteroids into new orbital zones, where they would succumb to the gravitational forces of the planets.

An object in space, like an asteroid, heats up slowly and gradually radiates this energy back into space. Because this process causes some momentum, the energy may eventually push the asteroids out of their orbits.

Computer models used to study numerous asteroid belts, which contain fragments from the collisions of large asteroids, support the idea that these heated bodies experience altered orbits. Many of the fragments seem to have moved into areas where tiny gravitational pulls from nearby planets such as Mars, Jupiter, or Saturn can push them out of the asteroid belt and send them crashing down towards a nearby planet.

To learn more about this, read ?Dark Matter, Missing Planets and New Comets? by Tom Van Flandern,click here.

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