Magazine article Science News

Asteroids Get Solar Push toward Earth

Magazine article Science News

Asteroids Get Solar Push toward Earth

Article excerpt

When it comes to luring asteroids into the inner solar system, a little nudge goes a long way.

Most asteroids inhabit an elliptical set of tracks, known as the main asteroid belt, between the orbits of Mars and Jupiter. Although unlikely to spell doomsday for Earth, rocks occasionally get flung from the belt onto paths that intersect our planet's orbit. A new study suggests that tiny motions induced by the sun's energy can play a crucial role in sending asteroids on such an inward journey.

Researchers realized in the 1980s that asteroids occupying certain zones, known as resonances, within the outer part of the main belt are profoundly influenced by Jupiter's gravity. The giant planet's pull can dramatically elongate the orbits of these asteroids, causing their paths to cross those of the inner planets. More recently, scientists have calculated that another set of resonances in the main belt nearer Mars also acts as an escape hatch, ejecting some rocks into the inner solar system.

These special zones are numerous but extremely narrow, making it hard to explain how so many asteroids end up in the inner solar system. In the March 5 SCIENCE, Paolo Farinella of the University of Trieste in Italy and David Vokrouhlicky of Charles University in Prague, Czech Republic, present computer simulations showing a nongravitational effect so tiny it has often been ignored could account for the migration.

Named for the Russian engineer who discovered it a century ago, the Yarkovsky effect results from the way a spinning asteroid absorbs and reradiates solar energy. …

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